Dry Tortugas National Park 

Dry Tortugas Light Station 

Lighthouse and Oil House 

Historic Structure Report 

Prepared for 

Dry Tortugas National Park 

Southeast Region, National Park Service 

by 

Lord, Aeck & Sargent Architecture 

2009
 

Cultural Resources 

Southeast Region 

National Park Service 

100 Alabama St. SW 

Atlanta, GA 30303 

(404) 507-5847 

2009 

Historic Structure Report 

Dry Tortugas Light Station 

Dry Tortugas National Park 

LCS#: 091383 (Dry Tortugas Lighthouse) 

LCS#: 091387 (Oil House) 

Cover Image: Undated nineteenth century 

image of Dry Tortugas Light Station, 

National Archives and Records 

Administration, Record Group 26. 

The historic structure report presented here exists in 

two formats. A traditional, printed version is 

available for study at the park, the Southeastern 

Regional Office of the NPS (SERO), and at a variety 

of other repositories. For more widespread access, 

the historic structure report also exists in a webbased format through ParkNet, the website of the 

National Park Service. Please visit www.nps.gov for 

more information. 
 

National Park Service v 

Contents 

Management Summary ...................................................................................................................................... 1 

Administrative Data ............................................................................................................................................ 7 

PART 1 DEVELOPMENTAL HISTORY 

Historical Background and Context ..................................................................................................... 11

 Discovery and Early Exploration of the Dry Tortugas ........................................................ 11

 Aids to Navigation in the Dry Tortugas ................................................................................. 13

 Lighthouse Illumination .......................................................................................................... 14

 A New Light in the Dry Tortugas ........................................................................................... 16

 Keepers and Their Duties ........................................................................................................ 17

 War and Disease ....................................................................................................................... 18

 The Hurricane of 1873 ............................................................................................................. 20

 Late Nineteenth Century Development ................................................................................ 21

 The Spanish American War ..................................................................................................... 23 

 Bureau of Lighthouses .............................................................................................................. 23 

 The Carnegie Institution Marine Biology Laboratory ......................................................... 23 

 Early Twentieth Century Modernization .............................................................................. 25 

 The U.S. Coast Guard ............................................................................................................... 26 

 The National Park Service ....................................................................................................... 28

 

Chronology of Development and Use .................................................................................................. 31

 Design and Construction ......................................................................................................... 31

 Early Repairs and Maintenance .............................................................................................. 36

 Hurricane Damage and Repairs .............................................................................................. 36

 Changes to the Light ................................................................................................................. 37

 Modernization of the 1920s ..................................................................................................... 40

 Coast Guard Era Modifications .............................................................................................. 42

 Recent Alterations by the National Park Service .................................................................. 44

 Dry Tortugas Light Station Timeline ..................................................................................... 45

Physical Description ............................................................................................................................... 51 

 Dry Tortugas Lighthouse ......................................................................................................... 51

 Character Defining Features ..................................................................................... 53

 Structural Systems ...................................................................................................... 54 

 Exterior Features ........................................................................................................ 59

 Interior Features ......................................................................................................... 63

 Utilities ......................................................................................................................... 70

 Summary of Conditions ............................................................................................. 72

 

 Dry Tortugas Light Station Oil House ................................................................................... 74
vi Dry Tortugas Lighthouse HSR 

 Character Defining Features .....................................................................................76

 Structural Systems .......................................................................................................76 

 Exterior Features ........................................................................................................78

 Interior Features .........................................................................................................81

 Utilities .........................................................................................................................86

 Summary of Conditions .............................................................................................87

PART 2 TREATMENT AND USE 

 Requirements for Treatment and Use ..................................................................................................91

 Ultimate Treatment and Use ..................................................................................................................95 

 

 Alternatives for Treatment and Use ......................................................................................................101 

 

 Recommendations for Treatment ........................................................................................................103 

Sources of Information .......................................................................................................................................113

Appendix A 

Draft National Register Nomination Form 

Appendix B 

Dry Tortugas Light Station Materials Analysis, Dry Tortugas, Florida, Building Conservation 

Associates, August, 2009. 
National Park Service 1 

Figure 1. 2008 photograph of Dry Tortugas Light Station on approach to the main dock from the east. 

Management Summary 

The Dry Tortugas Lighthouse (also referred to 

as the Loggerhead Key Lighthouse) was 

constructed in 1858 to better mark the 

dangerous shoals of the Dry Tortugas after the 

lighthouse on Garden Key was determined 

inadequate for this purpose. It was constructed 

during a period of transition and significant 

growth within the Lighthouse Establishment. 

The Light Station is made up of several 

structures originally built to accommodate the 

light keepers, their families and the equipment 

and supplies necessary to maintain the 

Lighthouse and support habitation in this 

remote location. The Lighthouse has 

continuously served as an active aid to 

navigation from the time of its construction to 

the present. 

The Light Station was manned by keepers or 

caretakers from its initial construction through 

the mid-1980s when the lamp or optic was 

automated, eliminating the need for continual 

occupation of the site. The decision to automate 

the lamp was made after the rotating mechanism 

of the existing second-order lens was damaged 

during repairs to the Lantern. 

In 1992, legislation was passed to abolish Fort 

Jefferson National Monument (designated by 

Franklin Delano Roosevelt in 1935) and 

establish Dry Tortugas National Park (DRTO). 

As part of the Park’s enabling legislation, 

Loggerhead Key, along with the resources of the 

Light Station (with the exception of the 

Lighthouse) were transferred from the United 

States Coast Guard (USCG) to the National Park 
2 Dry Tortugas Lighthouse HSR 

Service (NPS). Under the Park Service’s 

management, public visitation to the Key has 

been limited. However, a relatively constant 

presence has been maintained at the site through 

the NPS’s Volunteer-In-Parks (VIP) program 

and various research initiatives. 

In October 2008, Lord, Aeck & Sargent was 

contracted by the National Park Service to 

prepare a Historic Structure Report (HSR) for 

the resources of the Dry Tortugas Light Station. 

It was decided that three documents would be 

prepared, the first would address the Lighthouse 

and Oil House, the second, the Keeper’s 

Residence and the last document would address 

the remaining resources of the Light Station. 

This document addresses the Dry Tortugas 

Lighthouse and Oil House. 

During the first week of March 2009, a two 

member team from Lord, Aeck & Sargent (Rob 

Yallop and Glen Bennett) traveled to 

Loggerhead Key to undertake a physical 

inspection of the Light Station resources. In 

addition, Ms. Dorothy Krotzer of Building 

Conservation Associates Inc. also traveled to the 

site to collect mortar and paint samples for 

analysis (The results of this analysis are provided 

in Appendix B). Personnel from Lord, Aeck & 

Sargent spent a week on the island documenting 

the resources and collecting information to 

support preparation of the HSRs. A second brief 

visit was made to the site in June 2009. 

Field notes, measurements, material sampling 

and photographs were collected for all of the 

structures as a means to record the existing 

conditions. With the exception of the mortar 

and paint sampling, no destructive testing was 

performed and no historic fabric was removed 

to facilitate the collection of information. All 

portions of the buildings were accessible with 

the exception of the Lighthouse galleries. A 

hurricane-proof plywood insert had been 

installed at the Watch Room level door, 

restricting access to the galleries. Exterior 

conditions of the Lantern and Watch Room 

were therefore observed from grade using 

binoculars. 

Historic research included two trips to the 

National Archives and Records Administration 

in Washington D.C. and one visit to the 

Southeast Region National Archives and 

Records Office in Morrow, Georgia to review 

documents, drawings and photographs held 

primarily in Record Group 26. The files held in 

the National Park Service Southeast Regional 

Office and the archives of Everglades National 

Park were also reviewed. A visit was made to the 

USCG offices in Miami to review records 

pertaining to their management of the site. 

Numerous other secondary sources were 

consulted in preparation of the HSR. 

Current agreements call for transfer of the 

Lighthouse to the National Park Service in the 

near future, pending the fulfillment of several 

requirements, including completion of this 

report. Upon official transfer of the Lighthouse, 

the structure will remain an active aid to 

navigation and the USCG will retain 

management and maintenance responsibilities 

for the optic and its associated equipment. 

The Park’s General Management Plan has 

addressed treatment and use of the Light Station 

resources through the establishment of a 

Historic Preservation/Adaptive Use (HP/AU) 

Management Zone in the center of Loggerhead 

Key. Without being specific, this management 

zone prescribes that the resources of the Light 

Station will be primarily reserved for 

interpretive and educational opportunities. The 

structures will also be adaptively used to 

accommodate critical functions such as housing 

for volunteers, staff, and research personnel and 

the storage of utility components and 

equipment. 

Changes to the Lighthouse have been limited 

and the structure appears today much like it did 

after 1870 when the daymark was applied. This 

presents exciting opportunities for interpreting 

the architecture and history of the Lighthouse. 

By contrast, the Oil House has experienced 

extensive modifications to its original form and 

materials as its use has evolved over the years. As 

one might expect, the fabric of both structures 

has had to be constantly repaired and in some 

cases replaced as the marine environment and 

intensive storms that frequent this region have 

resulted in ongoing damage and deterioration. 

In addition, the limited manpower available and 

the remoteness of the site have made 

maintaining the resources a challenge. 

The desire of the National Park Service to 

provide greater access to the resources of the 

Light Station presents additional challenges. 

Establishing visitor access to Loggerhead Key is 

the first issue that must be addressed through 

renewed concession agreements or other special 

arrangements. 
Management Summary 

National Park Service 3 

The existing conditions of the Lighthouse do 

not present major obstacles to greater access but 

there are several issues that should be addressed 

before the structures can be fully occupied by 

the visiting public. These include increasing light 

levels in the stair tower and repairing broken 

stair treads and sections of handrail. The wedge 

shape of the stair treads and the physical 

dimensions of the upper landings will limit the 

number of visitors that can be safely 

accommodated in the Lighthouse at one time. 

Visitor access to the Watch Room and Lantern is 

more problematic due to the limited physical 

size of these spaces and their access points. 

There is no landing at the Watch Room level and 

it is therefore necessary to guide oneself through 

a narrow hatch in the Watch Room floor while 

ascending the last few stairs which are set at a 

steep incline. Also, the Watch Room and 

Lantern gallery railings are deteriorated and do 

not currently meet the requirements of 

applicable codes. Therefore, public access to the 

Watch Room gallery should not be permitted 

until modifications are made to the railing that 

address safety concerns. Access to the Lantern 

gallery by the public is not practical as this level 

can only be reached by an exterior-mounted 

ladder that requires the climber to wear fall 

protection. 

Access to the site by the physically disabled will 

require careful study of each leg of a potential 

trip to the site, beginning in Key West. The 

Lighthouse and Oil House have never been 

accessible structures. Implementing the changes 

required to fully comply with the requirements 

of the Architectural Barriers Act, the 

Rehabilitation Act and the Americans with 

Disabilities Act will not be possible without 

negatively impacting the historic character of 

these structures. Therefore the application of 

“minimum alternative access” as provided for in 

the procedures described in ADAAG 4.1.7 (2), 

and further discussed in 28 CFR 36.405 and 

ADAAG 4.1.7(3) should be applied. The types of 

responses appropriate under the “minimum 

alternative access” provisions could include 

such elements as accessible observation points 

on the ground to view building features, videos 

interpreting the experience of ascending the 

tower and viewing the surroundings from the 

Watch Room gallery, or scale models of the 

Lighthouse and Light Station resources available 

for viewing at a Visitor’s Center or other 

accessible facility. 

Summary of 

Recommendations 

The following is a summary of the treatments 

recommended to preserve and rehabilitate the 

Dry Tortugas Lighthouse and Oil House and to 

prepare them for continued, and potentially 

more intensive, use. The recommendations have 

been organized into five “Work Packages” 

presented in the general order of priority and 

also in response to limits on the amount of 

cyclical maintenance funding that can be 

requested by the Park in a given year. Work 

Package 1 represents those deficiencies that 

need to be addressed in the short term to 

address critical condition problems and issues of 

life safety. Following completion of this initial 

phase of work, the packages are generally 

organized to address repairs to the Lighthouse 

from the top down. The timeline for conducting 

repairs assumes that the work will be completed 

over an approximately 10 year period. 

Additionally, given the remoteness of the site 

and the significant costs associated with a 

potential contractor’s General Conditions and 

scaffolding, it may not be practical to phase the 

interior or exterior masonry repair and 

repainting scopes to fit within the established 

funding limits. Therefore it may be necessary for 

the Park to request “line item” funding for Work 

Package s 3 and 5. 

General 

 Prepare an updated national register 

nomination for the Light Station 

resources. 

 Limit public access to the Lighthouse to 

small groups of no more than 4-5 

visitors. 

 Explore the potential for reacquiring 

and installing the second-order bivalve 

lens. 



Work Package 1 – Priority Treatments and 

Activities 

Watch Room 

 Expose and treat corroded anchors in 

masonry wall. 
4 Dry Tortugas Lighthouse HSR 

 If existing stucco finish requires 

widespread removal to accommodate 

repair of anchors, replace with a more 

compatible stucco finish system. If not, 

repair existing stucco as needed. 

 Expose, remove corrosion and refinish 

I-beams and lintel supporting Watch 

Room level floor plate. 

Lighthouse Stair Tower 

 Repair broken sections of hand rail. 

 Replace failed stair treads (2). 

 Install lighting system to increase light 

levels in stair tower. 

Masonry Repair 

 Monitor vertical cracking below Watch 

Room level of Lighthouse. 

Concrete Passageway 

 Flood test roof of Passageway to 

confirm integrity. 

 As a priority repair concrete spalling by 

exposing rebar, removing corrosion, 

refinishing and then patching concrete. 

 Repaint interior and exterior of 

Passageway. 

Work Package 2 – Lantern and Watch Room 

Level Repairs 

 Complete Lantern roof repair project 

including replication of integral gutter 

system, vent ball and lightning rod. 

 Repair Lantern floor plates by removing 

corrosion and reapplying an appropriate 

protective finish. 

 Recast and replace corroded iron 

headers of Lantern structure. 

 Repair corroded gallery railing. 

 Remove exterior access ladder structure 

installed in 1978. 

Watch Room 

 Repair and make operable the circular, 

bronze ventilators in the Watch Room 

walls. 

 Repair historic Watch Room-level door 

and reinstall. If repair is not feasible, 

install new door that matches the 

historic door in material and design. 

 Repair Watch Room floor plates by 

removing corrosion and reapplying an 

appropriate protective finish. 

 If visitor access to galleries is desired 

replace corroded gallery railings with 

code-compliant railing. 

 Install a new smaller exterior ladder that 

is in keeping with the historic condition 

to provide access between the Watch 

Room and Lantern galleries. 

 Remove corrosion and refinish lens 

pedestal components. 

 Install new window and shutter 

assembly at Watch Room. Review 

design and monitor performance of unit 

over time to inform installation of 

remaining windows in tower. 

Work Package 3 – Interior Masonry and 

Miscellaneous Repairs 

Masonry Repair 

 Abate lead-based paint and reapply 

interior finish. 

 Quantify areas of mortar loss. 

 At locations of critical mortar loss, 

conduct masonry repointing and repair 

of the Lighthouse interior. 

 Repair vertical cracking with deep 

penetrating mortar. 

Lighthouse Stair Tower 

 Preserve Lighthouse entry door and 

install appropriate hardware to improve 

operability and security. 
Management Summary 

National Park Service 5 

Work Package 4 – Repair and Rehabilitation 

of Oil House 

Oil House Exterior 

 Abate lead-based paint and reapply 

exterior finish on Oil House. 

 Conduct minor masonry repairs. 

 Remove existing windows and install 

new windows and shutters in Oil House. 

 Install new roof on Oil House. 

 Repair and preserve existing Oil House 

door. 

Oil House Interior 

 Contingent on its ultimate use, remove 

modern faux wood paneling on first 

floor and relocate electrical panels 

associated with photovoltaic system. 

 Remove vinyl tile on second floor and 

install wood flooring. 

West Addition 

 Repoint and monitor horizontal crack in 

north and west walls. 

 Install new window in west elevation. 

South Addition 

 Retain South Addition to house critical 

equipment but do not commit resources 

to its long term preservation. 

Work Package 5 – Exterior Masonry Repair 

and Installation of New Windows 

Masonry Repair 

 Verify construction of tower walls. 

 Explore options for ventilating internal 

voids if present. 

 Quantify areas of critical mortar loss. 

 At locations of critical mortar loss, 

conduct masonry repointing and repair 

of the Lighthouse exterior. 

 Abate lead-based paint and reapply 

daymark on Lighthouse. 

Windows 

 Remove existing windows and install 

new windows and shutters in 

Lighthouse. 
6 Dry Tortugas Lighthouse HSR 

 
Dry Tortugas Lighthouse HSR 7 

Administrative Data 

Resource Names and Numbers 

Building Name: Dry Tortugas Lighthouse 

Structure No.: HS-21 

List of Classified Structures (LCS) No.: 091383 

Building Name: Dry Tortugas Light Station Oil 

House 

Structure No: HS-23 

List of Classified Structures (LCS) No.: 091387 

Resource Location 

The Dry Tortugas Lighthouse and Dry Tortugas 

Light Station Oil House are located on 

Loggerhead Key within Dry Tortugas National 

Park. Located 65 miles west of Key West Florida, 

Dry Tortugas National Park encompasses an 

area of approximately 100 square miles 

containing seven, small, sand and coral keys 

(islands) and the surrounding shoals and water. 

Loggerhead Key and Garden Key are the only 

inhabited keys within the Park. The Park’s 

central cultural feature, Fort Jefferson, is located 

on Garden Key, approximately 2 1⁄2 nautical 

miles east of Loggerhead Key. Access to the Park 

is by boat or seaplane. The visiting public 

generally travels to the Park on commercial 

ferries operated out of Key West. The primary 

public docking facilities and debarkation points 

are on Garden Key. 

Loggerhead Key is the largest key in the Park 

measuring approximately 1 mile long and 700 

yards across and containing approximately 35 

acres. The lighthouse and oil house are among 

several historically significant buildings at the 

Dry Tortugas Light Station. The Light Station 

complex is located in the approximate 

geographic center of Loggerhead Key. 

Location: Loggerhead Key, Dry Tortugas 

National Park 

 Coordinates: Latitude 24° 38’ 00.021” N, 

Longitude 82° 55’ 13.958” W 

County: Monroe 

State: Florida 

Lighthouse Data 

Active: Yes 

Construction: First Order conical brick tower 

constructed 1858

Focal Plane: 151’ 

Range 20 miles 

Original Light: Fixed, first-order Fresnel lens 

(Sautter & Company)

Current Light Single Flashing, White, 20s, VEGA 

VRB-25 

Daymark: lower half painted white, upper half 

and lantern painted black 

U.S. Coast Guard District: 7th

Cultural Resource Data 

In 1984, a draft National Register nomination 

was prepared for the Dry Tortugas Light Station 

by National Park Service staff as part of a 

submission to the USCG, Department of 

Transportation. No further action was taken by 

the USCG regarding the nomination. The 

National Park Service subsequently conducted a 

review of the nomination in 1989 anticipating a 

potential transfer of the Light Station from the 

USCG. Based on this review, the nomination 

was updated in 1993 and submitted to the Acting 

Chief Historian of the National Park Service’s 

Washington Support Office for a second review 

in 1995. No further action was taken with regard 

to the draft nomination. 

Dry Tortugas National Park was established in 

1992 by Public Law 102-525 to “preserve and 

protect for the education, inspiration, and 

enjoyment of present and future generations 

nationally significant natural, historic, scenic, 

marine, and scientific values in South Florida.” 

Under [36 CFR 60.1(b) (1)], historic units of the 

National Park System are automatically given 

National Register of Historic Places status by 

virtue of their incorporation into the park 

system. Thus, the Dry Tortugas Light Station 

was listed on the National Register of Historic 

Places as part of Dry Tortugas National Park. 
8 Dry Tortugas Lighthouse HSR 

Figure 2. Maps showing location of Dry Tortugas National Park, Loggerhead Key and the individual 

structures of the Dry Tortugas Light Station.

Oil House 

Loggerhead Key

Dry Tortugas National Park 

Cuba 

Florida 

Dry Tortugas Lighthouse 

Loggerhead Key 

Boathouse 

Kitchen Building 

New Oil House 

1922 Keeper’s Residence 

Concrete Cistern 

Brick Cistern 

Brick Cistern 

Concrete Cistern 
Administrative Data 

Dry Tortugas Lighthouse HSR 9 

Significance 

The draft national register nomination proposes 

a broad period of significance for the property 

spanning from its initial construction date 

through to the “present,” or 1995, the year the 

draft nomination was submitted to the 

Washington Support Office. This approach 

suggests the Lighthouse derives its primary 

significance from its function as an aid to 

navigation and is inclusive of the entire period it 

has been active. This approach acknowledges all 

epochs of the Light Station’s history including 

the National Park Service’s management of the 

site. 

Specifically, the draft nomination provides the 

following statement about the Light Station’s 

significance. 

The light station is significant primarily for its 

role in facilitating America’s ocean-borne 

commerce and as a notable example of the kind 

of civilian public works project undertaken by 

Army engineers prior to the Civil War. While 

the lighthouse is clearly the most important 

structure within the boundaries of the 

nominated area, there were several ancillary 

structures built at the same time as the 

lighthouse, and also from the 1920s, a period in 

which the station was extensively modernized. 

It is recommended that the draft national 

register nomination be updated based on the 

research collected in preparing the HSRs and 

resubmitted for formal acceptance. 

Related Studies 

Hellman, Robert and David M. Brewer. 

Archeological Survey of Loggerhead Key, 

Dry Tortugas National Park. Southeast 

Archeology Center (SEAC), National 

Park Service, 2003. 

Kenneth Smith Architects Inc., and Bender & 

Associates, Architects P.A. for the State 

of Florida Department of State, Division 

of Historical Resources and Department 

of Community Affairs, Florida Coastal 

Management Program. Florida 

Lighthouse Study 2002 

National Park Service Draft National Register of 

Historic Places Registration Form 1993 

National Park Service. General Management 

Plan Amendment, Dry Tortugas National 

Park. 2002 

National Park Service National Register 

Programs Division, Preservation 

Services Branch for the Department of 

Transportation, United States Coast 

Guard, Seventh District, Rehabilitation 

Report and National Register Nomination 

for the United States Coast Guard Light 

Station, Dry Tortugas Lighthouse, 

Loggerhead Key Florida. October 1984 
Dry Tortugas Lighthouse HSR 10 

 
National Park Service 11 

Lights on the Florida Reef 

The fixed white light of Fowey Rocks, 

 And Carysfort’s white flash, 

Both may be seen from the middle 

 Of a twenty-three mile dash. 

Alligator Reef’s red, white and white

 Lies thirty miles away. 

Log thirty more, Sombrero white 

 Points to Honda Bay. 

Then comes the Shoals American, 

White flashing through the night. 

Just fifteen miles from white Key West, 

 Twenty from Sand Key’s twinkling white. 

The Marquesas are unlighted; 

 But on Rebecca’s Shoal, 

A white and red is sighted, 

 Warning from wreck and dole. 

Sixteen miles to Dry Tortugas 

 With a white light on the fort, 

Three more to the flash of Loggerhead, 

 And all’s clear to a western port. 

 Kirk Monroe 
12 Dry Tortugas Lighthouse HSR 
National Park Service 11 

Historical Background and 

Context 

The historical background of the Dry Tortugas 

Light Station is documented by historians, 

Love Dean in Lighthouses of the Florida Keys

and Neil Hurley in Lighthouses of the Dry 

Tortugas: An Illustrated History. These along 

with Russ Holland’s America’s Lighthouses: 

Their Illustrated History since 1716 and Edwin 

C. Bearss’ Shipwreck Study-The Dry Tortugas

contributed to the development of the 

historical background and context. The 

following narrative draws upon these histories 

and references them when cited. The 

historical background also relies on the 

“clipping files” and other primary sources 

related to the Dry Tortugas Light Station 

found in National Archives Record Group 26. 

Discovery and Early Exploration 

Juan Ponce de Leon is credited with the 

discovery in 1513 of 11 sand and coral islands 

located at the southwestern tip of the Florida 

Keys. Because sea turtles were in abundance, 

he named the islands “Las Tortugas,” meaning 

the turtles. At the time of Ponce de Leon’s 

discovery, hundreds of turtles were present on 

the shores of these islands along with pelicans 

and the now-extinct Caribbean monk seal.1

Several accounts describe Ponce de Leon’s 

crews capturing over a hundred turtles in one 

night - turtles were a significant source of food 

for mariners. 

The first recorded shipwreck in the area 

occurred in 1622 when the Nuestra Senora del 

Rosario ran aground on one of the keys of the 

Tortugas. The survivors and their rescuers 

 

1

 Bearss, Edwin C., Shipwreck Study-The Dry Tortugas, 

Washington, DC: Eastern Service Center-Office of History and 

Architecture, United States Department of the Interior, 

National Park Service, April 15, 1971,1. 

reportedly camped on the island that would 

later be named Loggerhead Key.2

Florida was under Spanish rule from 1513 

until 1763, when it was ceded to Britain. While 

under British rule, Las Tortugas were surveyed 

by T. Jefferys in 1763, by Bernard Romans in 

1766, and by George Gauld in the 1770s. 

Gauld’s maps, published in 1773, were used 

widely for navigation of the gulf coast off 

British West Florida. Due to the lack of fresh 

drinking water, or possibly “in contradiction 

to the vast tract of wet reef which at low water 

nearly reaches the surface,” Las Tortugas 

eventually became known as the Dry Tortugas. 

On his charts, Gauld named the individual 

islands that made up the Dry Tortugas 

including Loggerhead “Turtle” Key.3

In 1783, following its participation in the 

American Revolution, Spain regained Florida, 

and maintained it as a colony until 1821. Spain 

encouraged settlement of the region through 

land grants, but Florida remained sparsely 

populated well into the nineteenth century. By 

1845 when Florida became a state it had only 

60,000 residents. 

Given their location at the intersection of the 

Gulf of Mexico and the Atlantic Ocean where 

the swift Gulf Stream current flows though the 

Straits of Florida, the Dry Tortugas witnessed 

considerable shipping traffic. Westward 

expansion in the United States led to an 

increase in the transport of goods from the 

interior of the continent to the urban centers 

along the east coast. After passing through the 

open waters of the gulf, most ships heading 

east avoided the Dry Tortugas by taking a 

 

2

 Hellmann, Robert and David M. Brewer, Archaeological 

Survey of Loggerhead Key, Dry Tortugas National Park,SEAC 

Accession No. 1341, 2003. 

3

 Dean, Love, Lighthouses of the Florida Keys, Inc., Sarasota, 

Florida: Pineapple Press, 1998, 75. 
12 Dry Tortugas Lighthouse HSR 

Figure 3. Map produced in 1838 based on Gauld’s earlier 1773 survey of the Dry Tortugas. Note the map 

identifies Loggerhead “Turtle” Key. 

Loggerhead “Turtle” Key 
Historical Background and Context 

National Park Service 13 

Figure 4. Undated nineteenth century view of 

Garden Key lighthouse within the parade 

ground of Fort Jefferson. 

southerly route and navigating along the 

Cuban coastline. Stormy weather or a 

captain’s inexperience could result in ships 

veering off course and foundering in the 

shallow reefs of the Keys. Not only did 

mariners have to be mindful of the hazardous 

sailing conditions, but they also had to keep a 

vigilant watch for pirates cruising these same 

waters in search of vessels they could exploit. 

Salvaging, or wrecking as it was also known, 

became a lucrative business in the Florida 

Keys. Dozens of vessels and hundreds of men 

were active in the trade which became highly 

organized and regulated. Wreckers had to 

hold a license issued by the Federal Court to 

legitimately take part in salvaging activities. 

During the nineteenth century, the Keys 

claimed hundreds of ships carrying millions of 

dollars of cargo which was eventually salvaged 

and liquidated in the auction houses of Key 

West. In the Dry Tortugas, the natural harbor 

at Garden Key provided safe anchorage for the 

wreckers from where they could observe the 

surrounding keys and quickly respond to any 

ship running aground or needing assistance.4

 

Aids to Navigation in the Dry 

Tortugas 

On August 7, 1789, the new Congress of the 

United States, with its ninth act, assumed 

responsibility for managing the nation’s 

lighthouses and navigational aids. Prior to this, 

each state sited, built, and managed 

lighthouses as needed. The U.S. Lighthouse 

Establishment was the body created by the 

government to oversee the construction and 

operation of the lighthouses. Initially, 

Secretary of the Treasury, Alexander 

Hamilton, directly appointed keepers and 

negotiated construction contracts. Even 

President Washington signed and approved 

lighthouse contracts during the first years of 

his presidency. In 1792 oversight of the 

lighthouses was passed to the Secretary of 

Revenue, and then back to the Secretary of 

Treasury in 1820 when Stephen Pleasonton 

became the Fifth Auditor of the Treasury. 

During the early part of the nineteenth 

century, after the U.S. acquisition of the 

 

4

 Ibid., 78 

Louisiana Territory, shipping through the 

Florida Straits increased. Lieutenant 

Commander Matthew C. Perry was assigned 

to survey the Keys in 1821, after portions of 

Florida became a U.S. territory. Perry noted 

the difficult sailing conditions and reported to 

Congress that four light stations would be 

necessary to alleviate nautical risk within the 

Florida Keys. These included Southwest Key, 

Sand Key, Key Largo and Cape Florida. 

Congress responded with a recommendation 

to build lighthouses at Key West, Cape Florida 

and the Dry Tortugas. In the Dry Tortugas, 

Garden Key was selected as the most suitable 

location for a lighthouse. Construction of the 

Garden Key lighthouse began in August of 

1824 and continued until the lamp was lit on 

July 4, 1826. The focal plane of the light was 70 

feet above sea level and the lantern was fitted 

with 23 lamps and 14-inch reflectors.5

 

Despite construction of a lighthouse on 

Garden Key, over the next two decades, 

mariners continued to complain about the 

inadequacy of navigational aids in the Dry 

Tortugas. The new light was not only difficult 

to see in the hazy conditions of the gulf, its 

location six miles from the outer southwest 

edge of the reefs, and another eight miles from 

the northeastern shoals, meant that ships 

would find themselves in dangerous waters 

before the light was visible. The light 

constructed on Garden Key was simply not tall 

enough to adequately mark the hazards of the 

Dry Tortugas. 

 

5

 Ibid., 77.
14 Dry Tortugas Lighthouse HSR 

Figure 5. Captain Horatio G. Wright. 

Numerous ship wrecks, including the Concord

and Florence in 1831 and the America in 1836, 

were blamed on the poor visibility of the 

Garden Key lighthouse. In an 1836 interview 

with the Key West Inquirer, John Thompson, 

assistant light keeper at Garden Key, described 

the need for two additional lighthouses in the 

Dry Tortugas—one on the easternmost and 

the other on the westernmost keys.6

 The 

newspaper endorsed Thompson’s position.

Others voiced their opinion directly to the 

Lighthouse Board. William Whitehead, the 

Collector of Customs at Key West, wrote to 

Stephen Pleasonton in1836: 

Should it not be thought advisable to have 

all the appropriations made in one year, I 

would designate as being worthy of 

attention first the two light houses 

recommended for the Tortugas in place of 

the one now there. Many vessels have 

grounded there during the last year in 

consequences of inadequacy of the 

present light which I have every reason to 

 

6

 Bearss, 14. 

believe does not arise from any neglect of 

those in charge.7

Meanwhile, in 1842, twenty-six year old 

Captain Horatio Gouvenor Wright was 

selected and charged with leading the 

construction of a massive fortification planned 

for Garden Key. Fllowing conflicts with Spain 

and England regarding border disputes, 

President Tyler and Congress were persuaded 

to set aside four million dollars for military 

installations at Key West, Key Biscayne and 

the Dry Tortugas. In June 1844, President 

Tyler signed appropriations for the initial 

phase of construction of the fortification that 

would later be named Fort Jefferson. With the 

capacity to house 1,500 men, arm three tiers 

with 450 weapons, and to stand 50 feet off the 

water, Fort Jefferson was designed to be the 

largest “Third System” fort in America. The 

walls of the proposed fort were to be laid out 

in a manner that would encompass the 

existing Garden Key lighthouse and keeper’s 

dwelling. 

Shipping activity in the Dry Tortugas escalated 

to an unprecedented level as supplies of men 

and material were sent to Garden Key. 

Complaints about the light continued until 

Pleasonton finally ordered several 

reconnaissance trips by his staff to assess the 

conditions. Adam Gordon, Lighthouse 

Superintendent at Key West, along with 

Captains William H. Chase and George 

Dutton of the Army Corps of Engineers, were 

sent to the Dry Tortugas to evaluate the light 

on Garden Key. They agreed the light was too 

low and dim to provide adequate aid to 

navigation and recommended that the light be 

relocated to Loggerhead Key. In the interim, 

Winslow Lewis was sent to inspect the 

lighthouse to see if anything could be done to 

improve its effectiveness. Lewis made minor 

adjustments to the lamp, but these proved to 

be ineffective and complaints continued. 

Lighthouse Illumination 

American lighthouses of the nineteenth 

century, including the one at Garden Key, 

were lit primarily with Argand oil lamps. In 

 

7

 Hurley, Neil E. Lighthouses of the Tortugas, An Illustrated 

History, Alexandria, Virginia: Historic Lighthouse Publishers, 

1990, 18. 
Historical Background and Context 

National Park Service 15 

Figure 6. Schematic showing how the Fresnel 

lens concentrated light from a single source into 

a horizontal beam. 

1781, Amie Argand developed a ring-shaped 

wick that allowed air to flow through and 

around the flame and thus produce a brighter, 

cleaner fire. The same Winslow Lewis that was 

sent to make adjustments to the Garden Key 

light had developed and promoted a silver 

metallic, parabolic reflector assembly to be 

used with the Argand lamp. Lewis had 

successfully lobbied the Collector of Customs 

in Boston, Congress, and members of the 

Lighthouse Establishment, and his apparatus 

became the standard used in American 

lighthouses during first quarter of the 

nineteenth century. Lewis was paid $60,000 

for a patent to the system, and most 

lighthouses were fitted with his apparatus by 

1815.8

 Lewis’ system was an improvement on 

the various wicks and fuels previously used, 

but the Fresnel lens was concurrently being 

developed and would eventually surpass the 

Argand lamp and Lewis’parabolic reflector 

system in light quality and intensity. 

Developed by Augustin Fresnel, a French 

physicist, the Fresnel lens resembled a large 

glass beehive surrounding a single lamp. Asked 

by the French Commission on Lighthouses in 

1819 to help improve the illumination system, 

Fresnel worked with Claude Mathieu, his two 

brothers—Lenor and Fulgence, and Monsieur 

Talbouret to develop the new lamp 

technology. He also worked with Francois 

Soleil, Sr., a Parisian optician and glass 

manufacturer. 

The design intent of the Fresnel lens was to 

refract all of the light emitted from the source 

into one concentrated horizontal beam. By 

compounding the light beams in the lens a 

stronger and brighter signal was produced. By 

1821, Fresnel’s design was refined into an 

assembly of eight panels of concentric circular 

lenses with catadioptric prisms at the top and 

bottom of the panels. The lenses were made 

with triangular shaped glass that concentrated 

the light into a narrow horizontal beam. In 

1824, the first fixed Fresnel lens was 

constructed along with separate flash panels 

that were made to revolve around the light and 

produce two or four flashes per revolution. 

The flashes helped to distinguish the lights 

 

8

 Holland, Francis Ross, America’s Lighthouses: Their Illustrated 

History Since 1716, Brattleboro, Vermont: Stephen Greene 

Press, 1972,15. 

from stars or other lighthouses. This new 

Fresnel technology produced a bright, narrow 

sheet of concentrated light emitting from the 

lighthouse, which could be manipulated 

multiple ways for signaling sailors.9

 

Under Pleasonton’s guidance, the lighthouse 

system grew from 55 lighthouses in 1820, to 

331 in 1852. Despite development of the 

French Fresnel lens and its widespread use in 

Europe, Pleasonton continued to favor the 

Argand lamps and parabolic reflector system. 

His reason for not using the newer Fresnel 

technology, he said, was based on budgetary 

considerations. It has also been suggested that 

Pleasonton’s personal friendship with 

Winslow Lewis translated into a loyalty to 

Lewis’ seemingly inferior system. Pleasonton’s 

resistance to adopt the Fresnel technology 

resulted in mounting criticism of the Treasury 

Department’s management of the lighthouse 

system. Eventually this led Congress to direct 

the Secretary of the Treasury to investigate the 

Lighthouse Establishment. Ultimately the 

decision was made to: 

discharge all the administrative duties of 

said office relating to the construction, 

illumination, inspection, and 

superintendence of light-houses, light 

vessels, beacons, buoys, seamarks, and 

their appendages, and embracing the 

security of foundations of works already 

existing, procuring illuminating and other 

apparatus, supplies, and materials of all 

 

9

 Ibid., p. 18. 
Dry Tortugas Lighthouse HSR 16 

Figure 7. Section through a typical first-order 

lantern equipped with a Fresnel lens. 

kinds for building and for rebuilding 

when necessary, and keeping in good 

repair, the light-houses, light-vessels, 

beacons, and buoys of the United States.10

 

An outcome of the investigation was the 

creation of the U.S. Lighthouse Board. This 

newly formed body would be made up of four 

high ranking military officers, two from the 

Navy and two from the Army along with two 

civilians of “high scientific attainments.” The 

Board would also divide the country into eight 

districts, expand inspection and engineering 

services, set up a central supply depot, begin 

publishing an annual “Light List”, and 

encourage the use of new technology such as 

the Fresnel lens. 

A New Light in the Dry Tortugas 

The Seventh District established by the 

Lighthouse Board included the Dry Tortugas, 

extending “from Cape Carnaveral [sic] light-

 

10 Light-house Appropriations Bill. Statutes at Large of the 

United States of America 1789-1873, 32nd Congress, 1st sess., 

vol.10, August 1852, 119. 

house, Florida, to include Cedar Keys, 

Florida.” The office of the Superintendent of 

the Seventh District was located at Key West.11

The newly formed Board began immediately 

equipping existing and new lighthouses with 

Fresnel lenses. In the Dry Tortugas, the focus 

of the Board was to respond to decades of 

complaints by providing additional 

navigational aids including the construction of 

a new lighthouse on Loggerhead Key. 

Additionally, the light on Garden Key was 

slated for retooling including the installation 

of a fourth-order Fresnel lens to service the 

immediate harbor traffic. The new lighthouse 

proposed for Loggerhead Key was to be 

equipped with a first-order lens—the largest 

lamp available. 

In 1855 Lieutenant T.A. Jenkins, United States 

Secretary of the Lighthouse Board, requested 

that Capitan H.G. Wright, overseer of 

construction at Fort Jefferson, submit a 

preliminary sketch and estimate for the new 

lighthouse. Wright provided a response to 

Jenkins on September 23rd, but it appears there 

was some confusion about the final location of 

the lighthouse, as his preliminary sketches, 

estimates, and letter are prepared for a project 

on Garden Key. 

It is proposed to first lay a grillage, as 

shown on the sketch, the top of which 

shall be on a level of those in the bastion of 

the fort....I cannot make any satisfactory 

estimate for the keeper’s dwelling, as I do 

not know what allowance of room for 

each person is authorized by the board, 

therefore none is submitted. There is now 

a wooden house, built for the keeper in 

1847, which contains two lower rooms, 

with hall, two half attic rooms and a 

detached kitchen, which if sufficiently 

capacious, will answer the purpose for 

some years to come...The privy should be 

built over a vault communicating with the 

sewers of the work, the cost of vault which 

will be not far from $100.

12

 

11 Organization and Duties of the Lighthouse Board: 

Regulations, Instructions, Circulars, and General Orders, 

Washington DC: Government Printing Office,1871, 53. 12 Dry Tortugas Light Station Clipping File, Appendix no. 17, 

H.G. Wright, Capitan of Engineers, Fort Jefferson, FL, to 

Lieutenant T.A. Jenkins, U.S.N., Secretary, Light-house Board, 

Washington, D.C., September 23, 1855, Record Group 26, NA. 
Historical Background and Context 

National Park Service 17 

Ultimately the location for the new lighthouse 

was resolved and on August 18, 1856, 

Congress appropriated “for rebuilding the 

light-house, on a proper site, at Dry Tortugas 

and fitting it with first-order apparatus, thirtyfive thousand dollars.”13 

In the same year, Wright was replaced by 

Captain Daniel P. Woodbury of New 

Hampshire. Woodbury who would now 

oversee construction of the fort and the 

lighthouse made several design changes to 

Wright’s original proposal. According to Love 

Dean, Woodbury modified the dimensions of 

the tower, construction of the steps, masonry 

detailing and connection details between the 

lantern and the tower. He also configured the 

brick to corbel out below the Watch Room, 

forming the floor of the galley above.14

Construction of the lighthouse on Loggerhead 

Key began in 1857 and within a year the tower 

was complete. The first-order Fresnel lens was 

manufactured by the L. Sautter & Company. 

During the conversion to Fresnel lenses, the 

U.S. Lighthouse Board generally divided their 

purchases equally between the two primary 

lens manufacturers; L. Sautter & Company 

and Henry LePaute. 

In 1852, Louis Sautter bought the business 

started by Francois Soleil, Sr., with whom 

Fresnel worked to develop the Fresnel lens. 

Soleil’s business passed to his son-in-law, Jean 

Jacques Francois and onto his son-in-law, 

Theodore Letrouneau before it finally left the 

Soleil descendants. Sautter & Company 

shipped their first lens to America in 1853 for 

the lighthouse at Alcatraz Island. 

Sautter continued working with the glass 

manufacturer St. Gobain in Paris to make 

bigger and better glass pieces. Through 

acquisition and mergers, the company evolved 

to include electrical generators and 

searchlights. The company’s lights were used 

to illuminate the Champs-Élysées and the Arc 

de Triomphe in the late nineteenth century.15

 

13 Light-house and Appropriation Bill, Statutes at Large of the 

United States of America 1789-1873, 34th Congress, 1st sess., 

August 1856, vol.11, 99. 

14 Dean, 84. 

15 Tag, Thomas, The Sautter Lens Works Producers of the 

Fresnel Lens, U.S. Lighthouse Society’s, The Keeper’s Log, 

Summer, 2005, www.uslhs.org. 

By 1858 the lighthouse and buildings of the 

Dry Tortugas light station were complete. The 

station consisted of several structures sited in 

the middle of Loggerhead Key including the 

150- foot brick lighthouse, a detached two 

story oil house, a two-story keepers’ dwelling, 

a separate two-story kitchen, and two brick 

cisterns and several privies. A boathouse 

would not be constructed until 1871. 

Keepers and their Duties 

Benjamin Kerr was the first keeper assigned to 

the light station on Loggerhead Key. He was 

transferred from Garden Key in 1858 with a 

salary of $600 a year and brought with him, 

Henrietta his wife, and seven children. Kerr 

was employed at the Dry Tortugas light station 

until 1861, when he was replaced by James P. 

Lightbourn. Besides being named the first 

keeper of the Dry Tortugas Lighthouse, Kerr’s 

notoriety stems from an incident in which 

both of his assistant keepers allied with his 

wife and one daughter to “make an attempt on 

his life.”16 According to G. Phillips who was 

stationed at Fort Jefferson at the time, Kerr 

and one of his daughters arrived at Garden 

Key in a small boat, after having escaped from 

Loggerhead Key. Kerr and his wife apparently 

reconciled and managed to finish their 

assignment with no further incidents. 

The Organization and Duties of the Lighthouse 

Board set forth the requirements for 

lighthouse keepers. A few of the fundamental 

requirements established by the Board are 

listed below: 

LIV. Keepers were required to be over 18 

and be able to read and write, and be in 

every respect competent to discharge the 

duties of the keeper.... 

LV. Men of intemperate habits and those 

who are otherwise mentally or physically 

incapable of performing the duties of the 

light keepers, must not be nominated for 

appointment by superintendents of lights. 

LVII. Women and servants must not be 

employed in the management of lights, 

except by the special authority of the 

Department.17 

 

16 Dean, 87. 

17 Organization and Duties of the Lighthouse Baord, 60. 
18 Dry Tortugas Lighthouse HSR 

Pay was established at the keeper’s 

appointment and was begun when they 

entered their duties. The keepers were 

permitted to select their assistants, but 

keepers’ families were allowed to be 

nominated only in “rare and exceptional 

cases.”18 The keeper’s duties included keeping 

all aspects of the light station clean and in 

good working order, lighting and maintaining 

lamps, painting and maintaining all finishes 

both inside and out of all buildings, and 

maintaining clothing and accessories 

necessary to service and protect the light. 

Other duties included providing reports to the 

district office, maintaining safe and dry places 

for cleaning supplies, and logging in and out 

supply deliveries. 19

As one might expect, life on Loggerhead Key 

was particularly isolated. With a few 

exceptions, keepers remained at the light 

station for short durations. There were 10 

keepers assigned to the Dry Tortugas station 

between 1858 and 1912. 

During the 1860s, rations for each lighthouse 

keeper and assistant keeper, in addition to 

their salary, included: 

40 pounds of salt pork, 52 pounds of salt 

beef, 100 pounds of flour, or 80 pounds of 

ship biscuit, 11 1⁄2 pounds of brown sugar, 

6 pounds of coffee, or 1 1⁄2 pound tea, 5 

pounds rice and 2 gallons beans or peas 

per quarter20 

A break in the monotony came for the keepers 

and their families when on occasion they 

would be invited to socialize with the families 

of officers stationed at Fort Jefferson. 

Alternately at times the lighthouse keeper 

would host parties on Loggerhead Key, usually 

in conjunction with turtle turning expeditions. 

“Turtle turning” involved turning large turtles 

on their backs, thereby rendering them 

helpless and unable to escape. The turtle 

turning parties were often accompanied by the 

sharing of food, music, and dancing. 

Later during the twentieth century, keepers 

were restricted to living on the island without 

 

18 Ibid. 

19 Ibid., 88-89. 

20 U.S. Lighthouse Board, Registers of Lighthouse Keepers, 

1845-1912, National Archives Southeast Region, Morrow, 

Georgia. 

their families. In a 1938 letter from the 

Superintendent of Lighthouses to the 

Commissioner of Lighthouses, the 

Superintendent advocates for familial visits for 

keepers during the summer months. 

Responding to a proposed change in policy 

that would eliminate this privilege, the letter 

emphasizes the remote and isolated conditions 

at the station: 

Dry Tortugas Light station, Fla., is possibly 

one of the most isolated as well as 

attractive and efficient stations in the 

Service... There is no intention to make 

the station a resort; it is a condition that 

has existed for many years with nothing 

but beneficial results to the keepers and 

their families and this office believes that 

the best interest of the Service is being 

conserved in making no changes. With 

unrestricted privileges of this nature being 

enjoyed by the Carnegie Institutions 

Biological Station on the same reservation 

together with the other reasons it is 

recommended that no changes or 

restrictions in this respect be made....In 

reference to inquiry as to whether or not 

they be quartered in the station buildings, 

Bureau is advise that such is the case and 

the keepers and their families are perfectly 

satisfied to subject themselves to the slight 

inconvenience for the pleasure and 

privilege of having these relatives and 

friends with them as requested. It has been 

the experience of this office that these 

keepers feel that these dwellings are their 

homes, for which they pay more rent than 

they are worth, in addition to having to 

maintain homes elsewhere.21 

Even into the 1980s, lighthouse keepers with 

the Coast Guard reinforced the lonesome and 

isolated nature of their duties. Most 

assignments for unwed officers were for six 

weeks with three weeks on shore and 

assignments for married officers were typically 

four weeks with two weeks on shore. “The 

biggest complaint was the absence of women 

and having to cook for each other.”22

 

21 Superintendent of Lighthouses to Commissioner of 

Lighthouses, 08 June 1938, Record Group 26, NA, Washington, 

DC. 

22 Hurley, 59. 
Historical Background and Context 

National Park Service 19 

Figures 8 and 9. Portions of an 1862 map of Dry Tortugas showing the first depictions of the light station. 

Loggerhead Key is shown in plan (above) and the lighthouse can be seen in elevation beyond Fort 

Jefferson within the cartouche (below). 
20 Dry Tortugas Lighthouse HSR 

Figure 10. Elevation of iron tower proposed to 

replace storm-damaged masonry tower 

War and Disease 

Florida seceded from the Union on January 

10, 1861, but the Dry Tortugas remained 

under the command of Union forces 

throughout the War. The Union successfully 

blockaded St. Augustine, Jacksonville, Key 

West and Pensacola. Still, some smaller vessels 

were able to smuggle goods such as cattle, 

crops and salt to Confederate sympathizers. 

While most of the battles of the Civil War took 

place in other states, approximately 16,000 

Floridians left home to fight in the war. The 

battles of Olustee (near Tampa Bay) and 

Natural Bridge (near Tallahassee) were both 

won by the Confederates and Tallahassee was 

the only state capital in the Confederacy not 

seized by Union Troops. 23

During the War, the 47th Regiment of the 

Pennsylvania Veteran Volunteers were 

stationed at Fort Jefferson and by 1865 nearly 

two thousand people were living on Garden 

Key. The installation was used primarily as a 

military outpost and prison during the war and 

was never fired upon or fired a shot in conflict. 

A yellow fever outbreak in 1867 resulted in the 

Light Station falling into disrepair for several 

years. During the period between 1867 and 

1871 Loggerhead Key was used as quarantine 

station for military personnel, which strained 

resources and impeded maintenance of the 

buildings. By 1871 the outbreak had subsided 

and various maintenance projects were again 

underway. 

A second outbreak of yellow fever affected the 

Dry Tortugas in September of 1873, requiring 

all healthy soldiers on Garden Key to once 

again be relocated to Loggerhead Key. During 

the outbreak, thirty people were infected 

resulting in 12 casualties. The healthy were still 

on Loggerhead Key when the hurricane of 

1873 hit the island. 

The Hurricane of 1873 

The hurricane that struck the Dry Tortugas on 

October 6, 1873, initially formed near the 

Leeward Islands, drifted west towards the 

Yucatan Peninsula, then backtracked through 

the lower Gulf of Mexico, before it curved 

northward and passed over the towns of Punta 

Rassa and Melbourne on the east coast of 

Florida. Although the track of the hurricane 

took the eye north of the Dry Tortugas, it 

delivered a damaging blow to the Light 

Station. 

The initial evaluation of the storm-damaged 

Light Station was bleak. The Lighthouse was 

reported to be in dangerous condition and it 

was initially recommended that the entire 

tower would need to be rebuilt. 

 

23 Florida Center for Instructional Technology, College of 

Education, Florida’s Role in the Civil War: “Supplier of the 

Confederacy”, University of South Florida, 2009 

http://fcit.usf.edu/Florida/lessons/cvl_war/cvl_war1.htm. 
Historical Background and Context 

National Park Service 21 

Figure 11. Undated nineteenth-century view of the Dry Tortugas light station looking northeast. 

Because Loggerhead Key was still under a 

yellow fever quarantine and contact with the 

island was limited, only temporary repairs 

could be made following the storm. 

The walk in front of the keeper’s dwelling 

has been cemented and the waterconductors to the cisterns repaired. The 

cisterns have been cleaned and repaired, 

and wooden shutters for the towerwindows have been made, painted and 

hung. It is proposed, during the coming 

season, to make careful examination with 

a view to determining on plans for the 

foundation of a new tower.24

Congress appropriated $75,000 for repairs to 

the Lighthouse and plans were prepared for a 

new structure. In contrast to the existing 

masonry tower, the design of the replacement 

structure would be entirely of cast iron. 

By 1875 the upper portion of the lighthouse 

had been extensively repaired, anchors were 

extended down through the lighthouse walls 

to secure the lantern and the tower received its 

distinctive daymark. The upper portion of the 

 

24 Ibid. 

tower was painted black and the lower portion 

was painted white. The black color was 

supposed to help dampen reflections, contrast 

with the white clouds and show a distinct 

color pattern for sailors.25 

The work was completed just as a second 

hurricane swept through the Dry Tortguas. 

The repairs held and were closely monitored 

during the ensuing years. Ultimately it was 

decided that a new lighthouse would not be 

necessary. 

During this same period, discussions were 

held about the inadequacies of the Garden 

Key Lighthouse and its placement within the 

parade ground of Fort Jefferson. After another 

hurricane damaged the Garden Key 

Lighthouse, plans were made to replace it with 

an iron structure to be located on top of 

bastion C of the Fort. The original Garden 

KeyLighthouse was demolished and on April 

5, 1876, the new cast iron light tower was lit.26

 

25 Hurley, 39. 

26 Hurley, 41. The choice to construct the new tower out of 

iron was a strategic military decision. If the fort came under 

attack, a brick tower was considered more dangerous because 

of the heavy shrapnel produced if hit by shells. 
22 Dry Tortugas Lighthouse HSR 

Figure 12. 1887 survey of Dry Tortugas Light Station by A. C. Bell. 
Historical Background and Context 

National Park Service 23 

Late Nineteenth-Century 

Development 

Through the late 1870s, minor repairs were 

made to several of the Station’s structures, and 

in 1880, a new boathouse was built. From 1888 

to 1910, Prussian George Billberry served as 

keeper of the Light Station. During his service, 

many repairs and upgrades were made to the 

Station buildings. From 1880 through the 

1890s, mineral lamps—otherwise known as 

Luchaire incandescent oil vapor lamps 

(i.o.v.)—became the method of illumination. 

New glass was installed in the lantern, wash 

houses were built, structures were painted and 

whitewashed, wire fence was installed, and on 

“April 30, 1893, the characteristic of the 

Loggerhead Key light was changed from fixed 

white to fixed white with a fixed red sector.”27

The implementation of red sector lighting was 

a navigational advancement for its time. A red 

pane of glass was installed on the side or sides 

of the lantern where the reefs or shoals were 

particularly dangerous. Shipmen knew not to 

navigate directly into the red light for this 

would signal imminently dangerous waters. 

For most of the 1890s, once again Loggerhead 

and Garden keys were used as quarantine 

stations, this time for those suspected of being 

infected with small pox. Despite an order in 

1893 from the War Department to discontinue 

the quarantine stations, the two keys would 

serve this purpose until 1900. 

The Spanish American War 

In 1898, the United States entered into war 

with Spain over the liberation of Cuba. The 

Dry Tortugas served as a harbor and staging 

area for ships in the area. The most notable 

incident of the war occurred with the U.S.S. 

Maine. On January 24, 1898, the ship sailed to 

Havana and a few weeks later it suffered a 

massive explosion that killed 260 of its 350 

sailors and sank the battleship. At the time, the 

explosion was blamed on an underwater 

Spanish mine, and as a result, the U.S. declared 

war against Spain on April 21. The war cry 

“Remember the Maine!” stems from this 

incident. The war was relatively short-lived 

 

27 Hurley, 45. 

and a treaty ending the conflict was signed in 

December 1898. 

In 1976, a Navy panel came to the conclusion 

that the blast on the Maine was the result of an 

onboard fire in the coal storage area. It is 

possible that the fire may have originated 

while the ship was in the harbor at Garden 

Key. 

Bureau of Lighthouses 

With the turn of the century, came a change in 

the management of the Lighthouse Board. In 

1903, the Board was moved from the Treasury 

Department to the Department of Commerce. 

In 1910, it officially became known as the 

Bureau of Lighthouses. Congress intended to 

accomplish several objectives with this 

reorganization. First, it sought to demilitarize 

the lighthouse service. Both the Army and the 

Navy were not allowed a prominent role on 

the Board, the goal being to shed a civilian 

light on a primarily civilian service. Secondly, 

the reorganization allowed for an increase in 

districts to accommodate the growing number 

of light stations. In 1910, George R. Putnam 

was selected to lead the new Bureau of 

Lighthouses. Serving for 25 year, Putnam’s 

most notable contributions include the 

introduction of radio beacons as an added 

means of navigation, electrification of many 

light stations and a retirement system for field 

employees.28

The Carnegie Institution Marine 

Biology Laboratory 

In 1904, a portion of the northern end of 

Loggerhead Key was granted through a 

revocable lease, to the Carnegie Institute for 

the establishment of a research laboratory to 

study marine life in the Atlantic. The Institute 

declared in their 1904 Year Book the 

establishment of the Marine Biological 

Laboratory at the Dry Tortugas, under the 

direction of Alfred G. Mayor. 

Mayor was a Harvard educated biologist who 

initially studied butterfly pigmentation. 

However, due to a serious eye inflammation 

he was forced to pursue research that relied 

 

28 Holland, 38. 
24 Dry Tortugas Lighthouse HSR 

Figure 13. Undated view of the Carnegie Institute’s Marine Biology Research Laboratory with the Dry Tortugas 

lighthouse in the distance. 

less on work with a microscope. Jellyfish 

offered the perfect specimen for him to study 

and he subsequently published a three volume 

work on the species. The Dry Tortugas offered 

an ideal location for collecting and observing 

jellyfish among other tropical plants and marine 

life. 

The laboratory complex was constructed 

between 1904 and 1906 and was comprised of: 

a main laboratory building and sleeping 

porch, a detached lab, a kitchen, a windmill 

for pumping salt water and air to 

aquariums, a dock, a shipways, two small 

outhouses and a cistern. The labs and 

outhouses were built in New York and 

shipped to Loggerhead for assembly, while 

the rest of the buildings were built on site. 

About 50 palm trees were planted around 

the lab to shade the buildings and provide 

hurricane protection. All the buildings, 

chemicals, lab glassware and furniture cost 

only $4,800. The lab’s research vessel was a 

57-foot-long ketch, with a 20 horsepower 

auxiliary engine.29

A vast and diverse program of research was 

conducted at the laboratory. Some of the most 

notable accomplishments include 

groundbreaking research on coral reefs and 

mangrove communities, the establishment in 

1908, of the Dry Tortugas as a wildlife refuge for 

the sooty tern, and the first underwater 

photographs—both black and white and color 

were taken there. 

Although the Institute viewed Mayor as a 

promising individual, his selection of 

Loggerhead Key for the research laboratory was 

seen as a poor choice. It was too remote and 

difficult to access and receive support from the 

mainland. In addition, working around 

hurricane season left for a brief research period 

from May until July each year. 

 

29 Hurley, 48. Carnegie Institute Yearbooks. 
Historical Background and Context 

National Park Service 25 

Figure 14. Ca. 1925 Plan of the Dry Tortugas Light Station. 

Mayor had some aspirations to relocate the lab 

to Jamaica to create a truly international 

biological station, but he suffered from 

tuberculosis and in June of 1922, his body was 

found face down on the shore of Loggerhead 

Key. He was 54 years old. The coroner ruled 

that Mayor died of “heart-failure and general 

debility contingent upon his tubercular 

condition.”30 A plaque erected in his honor in 
26 Dry Tortugas Lighthouse HSR 

Figure 15. Undated view of the Garden Key 

Keeper’s Residence with the iron lighthouse on 

bastion C in the distance. 

Figure 16. View of Dry Tortugas Keeper’s 

Residence shortly after completion. 

1929 stands near the site of the former 

laboratory complex. 

The Carnegie lab survived through the Great 

Depression and several hurricanes until 1939, 

 when Carnegie President Vannevar Bush 

closed the laboratory. Reduced funding and a 

shift in philosophical focus from macrobiology to microbiology have been reasons 

stated for the closure.31 During the thirty-five 

years of laboratory operation, more than 140 

scientists visited and conducted research on, 

and in the waters surrounding Loggerhead 

Key. 

Early Twentieth Century 

Modernization 

The early part of the twentieth century not 

only included the restructuring of national 

 

30 Calder, Dale R. and Lester D. Stephens. Seafaring Scientist: 

Alfred Goldsborough Mayor, Pioneer in Marine Biology, 

Columbia, South Carolina: University of South Carolina Press, 

147. 

31 Hurley, 49. 

lighthouse management and the birth of 

modern marine biology with the establishment 

of the Carnegie laboratory, but also ushered in 

modern technological advances at the Light 

Station. Radio beacons, electricity, concrete 

cisterns, a new lens and multiple construction 

projects were completed during this period. 

Two significant hurricanes during the 1910s, 

once again, caused serious damage to the Light 

Station and the laboratory complex. The 

hurricane of October 10, 1910, (hurricanes 

were not named until the 1950s) damaged the 

wharf, shattered panes of glass in the tower, 

and severely damaged the dormitory and blew 

the roof off the main building at the Carnegie 

laboratory complex. The machine shop was 

moved off its foundations nearly five feet. On 

September 8, 1916, Congress allotted $2,800 

and; 

a wrought-iron pile wharf with cast-iron 

caps and wooden girders, stringers, and 

decking was erected in place of the old 

wharf, which was destroyed. All work was 

completed in May, 1917. Amount 

expended to June 30, 1917, $2,631.19.32 

As a result of damage sustained in the 1910 

hurricane, the original first-order lens was 

replaced with a second-order lens. 

A second hurricane hit the island on 

September 10, 1919, severely damaging the 

laboratory by washing away snail breeding 

cages and resulting in damage to all the 

buildings. 

Fort Jefferson experienced a massive fire in 

1912 that destroyed the Garden Key light 

keeper’s dwelling, as well as the fort’s 

barracks, kitchen and latrine. The keeper’s 

house was not rebuilt and some years later the 

harbor light was deemed unnecessary for 

navigational purposes and decommissioned. 

In 1921, the lighthouse on Loggerhead Key 

became the primary navigational beacon in the 

Dry Tortugas. 

Following the decommissioning of the light on 

Garden Key, the Bureau of Lighthouses took 

several steps to upgrade and modernize the 

Light Station on Loggerhead Key. In 1922, a 

new dwelling for the primary keeper was 

constructed and two new concrete cisterns 

 

32 Ibid. 
Historical Background and Context 

National Park Service 27 

Figure 17. Image taken from the top of the 

tower showing the burned remains of the 

original keeper’s dwelling. 

installed. Five years later when the original Oil 

House was converted to a radio beacon 

equipment room, it was connected to the 

tower by a reinforced concrete passageway. 

The marine radio beacon was installed in 1926 

to assist ship traffic and provide basic 

communication. The new technology offered 

a means of communicating with mariners 

about weather, operations, and navigational 

issues. The marine radio beacons were able to 

transmit communications to ships in storms 

when the lighthouse was difficult to see. 

The introduction of electricity to the island 

was another technological advancement that 

changed the way the Lighthouse and Light 

Station operated. Powered by generators, 

housed in a frame addition constructed on the 

south elevation of the former Oil House, the 

new electric light installed in the Lighthouse in 

1931 had 3,000,000 candle-power, making the 

Dry Tortugas light the brightest in America. 

Several mariners reported that they could see 

the light up to 52 miles away. Before 

electrification, the Lighthouse had a range of 

approximately 19 miles. The existing 

incandescent oil vapor lamp was kept as a 

secondary system. 

In 1935 Fort Jefferson was designated a 

National Monument by President Franklin 

Roosevelt and was transferred to the National 

Park Service. 

The U.S. Coast Guard 

In 1939, the duties of the Bureau of Lighthouse 

were amalgamated into the operation of the 

United States Coast Guard. Light keepers 

were given the choice of becoming petty 

officers or remaining as civilian employees. 

During World War II keepers were utilized as 

lookouts for German U-Boats in the Florida 

Straits. The threat of attack by enemy U-boats 

was real as twenty-four American ships were 

sunk by German submarines during the war. 

Coast Guard keepers also took part in beach 

patrols and at times had to rescue or recover 

victims of U-boat attacks. 

During the war, there was some debate as to 

whether the lighthouse lights should be 

extinguished or dimmed. Exposing ships to 

enemies was considered less of a danger than 

running aground, so the Coast Guard 

implemented “dim-out” policies in which the 

intensity of the lamps was turned down.33 

In March of 1945 a fire destroyed the original 

1858 keeper’s dwelling and damaged the 

adjacent kitchen building. As a result, the 

keeper’s dwelling had to be demolished to its 

foundations. A second fire in 1964 destroyed 

several of the abandoned Carnegie laboratory 

structures. 

Under management of the USCG the Dry 

Tortugas Light Station remained manned with 

a crew of from two, to as many as twelve 

personnel. From the mid-twentieth century to 

the 1990s, numerous projects were planned 

and implemented at the Station beyond the 

required routine maintenance and minor 

repairs that took up much of the time of those 

stationed on the island. A majority of the 

projects centered on upgrading and repairing 

the various systems that were critical to 

habitation of the island such as those that 

provided potable water, sanitary systems, and 

generation of electrical power. In 1967, 

extensive improvements were made to the 

 

33 Hurley, 57. 
28 Dry Tortugas Lighthouse HSR 

tower including sandblasting the exterior and 

repainting the daymark. 

Projects in the 1970s focused on the 

installation of fuel and water tanks, upgrading 

electrical service and providing fire protection 

in the 1922 Keeper’s Residence or “barracks 

building” as it was referred to during this 

period. In 1975 during the construction of a 

new wharf on the eastern shore, a Seaman 

Apprentice, William H. Graves, was tragically 

killed. A small monument dedicated to 

Seaman Graves is located near the site of the 

accident. 

In 1984, the USCG commissioned National 

Park Service personnel to prepare a 

rehabilitation report and national register 

nomination for the Dry Tortugas Light Station 

property. This project was undertaken to 

document the history of the Light Station and 

to make recommendations for the appropriate 

repair of the historic lighthouse and support 

structures in advance of a planned automation 

and modernization program. The document 

included recommendations focused on repairs 

to the Lighthouse as well as both mortar and 

paint analysis. 

The following year an extensive program of 

repairs was completed on the Lighthouse, and 

in 1986, the USCG decommissioned the 

existing second-order bi-valve lens after 

aggregate from sand-blasting operations 

contaminated the mecury float mechanism. As 

a result the lens was no longer able to rotate 

and was replaced with an automated 24” 

Directional Code Beacon (DCB-24). The new 

lamp was programmed to create a flashing 

light every 20 seconds that could be seen up to 

24 miles away. The bivalve lens was removed 

and placed on display at the National Aids to 

Navigation School in Yorktown, Virginia 

where it remains today.34 

The National Park Service 

Following automation of the Lighthouse optic 

in 1986 the USCG continued to be challenged 

by mounting deferred maintenance and 

limited funding for repair or capital 

improvements. In an effort to reduce their 

burden, consideration was given to 

 

34 Dean, 99. 

demolishing several non-essential structures 

including the boat house and original kitchen 

building. In addition, advancements in the 

Long Range Navigation (LORAN) system and 

GPS (Global Positioning System) technology, 

as well as the expanded use of Satellite 

Navigation (SATNAV) resulted in diminishing 

reliance by mariners on visual aids such as 

lighthouses and beacons. 

About the same time, the National Park 

Service, and at least two other groups, 

expressed interest in taking over management 

of Loggerhead Key and the Light Station 

property from the USCG. The other groups 

vying for the property included the Key West 

Ports and Transportation Authority who was 

interested in establishing a marine hatchery 

and science camp on the island, and the Key 

West Art and Historical Society who 

expressed an interest in managing the 

lighthouse, but had not submitted a formal 

proposal. 

In 1991, the Coast Guard determined that the 

National Park Service presented the most 

viable proposal and several meetings were 

held between the two entities to evaluate the 

condition of the existing resources and to 

discuss the logistics of a transfer. Negotiations 

focused on resolution of several utility issues 

regarding the electrical generators and septic 

system and also a requirement for the USCG 

to remove all hazardous materials from the 

island as a condition of transfer. Despite their 

desire to divest themselves of the Light Station 

completely, the USCG would continue to 

maintain the light as an active aid to navigation 

and provide logistical support to the Park 

Service as part of the agreement. Transfer of 

the light station also provided opportunity for 

the USCG to eliminate permanent staff on the 

island and limit its obligation to routine site 

visits to maintain the optic. Establishment of 

Dry Tortugas National Park the following year 

provided the ideal mechanism for formally 

transferring Loggerhead Key and the Light 

Station to the National Park Service. 

Dry Tortugas National Park was created in 

1992 to “preserve and protect for the 

education, inspiration, and enjoyment of 

present and future generations nationally 

significant natural, historic, scenic, marine and 

scientific values in South Florida.” The Park 
Historical Background and Context 

National Park Service 29 

Figure 20. Aerial view of Loggerhead Key 

showing density of Australian Pine growth prior 

to de-vegetation project. 

Figure 18. Chug used by Cuban refugees to land 

at Loggerhead Key in 2008. 

Figure 19. Graffiti left by Cuban refugees on wall 

of Boathouse. 

boundaries established at the time 

encompassed all of the seven small islands that 

make up the Dry Tortugas as well as the coral 

reefs, shoals and waters within an 

approximately 100 square-mile area. As part of 

the enabling legislation for the Park, the USCG 

lands, including all of Loggerhead Key were 

formally transferred from the USCG to the 

National Park Service. The establishment of 

Dry Tortugas National Park also resulted in 

the Light Station resources being listed on the 

National Register of Historic Places. 

Through its Volunteers-In-Parks (VIP) 

program, the Park Service has been able to 

maintain a consistent presence on Loggerhead 

Key for much of the last two decades. The 

volunteers, who stay on the island for one to 

several months at a time, are housed in the 

former kitchen building and perform limited 

repair and maintenance of the resources. 

More importantly their presence provides a 

level of security for the island that serves as a 

deterrent to those that may seek to damage or 

cause harm to cultural or natural resources. 

Since the National Park Service assumed 

management of the Light Station they have 

had the additional challenge of dealing with 

Cuban refugees making landfall at Loggerhead 

Key. The Dry Tortugas have become a primary 

landing point for the refugees due to their 

proximity to Cuba and remote location. 

Since adoption of the “wet foot/dry foot” 

policy in the mid-1990s, the influx of refugees 

has been steady. The wet foot/dry foot policy 

generally states that if a refugee is able to make 

landfall on U.S. soil they will be allowed to stay 

and can pursue citizenship, on the other hand, 

if they are intercepted in the waters between 

Cuba and the United States, they will be sent 

back to Cuba or to a third country. 

Generally arriving at night, during periods of 

calm weather, the refugees cross the open 

waters between the two countries in makeshift boats referred to as “chugs.” These chugs 

accumulate on the keys and intermittently 

have to be removed to the mainland for 

disposal. 

After the Mariel Boatlift in 1980, the numbers 

of Cuban refugees attempting to enter the 

United States peaked again in 1994 and 2005. 

Refugees that make landfall within the Park 

are temporarily detained by the National Park 

Service until USCG officials can transfer them 

to the mainland for processing. Historic 
30 Dry Tortugas Lighthouse HSR 

resources, primarily the Boathouse on 

Loggerhead Key and the casemates within 

Fort Jefferson on Garden Key, are 

occasionally used to temporarily house landed 

refugees. In recent years the USCG has 

increased its patrols in the waters around the 

Park reducing the number of refugees making 

landfall on the Keys. 

The National Park Service has also recently 

completed an extensive landscape restoration 

program to remove the Australian Pine and 

other exotic plants from Loggerhead Key. 

These invasive species were introduced by 

Carnegie Institute personnel during the first 

quarter of the twentieth century dramatically 

changing the landscape character of the island. 

The program has been successful in removing 

the trees and returning the island to its preCarnegie appearance. 

With the exception of the Lighthouse which 

continues to function as an active aid to 

navigation, the resources of the Dry Tortugas 

Light Station are primarily used for housing 

and also to shelter critical components of the 

island’s utility systems. Volunteers from the 

VIP program occupy the former original 

kitchen building for most of the year and the 

1922 Keeper’s Residence is reserved for 

intermittent use by National Park Service 

personnel, researchers or contractors. The 

USCG also maintains a room in the Keeper’s 

Residence for its use during routine visits to 

service the light. Visitation to the Park is 

limited by the Park’s General Management 

Plan Amendment which currently limits the 

numbers of visitors allowed on the island to 

24. It also establishes permissible activities 

allowed on the island which include hiking, 

picnicking and exploring. The GMPA 

currently restricts access to the Lighthouse 

and Light Station buildings by the visiting 

public until such time as they can be “made 

safe” for this level of use.
 National Park Service 31 

Chronology of Development 

and Use 

Design and Construction 

Construction of the lighthouse on Loggerhead 

Key was a priority for the Lighthouse Board; in 

fact, in 1852, the agency “listed projects to 

improve the Dry Tortugas light as number three 

in the nation in terms of importance.”35

Initial planning for the new lighthouse began in 

1855 when T. A. Jenkins, U.S.N., Secretary of the 

Light-House Board requested H.G. Wright, 

Chief Engineer in charge of construction at Fort 

Jefferson develop an estimate for the proposed 

project. Wright’s proposal provides unique 

insight into the planning and consideration that 

went into designing a new lighthouse in the midnineteenth century. By his request, it is certain 

Jenkins sought to take advantage of Wright’s 

construction expertise and experience working 

in the Dry Tortugas to gain an understanding of 

the challenges and potential costs that would be 

associated with constructing the new lighthouse. 

Based on Wright’s response , it appears that 

Jenkins’ instructions were vague causing Wright 

to make a number of assumptions in order to 

develop the design estimate. It is also clear that 

although Wright gave the exercise considerable 

thought, he was not entirely comfortable 

engineering a lighthouse structure. 

The following excerpts are taken from Wright’s 

proposal letter. 

Your instructions indicated the height 

without fixing the other important 

dimensions. This has perplexed me very 

much, as I do not know and have no means 

of ascertaining what experience has shown 

to be suitable in regard to convenience and 

stability for the upper and lower diameters, 

and the thickness of the walls for a tower so 

 

35 Hurley, Neil E. Lighthouses of the Tortugas, An Illustrated 

History, Alexandria, Virginia: Historic Lighthouse Publishers, 1990, 

30. 

much higher than our ordinary structures. 

But should any of the dimensions I have 

assumed not meet the approval of the board, 

the estimates may be readily modified to suit 

the necessary changes, as an analysis of the 

costs of the principal items of masonry is 

appended.36

Wright goes on to provide considerable detail 

about how he proposes to construct the 

lighthouse foundation and the ability of the 

sandy soils to support the weight of the 

structure. 

A sufficient foundation being important to 

the stability of the tower, I have endeavored 

to make one that shall fulfill all the necessary 

conditions. It is proposed to first lay grillage, 

as shown on the sketch, the top of which 

shall be on a level of those in the bastions of 

the form, and being always under water is 

secured from decay. On this rests the 

foundation three feet high, with a batter of 

two feet on each side. The outlines of the 

grillage and foundation are made polygonal, 

instead of circular, for convenience of 

setting the curbing for the concrete. With 

such a foundation the pressure on the bed 

will be, for project No.1, a little over 36 cubic 

feet to the square foot, a pressure shown by 

experiments made here to be admissible, as 

the settlement under nearly twice the weight, 

at a point not far distant from the probable 

location of the tower, did not exceed threefourths of an inch. If the grillage is not used, 

an additional and equivalent spread must be 

given to the masonry of the foundation, 

which must go down to the water to secure it 

from being undermined by rats and crabs.37

 

36 Dry Tortugas Light Station Clipping File, Appendix no. 17, H.G. 

Wright, Capitan of Engineers, Fort Jefferson, FL to Lieutenant T.A. 

Jenkins, U.S.N., Secretary, Light-house Board, Washington, DC, 

 23 September 1855, Record Group 26, NA. 

37 Ibid. 
32 Dry Tortugas Lighthouse HSR 

Figure 21. Portion of sketch from Wright’s 1855 

proposal showing the foundation and wall 

construction of the proposed lighthouse. 

He also discusses the proposed wall 

construction including formulation of the 

mortar and brick selection. 

There being nothing in your instructions 

relative to the kind of materials to be used 

for the masonry, I have assumed the 

foundations of the tower to be entirely 

concrete, and the walls for concrete faced 

inside and out with hard burned Pensacola 

or Mobile bricks, the facing being employed 

as better resisting the action of the sea air 

than the concrete. The bond assumed for 

this facing is the same as is now used on the 

fort, and is represented in the sketch. 

I am disposed to believe that the mortar for 

both brickwork and concrete should be 

made of cement and sand without any 

admixture of lime, and in the proportion of 

two parts of the latter to one of the former in 

powder. The voids in the sand being about 

one-third, and the shrinkage of the cement 

about one quarter when reduced to a paste, 

the latter will a little more than suffice to fill 

the voids of the former when mixed in the 

above proportions. Experience here has 

shown that lime mortar does not fully resist 

the action of the atmosphere, and therefore 

should not be relied upon...38 

The proposal also discusses at the superiority of 

Pensacola or Mobile brick over bricks supplied 

from the north. Despite their higher freight 

costs, Wright favored the Pensacola and Mobile 

bricks because they withstood the harsh 

elements of the region better than the northern 

bricks. A lesson learned during construction of 

Fort Jefferson. Wright proposed that the 

northern brick could be used in all unexposed 

areas as a cost savings measure. 

The potential cost impact of having to elevate 

materials to the top of the tower was also 

considered by Wright. 

An important item of cost, and one not 

easily estimated for with accuracy is 

raising the materials for so high a tower. 

When the ordinary means of hodding them 

[carrying materials with a hod or wooden 

contraption that is strapped over the 

worker’s shoulders] is employed, it is known 

that the cost increases rapidly after the 

structure is carried above a medium 

elevation. For this work to be hoisted, but 

this process will be a slow one, owing to the 

want of room for more than a single derrick, 

and will probably be found inadequate 

unless steam is employed. There is a small 

steam engine now in use here which may be 

available for this purpose...39

The effects of hurricane wind loads also 

influenced Wright’s design assumptions. 

The arm lever, on which the weight of the 

tower acts against any force overturning it 

 

38 Ibid. 

39 Ibid. 
Chronology of Development and Use 

 National Park Service 33 

about its base, is taken at 14 feet, or one foot 

less than the radius of the base. The pressure 

of wind in the strongest hurricanes has been 

taken at 50 pounds per square foot, and as 

the tower is conical, the pressure against it is 

less than it would be against a plane surface 

equal to the central section, and has been 

assumed at two-thirds of 50 or 33 1/3 

pounds to the square foot of this section. 

The central section of the tower and Lantern 

is taken at 160 x 30 x 15/2, which is probably 

in excess and the leverage at 71.1 feet, or the 

distance of the centre of gravity of the 

section above its lower base. 

Because Wright was not well-versed in 

lighthouse construction and was provided little 

dimensional information from Jenkins, he 

developed two variations of his design and two 

separate cost estimates. He refers to these in his 

proposal as Project No. 1 and Project No. 2. The 

only difference between the scenarios was the 

thickness of the tower walls. The costs varied 

only slightly with Project No. 1 totaling 

$34,464.80 and Project No. 2 coming in at 

$35,806. 25.40 

Both scenarios included costs for excavation and 

embankment, lumber for grillage, concrete for 

the foundation, brick masonry and concrete for 

the tower walls, costs for raising the materials, 

derricks, lumber for the upper floors and 

landings, 10 windows, sills, and lintels, one door 

frame, sills and lintels, ladders, landings and 

costs for storing materials. 

In both cases Wright included the cost for a castiron stairway, a $10,000 allowance for the firstorder Fresnel lens and a 10% contingency for 

unforeseen conditions. Relying on the accuracy 

of Wright’s computations, Congress 

appropriated $35,000 in 1856 for construction of 

the new lighthouse. 

The same year the project received its funding 

Wright was replaced at Fort Jefferson by Captain 

Daniel P. Woodbury.41 After nearly nine years of 

supervising construction at Fort Jefferson, 

Wright requested a transfer to escape the heat in 

favor of a “more temperate climate.”42He was 

reassigned as the assistant to the Chief Engineer 

 

40 Ibid. 

41 Bearss, Edwin C., Historic Structure Report – Historical Data 

Section Fort Jefferson 1846-1898, Fort Jefferson National 

Monument, Monroe County, Florida, 1983,141. 

42 Ibid., 55-56. 

in Washington, D.C. He would later command 

the 6th Army Corps during the last years of the 

Civil War and then supervise completion of the 

Washington Monument. 

From the beginning, Woodbury was not happy 

with his assignment to Fort Jefferson. He did not 

like the remote location or the tropical climate. 

He was continually asking for assistants to help 

him with his work and trying to arrange for 

transfers. General Totten, who had assigned 

Woodbury to Fort Jefferson, insisted he remain 

in the Dry Tortugas. Informed of his increased 

duties to oversee construction of the lighthouse 

at Loggerhead Key in the fall of 1856, Woodbury 

again asked for assistance and finally arranged 

for a local draftsperson to help him for four 

dollars a day.43 

It is said that Woodbury made several design 

changes to Wright’s initial proposal including 

modifying the dimensions of the tower and 

changing the construction of the steps from castiron to stone. Woodbury is also attributed with 

eliminating the use of iron brackets to support 

the galleries in favor of corbelled masonry. This 

design approach may have been employed in 

response to the harsh environment of the region 

and its known detrimental effects on metals, or 

more likely, was influenced by Woodbury and 

the skills of his available labor force. 

The original architectural plans for the 

Lighthouse were developed in 1857 by the 

engineers of the Seventh District. The plans 

consist of a single drawing that includes a plan of 

Loggerhead Key as well as plans and sections for 

the proposed Lighthouse and Keeper’s Dwelling 

(Figure 21). A second undated drawing, which is 

referred to in correspondence from the 1920s as 

an “original drawing of Dry Tortugas light 

tower” shows the lighthouse in plan, section and 

elevation (Figure 22). 

Construction of the Lighthouse began in 1857 

and within a year the tower was complete. The 

first-order Fresnel lens, manufactured by the L. 

Sautter & Company was ordered and installed in 

the Lantern. The receipt sent to Captain 

Woodbury on April 16, 1857 contains an 

itemized list of components for the lens that 

tallies $41,467.02 (presumably, the units are 

 

43 Ibid., 143. 
34 Dry Tortugas Lighthouse HSR 

Figure 22. Architectural plans for Dry Tortugas Lighthouse and Keeper’s Residence prepared in April 1857.

French francs as Wright had only set aside a 

$10,000 allowance in his proposal). 

The Lighthouse was generally constructed 

according to the original plans with the 

exception of the oil house which is shown on the 

drawings attached to the base of the tower, but 

was constructed as a free-standing building. The 

reasons for this change could not be determined 

from the available historic documentation. 

The simple, two-story, gable-roofed Oil House 

was constructed approximately 12’ west of the 

Lighthouse. The building was constructed with 

load-bearing masonry walls, wood joists 

supporting the second floor and wood rafters. 

Although the original architectural plans show 

the roof with wide overhangs supported by 

brackets, the earliest images of the Light Station 

show only a simple eave configuration. It is 
Chronology of Development and Use 

 National Park Service 35 

Figure 23. Drawing described as “original” plans for Dry Tortugas Lighthouse (Note the “X” through 

the attached Oil House). 
36 Dry Tortugas Lighthouse HSR 

possible that the roof was replaced and the 

overhangs eliminated following the 1873 

hurricane. 

The drawing also shows the first floor of the Oil 

House divided into three narrow rooms which 

was a typical plan configuration found in similar 

structures from the period. The building 

contained a fireplace in the southeast corner of 

the first floor and the windows are shown as 

eight-over-eight double-hung units. The first 

floor of the Oil House was used for the storage 

of oil while the second floor likely functioned as 

a work room. Correspondence from the 1920s 

describes the first floor room as containing eight 

250 gallon steel kerosene storage tanks. 

Although it is not recorded, sperm oil was most 

likely the type of oil that was burned in the Dry 

Tortugas light when it was first constructed. 

Early Repairs and Maintenance

Descriptions of repairs made to the Light Station 

between 1858 and the turn of the century are 

synthesized in the clipping files for the Dry 

Tortugas Light Station. These files contain 

excerpts taken from the Annual Reports of the 

Lighthouse Board for each lighthouse. 

In 1861 minor repairs were made to the 

Lighthouse including the replacement of the 

tower windows. Several years later in 1867 more 

improvements were made when “new wick rings 

[were] provided, new supply tubes put on 

burners, burners packed, and curtain hooks put 

up into Lantern.”44 

Descriptions of improvements conducted in the 

late 1860s are as follows: 

1868—The old and rusty lightning 

conductor has been replaced by a new one 

of copper with horn insulators; supply pipes 

of burners repaired; eight panes of glass set 

in the lantern. This tower also shows the 

effects of the heavy rains in this climate. 

Much of the mortar on the south and 

southwest sides is washed out, in some 

places to the depth of nearly half an inch. 

These walls should be repointed with 

cement. The plastering of the oil room and 

kitchen has fallen down and needs repairs. 

A suitable enclosure fence is recommended.” 

1869—The necessarily rigid quarantine kept 

up at Fort Jefferson, Dry Tortugas, has 

 

44 Dry Tortugas Light Station Clipping File. 

prevented the needed repairs on the tower at 

the station from being made during the past 

summer. The tower requires to be repointed, 

and painted with alternate white and black 

bands from the base to the lantern, to render 

it a better day-mark. These repairs will be 

made during the autumn. The illuminating 

apparatus is in good order and condition.” 45

In the early 1870s improvements to the light 

station included the construction of a boathouse 

and the application of the daymark. The interior 

of the Lighthouse was also” whitewashed” at this 

time. 

Hurricane Damage and Repairs 

The hurricane of October 6, 1873 caused severe 

damaged to the light station. In particular the 

force of the storm displaced the Lantern and 

lens apparatus of the Lighthouse and damaged 

the masonry at the top of the tower. The 

Lighthouse was described as being in 

“dangerous condition” after the storm and 

preliminary recommendations called for the 

structure to be demolished and rebuilt. 

Several sources describe the damage caused by 

the hurricane. A letter prepared five days after 

the storm by the Seventh District Lighthouse 

Inspector to Prof. Joseph Henry, Chairman of 

the Lighthouse Board reads: 

Sir, 

I have the honor to submit for your 

information the following abstract of 

Inspections made since the hurricane of the 

6th ...At Dry Tortugas Station No. 365 

Loggerhead Key. Joints of masonry at top of 

tower broken. Illuminating Apparatus 

turned from right to left 27 inches, pedestal 

and all. Lightning conductor loose, all the 

insulators are gone up to top of tower. 

Three panes of glass broken in Lantern. 

Ventilators in watch room out of order, 

won’t work. Lock to tower door broken. 

Oil room door blown down. Dwelling and 

outbuildings badly shaken and a great deal 

of shingling blown away. Tin gutters torn 

off. Gutters to cistern blown away and 

destroyed. Our cistern burst above ground. 

Plastering on ceilings and walls of dwelling, 

and oil room fallen off. Fences all down. 

Tower and dwelling are very much in need 

 

45 Ibid. 
Chronology of Development and Use 

 National Park Service 37 

Figure 24. Ca. 1892 image of the Light Station 

looking southwest.

of whitewash. Boat houses blown 

completely away two of the front 

Standiaous[sic.] of dwelling were rotted. 46

The same inspector later elaborated further on 

the damage to the Lantern and described the 

conditions faced by the keepers during the 

storm. 

I do not think that the efficiency of the light 

is impaired to the extent as to require it to be 

replaced. At the top of the tower the joints 

of masonry are broken, another of equal 

intensity would place the keepers who had 

to be in the tower, in a very perilous 

position. When the lamp was lighted on the 

evening of the 6th the two Ass’t Keepers had 

to keep be of the apparatus, to steady it 

sufficiently to enable the Principal Keeper to 

light the lamp and the tower swayed to and 

fro, so much as to swash the oil out of the 

lamp (a mechanical---). Three panes of 

plate glass were broken in the lantern, one 

of them completely... 

Because the Lantern had been displaced by the 

high winds, iron anchors were extended down 

through the Watch Room walls to better secure 

the Lantern to the masonry tower. In order to 

maintain the structural integrity of the tower, the 

repairs were made by removing thin columns of 

masonry, installing the anchors and replacing 

each section before moving on to the next. 

Despite these repairs, three years later, keepers 

continued to report that the Lantern would 

vibrate significantly in high winds. Post-storm 

repairs also included the fabrication and 

installation of shutters on the tower windows. 

On March 3, 1875 Congress appropriated 

$75,000 for a new lighthouse to replace the 

storm-damaged tower. This figure was one-half 

of the initial estimate developed by the 

Lighthouse Board inspectors. The repairs were 

monitored during the next several years, and 

although plans were prepared for a new castiron tower, it was ultimately decided that 

reconstruction would not be necessary. 

In September of 1875 a second hurricane hit the 

Dry Tortugas and caused damage to the Light 

Station. Many doors and windows were 

damaged, the lightning rod on the tower was 

 

18United States Lighthouse Board, List of General Correspondence, 

1791-1900, National Archives and Records Administration, 

Washington, DC. Record Group 26. NC-31. Series 38. 

broken, gutters were destroyed and the masonry 

Lighthouse was “severely shaken.”47

Over the next decade improvements were 

limited to routine maintenance such as 

whitewashing the interior and exterior of the 

tower, refastening window frames, intermittent 

repair of Lantern glazing, and the installation of 

a new iron cone, damper pipe and oil lamps in 

the Lantern. 

Changes to the Light 

On April 30, 1893, “the characteristic of this light 

was changed from fixed white to fixed white 

with a fixed red sector.”48 This change was 

implemented by adding sheets of red glass to the 

lantern that aligned with navigational hazards. 

 

47 Ibid. 

48 Dry Tortugas Light Station Clipping File. 
38 Dry Tortugas Lighthouse HSR 

Figure 25. Section through lamp and lens platform prepared in 1911 showing new incandescent oil-vapor 

lamp. 

 Repairs to the lighthouse continued. 

The iron work of the tower was thoroughly 

scraped, scaled, and given two coats of paint 

from the top of the dome to the bottom of 

the tower. New storm doors were made and 

put in; five windows were fitted with new 

frames and storm windows. The watchroom 

[sic.] was ceiled and painted....49 

In 1910-1911 the original first-order lens was 

replaced with a second-order bivalve lens 

manufactured by the French rival to Sautter, 

Henry Lepaute. The new lens was given the 

designation “USLH 213.”50

 Replacement of the lens required extensive 

work within the Lantern and Watch Room, 

including the installation of a new lens platform, 

pedestal and Watch Room floor plate. 

Essentially all of the apparatus currently present 

within the Watch Room and Lantern was 

installed during the 1911 lens replacement. Also 

at this time, the existing lamp was replaced with 

an incandescent oil-vapor lamp (i.o.v.). 

 

49 Ibid. 

50 Hurley, 50. 

The bivalve lens, also known as a “clam shell 

lens” was accompanied by clockworks that 

drove the rotation of the lens. Like a mechanical 

clock the lens was rotated by the falling of 

weights set within the hollow column at the 

center of the tower. The lens pedestal sat in a 10” 

deep pool of mercury designed to eliminate 

friction in the rotation of the apparatus. 

Despite a downgrade in size, the new secondorder lens provided a brighter light with 

increased range. Correspondence from the 

period states “the candle power of the flash of 

the present second-order light is about 220 times 

as great as that of the former first-order fixed 

light and the luminous range for clear weather 

has been more than doubled by the change in 

the light.”51 

Following installation of the new lens mariners 

complained that the interval between flashes was 

too long. It was requested that the flashes be 

increased from one every forty seconds to one 

every ten seconds. In order to make this 

adjustment, modifications were made to the 

 

51 Department of Commerce, Recommendation as Aids to 

Navigation, 10 March 1911, RG 26, NA. 
Chronology of Development and Use 

 National Park Service 39 

Figure 26. Ca. 1910-1911 drawing of the second-order lens and associated apparatus prepared by the 

Societe des Etablissements Henry-LePaute of Paris. 

 
40 Dry Tortugas Lighthouse HSR 

Figure 27. 1926 drawing prepared for the conversion of the Oil House to a Radio Beacon House. 

routing of the clockwork cord. Originally fed 

through the center of the Watch Room floor 

plate, the cord was re-fed through a slot that had 

to be made in the side of the newel. The newly 

installed system required the keeper to wind the 

mechanism every 16 hours. 

Modernization of the 1920s 

In July of 1922 the Superintendent of 

Lighthouses requested that parallel copper 

screens be installed in the Lantern. These 

vertical curtains were designed to reduce the 

intensity of reflected eccentric rays “without 

diminishing the brilliancy of the primary rays.”52

 

52 Department of Commerce, Recommendation as Aids to 

Navigation, 18 July 1922 RG 26, NA. 

A purchase order from the Superintendent of 

Lighthouses, W.W.Demeritt, describes that the 

copper screens would be aligned with the center 

of the bulls eye on each side of the clamshell 

lens. The project was estimated to cost $170.00. 

J.S. Conway, the Commissioner of the 

Lighthouses approved the request with the 

requirement that a trial run be conducted prior 

to installation. 

Also in 1922, H.B. Haskins, the Assistant 

Superintendent of Lighthouses made a request 

to install a four button, five phone 

interconnecting telephone system at the station. 

The intent was to provide a means for a keeper 

located at the top of the tower to communicate 

with the other keepers in the structures below. 

This system would be most useful during the 
Chronology of Development and Use 

 National Park Service 41 

many “storms which menace the station.” 

Funding for the project was approved by the 

Commissioner of the Bureau of Lighthouse and 

the system was installed. 

In the mid-1920s plans were made to change the 

function of the Oil House from storing oil and 

materials to housing radio beacon equipment. 

This relatively new technology provided a means 

for vessels to determine their location during 

inclement weather when the light was not 

visible, and to communicate with the light 

keepers. The radio beacon was to be operated 

for “30 minutes every 6 hours during ordinary 

weather and continuously during hurricane 

weather.”53 

Drawings for the conversion of the Oil House 

were prepared in October 1926 and show the 

first floor being used to house generators and 

the second floor reserved for the radio receiving 

equipment. Modifications made to the building 

to accommodate the new function include the 

installation of bead-board wall and ceiling 

finishes, and new flooring and base-boards. The 

windows shown in the 1926 drawing are fourover-four double hung units. The drawings do 

not state whether these were existing or to be 

installed as part of the repurposing of the 

structure. Because the station still required a 

space to store oil and materials, a new one-story 

concrete oil house was constructed just to the 

north of the original structure. 

The following year, the new radio beacon house 

was connected to the tower by a concrete 

passageway. The passageway was constructed to 

protect the keeper when passing between the 

buildings during stormy weather. The 

passageway was constructed with 8” reinforced 

concrete walls and a concrete roof slab with 

flanking parapets. Two aligned doorways 

adjacent to the tower provide access through the 

passageway. The passageway was also intended 

to keep the doors of the tower from blowing 

open during driving winds. Should the door to 

the tower be left open or torn off, loss in 

pressure within the tower could potentially 

cause a vacuum that would pull the glass in the 

Lantern Room in and out, subsequently blowing 

out the light.54 The passageway was estimated in 

 

53 Ibid., October 1926. 

54 Ibid., 10 November 1926. 

November of 1926 to cost $315.00 in material 

and $478.63 in labor.55

By the fall of 1929, the Superintendent of 

Lighthouses requested the repair and 

refurbishment of the clockworks. A requisition 

from October 31, 1929 states that the Mallory 

S.S. Co. would supply the new components. 

A year later, a request was made to convert the 

main lamp of the Lighthouse from incandescent 

oil vapor to electric lights. After much 

correspondence between the manufacturers and 

the Department of Commerce about how to 

light the tower, a group of inspectors and 

engineers were assembled on Fort Jefferson on 

the evening of October 8,1931 to test several 

bulb configurations. The original 55 mm Type A 

IOV was tested against 3-250 Watt frosted bulbs 

placed 1-7/8” apart, 2- 250 Watt frosted bulbs 

placed in a similar configuration and 1-500 Watt 

G-40 frosted bulb. The testing team had 

photometers, timers, and obscuring screens at 

Fort Jefferson to measure the light levels from 

across the 2-1/2 mile distance to Loggerhead 

Key. The 500 Watt bulb was chosen as the best 

lamp for the tower.56 According to several 

accounts, the Dry Tortugas Lighthouse became 

“the most powerful in the United States in 1931 

when a three-million-candlepower electric light 

was switched on, about 250 times the intensity of 

the kerosene lamps it replaced.”57

Requests in 1933 included funding to repair the 

Lantern gallery and install an electric drive and 

alarm for the lens. Converting the lens to an 

electric drive would alleviate the keeper from 

having to climb the tower twice each evening to 

wind the clockworks. 

Repairs to the iron work of the Lantern Room, 

including the replacement of 16 gallery plates 

were also conducted this same year. In order to 

replace the iron floor plates, several courses of 

brick at the top of the Watch Room walls had to 

be removed. As part of the same program of 

improvements a window was added to the east 

elevation of the radio beacon house (former Oil 

House) to provide additional ventilation. Storm 

shutters for all of the dwellings were also 

installed. H.D. King, Deputy Commissioner of 

 

55 Ibid. 

56 Ibid., October 13, 1931. 

57 Cipra, p.29. 
42 Dry Tortugas Lighthouse HSR 

Figure 28. Image of wood-frame addition to Oil 

House constructed between 1943 and 1951. 

the Bureau of Lighthouses approved $3,000 for 

the improvements. 

This repair package was funded by the National 

Industrial Recovery Act (NIRA) of June 16, 

1933.58 NIRA was a pivotal act that sought to 

restructure the industrial economy, promote fair 

competition, establish boundaries for worker’s 

rights and lay the groundwork for President 

Franklin D. Roosevelt’s New Deal program. The 

NIRA program was in place for two years until it 

was deemed unconstitutional and discontinued. 

Prior to 1939, a reinforced concrete addition 

was constructed on the rear elevation of the 

former Oil House to house batteries. The 

drawings for the project are undated but show 

an 11’ x 11’ one room extension with 8” 

reinforced concrete walls. The addition has a 

continuous concrete foundation with a 2’-0” 

wide footing. The floor is a 5” concrete slab on 

fill. Two, 2’ x 6’ windows are located on the 

north and south elevations. The drawings call 

for the original window in the west elevation of 

the radio beacon house to be replaced by a door 

and the window salvaged and installed in the 

west elevation of the addition. 

Coast Guard Era Modifications 

In 1939 the US Coast Guard assumed 

management of the Light Station from the 

Lighthouse Board. Construction and 

maintenance projects were limited during the 

early 1940s—presumably due to resources being 

diverted to the war effort. 

 

58 Ibid., July 31, 1933. 

Between 1943 and 1951 a second addition was 

constructed on the former Oil House. An 

undated image shows the addition as a wood 

frame gable roof structure extending 

perpendicularly from the south wall of the 

building. The addition contains a central 

doorway with flanking six-over-six, doublehung wood windows on its east elevation and 

two similar windows on the south elevation. The 

building is clad with wide board siding and has a 

shingle roof. It is likely the building was 

constructed to house generators as the former 

Oil House is consistently labeled as “Gen. & R.B. 

Bldg.” on subsequent site plans of the Station. 

Construction of the addition’s gable roof 

required modification of the original second 

floor window opening. 

The wood frame addition was removed in 1969 

when a new much larger generator and radio 

beacon building was constructed just to the west 

of the former oil house. This metal building 

remained in service until the 1980s when it was 

demolished. 

In 1967 the USCG conducted extensive repairs 

to the Lighthouse. The exterior of the tower was 

sand-blasted to remove the existing paint, 

deteriorated mortar joints were repointed and 

the daymark was reapplied. Repainting included 

the application of a white prime coat over the 

entire surface of the tower followed by coats of 

black and white paint. The painting and masonry 

repairs were conducted from a bucket 

suspended from the Lantern level. On the 

interior, a new handrail was installed in the stair 

tower. 

The exterior of the Watch Room was also 

extensively repaired. The stucco finish of the 

interior and exterior Watch Room level walls 

was removed and a new multi-coat stucco 

system was applied. The mortar floor surface of 

the Watch Room gallery was completely 

removed and replaced and an 8” wide stainless 

steel tension ring was installed to secure the 

masonry at this level. 

The metal work of the Lantern, including the 

galleries and copper dome roof, were also sandblasted and repainted. Other repairs at the 

Lantern level included the scaling and cleaning 

of corroded metal and repair of the dome roof 

soffit and integral gutter. 

 
Chronology of Development and Use 

 National Park Service 43 

Figure 29. Image taken in 1982 during repairs and improvements to the Oil House conducted by the crew of the 

CGC White Sumac. 

The tower windows were also replaced at this 

time with three-pane, aluminum, awning 

windows. Because the new windows would not 

completely fill the original rough opening, a twoinch concrete sill was fashioned to make up the 

difference. 

In 1982 the crew of the CGC White Sumac was 

engaged to construct an addition to the former 

Oil House and complete various repairs to the 

Lighthouse and other buildings of the Light 

Station. As part of this work, the interior of the 

Lighthouse was “water-blasted” to remove 

peeling and flaking paint and partially repainted. 

New “heavy-duty type windows capable of 

withstanding high winds and foul weather” were 

installed in the tower. These are likely the same 

bronze aluminum units that are present today. 

The existing windows that were removed at the 

time were described as “aluminum framed, light 

weight windows suitable for a house trailer.”The 

former Oil House was re-roofed and a “drop 

ceiling” and paneling were installed on the 

second floor. New lights were also installed in 

the building. The concrete block “generator 

room” was constructed on the foundation of the 

previous frame addition. 

Three years later in 1985, additional repairs were 

made to the Lighthouse. Included in the scope 

of repairs was the re-pointing of the exterior 

masonry and repair of the Watch Room level 

stucco walls, replacement of glass panes in the 

Lantern Room, replacement of the Lantern and 

Watch Room gallery railings, painting of the 

copper roof and other minor repairs. 

The following year, after an incident that 

resulted in the mercury spilling from the float 

drum, a decision was made to decommission the 

second-order lens and install an automated 
44 Dry Tortugas Lighthouse HSR 

Figure 30. Image taken in early 2009 during repair 

of the Lantern roof. 

navigational beacon. The second-order lens was 

removed from the Lantern and placed on display 

at the National Aids to Navigation School in 

Yorktown, Virginia. A new 24” Directional Code 

Beacon (DCB-24) was installed and powered by 

solar panels mounted to the wall of the Watch 

Room gallery. The new lamp created a flashing 

light every 20 seconds that could be seen up to 

24 miles away.59 The DCB-24 was replaced in 

1996 with a new marine rotating beacon (VRB25). 

Recent Alternations by the National 

Park Service 

Given that the Lighthouse has remained an 

active aid to navigation since the transfer of the 

light station property, the USCG has continued 

to conduct routine maintenance and minor 

repairs to the Lighthouse and Oil House. 

Through its VIP program the National Park 

 

59 Dean, p. 99. 

Service has also committed resources to the 

maintenance of these buildings and have 

completed at least two significant repair 

projects. 

In 2005, the National Park Service replaced the 

doors in the concrete passageway as well as the 

windows in the west addition of the original Oil 

House. The designers of the project used 

historic photographs to replicate the detail of 

the original doors and windows. The door 

openings in the passageway were widened 

slightly as part of this improvement project. 

During the approximately 25 years between 

1985 and 2009 the Lighthouse Lantern structure 

and roof had deteriorated significantly to the 

point that the structure was open to the weather 

for an extended period of time. This prompted a 

recent emergency stabilization effort by the 

National Park Service to replace the copper roof 

and Lantern glazing, and scale and paint the iron 

elements of the Lantern structure. 

The project began with removal of the 

deteriorated roof panels followed by removal of 

the vent ball and lightning rod which were 

placed in storage at the Everglades National 

Park collections facility. Due to the limited 

funding available only a partial restoration of the 

roof could be accomplished. The dome of the 

roof was replaced, but reconstruction of the 

integral gutter system and replication of the vent 

ball and reinstallation of the lighting rod could 

not be completed. The new copper panels were 

attached to the existing iron skeleton with 

stainless steel clips and a roof access hatch was 

added. The Lantern glass was replaced with 

7/16” tempered hurricane glazing and the iron 

frame was scaled and painted. The project was 

completed in early 2009. 
 National Park Service 45 

Dry Tortugas Light Station Chronology 

1825 Lighthouse constructed on Garden Key, Dry Tortugas 

1837 Recognition that additional aids to navigation are needed in the Dry Tortugas.

 1838 Vessel America wrecks near Garden Key, Dry Tortugas. 

 1838 Recommendation to increase height of Garden Key Lighthouse. 

 1846 Construction of fortification commences on Garden Key. 

1849 Collector at Key West, S. R. Mallory makes recommendation for establishment of a 

light on Loggerhead Key. 

1851 Congress directs Treasury to establish a board to investigate the Lighthouse Service.

1852 Congress establishes the Lighthouse Board. Florida, including the Dry 

 Tortugas is assigned to the 7th District. 

 1853 Letter from Lieutenant George G. Meade, Corps of Topographical Engineers to 

Lighthouse Board October 26, 1853: “A day beacon is wanted on one of the outer 

shoals of the Tortugas, which is at such a distance from the light on Garden Key, that 

navigators should have their attention called to it before getting to near.” 

 Sept. 25, 1855 At the request of the Light House Board, Captain Horatio Wright, Captain of 

Engineers overseeing construction of the fortification on Garden Key, submits a letter 

of description, estimate and preliminary sketch of a proposed 150’ lighthouse for the 

Dry Tortugas (the letter reveals some confusion between Wright and the Light House 

Board over the location of the proposed lighthouse). 

1856 – August 18th Congress appropriates $35,000 for first order lens and lighthouse at Dry 

 Tortugas (Loggerhead Key). Captain Daniel Woodbury in charge of design 

 and construction. 

 1856 Plans being prepared for Dry Tortugas Light Station

 1857 Dry Tortugas Light Station under construction

1858 Dry Tortugas Light Station completed. 

July 1, 1858 Lantern lit at Dry Tortugas Lighthouse.

1858 Light List refers to Dry Tortugas Lighthouse as “brick-color”. 

1858 Benjamin Kerr appointed lighthouse keeper (transferred from Garden Key). 

1860 Domestic disturbance involving Benjamin Kerr and family. 

1860 Repairs made to roof of dwelling and new windows installed in tower.

1861 James Lightbourn appointed lighthouse keeper.

1861- 1865 Civil War
46 Dry Tortugas Lighthouse HSR 

1862 Robert H. Thompson appointed lighthouse keeper.

1866 Extensive repairs and renovations made to Dry Tortugas. 

1867 “New wick rings provided, new supply tubes pan burners, burners packed, curtain 

hooks put up into lantern.” 

1867 Yellow fever outbreak on Garden Key. Loggerhead Key used for quarantine 

1868 “The old and rusty lightning conductor has been replaced by a new one of copper with 

horn insulators; supply pipes of burners repaired; eight panes of glass set in the 

lantern. This tower also shows the effects of the heavy rains in this climate. Much of 

the mortar on the south and southwest sides is washed out, in some places to the 

depth of nearly half an inch. These walls should be repointed with cement. The 

plastering of the oil room and kitchen has fallen down and needs repairs. A suitable 

enclosure fence is recommended.” 

1871 Repairs made to Boathouse.

1872 William B. Taylor appointed lighthouse keeper.

1872 Thomas Moore appointed lighthouse keeper.

1873 Yellow fever outbreak on Garden Key. Loggerhead Key used for quarantine. 

1873 – October 6th Dry Tortugas Light Station severely damaged by hurricane. 

1874 Temporary repairs made to hurricane-damaged tower.

1875 Upper 8’-9’ of tower rebuilt. Anchors of lantern (rods) extended downward through 

structure. Tower received black and white paint scheme (daymark) 

1875 Congress appropriates $75,000 for new tower to replaced hurricane-damaged 

lighthouse. 

1878 Station repainted and miscellaneous repairs completed.

1880 “A new boat-house, 16 by 30 feet in plan was built. Twenty pairs of window blinds 

were hung, and three window frames in the tower were refastened. The station is in 

good order.” 

1881 Harry W. Magill appointed lighthouse keeper.

1881 Robert H. Thompson appointed lighthouse keeper.

1884 “New mineral lamps were put in and work well. A few minor repairs were made.”

1885 “A new iron cone and damper piper were fitted for the illumination apparatus, and 

two sheets of plate glass for the lantern were cut and sent to the station.” 

1887 “A survey of the site was made, also tracings of the reservation and buildings. Three 

lights of plate-glass for use in the lantern were furnished.” 

1888 Light List refers to Oil House and Keeper’s Dwelling as yellow brick. 

1888 Charles A. Roberts appointed lighthouse keeper.

1888 George R. Bilberry appointed lighthouse keeper. 

1889 “This station was thoroughly repaired. Two new washhouses were built. All new 

work was painted or whitewashed. “ 
Chronology of Development and Use 

 National Park Service 47 

1893 “On April 30, 1893, the characteristic of this light was changed from fixed white to 

fixed white with a fixed red sector. A few minor repairs were made. This station will 

require extensive repairs during the ensuing year.” 

1896 “Some 728 feet of wire fence were put up and painted. Various minor repairs were 

made.” 

1898 Spanish American War

 1899 “The iron work of the tower was thoroughly scraped, scaled, and given two coats of 

paint from the top of the dome to the bottom of the tower. New storm doors were 

made and put in; five windows were fitted with new frames and storm windows. The 

watch room [sic.] was ceiled and painted. An addition 10 feet long was made to the 

boathouse. New floors were laid throughout the house. The roof was thoroughly 

repaired, one entire side being supplied new. Walks were constructed leading from 

the kitchen to the washhouse and main building. Various repairs were made.” 

 1901 November 1, 1902, temporary change in character of light. 

1904-1905 “The Carnegie Biological Laboratory was granted a site for laboratory 

 buildings on the light-house reservation, and the limits of this grant were 

 surveyed and marked.” 

 1906 “Two storerooms and new porches were built. About 164 feet of walk, 5 feet wide, was 

built, as was some 200 feet of picket fence 5 feet high. Various repairs were made.” 

 1907 Edgar J. Russell appointed lighthouse keeper. 

1910 Light House Board reorganized as the U.S. Bureau of Lighthouses (better 

 known as the Lighthouse Service) under the Department of Commerce. 

 1910 Source of illumination or lamping changed to incandescent oil vapor (I.O.V.).

 1910-1911 Original first-order lens removed and a new second-order bivalve lens (by Henry 

Lepaute) and lens pedestal installed in Lighthouse. Lens pedestal includes mercury 

float apparatus to rotate lens. 

 1911 Repairs to Lighthouse and roof of Keeper’s Dwelling.

1914-1918 World War I

 1916 Old wharf destroyed in hurricane of July 5, 1916.O

 1917 “The act of September 8, 1916, appropriated $125,000 for repairing and rebuilding 

aids to navigation. Gulf of Mexico, from which an allotment of $2,800 was made for 

this station. During the year a wrought-iron pile wharf with cast-iron caps and 

wooden girders, stringers, and decking was erected in place of the old wharf, which 

was destroyed. All work was completed in May, 1917. Amount expended to June 30, 

1917, $2,631.19.” 

 1917 Preliminary plans for new Keeper’s Dwelling prepared. 

 1919 Boathouse destroyed by hurricane.

 1919 Keeper – Charles H. Johnson
48 Dry Tortugas Lighthouse HSR 

 1920 $6,500 authorized for a two-family dwelling. Repairs made to roof of Keeper’s 

Dwelling. 

 1921 Garden Key lighthouse decommissioned Dry Tortugas light becomes primary aid to 

navigation 

 1922 June – Materials and construction crew arrive to complete new dwelling. 

 1922 Request made for telephone system between Watch Room and keeper’s residences. 

 1922 Copper parallel screens installed on lens.

 1922 Dr. Alfred G. Mayor, Director of the Carnegie Marine Biology Research Laboratory 

 dies on Loggerhead Key. 

 1923 New Keeper’s Dwelling 90% completed. Interior trim work remains to be completed.

 1926-1927 Original Oil House repurposed to house radio beacon equipment including 

construction of a concrete passageway connecting oil house to lighthouse. 

 1931 September 1, 1931 Dry Tortugas Lighthouse becomes most powerful light in America 

with 3,000,000 candlepower from newly installed electric light. 

 1933 Walls of watch room in poor condition due to corrosion and jacking of Lantern

anchor rods embedded in masonry. 

 1935 Fort Jefferson designated a National Monument.

1939 U.S. Bureau of Lighthouses is amalgamated into the operations of the U.S. 

 Coast Guard 

 1939 Carnegie Institute ceases operations at Marine Research Laboratory 

1940-1945 World War II 

 1940-1945 Lighthouse used for lookouts during WWII.

 1945 Fire destroys original Keeper’s Dwelling.

 1964 Fire destroys majority of abandoned structures of the Carnegie Institution’s former 

Marine Research Laboratory. 

 1967 Extensive modifications made to Lighthouse and Oil House by USCG. Work included 

sandblasting and repainting of the Lighthouse, window replacement in the Lighthouse 

and Oil House, and extensive work in the Watch Room. 

 1977 Proposal by National Park Service to install solar power electrical generation system 

for Fort Jefferson and Dry Tortugas light station operations. 

 1982 Extensive repairs and improvements made to Lighthouse and Light Station structures 

by USCG crew of White Sumac

 1984 Development of draft National Register of Historic Places nomination form for Dry 

Tortugas Light Station. 

 1985 Extensive improvements to Light Station’s electrical system

 1986 Second-order Fresnel lens decommissioned, removed and displayed at National Aids 

to Navigation School in Yorktown, Virginia 

 1986 Directional Code Beacon (DCB-24) installed in lighthouse.
Chronology of Development and Use 

 National Park Service 49 

1992 Dry Tortugas National Park established and Loggerhead Key and light station

 property transferred from USCG to the National Park Service 

 1996 VRB-25 Marine Rotating Beacon installed

 1998 Emergency repair of underground fuel lines

 2002 Photovoltaic solar array installed for generation of electrical power. Diesel fuel 

generator system abandoned. 

 2003 Two 3,000 gal. above-ground diesel fuel storage tanks and associated components 

removed from site. Diesel fuel system no longer necessary. Electrical power 

generation provided by photovoltaic array.

 2003 Installation of water and wastewater disposal system

 2003 Kitchen building septic system replaced.

 2008 Testing of lead contaminated soils at base of light tower by USCG 

 2009 Lantern repair project completed

 2009 Development of HSR
50 Dry Tortugas Lighthouse HSR 
National Park Service 51 

Figure 31. 2008 view of Dry Tortugas Lighthouse 

upon approach to main dock from the east. 

Physical Description 

Dry Tortugas Lighthouse 

Politics, need, cost, location, and geography of the 

site, as well as technology available at the time of 

construction influenced lighthouse designs.60

The Dry Tortugas Lighthouse is a terrestrial, or 

on-shore, brick conical tower constructed in 

1858 to aid mariners in navigating the hazardous 

islands and shoals of the Dry Tortugas. The 

Lighthouse was designed to be the central 

element of a manned light station that originally 

consisted of several structures, including the 

tower, a keeper’s dwelling, kitchen building, and 

brick cisterns for fresh water. 

In response to numerous requests by mariners 

for additional navigational aids in the Dry 

Tortugas, $35,000 was appropriated by Congress 

in August 1856 for construction of the light 

station. The plans for the Lighthouse and 

Keeper’s Dwelling were prepared by the 

engineers of the Lighthouse Board’s 7th District. 

Captain H.G. Wright who was at the time 

overseeing construction of Fort Jefferson on 

nearby Garden Key, was solicited by the Board 

for design input as early as 1855. Wright 

prepared preliminary sketches for a lighthouse 

and developed a cost estimate for a project he 

assumed at the time would be constructed on 

Garden Key. Prior to commencing construction 

of the Lighthouse, Wright was replaced by 

Captain Daniel Phineas Woodbury of New 

Hamphire. Woodbury, who was an expert in 

masonry arch construction made a number of 

design changes to Wright’s initial proposal. 

Woodbury, along with his master mason, 

George Phillips, would oversee construction of 

the fort and the light station during the 1850s. 

The proximity of the large scale military 

construction and engineering project on Garden 

Key, undoubtedly provided logistical advantages 

 

60 National Park Service, Maritime Heritage Program, Historic 

Lighthouse Preservation Handbook, 2009 

http://www.nps.gov/history/MARITIME/handbook.htm 

to the Light Station project. Construction of the 

Lighthouse would not only benefit from the 

oversight provided by Woodbury and Phillips, 

but was also able to take advantage of an already 

assembled labor force. When the lighthouse 

project was started, the walls of the fort had 

barely risen above the waterline. It is likely that 

construction of the Light Station was 

supplemented with workers from the fort 

project. The labor force at the fort was made up 

of skilled workers primarily from the north as 

well as slaves borrowed or leased from their 

owners in Key West. 

The height of the tower at over 150’, its slim 

form, and lack of “ornamental flourishes,” 

categorize the Dry Tortugas Lighthouse as an 

“Early Classic” brick tower. A majority of the 

early classic towers were constructed between 
52 Dry Tortugas Lighthouse HSR 

Figure 32. Section through Lighthouse and Oil 

House from 1857 architectural plans 

Figure 33. View of Lighthouse Lantern and 

corbelled masonry supporting the Watch Room 

gallery. 

1857 and 1860. The designs executed during this 

period are indicative of a transition that was 

occurring within the Lighthouse Establishment 

that saw the civilian leadership replaced with 

military engineering personnel in the early 

1850s. 

The Lighthouse is generally constructed 

according to the standard specifications issued 

by the Lighthouse Board in 1861 for brick tower 

lighthouses.61 Its design is strikingly similar to 

that of the Pensacola Lighthouse, another early 

 

61 Specifications for a First Order Light-House, (Brick Tower,) , 

Washington: Government Printing Office, 1861. 

classic tower, built the same year. The primary 

difference between the towers is that the 

Pensacola Lighthouse is taller and was built with 

its oil house attached directly to the base of the 

tower, where the oil house at Dry Tortugas was 

built as a separate free-standing structure. A 

reinforced concrete passageway connecting the 

Oil House to the tower was constructed in 1927. 

The diameter of the tower is approximately 28’ 

at its base tapering to approximately 15’ at the 

belt course below the watch room gallery. 

Although the actual material, depth and 

configuration of the foundation could not be 

confirmed the architectural plans show a 

battered “cement” foundation. 

In his 1855 correspondence, Wright proposed 

the walls of the tower to be constructed of solid 

concrete with a brick veneer. The original 

architectural plans from 1857 and standard 

specifications issued a few years later, call for the 

exterior walls to consist of two “shells” of 

brickwork with an interior air-space or void. 

The plans show the outer shell at approximately 

3’-9” thick at the base of the tower reducing to 

1’-10 1⁄2” in thickness at the top. Radiating brick 

walls divide the interior void into six equal 

segments. The void becomes thinner as the 

exterior walls taper. 

The bricks used in the construction of the 

Lighthouse have similar characteristics to those 

used in the construction of Fort Jefferson’s scarp 

wall and were likely obtained from the same 

brick yards in Pensacola or Mobile. The bricks 

range in color from light orange to salmon and 

brown and contain dark inclusions. The bricks 

measure approximately 8 1⁄2” x 2 1⁄4” x 4” and are 

laid in a Flemish bond, the same coursing used at 

the fort. Originally unpainted, the tower’s 

daymark or paint scheme (lower half painted 

white and the upper half painted black) was first 

applied ca. 1870. 

The Lighthouse contains an entrance at grade. 

There are five windows in the brick portion of 

the tower corresponding to each of the interior 

landings. Two windows, vertically aligned over 

the tower entrance are oriented to the west. The 

remaining three windows are vertically aligned 

on the east elevation facing Fort Jefferson. The 

interior stair tower has a diameter of 10’-6” and 

a hollow central brick newel or column at its 

center. The blue slate stair slabs are set into the 

interior wall and central column. There are 30 
Physical Description 

National Park Service 53 

treads between each of the five intermediate 

landings. 

Above the belt course, the exterior wall of the 

tower corbels out for sixteen courses to support 

and form the floor of the Watch Room gallery. 

One of the signatures of the Early Classic Style, 

particularly in the south, is the use of corbelled 

masonry to support the gallery in favor of iron 

brackets. Cape Lookout Lighthouse in North 

Carolina, and the Pensacola Lighthouse share 

this construction characteristic. Among these, 

the Dry Tortugas Lighthouse was completed 

first, suggesting it may have served as the 

prototype for this design innovation. 

The Watch Room level of the tower contains the 

lens pedestal and the mercury float apparatus 

associated with the second-order bivalve lens 

installed in 1910-1911. The interior and exterior 

walls of the watch room are stucco-covered 

masonry. The Watch Room elevations contain a 

window oriented to the east and an arched 

doorway oriented to the west. The doorway 

provides access to the gallery. 

The Lantern is generally constructed according 

to the standard specifications for first order 

lanterns issued by the Office of the Lighthouse 

Board in 1862. The Lantern is a sixteen-segment 

structure with a skeleton of iron posts and ribs 

with bronze mullions and astragals. The exterior 

walls are entirely glazed with each bay 

containing three rectangular glass panels. 

Originally outfitted with a first-order Fresnel 

lens purchased from Sautter & Company of 

Paris, the existing light is a VRB-25 rotating 

marine beacon installed in 1996. The roof of the 

Lantern is copper and its form is referred to as a 

“French dome with ventilation ball.” The vent 

ball and lightning rod, along with the Watch 

Room-level door were removed during a recent 

program of repairs conducted in early 2009. The 

removed ventilation ball, lightning rod and door 

are currently being stored at Everglades 

National Park’ collection facility. 

Character-Defining Features 

Character-defining features of the Lighthouse 

are those visual and tangible elements of the 

structure that are significant and give the 

resource its distinct character. These features 

include elements of its original design and 

construction as well as modifications made 

during the historic period. The characterdefining features of the Lighthouse should be 

retained and preserved as part of ongoing 

maintenance and repair activities. The identified 

character-defining features of the Lighthouse 

include: 

 Isolated and sparsely vegetated 

subtropical setting – The character of the 

surrounding landscape is one of Light 

Station’s most unique and important 

features contributing greatly to the 

resources sense of place. The relatively 

recent program to remove invasive species 

introduced by the Carnegie Institute in the 

early twentieth century has returned the 

landscape to a condition that is generally 

consistent with its nineteenth century 

appearance. 

 360 degree view shed of the surrounding 

gulf waters, shoals and keys including 

Garden Key and Fort Jefferson. 

 “Early Classic” brick tower form with 

corbelled masonry support for Watch 

Room gallery. 

 Flemish bond brick exterior walls. 

 1870s applied daymark – Lower portion of 

tower painted white and upper portion 

painted black. 

 Windows are considered characterdefining features of the Lighthouse. 

However, the existing modern units 

installed in the 1980s diminish rather than 

enhance the historic character of the 

structure. 

 Painted brick stair tower with hollow 

brick newel, blue slate slab stair treads and 

granite landings. 

 Carved initials (J.N. 58) in niche wall at 

third level 

 Watch Room with stuccoed walls, 

diamond-pattern iron floor plate, bronze 

ventilation dampers, and arched iron door 

to gallery. 

 Typical first-order Lantern with 

rectangular glazed panels and French 

dome copper roof with ventilation ball 

(now removed) 

 Five-panel wood door and door frame at 

tower entrance. 

 
54 Dry Tortugas Lighthouse HSR 

Figure 34. Undated aerial image of Loggerhead Key and the Dry Tortugas Lighthouse. 

 Lens pedestal with mercury float assembly 

associated with installation of the secondorder bivalve lens in 1910-1911. 

 Second-order bivalve lens removed from 

the Lighthouse in 1986 and placed on 

display at the National Aids to Navigation 

School in Yorktown, Virginia. 

Structural Systems 

Foundation: There are several references to 

proposed designs for the Lighthouse foundation 

in the historic documentation, but its actual 

material, depth, and configuration could not be 

confirmed. 

Captain H. G. Wright’s 1855 correspondence 

proposes a battered concrete foundation set 

upon a grillage of 8” x 6” yellow pine timbers. As 

mentioned previously, the correspondence and 

accompanying sketch refer to a project Wright 

assumed at the time was going to be constructed 

on Garden Key. It is unclear whether the system 

described by Wright was ultimately constructed 

at the Loggerhead Key site. 

The architectural plans for the Lighthouse 

prepared by the 7th District engineers dated 

April 1st, 1857 show the outline of a battered 

foundation below the tower. The shape appears 

to be labeled “cement foundations.” Although 

no detail is given, what is shown on the drawings 

appears generally consistent with both Wright’s 

proposed system as well as the foundation 

description provided in the 1861 standard 

specifications for first-order brick towers: 

If the ground on which the tower is to be 

built is good and solid, the foundation pit 

must be excavated to the depth of ten (10) 

feet and suitably leveled for the bed of 

concrete which must be from two to three 

feet in thickness. But if in the judgment of the 

Superintendent, the ground be not 

sufficiently firm to build directly upon, then 

it must be closely piled, and covered with a 
Physical Description 

National Park Service 55 

Figure 35. Dorothy Krotzer of Building 

Conservation Associates Inc. (BCA) works to 

remove a sample of the original mortar from 

the base of the Lighthouse. 

grillage of heavy timbers, say 12” x 12”. The 

upper side of the grillage to come within 

eight feet of the surface of the ground. All 

excavated material to be graded around the 

premises as may be directed. The foundation 

to be of good rubble masonry in random 

courses with level beds. The extreme 

diameter of the lowest course to be forty (40) 

feet. The largest stones obtainable must be 

used for this course. 

In 1900 Keeper George Bilberry prepared a 

sketch of the base of the tower as part of an 

exercise in establishing the height of the focal 

plane. The sketch shows the base of the tower 

stepping out for four courses above grade. Once 

again, no information is provided about the 

below-grade construction of the foundation. 

The stepping out of the base of the tower as 

shown in the sketch is no longer visible having 

been modified or obscured by construction of a 

concrete walkway around the base of the tower. 

Finally, construction data provided by the Coast 

Guard on their Web site lists “stone” as the 

foundation material for the Dry Tortugas 

Lighthouse. The source of this information is 

not provided. 

Existing Condition: No evidence of foundation 

settlement or other foundation-related problems 

were noted during inspection of the tower. The 

build-up of paint on the brick exterior makes it 

difficult to detect the presence of repaired 

cracks that may have occurred as a result of 

previous settlement. 

Floor: The floor at the base of the Lighthouse 

appears to be a granite slab divided into several 

segments. 

Existing Condition: No signs of settlement 

cracking or deterioration of the granite slab were 

noted. 

Exterior Walls: The exterior walls of the 

Lighthouse form the masonry structure of the 

tapered cylindrical tower. Constructed of bricks 

laid in a Flemish bond, the masonry portion of 

the Lighthouse, from the tower base to the 

Watch Room gallery floor is approximately 135’ 

in height. 

The use of Flemish bond for the Lighthouse 

walls is first proposed by Captain Wright in his 

1855 sketch of the Lighthouse planned for 

Garden Key. This bonding pattern is consistent 

with that used in the construction of Fort 

Jefferson’s scarp wall. 

Wright’s correspondence also proposes the 

mortar mix to be used in the walls should be one 

part powdered cement to two parts sand. Wright 

further suggests that lime be omitted from the 

mortar as it was found not to “fully resist” the 

extreme conditions of the area. Analysis of 

mortar samples extracted from the exterior wall 

of the Lighthouse revealed the composition of 

the mortar to be one parts natural cement to 

one-and-one-half parts local carbonate sand, 

not a precise match, but consistent with Wright’s 

proposal (See Appendix B). 

At its base, the Lighthouse is approximately 28’ 

in diameter tapering to approximately 15’ in 

diameter at the belt-course below the Watch 

Room. The architectural plans show voids in the 

exterior walls that get smaller as the walls taper 

towards the top of the tower. The 1861 standard 

specifications for brick towers call for these 

internal voids to be ventilated by the addition of 

4” x 4” weep holes at the base of the tower and 

five inch diameter copper ventilators installed 

below the Watch Room gallery. No evidence of 

this ventilation system was observed. 

Below the Watch Room, the masonry wall 

corbels out for 16 courses, the extension of each 

corbel increases from bottom to top. The 

corbelled masonry supports the Watch Room 

gallery. The interior stair tower maintains a 

diameter of approximately 10’-6” throughout 

the height of the tower. A 2’-2”diameter hollow 

brick column is at the center of the stair shaft. 
56 Dry Tortugas Lighthouse HSR 

Figure 36. 2008 view of Lighthouse looking north. 

The painted finish of the tower is showing signs of 

weathering and deterioration. There is no 

discernable pattern to the paint loss. 

Originally, the mechanism to deliver oil to the 

lamps was driven by weights which would rise 

and fall within the column. The interior ends of 

the stair slabs are set into the column. 

 Window openings are present at each of the 

intermediate landings. The windows are stacked 

vertically within the exterior wall. The windows 

on the first, third and fifth levels face east, 

towards Fort Jefferson and the entry door at the 

base of the tower and windows on the second 

and fourth levels face west. 

Existing Condition: With the exception of 

window placement, the characteristics of the 

tower are similar on each elevation. The 

observed conditions will be discussed according 

to the zones of the daymark, first the lower half 

of the tower or white zone followed by the 

upper half or black zone. Inspection of the 

conditions was made from grade using 10x25 

binoculars. 

There is universal deterioration and weathering 

of the painted finish of the tower. In general the 

paint continues to adhere well to the brick 

surface. However, it has deteriorated more 

rapidly from the mortar joints. There are broad 

areas where this condition is more severe. In 

general terms, the white paint of the lower half 

of the tower appears to be adhering to the brick 

better than the black paint of the upper zone. 

East Elevation: The lower half of the east 

elevation is in generally good condition. 

The brick, mortar and painted finish 

show only limited deterioration and 

weathering. A localized area of 

deteriorated mortar was noted around 

the lintel and above the first level 

window. 

The upper half of the east elevation is 

showing signs of moderate mortar 

deterioration as well as an area of 

significant spalling just below the belt 

course. Two significant vertical cracks 

and several other small areas of mortar 

deterioration were noted as having been 

repaired. The first crack extends 

vertically from the top of the fifth-level 

window for approximately 10’. The 

second crack is located toward the 

bottom of the upper zone and extends 

into the lower zone. These cracks as well 

as several spot repairs were easily 

identifiable due to the liberal application 

of a relatively light-colored mortar. 

West Elevation: The lower half of the 

west elevation is in generally good 
Physical Description 

National Park Service 57 

Figure 37. Vertical crack extending from head of 

fifth-level window. 

Figure 38. Close-up view of paint deterioration 

on exterior wall. 

Figure 39. Middle zone of north elevation. There is 

a perceptible seam or strip on this elevation that 

may be the attributed to the 1967 sand blasting 

project. 

condition. An area of minor 

deterioration, requiring repointing was 

observed near the transition to the black 

zone. 

The upper half of the west elevation has 

experienced more severe mortar degradation. A 

large percentage of this elevation is in need of 

repointing. Mortar joints appear weathered and 

recessed throughout much of the elevation. 

Joints that remain intact appear to have been 

repaired as part of several previous repointing 

campaigns. The belt course below the 

corbelling at the top of the zone is severely 

deteriorated. A small plate with a bolt and 

threaded rod is located below the fourth-level 

window. The threaded rod extends to the 

interior where it is bolted to a much larger iron 

plate. Its function is unknown 

North Elevation: The lower half of the north 

elevation is in generally good condition. In 

addition to the areas of paint loss there appears 

to be a perceptible strip extending from the 

upper zone to the lower zone. This may be 

attributed to the sand blasting that was 

completed in 1967 by the USCG. During this 

project an adjustment had to be made to the 

aggregate from silica sand to beach sand when 

it was discovered after the first pass that the 

cleaning process was damaging the host 

masonry. There are no windows in this 

elevation. 

The upper zone is experiencing significant 

deterioration of the mortar joints. The most 

severe weathering appears to be concentrated at 

the head joints. Near the top of the zone, just 

below the corbelling, spalling of the host 

masonry was noted. Also in this area there 

appears to be a subtle bulge in the masonry 

extending downward from the belt course. 

Portions of the belt course are severely 

deteriorated. 

South Elevation: The lower zone of this elevation 

is typical of the others in that it is in generally 

good condition but there are areas of minor 

mortar deterioration. There are no windows in 

this elevation. 

The central portion of the upper zone is 

experiencing moderate to severe mortar 

deterioration requiring repointing. There is 

evidence of a vertical crack in the lower half of 

the zone. The crack appears to have been 
58 Dry Tortugas Lighthouse HSR 

Figure 40. Exterior masonry conditions observed during site inspection conducted in 2009. 
Physical Description 

National Park Service 59 

Figure 41. Typical aluminum double-hung window 

unit. 

Figure 42. A concrete sill has been formed on top 

of the original granite sill at each window location 

to accommodate the installation of the modern 

aluminum sash. 

repointed in the past with non-matching mortar. 

The area of mortar deterioration extends into 

the corbelling at the top of the zone. 

Degradation of the head joints is most prevalent 

in this area. 

Analysis of the paint finish at the base of the 

tower revealed multiple layers of white or 

cream-colored paint. Observed under a 

microscope, the surface of the masonry, below 

the painted finish, appears weathered. This 

weathering would have occurred between 1858 

and the 1870s when the Lighthouse was 

unpainted. The earliest layers of finish appear to 

be a white lime wash followed by subsequent 

layers of paint. The Lighthouse, Kitchen and 

cisterns share a similar finish history (See 

Appendix B). 

Exterior Features 

Windows: There are five windows in the brick 

masonry portion of the tower and one window 

at the Watch Room level. The first, second, and 

third-level windows are in the lower or white 

zone of the daymark and the fourth and fifthlevel windows are in the upper or black zone. 

Each of the windows is recessed within the 

masonry wall of the tower approximately 6” 

from its face. No elements of the original 

windows survive. With one exception, the 

existing windows are modern bronze aluminum 

double-hung units installed in 1982. The 

window at the fifth level has been infilled with a 

simple plexi-glass panel set in a rough wood 

frame. 

The window rough openings are defined by an 

approximately 10” granite lintel and 4” granite 

sill with side walls of masonry. There is a row of 

brick headers above each lintel. The masonry of 

the rough opening steps in approximately 1 1⁄2” 

at the plane of the window providing a lip 

against which the unit is set. Clips have been 

installed on the window rails rendering them 

inoperable. A 2” high concrete sill reduces the 

height of the historic window opening. The sill 

was installed in 1967 to accommodate an earlier 

set of replacement windows. 

There have been several generations of windows 

installed in the Lighthouse. The historic 

documentation reveals that the original 

windows required replacement as early as 1860, 

two years after completion of the Lighthouse. 

Undated drawings of the tower show eight-overeight, double hung windows in each opening. 

This was the predominant window type used in 

nineteenth century lighthouse construction. The 

1861 standard specifications describe the 

windows as being constructed of iron and gun 

metal with inner and outer sashes. 

Images of the Lighthouse show both four-overfour double-hung windows and awning 

windows installed in the tower. The awning 

windows were installed in 1967. Exterior wood 

shutters were present on the windows up until 

the 1967 window replacement. Each of the 

tower windows had a pair of paneled shutters set 

within the rough opening that were held open 

with a member that spanned between the 

shutters (See images on p. 107). No evidence of 

the shutters remains. 
60 Dry Tortugas Lighthouse HSR 

Figure 43. Five-panel wood entry door to tower. 

Figure 44. This escutcheon plate and the mortise 

lockset are the only remaining hardware 

components. 

Tower Door: Originally exposed to the exterior, 

today the entry door to the tower is located 

within the 1927 concrete passageway. The door 

is set in a niche recessed approximately 3’ within 

the exterior wall of the tower. The entry 

sequence is rather plain when compared with 

Existing Condition: The existing aluminum 

window units are not in keeping with the 

historic character of the Lighthouse. In several 

locations, the existing windows have become 

loose in their rough openings, and at the second 

level, the window and frame have become 

completely unseated and the window is missing 

the upper glazed pane. Caulks or sealants have 

been applied to the interior perimeter of the 

windows. In some locations excessive amounts 

of the sealant have been applied in a haphazard 

manner. The caulks and sealants have become 

brittle and deteriorated and are not adhering to 

the material on which they have been applied 

and are no longer effective. other lighthouses 

constructed during the second half of the 

nineteenth century that have much more 

embellished entry ways including elaborate 

pedimented stone surrounds that are often 

adorned with a plaque commemorating the date 

the lighthouse was constructed. 

The date of installation of the existing door is 

not known and it is possible that it was relocated 

from another structure. It is a large, single-leaf 

wood unit with five horizontal molded panels. 

The door measures 3’-9 1⁄2” x 7’-8” x 2” and is 

hung with two large strap hinges. The strap 

hinges fasten to the door in an illogical manner 

(not centered on horizontal rails) and the 

proportions of the stiles and rails suggest the 

hinges do not relate to the existing door. A flat 

wood panel insert has been installed in the top 

and bottom panels to accommodate fastening of 

the hinges. The ghosting of four smaller hinges 

on the frame suggests that at least one other 

door was hung in the existing frame. A catch on 

the interior of the frame also does not relate to 

the existing door (See drawings on p. 72). 

The knobs and exterior key escutcheon have 

been removed. A mortise lockset is set within the 

door. The lockset was not removed to try and 

determine a date of manufacture. A rope 

threaded through the door provides a pull and 

the unit is secured by a modern hasp and 

padlock. 
Physical Description 

National Park Service 61 

Figure 46. 2009 image of Lantern following repairs 

(Photo Courtesy of Enola Contracting Services Inc.). Figure 45. 2008 image showing condition of 

Lantern prior to recent repairs. 

An analysis of the paint layers on the door and 

frame revealed that the frame contained more 

layers of paint when compared with the door. 

This suggests the frame predates the door (See 

Appendix B). 

Existing Condition: The existing tower door is in 

fair to poor condition. The door appears to be 

structurally intact, but many of its original 

hardware components are missing or have been 

modified. 

Watch Room: The exterior brick masonry walls 

of the tower terminate at the floor of the Watch 

Room gallery. The Watch Room walls are 

formed by the continuation of the walls of 

interior stair tower. The walls of the Watch 

Room are stuccoed on the interior and exterior. 

According to the historic documentation, the 

existing stucco was applied during a project 

completed in 1983. The floor of the Watch 

Room gallery was also repaired at this time. 

There is a window on the east elevation with a 

granite lintel and sill. The window frame and 

sash have been removed and a plywood panel 

has been installed in the opening. Opposite the 

window on the west elevation is an arched 

doorway that provides access to the Watch 

Room gallery. The iron door was recently 

removed during the Lantern repair project and 

is being stored at the Everglades National Park 

collection facility. A storm-proof plywood insert 

has been installed in the door opening. 

There are four solar panels mounted to the 

exterior wall of the Watch Room along the south 

elevation. The solar panels provide electrical 

power to the VRB-25 beacon. In addition to 

these, there are a number of other pieces of 

equipment along with their support members 

fastened to the Watch Room and Lantern 

galleries. 

There is a steel access ladder extending from the 

Watch Room gallery to the Lantern roof. The 

ladder was installed in 1978. Originally fastened 

to the Lantern with cables, the cables were 

replaced by steel straps after 1983. 

The existing Watch Room and Lantern gallery 

railings were installed in 1985. An 8” stainless 

steel tension ring located just below the floor of 

the Watch Room gallery was installed in 1967 by 
62 Dry Tortugas Lighthouse HSR 

Figure 47. Isometric of lantern structure developed 

by Mesick, Cohen, Wilson, Baker Architects as part 

of the construction document package for the 

2009 Lantern repair project. 

Figure 48. A member of the construction crew 

works on the Lantern structure in 2009. 

the USCG. This feature was installed to secure 

the masonry of the Watch Room gallery floor 

which was extensively repaired at the time. 

Existing Condition: Access to the Watch Room 

gallery could not be gained at the time of 

inspection therefore exterior conditions were 

reviewed from grade using binoculars. The black 

painted finish of the Watch Room exterior has 

deteriorated exposing the light-colored stucco 

beneath. The stucco finish is in deteriorated 

condition with moderate to severe cracking on 

all elevations. There is a significant vertical crack 

on the east elevation that extends through the 

brick masonry wall to the interior. There is 

evidence that some attempt has been made in 

the past to patch the cracked stucco. 

The existing modern access ladder is severely 

corroded. 

Lantern: The Lantern is a round, 16-segment 

structure with a skeleton of bronze and steel 

components and glazed walls. Until recently the 

Lantern was in an extremely deteriorated 

condition. A comprehensive repair project 

occurred in early 2009 and included the scaling 

and painting of corroded iron elements, new 

lantern glazing, fabrication and installation of a 

new copper roof and a new lightning protection 

system. 

Each bay of the exterior wall consists of three 

rectangular glazed panels separated by 

horizontal bronze mullions and vertical iron 

ribs. Each of the newly installed panels differ in 

height, the bottom panels measure 2’-6 13⁄16” X 2’ 

4 1⁄2”, the middle panels measure 3’-3 1

⁄8” X 2’-4 

1⁄2” and the top panel measures 3’-2 3⁄4” X 2’-4 

1⁄2”. The panels are 7

⁄16” thick tempered 

hurricane glass. Two bronze hand holds are 

present on the vertical astragals between each of 

the glazed panels. The new Lantern roof is 

composed of copper panels fastened with 

stainless steel clips to iron bar rafters. 

When the recent Lantern repair project was first 

envisioned, temporary means were going to be 

used to protect the deteriorated Lantern 

elements from further damage or loss. A review 

of the project budget revealed that a limited or 

partial restoration of the copper roof was 

possible with the available funds. It is for this 

reason that the newly installed roof does not 

fully replicate the historic condition. The agreed 

upon scope of work did not include restoration 
Physical Description 

National Park Service 63 

Figure 49. Image showing pitting corrosion on 

Lantern gallery floor plates. 

Figure 50. Undated image of the Lantern showing 

the second order bivalve lens in place. Note also 

the original ladder and pipe railings on the 

Lantern and Watch Room-level galleries. 

of the roof gutter system or repair or replication 

of the historic vent ball and lightning rod. As an 

interim design solution the copper roof panels 

have been extended behind the gutter support 

rail allowing rainwater to be shed from the 

structure and the vent ball was removed for 

reinstallation at a later date. 

The floor of the gallery is made up of flat plate 

iron segments that extend into the interior of the 

Lantern. The existing galvanized steel bar railing 

was installed in 1985 and generally matches the 

original in design with widely spaced support 

stanchions. The original rail appears from 

historic photographs to have been a tube railing 

that was threaded through eyelets on the 

support stanchions. The existing railing does not 

meet current safety codes. Undated twentiethcentury historic images of the Lighthouse show a 

ladder present at the Lantern and Watch Room 

gallery levels. A ladder on the galleries was a 

standard piece of equipment necessary for the 

keeper to clean the lantern glass and maintain 

the lantern roof. The ladder hooked over the rail 

that formed the edge of the integral gutter 

system. Below this another rail was provided for 

the Keeper to tie-off to as a means of fall 

protection. There is no ladder present on the 

Lantern or Watch Room galleries today. 

Existing Condition: The recently completed 

Lantern repair project has corrected a number 

of deficiencies and provided a secure and 

weather-tight enclosure to protect the lens and 

Lantern interior from the elements. Generally, 

the bronze components of the Lantern are in 

good condition and show few signs of 

deterioration or corrosion. Some of the iron 

head and rib components have experienced 

deep corrosion and have become deformed. 

During the recent repair project these elements 

were preserved in place, scaled and painted to 

slow the corrosive process and increase 

longevity. All of the newly installed glazing and 

the copper roof are in good condition. 

The iron floor plates of the gallery are showing 

signs of pitting corrosion. Pitting corrosion is a 

localized break down of metal that is common in 

marine environments where waterborne salts 

attack the metal surface. This type of corrosion 

can be problematic in that it can form deep holes 

and ultimately undermine the integrity of the 

material. 

The Lantern gallery railing is also showing signs 

of corrosion, specifically at its connection 

points. 

Interior Features 

Stairs: A spiral stair of approximately 4” thick 

solid blue slate treads ascends the tower from 

grade to the Watch Room level. There are 30 

individual treads between each of the five 

intermediate landings. The wedge-shaped treads 

are identical in dimension measuring 

approximately 6 1⁄2” where they meet the central 

brick column and 17” at the exterior wall. The 

treads are approximately 49 1⁄2” in width and 

have an 8” open riser. A row of headers is set 

above and below each tread where they are 
64 Dry Tortugas Lighthouse HSR 

Figure 51. 2009 view of Lighthouse upon completion of Lantern repair project (Photo courtesy of Enola 

Contracting Services Inc.). 
Physical Description 

National Park Service 65 

Figure 52. View of first four treads at base of 

tower. 

embedded within the tower wall. The surface of 

each tread has been textured with delicate 

striations made with a chisel in order to improve 

slip resistance. The textured surface is only 

visible in limited areas as the surface of the 

treads has been painted with a black slipresistant coating. 

The original architectural drawings for the 

Lighthouse show the central stair constructed of 

thick slabs set into the interior wall and central 

column. Constructing the stair of masonry 

deviated from the 1861 standard specifications 

which called for cast iron stairs for first-order 

towers. The similar Pensacola Lighthouse built 

the same year has an iron stair. The use of stone 

slabs at Dry Tortugas was likely influenced by 

the availability of the blue slate, as this is the 

same material used for flooring in casemates at 

Fort Jefferson, and was therefore readily 

available. 

It is much less likely that the deteriorative effects 

of the environment on iron was a consideration 

given that 20 years later the Lighthouse Board 

proposed a new structure entirely made of iron 

to replace the tower after it was damaged in the 

hurricane of 1873. 

The existing 11⁄4” diameter, schedule 40, 

aluminum hand rail was installed in 1967 by the 

U.S. Coast Guard. The aluminum hand rail 

brackets are fastened with 3

/8” lag bolts 

embedded 2” into the brick masonry wall. At the 

time of installation, existing original eye-bolts 

were removed and the anchor holes drilled out 

to accommodate the new anchors. The original 

railing was likely tubular steel threaded through 

the removed eye-bolt anchors, similar to the 

Watch Room and Lantern gallery railings visible 

in early photographs. What appears to be an eyebolt from the earlier railing system remains 

present between the fifth and sixth level. 

Existing Condition: The stone stair slabs appear 

to be in good condition. No signs of cracking of 

the slabs or failure at the connection to the 

masonry walls were noted. The underside of 

some of the slabs appears eroded or pitted, but it 

was unclear if this was the original condition of 

the slabs or the result of some kind of 

deteriorative process. Two treads, the fifteenth 

tread of the fourth flight and second tread of the 

fifth flight, have experienced cracking and 

therefore have been stabilized by sandwiching 

the slab between plywood boards. 

The existing hand rail is broken and loose in 

several areas. 

Interior Walls: The interior walls of the tower 

are identical from the ground level to the Watch 

Room. They are constructed of brick masonry 

laid in a Flemish bond. The walls have been 

painted white throughout the tower. At each 

landing there is a niche within the exterior wall 

that leads to a window. The brick walls of the 

niches are laid in a Common bond. The niches 

get smaller as the thickness of the exterior walls 

taper towards the top of the tower. Granite 

lintels form the ceiling of each niche. 

At the center of the tower is a hollow masonry 

column sometimes referred to as the “newel.” 

The column is made up of header courses and 

has an approximately 8” void in the middle. The 

inner ends of the stair treads are set into the 

masonry column. The column is painted white 

like the walls. The interior of the column has a 

smooth finish. There are two openings in the 

column, one at the base of the tower and one 

just below the Watch Room floor. The opening 

below the Watch Room floor was made to 

accommodate the lead weight for the clock 

works apparatus as shown in drawings from 

1911. Drawings from a year earlier show the 

ropes holding the weights descending through a 

hole in the center of the floor plate. This change 

was made in an effort to increase the rotation 

speed of the lens and thus achieve more flashes 

per time interval. 

The painted finish of the area above the fifth 

level appears much thicker than that on the 
66 Dry Tortugas Lighthouse HSR 

Figure 53. Hollow masonry “newel” at center of 

stair tower. 

Figure 54. Close-up view of deteriorated mortar 

joints of stair tower walls. Almost universally the 

surface of the mortar has become friable, falling 

from the wall as powder. 

Figure 55. Typical view of interior wall surface 

showing deterioration of mortar. Note the paint is 

adhering well to the brick but has failed at the 

mortar joints. 

Figure 56. The hollow shaft within the central 

masonry newel accommodated weights that drove 

various components of the lamp and lens 

apparatus. lower levels. The finish applied to the central 

brick column is so thick it obscures the bonding 

pattern. The heavy application of paint in this 

area may be the result of attempts to repair and 

seal these upper level walls as they became 

saturated and then deteriorated from moisture 

entering the wall system from above. 

Existing Condition: The primary condition 

problem noted on the interior walls of the tower 

is the deterioration of the cement mortar and the 

associated painted finish. These condition 

problems were observed universally at all levels 
Physical Description 

National Park Service 67 

Figure 57. Vertical crack extending down from 

Watch Room level floor plate. 

Figure 58. View looking up at the I-beams 

supporting the Watch Room level floor plate. 

of the tower, but the severity of the condition 

varied significantly from location to location. No 

discernable patterns of deterioration could be 

identified that would lead one to a specific cause 

for this condition. In general, the outer 1

/8” to in 

some cases 1” of the mortar has become friable. 

In some areas, the friable mortar remains 

trapped behind the painted finish. However in 

most cases the painted finish has also failed and 

the deteriorated mortar has fallen from the wall 

as fine sand. The head joints of the wall seem to 

be affected more severely than the bed joints. 

This condition was observed on the walls and 

the central column. The processes that are 

causing this condition are not entirely clear, but 

the migration of moisture through the wall 

assembly is thought to be at the root of the 

problem. 

The mortar joints and painted finish of the 

window niche walls were found to be more 

severely eroded than the tower walls. This was 

especially true at the lower level window niches. 

This condition has been most likely caused by 

the effects of wind and rain on these walls due to 

the windows being left open for prolonged 

periods of time. 

Several vertical cracks were noted above the fifth 

level landing. The cracks extend down from the 

iron ring embedded in the masonry wall as part 

of the structure of the Watch Room level floor 

plate. These cracks may be associated with 

corrosion and expansion of anchor rods placed 

within the walls to secure the Watch Room floor 

plate to the masonry tower. 

Watch Room: Today, the Watch Room contains 

the lens pedestal installed in 1910-1911. The 

center portion of the Watch Room floor is a cast 

iron plate supported by four I-beams set upon 

an iron shelf embedded in the exterior masonry 

walls. Two of the I-beams span over the central 

brick column. The flooring around the 

perimeter of the room is diamond-plate panels 

hung by brackets from the exterior masonry wall 

and then secured to th e central plate 

Architectural drawings from the 1911 

modifications of the lens show the floor was 

designed to be 2 1⁄2” x4” tongue-and-groove 

wood flooring. It is unknown if the wood 

flooring was installed and then later removed. 
68 Dry Tortugas Lighthouse HSR 

Figure 59. Vertical crack in watch room wall 

extending down from Lantern level floor plate. 

Figure 60. The original arched iron door has been 

recently removed and replaced with a plywood 

insert. 

The walls of the Watch Room are painted stucco 

over brick masonry. Beneath the painted finish, 

the stucco is grey in color and very hard 

suggesting it is a Portland cement based mixture. 

There are three bronze vent holes that penetrate 

the walls of the Watch Room. Air flow through 

the vents is controlled by a rotating damper. 

The vents were necessary in order to maintain 

air flow through the lantern so that fumes and 

smoke created by the oil-fired illuminant would 

be expressed through the ventilation ball in the 

roof of the lantern. The draft that was created 

also helped to keep the lantern glass free of 

condensation. A number of the vents are being 

used as conduit to route cables from the interior 

to the exterior of the Lighthouse and therefore 

by default are left fully open all of the time. 

The pedestal that originally supported the 

rotating second-order lens is positioned in the 

center of the room. All of the components of the 

pedestal, as depicted on the original drawings, 

remain present with the exception of the 

clockworks. The largest component of the 

pedestal is the mercury float drum. In December 

1986 a minor mercury spill occurred in the 

Watch Room. The contaminated area was 

subsequently cleaned and the spilled mercury 

removed and disposed of according to 

applicable requirements. This spill likely 

influenced the decision to upgrade the optic to 

an automated beacon. 

A window opening present on the east wall of 

the Watch Room contains a plywood insert. No 

components of the original window remain 

present. 

An arched doorway located on the west wall 

provides access to the Watch Room gallery. The 

door was removed during the recent Lantern 

repair project and a plywood insert installed. 

A set of iron stairs are located along the west 

wall. The open stair treads are set into the 

exterior masonry wall and hung from the 

Lantern level floor to provide access between 

the two spaces. 

There are several equipment panels mounted to 

the wall that are associated with the solar power 

generation for the VRB lamp. The panels are the 

panels, there are several weather-proof 

equipment cases stored under the mercury float 

drum. mounted to a channel frame that is 
Physical Description 

National Park Service 69 

Figure 61. Portion of lens pedestal and support 

structure. 

Figure 62. Iron stair between Watch Room and 

Lantern. 

through-bolted through the exterior wall. In 

addition to 

Existing Condition: The general character of the 

Watch Room appears today much as it would 

have in 1911 when the second order rotating 

lens was installed. There is extensive cracking of 

the stucco wall surface. Cracks range in size 

from hairline cracks to a vertical crack on the 

east wall that is 1⁄4” in width. This crack and a 

number of others originate where the ribs of the 

Lantern level floor plates enter the wall. These 

cracks may be the result of the corrosion and 

expansion of the iron anchors that were 

extended within the masonry wall as part of the 

repairs following the 1873 hurricane. The large 

1⁄4” crack extends through the masonry wall and 

is expressed on the exterior of the Watch Room. 

The bronze components of the ventilation 

dampers are in good condition, but the center 

cap is missing on at least two of the vents. The 

missing caps inhibit the correct operation of the 

vents as do the numerous cables that have been 

routed through the vents. 

The iron components of the lens pedestal as well 

as the diamond-plate floor panels, brackets, and 

iron stair to the Lantern room are experiencing 

moderate surface corrosion. 

Lantern Room: The Lantern Room underwent 

an extensive program of repairs in early 2009. 

The floor of the Lantern Room, around the 

perimeter of the space, consists of individual 

iron plates that extend under the glazed wall to 

form the floor of the gallery. The lens pedestal 

assembly extends up from the Watch Room 

below filling the void in the center of the room. 

There is a bronze ladder incorporated into the 

pedestal assembly that originally provided access 

into the center of the bi-valve lens. 

The segmented walls of the Lantern Room are 

entirely glazed. Vertical iron ribs and horizontal 

bronze mullions separate the glazed panels. The 

bronze sill of the glazed wall panels is shaped 

like a trough to collect water and condensation. 

The water is shed to the exterior through small 

weep holes. 

A second inverted beacon is hung from the iron 

ribs of the roof structure by threaded rods. This 

beacon provides back up to the main optic and is 

only lit when there is a problem with the primary 

light. 
70 Dry Tortugas Lighthouse HSR 

Figure 63. 2009 view of Lighthouse Lantern. 

Figure 64. VRB-25 marine rotating beacon 

currently installed in tower. 

The original liner or lantern hood remains 

present and is mounted within the roof structure 

of the Lantern. This hood funneled smoke from 

the oil burning lamp toward the ventilator ball. 

The second-order lens manufactured by Henry 

Lepaute and installed in 1911 was removed in 

1986 and is now on display at the National Aids 

to Navigation School in Yorktown, Virginia. The 

platform on which the lens was mounted 

remains in place as part of the pedestal assembly. 

The new VRB-25 marine rotating beacon is 

platform. The optic was manufactured in New 

Zealand and installed in the Lighthouse in 1996. 

Existing Condition: The Lantern elements are in 

generally good condition due to the recent 

program of repairs. The character of the Lantern 

Room interior has been diminished by the 

removal of the earlier prismatic lenses and 

installation of the much smaller modern 

electronic beacons. The glazed wall and roof 

elements are all in good condition. 

The underside of the iron floor plates are 

experiencing moderate to severe corrosion. The 

corrosion appears to extend into the masonry 

wall where it may be exerting pressure on the 

masonry and causing cracking of the walls 

below. 

The Lantern hood has been dented and 

deformed but remains in stable condition. This 

feature was removed and reinstalled as part of 

the recent repair program. The surface of the 

hood is rusted and the painted finish is 

substantially deteriorated. 

The gallery level railing is experiencing 

moderate corrosion, particularly at its 

connection to the gallery floor. 

Utilities 

Electrical System: The lights that illuminate the 

interior stair of the Lighthouse are powered by 

the photovoltaic (pv) system installed by the 

National Park Service in 2002. This system also 

provides power to the Oil House and all of the 

other Light Station structures. The Lighthouse 

beacons are powered by solar array panels 

mounted to the south wall of the Watch Room 

gallery. The inverter and distribution panels for 

this system are mounted to the wall of the Watch 

Room. Also in the Watch Room are several 
Physical Description 

National Park Service 71 

Figure 65. Equipment mounted to the Watch Room 

wall associated with the solar collection system 

that provides power to the primary and secondary 

beacons. 

Figure 66. Exterior elevation of Lighthouse entry 

door. 

Figure 67. Section though entry door jamb. 

Figure 68. Section though entry door. 

 
72 Dry Tortugas Lighthouse HSR 

weather-proof cases that contain banks of 12V 

Delco – 2000 Series batteries used to back up the 

system. This system is maintained by the USCG. 

The Lighthouse is not serviced by any other 

utilities. 

Summary of Conditions 

The following is a summary of the condition 

issues observed during inspection of the 

Lighthouse. 

Description of observed condition 

Tower Exterior 

 Painted finish of the daymark has 

weathered/deteriorated reducing its 

intensity and protective qualities. 

 General weathering/deterioration of the 

tower’s mortar joints. 

 Localized areas of severe 

weathering/deterioration of the tower 

brick and mortar joints. 

 Vertical cracking of masonry walls 

below Watch Room and at fifth level 

window 

 Existing bronze aluminum window units 

are in poor condition and are not in 

keeping with the historic character of 

the Lighthouse. Installation of a raised 

concrete sill at window openings. 

 Tower entry door is missing hardware 

components. 

 Deterioration of exterior paint at Watch 

Room level walls. 

 Deterioration/cracking of stucco finish 

at Watch Room level walls. 

 Through-wall crack on south elevation 

of Watch Room. May be associated with 

corrosion of embedded iron anchors. 

 Corrosion and code compliance of 

Watch Room gallery railing. 

 Installation of solar panels on Watch 

Room gallery. 

 Moderate to severe corrosion of gallery 

access ladder. 

 Moderate to severe pitting corrosion of 

Lantern gallery floor plates. 

 Several iron headers of Lantern 

structure have become severely 

deformed and weakened due to 

corrosion. 

 Full replication of dome roof features 

was not completed as part of recent 

repair program. Roof edge and integral 

gutter system were not replicated. 

Existing ventilation ball and lighting rod 

assembly was found to be in poor 

condition and removed. 

 Arched iron door to Watch Room 

gallery was dislocated from hinges and 

found to be in poor condition and 

removed during recent repair project. 

 Corrosion and code compliance of 

Lantern gallery railing. 

Tower Interior 

 General deterioration of painted finish 

of stair tower walls and central newel. 

 General deterioration of mortar joints of 

the stair tower walls and central newel. 

 Localized moderate to severe 

deterioration of the mortar joints of the 
Physical Description 

National Park Service 73 

Figure 69. View of oil house looking northwest. Reinforced concrete passageway and concrete block addition 

are also visible in this image. 

stair tower walls and central newel. 

 Broken/temporarily stabilized stair 

treads (2). 

 Stair rail is broken in several areas. 

 Moderate corrosion of iron sill plate and 

ends of I-beams supporting Watch 

Room level floor plate. 

 Missing caps on bronze vent hole 

dampers as well as the fishing of cables 

through the vent holes to the galleries 

preventing their correct operation. 

 Hatch through Watch Room floor plate 

is no longer extant. 

 Modern conversion and distribution 

panels for the solar collection system 

installed on the Watch Room walls. 

 Second-order bivalve lens was removed 

in 1986 and replaced with the VRB-25 

rotating beacon changing the character 

of the Lantern Room. 

 Corrosion of iron floor plates and their 

potential impacts on masonry. 

 General surface corrosion of lens 

pedestal components. 
74 Dry Tortugas Lighthouse HSR 

Figure 70. Portion of undated historic image 

showing unpainted oil house. Note also the 

presence of a chimney on the south elevation. 

Dry Tortugas Light Station Oil House 

The Dry Tortugas Light Station Oil House was 

constructed in 1858 as an original component of 

the Light Station. Originally a free-standing 

building, the small (14’ x 16’), two-story, loadbearing brick masonry structure was connected 

to the Lighthouse in 1927 and further altered by 

the construction of two additions. Although the 

original building remains discernable, the 

additions have altered the structure’s massing 

and character. 

The 1857 architectural plans for the Lighthouse 

show an Oil House attached directly to the base 

of the tower, consistent with the standard 

specifications developed by the Lighthouse 

Board from just after the construction period. 

This suggests that the decision to construct the 

Oil House as a free-standing building was an 

afterthought, possibly made following initial 

design or during construction. It is unknown 

why the decision was made to depart from the 

standard design for the Dry Tortugas 

installation. 

A concrete passageway connecting the Oil 

House to the base of the tower was constructed 

in 1927 when the function of the building was 

changed from storing oil to housing radio 

beacon equipment. At the time of its conversion 

a new one-story Oil House was constructed just 

to the north of the existing structure. 

Between 1935 and 1941 a one room reinforced 

concrete addition was constructed on the west 

elevation of the former Oil House. A second 

wood-frame gable roofed addition was 

constructed after 1943 extending from the south 

elevation. This addition was removed in 1969 

and then later in 1982 was replaced with a 

slightly larger reinforced concrete structure. 

Construction of the additions and changes in 

building’s function over time resulted in the 

modification of all but two of the Oil House’s 

original openings. The original openings are 

identifiable by their granite lintels and sills. 

None of the original windows or frames has 

survived. 

The cornice of the front facing gable roof is 

distinctive in that the roof slope terminates at 

the top of the exterior masonry walls with no 

overhang. Although this design is not consistent 

with the original Lighthouse plans which shows 

the proposed Oil House with overhanging eaves 

supported by brackets, this same minimalist 

cornice detail is seen on structures at other 

nineteenth century light stations. Historic 

images of the Dry Tortuga Light Station dating 

from the turn of the century show this simple 

cornice arrangement employed on all of the 

station’s buildings. Elimination of the traditional 

overhanging eaves can almost certainly be 

attributed to the desire to reduce building 

features that would be susceptible to damage in 

the high winds and hurricanes common to the 

region. Originally slate, the roof is currently 

covered with modern asphalt shingles. 

Originally unpainted, the exterior of the Oil 

House received a white lime-wash finish in the 

1880s or 1890s. Analysis of paint samples taken 

from the building exterior reveals multiple layers 

of white or cream-colored paint have been 

applied to the building over the years (See 

Appendix B). 

The interior of the Oil House has also been 

extensively modified. The original Lighthouse 

plans show the first floor of the proposed Oil 
Physical Description 

National Park Service 75 

House divided into three sections, a central 

corridor with small narrow rooms on each side. 

This common plan configuration included an oil 

storage room on one side and a work room on 

the other. Currently the first floor of the Oil 

House is a single undivided space. Due to the 

installation of later wall, floor and ceiling 

finishes it could not be determined if this space 

was originally divided as indicated on the 

original plans. It is possible that due to the 

remoteness of the Station, and the need to 

stockpile materials, that the entire first floor may 

have been dedicated to the storage of oil and 

that the second floor was reserved for 

workroom functions. Correspondence from the 

1920s states that there were eight, 30-inch steel 

oil tanks housed on the first floor of the 

building. 

The original drawings and historic images show 

a chimney or flue penetrating the roof in the 

southeast corner of the building. The first and 

second floor bead-board ceiling finishes have 

been disrupted where the flue would have 

penetrated the ceiling, suggesting the small 

fireplace shown on the original building section 

was removed after the 1920s modifications. In 

addition to servicing the fireplace, it is likely the 

flue was also used to ventilate fumes that would 

accumulate in the oil storage room. 

The interior finishes of the second floor are 

primarily the product of the1920s renovation 

that occurred as part of the buildings conversion 

to a radio beacon house. Originally plaster, the 

walls and ceilings of the first and second floors 

were furred out and covered with bead board at 

this time. Modern wood paneling has been 

applied directly onto bead board walls on the 

first floor. There is an open stair along the north 

wall as indicated on the original architectural 

plans. This feature may date to the original 

construction. 

Character-Defining Features 

Character-defining features of the Oil House are 

those visual and tangible elements of the 

structure that are significant and give the 

resource its distinct character. These features 

include elements of its original design and 

construction as well as modifications made 

during the historic period. The characterdefining features of the Oil House should be 

retained and preserved as part of ongoing 

maintenance and repair activities. The identified 

character-defining features of the Oil House 

include: 

 Isolated and sparsely vegetated 

subtropical setting – The character of the 

surrounding landscape is one of light 

station’s most unique and important 

features contributing greatly to the 

resources sense of place. The relatively 

recent program to remove invasive species 

introduced by the Carnegie Institute in the 

early twentieth century has returned the 

landscape to a condition that is generally 

consistent with its nineteenth century 

appearance. 

 Two-story building form with projecting 

one story concrete and concrete block 

additions. 

 Front facing gable roof with simple 

cornice. 

 Painted brick exterior walls. 

 Bead-board wall and ceiling finishes 

installed beneath modern wood paneling. 

 Interior open wood stair to second floor. 

 Windows are considered characterdefining features of the Oil House. 

However, the existing modern units 

diminish rather than enhance the historic 

character of the structure. 

 Although the existing door of the Oil 

House has been modified and its date of 

installation is unknown, it should be 

considered a character defining feature. 

Structural Systems 

Foundation: The level of grade around the 

perimeter of the Oil House did not permit 

inspection of the building foundation. The 

exterior load-bearing masonry walls extend 

below grade without interruption. Information 

on the original architectural drawings stops at 

grade providing no detail about the designed 

depth or configuration of the foundation of the 

Oil House. The 1861 standard specifications 

issued by the Lighthouse Board calls for an 18” 

thick rubble masonry foundation extending 

three feet below and three feet above grade. 
76 Dry Tortugas Lighthouse HSR 

Figure 71. Image of roof framing members taken 

in attic of Oil House. Note evidence of moisture, 

minor termite damage and the different patina of 

the members. 

Undated early drawings of the Keeper’s 

Residence and detached kitchen building show 

load-bearing brick masonry walls extending 

approximately 1’-6” below grade to a concrete 

foundation 2’-3” in width and 1’-6” in depth. 

Given these structures were built 

contemporaneously with the Oil House it is 

plausible that the foundation design for the Oil 

House would be substantially consistent with 

these other buildings. 

Existing Condition: No cracking of the exterior 

walls that would suggest active settlement or 

movement of the foundation was noted. The 

build-up of finishes on the brick exterior made it 

difficult to detect the presence of repaired 

cracks that may have occurred as a result of 

previous settlement. 

Floor Structure: The first floor of the Oil House 

is concrete slab installed after 1926. The existing 

slab is raised approximately 6” above the 

elevation of the original threshold suggesting it 

was poured on top of an earlier floor slab. 

The same undated drawings of the keeper’s 

residence and kitchen building mentioned above 

show the floor framing of these structures raised 

above grade on wood joists with a 2’-6” crawl 

space below. 

The 1861 standard specifications calls for oil 

house floors to be paved with hard bricks laid on 

edge. Given the first floor structure would have 

been required to carry the substantial weight of 

the stored oil, it is likely that the first floor 

structure would have been installed as a slab or 

brick pavers directly over compacted sand or 

soil. 

The 1926 construction drawing prepared when 

the Oil House was converted to a radio beacon 

house shows the first floor structure as a 

concrete slab in line with the original stone 

threshold. The existing raised slab may have 

been installed due to the poor condition of this 

earlier slab or to protect the radio beacon 

equipment from potential flooding (See drawing 

on p.91). 

The second floor framing was not accessible at 

the time of inspection, but the 1926 documents 

mentioned above shows the framing as 2” x10” 

joists spanning the building from north to south. 

The joists are shown to be fire-cut at one end. 

Fire-cutting refers to the technique of cutting 

the ends of the joists at an angle so that in the 

event of a fire, the joists would burn through and 

fall out of the masonry wall without collapsing 

the wall itself. Application of this construction 

technique is consistent with the original purpose 

of the structure as a storage space for highly 

flammable materials. 

Existing Condition: The first floor slab is in good 

condition. No major cracking or signs of 

settlement or deterioration were noted. 

Although, installation of floor and ceiling 

finishes prevented the visual inspection of 

second floor wood framing members, no signs of 

settlement were noted. 

Roof Structure: Access to the attic of the Oil 

House is provided through a hatch in the second 

floor ceiling. The gable roof of the building is 

framed with 3” X 5” circular-sawn rafters spaced 

at 16” on center with no ridge board. One of the 

rafters appears to have been recently replaced. 

The ceiling joists are 2” x 6” circular-sawn 

boards spanning the width of the structure. The 

joists are fastened to the rafters approximately 

1

/3 up their slope increasing the height of the 

second floor ceiling. The finish or patina of the 

rafters and the ceiling joists differs significantly. 
Physical Description 

National Park Service 77 

Figure 72. Image showing interruption of second 

floor ceiling finishes in the southeast corner of the 

room where the chimney for the fireplace would 

have penetrated the roof. 

The rafters are dark brown unfinished wood 

while the joists have a deteriorated white-wash 

or white paint finish. 

Historic images of the Oil house indicate a 

chimney penetrating the roof at the southeast 

corner of the building. No indication of the 

chimney was visible within the attic space. The 

Oil House underwent extensive roof work 

during the 1982 improvements. 

Existing Condition: The attic space was dry at the 

time of inspection. No evidence of active leaks 

was observed, but some moisture staining was 

noted on the ceiling joists. In addition minor 

termite damage was observed on several rafters. 

No active termites were observed. 

Exterior Features 

Roofing: The gable roof of the Oil House is clad 

with modern, gray, thee-tab asphalt composition 

shingles. Reference to the Oil House’s original 

roofing material is not recorded in the historic 

documentation. However, it is likely the building 

was originally clad with slate, as this is the 

material called for in the 1861 standard 

specifications. In addition, an archaeological 

survey conducted in 1998 of the area around the 

Lighthouse and Oil House yielded significant 

amounts of slate roofing tile. 

An undated twentieth century image of the Oil 

House shows the building with a standing seam 

metal roof. 

The roof sheathing, visible from the attic space, 

is relatively new plywood. The roofing finish is 

attached to the sheathing with wire cut nails. 

The 1861 standard specifications call for a 

sheathing of 1” boards and for the slates to be 

fastened with zinc nails. 

The building currently does not have gutters or 

downspouts. Historic images show no evidence 

of these features having been installed on the 

building in the past. 

Existing Condition: The existing composition 

shingle roofing is in generally good condition, 

but several shingles are missing. 

Roof Cornice: The top of the exterior wall is 

corbelled out for two courses creating a simple 

masonry cornice along the sides of the building. 

The roof rafters have been cut so that the roof 

finish intersects with the top of the masonry wall 

eliminating a roof overhang. The corbel has been 

painted dark green along the north elevation but 

remains white, like the body of the structure, 

along the south elevation. On the east and west 

gable ends a simple 1” x 6” rake board makes up 

the cornice. Copper roof flashing covers 

approximately one-half of the fascia board at the 

gable ends and covers the top masonry course 

along the sides of the building. Elimination of 

roof overhangs and millwork cornice 

components is likely a response to the climatic 

conditions of the region. 

Existing Condition: The wood elements of the 

cornice are in fair to good condition. The 

painted finish shows minor signs of 

deterioration, but remains intact. 

Exterior Walls: The exterior walls of the Oil 

House are load-bearing brick masonry. Visible 

from within the attic, the bricks range in color 

from a light orange or salmon to a deep red or 

purple and contain dark inclusions similar to the 

bricks used in the construction of Fort 
78 Dry Tortugas Lighthouse HSR 

Figure 73. East elevation of Oil House with 

reinforced concrete passageway. 

Jefferson’s scarp wall. The coursing of the 

masonry in the attic is consistent with the 

Common bond pattern (header row every 6th

course), but the extreme build-up of finishes on 

the exterior of the building makes it difficult to 

verify if this coursing is carried to the exterior. 

Lime-washing of the Oil House’s exterior 

occurred sometime after the 1880s or 1890s. An 

early undated image of the Light Station shows 

the Oil House unpainted. 

Paint analysis showed the exterior of the Oil 

House, lower half of the Lighthouse and brick 

cistern had a similar finish history. The earliest 

finish layers indicate that a lime wash was first 

applied to the structure followed by successive 

layers of white or cream-colored paint. 

Sampling and analysis of the Oil House mortar 

revealed that it consists of one part natural 

cement to one–and-one-half parts local 

carbonate sand. Analysis further determined this 

mix is common to all of the original Light Station 

structures (See Appendix B). 

Existing Condition: The build-up of finishes 

makes it difficult to assess the underlying 

condition of the exterior bricks and mortar. No 

obvious signs of masonry deterioration were 

noted. No flaking or bubbling of the painted 

finish was observed and there were no signs of 

spalling or deterioration of the underlying host 

masonry. The mortar joints did not exhibit any 

perceivable tooling, appearing to be brought 

flush with the brick. 

In numerous locations, iron anchors and 

eyebolts have been embedded within the 

exterior masonry wall. In a few areas these items 

are corroding and staining the exterior paint. 

Continued corrosion and expansion of these 

elements may result in localized damage to the 

masonry. 

East Elevation: The east, or primary elevation of 

the Oil House, faces the Lighthouse. The main 

entrance to the Oil House is located on this 

elevation. The ca. 1890s image of the Light 

Station does not show a second floor window 

present on this elevation. It is likely the second 

floor window was added after 1933 when a 

request was made to install two new windows in 

the building to provide increased ventilation to 

help dissipate the summer heat from the 

structure. 

Originally exposed, most of the first floor of this 

elevation is now enclosed within the concrete 

passageway constructed between the Oil House 

and Lighthouse in 1927. Evidence of a small 

window south of the first floor entryway outside 

of the connector was noted during inspection. 

Now infilled with masonry, the distinct outline 

of a small window and its associated lintel and 

sill could be discerned within the masonry wall. 

An undated image of the Oil House shows a 

window present in this location. 

West Elevation: The lower portion of this 

elevation is covered by the radio beacon 

equipment room addition added to the rear of 

the Oil House between 1935 and 1943. As part of 

the expansion, the first floor window in the west 

elevation was replaced by a 3’ x 7’ door installed 

to provide access to the addition. According to 

the construction drawings, the removed window 

was to be salvaged and installed in the west 

elevation of the addition. This window has since 

been removed and there is currently no window 

in the opening. 

 
Physical Description 

National Park Service 79 

Figure 74. North elevation of Oil House. 

Figure 75. West elevation of oil house with 1935-

1943 addition in foreground. 

The second floor of the west elevation contains a 

window. With the exception of the entrance on 

the east elevation, this is the only original 

opening that has not been altered. 

North Elevation: This elevation contains no 

openings. No physical evidence of previous 

openings is present and historic photographs do 

not indicate openings on this elevation during 

the historic period. There are two small holes 

penetrating the wall just below the cornice. 

Their purpose is unknown. There are several 

anchors or iron elements embedded within the 

masonry. The interior stair from the first to 

second floor is located on this wall which may be 

the reason for the absence of fenestration. 

South Elevation: The south wall of the Oil House 

is exposed within the concrete addition. There 

are several electrical panels installed on the east 

half of the wall and evidence of a previous door 

opening is present on the west half of this 

elevation. Originally a window, the opening was 

extended to the floor at some point in the past to 

accommodate a door. The opening has been 

infilled with brick. Historic images as well as the 

1926 architectural plans of the Oil House show 

window openings on the first and second floor. 

The original opening on the second floor was 

altered when the gable-roofed, wood-frame 

addition was constructed. A single “propellertype” shutter dog or tie-back remains embedded 

in the wall at bottom corner of the second floor 

opening, just above the roof line of the concrete 

block addition. Images from the 1960s show 

shutters present on the window openings and 

correspondence from 1933 talks about replacing 

the “old wooden shutters” on the Oil House 

with storm shutters. 

Doors: The entry door to the Oil House is 

located on the east elevation. The existing 1 3⁄4” 

thick wood door has been modified. The door 

appears to have originally been a screen door 

with a central rail separating large, open, upper 

and lower panels. A plywood panel has been 

applied to the exterior side of the door giving it 

the appearance of a flush door. The door does 

not have any hardware with the exception of a 

modern hasp and padlock that secures the door, 

and a rope for a pull. The door is attached to the 

frame with two bronze butt hinges. 

 
80 Dry Tortugas Lighthouse HSR 

Figure 76. Propeller type shutter dog in wall below 

second story window on south elevation. 

Figure 77. North elevation of Oil House. 

Existing Condition: The door and frame are in 

fair condition. Like the tower door, the handle 

set and locking hardware are no longer present. 

two-pane, awning windows with bronze 

aluminum frames. The window on the west 

elevation is a five-pane, awning window with an 

unfinished aluminum frame. Hurricane shutters 

were installed over all of the windows at the time 

of inspection. 

Historic images of the Oil House from the latenineteenth century show six-over-six or eightover-eight double hung windows with a lightcolored painted finish on the sash and frames. 

By 1926 it appears these windows had been 

changed to four-over-four, double-hung units. 

Existing Condition: The existing modern 

aluminum windows are in fair to poor condition. 

In all instances the hardware is broken rendering 

the windows inoperable. A pane is broken out of 

the window on the east elevation. The metal 

components of the windows are significantly 

corroded. 

Interior Features 

Room OH101 

Floor: The existing floor of the Oil House is a 

concrete slab installed sometime after 1926. The 

floor is currently painted gray. There are several 

layers of paint on the floor including an 

intermediate layer of bright red paint. There are 

discernable ghost patterns in the floor that may 

correspond to the placement of radio beacon 

equipment. The ghosting does not appear to 

correspond to previous partition locations. A 

raised pedestal is located beneath the stair. 

covers the walls. The wood paneling has been 

applied directly over 4” wide bead-board walls. 

The bead-board wall is furred out from the 

masonry wall on 3 1⁄2” framing. A hole through 

the wall allowed this assembly to be recorded. 

From this hole, it was observed that there is an 

approximately 5

/8” layer of plaster applied to the 

interior face of the masonry. The historic 

documentation confirms that the original wall 

finish in the oil house was plaster. It appears 

from the 1926 architectural drawings for the 

addition that the installation of the furred out 

bead-board walls occurred as part of the 

conversion of the Oil House to Radio Beacon 

House. It should be noted that the wood 
Physical Description 

National Park Service 81 

Figure 78. Image showing bead board wall finishes 

below wood paneling. 

Figure 79. An open stair leading to the second 

floor is located along the north wall of Room 

OH101. 

paneling and bead-board walls terminate at the 

infilled opening on the south wall suggesting this 

opening was present when the modern paneling 

was installed. 

Ceiling: The ceiling is covered with 3 1⁄2” beadboard running east-west. The bead-board has 

been patched in the southeast corner of the 

room where the fire place flue would have 

penetrated the ceiling. There is also an oval 

stove-pipe cover centrally located in the room. 

Stair: A flight of stairs along the north wall 

ascends in a straight run up to the second floor. 

The stairs have 7 1⁄2” open risers attached to a 2” 

stringer that extends down to the floor. The 

backside of the stair is clad with 3 1⁄2” beadboard. The treads measure 10” and have a 

rounded nose. A simple 1 1⁄2” diameter pipe 

railing is attached to the wall. 

Existing Condition: The stair is not exhibiting any 

signs of deterioration and its materials are in 

generally good condtion. 

Walls: Quarter-inch, modern-era wood paneling 

Moldings: A simple 3” baseboard with a natural 

finish is present in Room OH101. There is no 

shoe-molding present. The 1927 door opening 

in the west elevation has a simple 6” wide casing 

at the head and jambs. The jamb casings 

terminate into the head which extends past the 

jamb casings approximately 1⁄2”. 

Although the casing and jamb assembly at the 

main entry door is different, it was likely 

installed as part of the same 1927 renovation of 

the building. The casing is 3 1⁄2” wide and is 

chamfered to meet a 1” half-round molding that 

forms the transition between the jamb and 

casing. 

Existing Conditions: The condition of the 

finishes in Room OH101 is good. Items noted 

include paint build-up, loose boards and 

moldings and isolated holes or damage. 

Room OH201 

Floor: The flooring of the second floor is 12” x 

12” vinyl tile. The 1926 architectural drawings 

indicate 1”x 6” wood flooring applied directly to 

the wood floor joists. 

Walls: The walls are clad with 4” bead-board, 

furred out from the masonry wall as indicated 
82 Dry Tortugas Lighthouse HSR 

Figure 80. Interior image of second floor of Oil 

House. 

Figure 81. South elevation of Oil House. 

on the 1926 drawings. The original plaster finish 

is visible through a small hole in the bead-board. 

A patch in the bead-board is present below the 

south window confirming the window was 

modified following the 1927 renovations. The 

stair is enclosed by a thin frame wall clad with 

flush vertical boards. 

Ceiling: The ceiling is clad with 4” bead-board 

running east-west and may have been installed 

during the 1982 repairs. The ceiling angles down 

to meet the walls and is trimmed with a simple 

cavetto profile wood molding. A patch is present 

in the ceiling in the southeast corner of the room 

where the masonry from the fireplace was 

removed. 

Moldings: All of the windows are cased with flat 

1” x 6” boards with mitered corners. A simple 3 

1⁄2” baseboard is installed around the perimeter 

of the room. 

Existing Condition: The condition of the finishes 

in Room OH201 is good. Items noted include 

paint build-up, loose boards and moldings and 

isolated holes or damage. 

Concrete Passageway (1927) 

The Concrete Passageway connecting the 

original Oil House to the Lighthouse was 

constructed in 1927. The passageway was 

constructed as part of the Oil House’s 

conversion to a Radio Beacon House. The stated 

purpose of the passageway was to protect the 

radio beacon equipment from getting wet when 

opening the door during inclement weather and 

also to provide safe passage for the keeper when 

passing between the radio beacon room to the 

Lighthouse during the same. 

The Passageway is a one-story reinforced 

concrete structure that spans between the 

original Oil House and the Lighthouse. The 

structure has a flat roof with flanking parapet 

walls and provides a 5’-0” corridor between the 

two structures. The walls are 8” thick and the 

foundation is shown on the original 

architectural drawings to extend 3’-0” below 

grade. The interior and exterior of the 

passageway is painted concrete. Aligned 

doorways at the east end of the structure, 

adjacent to the tower, provide access through 

passageway. The concrete at the head of the 

doors projects to provide a drip edge over the 

door opening. The roof is sloped 1⁄2” per foot to 

the north and is drained by two, 2” galvanized 

pipes that penetrate the parapet. 

Correspondence from the period of 

construction indicates the use of reinforcing in 

the construction of the Passageway was a 

contentious issue. Although the original 

architectural drawings call for its use, the 

Superintendent of Lighthouses cites at the time 

that present practice and experience within the 

region dictate that reinforcing should be 
Physical Description 

National Park Service 83 

Figure 82. Original 1926 drawing of the reinforced concrete passageway connecting the Radio Beacon House 

(former Oil House) to the Lighthouse. 

eliminated from the design. He goes on to more 

strongly state his position: 

“Notwithstanding the distance it is to be 

located from the surface the reinforcing will 

eventually result in extensive repairs from 

time to time and the ultimate destruction of 

the walls and roof. In the opinion of this 

office it is unnecessary and detrimental rather 

than beneficial. As a matter of information it 

might be stated that this office does not know 

of a single piece of reinforced concrete in this 

district, similarly situated, that has been in 

service 10 years but what is now seriously 

affected and in some instances replacements 

are only a question of a short time.” 3

The reinforcing was ultimately installed in the 

walls. The original architectural drawings call for 

the reinforcing to be “thoroughly covered with a 

thin coating of Portland cement,” presumably in an 

effort to prevent moisture from attacking the 

metal. 

The wood doors shown on the original 

architectural plans measure 2’-6” X 6’-8” and 

 

3

 Superintendent of Lighthouses to Commissioner of Lighthouses, 

04 May1927, Record Group 26, NA, Washington, DC. 

have three horizontal molded panels below an 

eight-light glazed upper panel. The original 

doors were replaced in 2005. The new units are 

wider than the original doors at 3’-0” but 

replicate the original doors in all other detail. 

Existing Conditions: Isolated areas of concrete 

spalling on the interior walls and ceiling of the 

passageway were noted during the review of 

conditions. In addition, identical patterns of 

horizontal and vertical cracking are present on 

the exterior of the north and south elevations 

and around the through-wall galvanized roof 

drain pipes. Both the spalling and the cracking 

can be attributed to corrosion and expansion or 

“jacking” of the internal reinforcing and drain 

pipes. Given that segments of the reinforcing 

have now been exposed and the cracking that 

has formed is providing a pathway for water to 

infiltrate the walls, it is expected that this 

condition will continue to worsen in the short 

term. 

Other items of note include the jagged edges and 

unfinished appearance of the modified door 

openings and the deterioration of the interior 

and exterior painted finish. 
84 Dry Tortugas Lighthouse HSR 

Figure 84. Section through West Addition to Oil House (Battery Room). 

West Addition (ca. 1935-1941) 

The one-story addition to the west wall of the 

Oil House was constructed between 1935 and 

1941. Initially in 1926 when the Oil House was 

converted to house radio beacon equipment 

there was much discussion about the ability of 

the structure to accommodate the new function. 

Several options were considered for relocating 

the oil tanks from the first floor of the Oil House 

including storing them outside, lengthening the 

existing building or building a new oil house. At 

the time, the Lighthouse Board decided to build 

a new structure for storage of the oil and 

renovate the first and second floors of the 

existing Oil House to accommodate the radio 

beacon equipment. It appears from the drawings 

that the generators were installed on the first 

floor with the radio receiving equipment on the 

second floor. 

The west extension to the original oil house is 

present in the background of a 1941 image of the 

pump house. It is possible the extension was 

constructed to house batteries as it is labeled 

“Battery Rm. Extension” on a site plan of the 

station prepared in 1943. 

Although the original architectural drawings for 

the addition are available, they are undated. The 

drawings show the concrete addition 

constructed upon a 1’-0” wide foundation wall 

set upon a 2’-0” wide footing. The depth of the 

foundation is not provided on the drawings. The 

walls, floor, and roof slab of the addition are 

constructed of reinforced concrete. A 14” deep 

reinforced concrete beam supports the roof slab. 

The beam is set against the exterior wall of the 

Oil House. The roof slab is sloped to the west 

and was covered with a built up roofing system. 

Two, 2” drain tiles in the west wall allow 

rainwater to drain through the exterior wall. 
Physical Description 

National Park Service 85 

Figure 85. Concrete block addition constructed in 1982 by the crew of the USCG vessel White Sumac. When 

originally constructed the addition did not have any openings. 

The original window in the west wall of the Oil 

House was converted to a 3’-0” x 7’-0” door to 

provide access to the new room. This window 

was salvaged and moved to the west wall of the 

addition. Paired, four-light, wood awning 

windows were installed in the north and south 

elevations. 

Existing Conditions: The addition to the Oil 

House is in relatively good condition with no 

significant signs of component failure or 

deterioration. A horizontal crack was noted on 

the interior extending from the middle of the 

window on the west elevation to the bottom 

corner of the window on the north elevation. 

The interior painted finish is experiencing 

localized flaking. The west window has been 

removed. 

South Addition (1982) 

The south addition to the former Oil House was 

constructed in 1982. An undated image of this 

structure shows the south and west elevations 

void of openings with the exception of a small 

opening on the south elevation for a throughwall air conditioning unit. Since the time the 

image was taken, a number of windows and 

doors have been added to the structure. The 

building is currently being used as a garage for a 

small utility vehicle and also houses reverse 

osmosis water purification equipment. 

Existing Conditions: The south addition to the 

Oil House has been modified from its original 

construction by the addition of several openings. 

As the function of the building has evolved over 

the past 27 years it has been necessary to add 

new openings for both ventilation and access. 

The building components are performing well 

with no significant signs of deterioration. 

Utilities 

Electrical System: Electrical power is provided to 

the Oil House and other Light Station structures 

by the photovoltaic (pv) system installed by the 
86 Dry Tortugas Lighthouse HSR 

Figure 86. View of photovoltaic array located west 

of the Lighthouse and Oil House. 

National Park Service in 2002. Prior to 

installation of the pv system, electricity was 

produced by two diesel-powered generators. 

Fuel for these generators was provided by the 

USCG. However, due to the cost and hazards 

associated with delivering fuel to the island, the 

Coast Guard installed solar panels on the tower 

to power the Lighthouse optic. Shortly 

thereafter, the National Park Service installed an 

expanded pv system to service all of the 

structures of the Light Station. 

Today power for the Light Station utility systems 

and structures, including the Oil House, is 

generated by the large photovoltaic array located 

west of the tower. A bank of batteries, located in 

the rear addition of the Oil House stores power 

from the system for use at night and for times 

when the array cannot provide enough current 

for demand during the day. The system’s 

controllers and conversion panels are located on 

the south wall of the Oil House and the 

distribution load centers are located in the south 

addition. From here electricity is delivered to the 

Light Station structures through underground 

conduits. 

Existing Conditions: The photovoltaic array has 

an anticipated useful life of 20 years, which 

leaves a minimum of 13 years before it will need 

to be replaced. However, the lifespan of the 

individual components of the system, and the 

batteries range from one to three years. Regular 

maintenance of the system is required primarily 

due to the effects of the environment on 

individual system components. 

The existing system has sufficient capacity to 

service the demand required by a general level of 

use. However, at certain times when the housing 

units are filled and demand for cooling is 

highthe system is required to operate near its 

capacity. It has been suggested that better 

educating those that use the housing facilities 

about the limits of the system and energy saving 

measures would help to mediate these periods of 

peak demand and reduce strain on the system. 

Summary of Conditions 

The following is a summary of the condition 

issues observed during inspection of the Oil 

House. 

Description of observed condition 

Oil House 

 Exterior painted finish shows only very 

minor signs of deterioration and is in 

good condition. 

 Exterior masonry appears to be in good 

condition with only minor signs of 

deterioration noted. 

 Existing bronze aluminum window units 

are in poor condition with broken 

hardware and missing panes noted. The 

windows are not in keeping with the 

historic character of the Oil House. 

 Oil House entry door is missing 

hardware components. 

 The roof of the Oil House is performing 

well, but several missing shingles were 

noted. 

 Modern faux wood paneling has been 

installed over the 1920s era bead board 

walls. 

 Panels associated with photovoltaic 

system installed on south interior wall. 
Physical Description 

National Park Service 87 

Figure 87. First floor plan of Oil House

Figure 88. Second floor plan of Oil House

1935-1941 

1982 1858 

1927 

 
88 Dry Tortugas Lighthouse HSR 

Figure 89. Oil House entry door jamb. 

Figure 90. Oil House entry door threshold. 

Oil House Interior 

Passageway Previous floor level 

Concrete Passageway

 Corrosion and expansion of internal 

reinforcing has caused spalling in several 

areas. 

 The interior and exterior painted finish 

of the passageway is deteriorated and 

requires repainting. 

West Addition

 Significant horizontal crack in west wall. 

 No window or window frame in west 

elevation. 

South Addition

 No significant signs of deterioration. 
National Park Service 91 

Requirements for Treatment and 

Use 

The treatment and use of the Dry Tortugas 

Lighthouse and Oil House must be considered 

within a framework of applicable laws, policies 

and agreements. These various mandates 

govern a wide range of management issues 

beyond the preservation, protection and 

interpretation of the Park’s cultural resources. 

They extend to issues of visitor and staff use, 

safety, and universal accessibility among 

others. Also, because the Lighthouse remains 

an active aid to navigation, treatment and 

management of the Lighthouse will in part be 

bound by current and future cooperative 

agreements between the National Park Service 

and the U.S. Coast Guard. 

The National Historic Preservation Act 

Section 106 of the National Historic 

Preservation Act mandates that Federal 

agencies, including the National Park Service 

take into account the effects of their actions 

on properties listed or eligible for listing on 

the National Register of Historic Places. The 

goal of this directive is to encourage agencies 

to avoid or minimize adverse impacts to 

cultural resources and to make sure 

preservation is fully considered as part of the 

planning process. The Section 106 process also 

requires consultation with parties outside the 

National Park Service that may have an 

interest in the property. 

In 1995, in an effort to expedite the review 

process, a programmatic agreement was made 

between the Advisory Council and the NPS 

that allows for exclusion of some activities 

from the full Section 106 review process. 

These excluded activities are limited to routine 

repairs and maintenance that do not alter the 

appearance of the historic structure or involve 

widespread or total replacement of historic 

features or materials. The programmatic 

agreement was revised in 2008. 

Accessibility 

The National Park Service is committed to 

providing persons with disabilities the highest 

feasible level of physical access to historic 

properties. 

The Architectural Barriers Act of 1968, the 

Rehabilitation Act of 1973 and the Americans 

with Disabilities Act of 1990 set forth the 

federal mandate for making buildings and 

facilities more accessible. The guidelines that 

accompany these Acts as well as the Uniform 

Federal Accessibility Standards (UFAS; 41 

CFR 19.6; 49 FR 31528) provide design 

direction for accessibility modifications to 

historic structures in the national park system. 

With regard to outdoor developed areas, such 

as trails, beaches and picnic and camping 

areas, the National Park Service has adopted 

the U.S. Access Board’s Outdoor 

Environments Guidelines. 

Given that full compliance with these 

mandates in many cases would require 

alteration of significant features of a historic 

property, provisions have been made within 

the acts for achieving alternative means of 

compliance. This approach has been used at a 

number of lighthouse sites where providing 

access to the Lantern would not be 

practicable. In some cases an accessible route 

is provided to the base of the tower and the 

experience of ascending the stair and viewing 

the lens and surrounding landscape is 

delivered through alternative means such as 

wayside exhibits, videos or slide shows. 

In addition to building-related accessibility 

issues, the primary challenge at the Dry 

Tortugas Light Station is accessing 

Loggerhead Key itself. Although at least one of 

the commercial vessels used to transport 

visitors to the Park is accessible and equipped 

to accommodate a wheelchair, currently the 

only debarkation point within the park is on 
92 Dry Tortugas Lighthouse HSR 

Garden Key. There are currently no public 

docking facilities provided at Loggerhead Key. 

Thus there is currently no accessible route that 

could bring a mobility-impaired visitor to 

Loggerhead Key or the Light Station. If 

accessible access to the island could be 

established, improvements to the wharf and 

walkways would have to be completed to 

access the Light Station. Due to the 

topography of the Key, providing an accessible 

route from the dock to the Light Station may 

require significant alteration of the historic 

landscape. 

Recognizing its obligation to make the Park 

accessible to the widest audience possible, the 

Park has outlined its management direction in 

the General Management Plan Amendment. 

Make visitor and management facilities as 

accessible as practicable, depending on the 

nature of the area and of the facility, to 

persons with visual, hearing, mobility and 

mental impairments. Strive to provide the 

highest level of accessibility possible to 

facilities, programs, and services 

consistent with the nature of the area, the 

conservation of resources and the 

mandate to provide a quality experience 

for everyone. 

Meet accessibility standards on visitor 

transportation vessels and aircraft with the 

limits of marine and aircraft design and 

safety requirements. Work with 

organizations that encourage and enable 

use of the park areas by special 

populations, which will increase 

awareness o f the needs of these 

populations and help to ensure that 

potential visitors with particular needs are 

aware of the opportunities offered at the 

Dry Tortugas. 

International Building Code 

As a matter of policy, the National Park 

Service has adopted the International Building 

Code which establishes minimum regulations 

for the design and installation of building 

systems with an emphasis on preserving public 

health and safety. Its requirements are 

applicable to both new construction and the 

repair and alteration of existing buildings. 

Full compliance with IBC requirements is not 

mandatory for historic buildings where there 

is no threat to life safety. 

3407.1 Historic Buildings: The provisions 

of this code related to the construction, 

repair, alteration, addition, restoration and 

movement of structures, and change of 

occupancy shall not be mandatory for 

historic buildings where such buildings are 

judged by the building official to not 

constitute a distinct life safety hazard

[emphasis added]. 

Alternatives to full code compliance can be 

sought where compliance would needlessly 

compromise the integrity of the historic 

building. 

DO #58 and NFPA Code 914 

Among many other issues, the National Park 

Service Management Policies address the 

protection of historic resources against fire. 

Section 5.3.1.2 of the policy document states 

that: 

In the preservation of historic structures 

and museum and library collections, every 

attempt will be made to comply with 

national building and fire codes. When 

these cannot be met without significantly 

impairing a structure’s integrity and 

character, management and use of the 

structure will be modified to minimize 

potential hazards rather than modifying 

the structure itself. 

Introduction of a fire suppression system 

within the Lighthouse would result in a 

significant negative impact on the historic 

character of the structure since these systems 

would have to be exposed. Based on the 

anticipated level of use and the non-flammable 

nature of the building materials that make up 

the Lighthouse, protection against fire should 

be addressed by minimizing hazards and 

implementing appropriate management 

policies. 

The Secretary of the Interior’s Standards 

Treatment of historic resources associated 

with the Light Station is to be guided by The 

Secretary of the Interior’s Standards for the 

Treatment of Historic Properties. These 

standards provide a framework for planning 

and implementing responsible preservation 

practices and ensuring there is a philosophical 
Requirements for Treatment and Use 

National Park Service 93 

consistency to the work. A series of guidelines 

have been developed to accompany the 

standards and assist with their interpretation. 

Additionally, the Preservation Briefs published 

by the National Park Service provide technical 

guidance for the appropriate treatment of a 

variety of materials, features and conditions 

found in historic buildings. 

Cooperative Agreements with USCG 

When Dry Tortugas National Park was 

established in 1992 the U.S. Coast Guard 

determined the facilities on Loggerhead Key 

to be “excess to its needs” and transferred the 

property (the entire key) to the National Park 

Service. The transfer of property excluded the 

Dry Tortugas Lighthouse with the stipulation 

that the USCG would continue to “maintain 

and utilize” the structure for its own purposes, 

primarily as an active aid to navigation. In 2007 

the USCG and National Park Service entered 

into a cooperative agreement regarding the use 

of facilities and utilities on 

Loggerhead Key. This agreement requires the 

NPS to reserve a room within the Keeper’s 

Residence for the exclusive use of USCG 

personnel and provide water and power to the 

building. Among other minor items the USCG 

agreed to provide propane and gasoline 

storage tanks to the island and to refrain from 

making modifications to the Keeper’s 

Residence with the exception of rehabilitating 

the rainwater collection system. 

In 2008 a Memorandum of Agreement was 

prepared between the USCG and the National 

Park Service that establishes the parameters 

for the formal transfer of ownership of the 

Lighthouse. Transfer of the Lighthouse is 

contingent upon several requirements, one 

being completion of this Historic Structure 

Report. Upon transfer of the Lighthouse, the 

USCG will retain ownership of the lens, radio 

beacon and associated equipment and require 

continued access to the Lighthouse to 

maintain this equipment. 
94 Dry Tortugas Lighthouse HSR 

 
National Park Service 95 

Ultimate Treatment and Use 

Use 

The Dry Tortugas Lighthouse has served 

continuously as an aid to navigation since its 

light was first lit in 1858. Current cooperative 

agreements with the USCG call for this use to 

continue for the foreseeable future. These 

agreements primarily affect the lighthouse 

optic and are not anticipated to limit potential 

use of the Lighthouse or the Oil House. 

The Park’s 2002 General Management Plan 

Amendment (GMPA) calls for the resources of 

the Light Station to be preserved and 

protected according to the Park’s authorizing 

legislation and also that they be managed to 

support operational needs and public 

visitation. An important outcome of the 

GMPA has been the establishment of 

management zones that prescribe the types 

and levels of visitor use and the amount of 

manipulation of the natural or cultural setting 

that is appropriate for different areas of the 

Park. 

Two management zones have been applied to 

Loggerhead Key. The Historic 

Preservation/Adaptive Use (HP/AU) Zone 

encompasses the resources of the Light 

Station in the center of the Key and the 

remainder of the island falls within a Research 

Natural Area (RNA) Zone. The HP/AU zone 

applies to those areas within the Park that 

contain historic and cultural resources and 

where the visitor experience will be primarily 

focused on educational and interpretive 

opportunities. 

The parameters established by the GMPA for 

Loggerhead Key’s HP/AU zone, limit the 

number of visitors that can be on the island 

per day to 24 (12 originating from the 

commercial carriers and 12 from private 

vessels). This number has been established as 

an initial baseline that may be adjusted in the 

future pending the results of a monitoring 

program and the completion of the revegetation project. 

Permissible uses within Loggerhead Key’s 

HP/AU zone include unrestricted picnicking, 

hiking, and exploring. The GMPA currently 

restricts visitor access to the buildings until 

such time as the structures can be “made safe” 

and the appropriate programs are in place to 

support this level of use. 

Since the transfer of Loggerhead Key and the 

Light Station to the National Park Service in 

1992, public visitation to the Key has been 

limited. Existing concession agreements do 

not include provisions for transporting visitors 

to Loggerhead Key. Therefore the site is only 

accessible to those reaching the island by 

private boat or through special arrangements 

with the National Park Service. 

Looking forward, the Park administration is 

exploring ways that it can increase public 

access to the Key through renewed concession 

agreements. In addition, consideration is being 

given to using the Light Station as a “base of 

operations” for an expanded program of 

research. 

Under these scenarios, the use of the 

Lighthouse is not anticipated to change. It will 

serve a dual purpose as an active aid to 

navigation that will also be interpreted as the 

central component of the Light Station and as 

a significant example of Pre-Civil War 

maritime architecture. It should be noted that 

the ultimate treatment and use of the 

Lighthouse must not interfere with its primary 

function as a navigational aid. 

Challenges of Increased Public 

Access 

Visiting Loggerhead Key and exploring the 

resources of the Dry Tortugas Light Station 

provides an impressive, and for some, likely a 

once-in-a-lifetime experience. With this said, 
96 Dry Tortugas Lighthouse HSR 

increasing public access to the site carries with 

it several limitations and challenges. 

Assuming that transportation to the Key is 

resolved, visitors to Loggerhead will likely 

disembark onto the main dock on the east 

shore of the island and then walk a short 

distance on concrete walkways to the Light 

Station. The incline from the dock to the Light 

Station is gradual but in certain areas exceeds 

permissible slope limits for wheelchair use. In 

addition, wind-blown sand often covers the 

surface of the concrete walks. 

Providing full access to the interior of the 

Lighthouse and Oil House to the mobility 

impaired may not a practicable expectation. 

The limited space within the Lighthouse, Oil 

House and connecting passageway, as well as 

the height of the existing thresholds, make this 

unfeasible without extensive modifications to 

the historic fabric. Therefore as discussed in 

the Requirements for Treatment, an 

“alternative minimum” approach to 

accessibility should be explored to extend the 

interpretive experience to those who cannot 

witness it firsthand. 

The extent to which it is practical to permit 

able-bodied visitor’s to explore the interior of 

the Lighthouse and ascend the tower must 

also be considered. The Watch Room and 

Lantern levels at the top of the tower have a 

limited physical capacity. It is estimated that 

no more than four or five people could be 

comfortably or safely accommodated within 

these spaces. In addition, these spaces are 

accessed by a non-compliant stair and a small 

access hatch in the Watch Room floor. 

Another factor to be considered when 

evaluating the practicality of visitors accessing 

the top of the tower includes the physical 

exertion required to ascend the tower, the 

warm climate of the site, the temperatures 

within the tower, and the limited access to 

medical assistance in case of an emergency. 

Additionally, the wedge shaped stairs and the 

decreasing capacity of the landings will limit 

the number of visitors that can be in the stair 

tower at the same time. It would be 

undesirable to have larger groups passing on 

the stairs or congregating on the landings. This 

may require that access to the interior of the 

tower be limited to a few small groups that can 

use the landings to let other groups pass. 

Managing visitor use in this way may require 

supervision by several volunteers or staff. 

The low light level in the stair tower is also a 

safety consideration that will need to be 

addressed if visitors are allowed to access the 

Lighthouse interior. 

The windows are another component that has 

to be considered when assessing visitor use 

and safety. Since the windows are accessible 

from the landings and should remain operable, 

screens should be installed to prevent visitors 

from dropping objects from the windows. The 

existing windows are loose in their frame and 

do not have integral screens. These factors, 

along with the importance of ventilating the 

tower interior must be taken into account 

when designing replacement window units. 

Finally, the Watch Room level gallery would 

not be considered safe for visitor use unless 

modifications are made to the railing to 

address safety concerns. The addition of a 

higher railing with closely spaced balusters on 

the galleries would have a visual impact on the 

character of the Watch Room/Lantern. An 

option that may be less visually intrusive 

would be to span a mesh grid between the 

widely-spaced balusters. 

Recommendation: Taking into consideration 

both life safety and visitor experience, it is 

recommended that groups of no more than 4-

5 persons be allowed in the Watch 

Room/Lantern level at one time. Additional 

small groups could be held on intermediate 

landings while others descend the tower stairs. 

The Oil House and its additions have become 

the control center for the island’s critical 

utility systems. Utility-related components and 

equipment are housed in the additions where 

they can be secured and protected from 

storms. There are several electrical panels 

associated with the photovoltaic system 

mounted to the south wall of the Oil House. If 

consideration is given to allowing visitor 

access to the Oil House for interpretive 

purposes, it would be necessary to relocate 

these panels. 

Building Fabric 

The appearance of the Dry Tortugas 

Lighthouse has changed little since the early 
Ultimate Treatment and Use 

National Park Service 97 

1870s when the black and white painted 

daymark was first applied. A great majority of 

the existing building fabric dates to the 

Lighthouse’s original construction. 

Architecturally the Lighthouse is a relatively 

simple structure with a few basic components; 

the brick masonry tower penetrated by several 

window openings and a door at grade, the 

stone stair treads, the Lantern structure made 

up of iron and glass and finally, within the 

Lantern, the iron lens pedestal and platform 

assembly. Changes to these building elements 

have been limited. In some cases minor repair 

or replacement has been made as these 

components have worn out with age or have 

been damaged by storms. In other cases, 

advancements in technology have resulted in 

the removal and replacement of original 

equipment. 

The structure’s largest mass of material, the 

load-bearing, brick masonry walls, remain 

intact having only been intermittently 

repointed and repaired. The daymark, first 

applied ca. 1870 has been repainted a number 

of times throughout the history of the 

structure. Today its intensity has been 

diminished due to removal of the paint in 1967 

and subsequent weathering. 

The existing windows in the tower were 

installed in 1982 by the USCG. The windows 

are bronze aluminum, one-over-one, doublehung units that differ greatly from the multipane, wood, double-hung windows that were 

present in the tower from the late nineteenth 

century through the mid twentieth century. In 

addition, the wood shutters that were installed 

over the windows following the 1873 

hurricane were removed in 1967 and not 

reinstalled as part of the most recent window 

replacement projects. The 1967 and 1982 

installation of aluminum windows in the 

Lighthouse were reactions to an immediate 

need and were not completed in a manner 

consistent with the Secretary of the Interior 

Standards. Although installed during the 

USCG era, the existing windows are not 

architecturally significance and they detract 

from the Lighthouse’s historic character. 

The recently repaired Lantern exists today in a 

state of partial completion. The 2009 project 

repaired the deteriorated iron skeleton of the 

Lantern and replaced the copper panels of the 

dome roof but did not have sufficient funds to 

reconstruct the integral gutters and replicate 

and reinstall the vent ball and lighting rod. 

Once the full scope of the repair project has 

been completed, the Lantern will appear much 

like it did when it was originally constructed. 

The interior features of the masonry tower 

date from its original construction. The 

masonry walls, newel, and blue slate stair 

treads are original fabric and remain intact. At 

the Watch Room and Lantern Levels the lens 

pedestal, including the mercury float assembly 

date from 1910-1911 when the original firstorder lens was replaced with the second-order 

bivalve lens. These components represent an 

important milestone in the evolution of the 

lighthouse and are historically and 

architecturally significant. 

In contrast with the Lighthouse, the Oil House 

has experienced extensive modifications that 

have impacted the building’s original form, its 

fenestration and interior and exterior finishes. 

With the exception of the masonry bearing 

walls, little of the Oil House’s original building 

fabric has survived. The modifications made to 

the Oil House are indicative of its evolving use 

and in some cases have acquired historical 

importance. For example the concrete 

passageway and the interior wall finishes that 

survive below the existing wood paneling date 

from the 1920s when the Oil House was 

converted to a Radio Beacon House. More 

recent changes to the Oil House such as the 

installation of aluminum windows and the 

construction of the concrete block addition on 

the south elevation have diminished the 

historic character of the structure. 

Recommended Ultimate Treatment 

and Use 

It is recommended that the ultimate treatment 

and use of the Light Station resources remain 

consistent with the guidelines established in 

the GMPA for the HP/AU Management Zone. 

As the name implies, this zone calls for the 

preservation, protection and interpretation of 

cultural resources yet recognizes the need to 

adaptively use these resources to 

accommodate critical functions, such as 

housing, sheltering essential equipment and 
98 Dry Tortugas Lighthouse HSR 

maintaining the Lighthouse optic as an active 

navigational aid. 

The Recommended Ultimate Treatment 

therefore proposes actions that will repair 

deteriorated building fabric while 

rehabilitating the exterior and interior of 

the Lighthouse. It is further recommended 

that key features of the Lighthouse that are 

in need of replacement, such as the 

windows, be returned to their pre-1967 

appearance. 

Although not a pivotal date in the history of 

the Lighthouse, the 1967 restoration date was 

chosen because it was during this year that 

significant modifications were made to the 

Lighthouse and Oil House that removed 

important character-defining features and 

either did not replace them or installed new 

components that were not in keeping with the 

historic character of the structures. This 

philosophy of repair was continued during the 

last decades of the twentieth century. It is 

therefore recommended that this date be used 

as a framework for making design and 

treatment decisions. This approach has the 

following advantages: 

Lighthouse 

 Addresses deferred maintenance and 

needed repairs to prevent further 

deterioration or loss of historic fabric. 

 Preserves in place for interpretation, 

building fabric from a broad spectrum 

of the Lighthouse’s history. 

 Removes modifications made during 

the recent past that are in poor 

condition and are not in keeping with 

the historic character of the 

Lighthouse (such as the aluminum 

windows and associated sill 

modifications). 

 Restores character defining features 

such as the multi-pane, wood 

windows and shutter assemblies that 

were present prior to 1967 and 

throughout much of the structure’s 

history. Replacement units should 

address considerations of durability, 

visitor safety and tower ventilation. 

 Retains the option to reinstall the 

second-order bivalve lens if feasible. 

 Potentially removes the deteriorated 

steel access ladder mounted to the 

Lantern exterior. 

 Allows for the continued 

reconstruction of the Lantern roof 

and reinstallation of the vent ball and 

lightning rod. 

Oil House 

 Addresses deferred maintenance and 

needed repairs to prevent further 

deterioration or loss of historic fabric 

 Preserves in place for interpretation, 

building fabric from a broad spectrum 

of the Oil House’s history. 

 Removes modifications made during 

the recent past that are in poor 

condition and are not in keeping with 

the historic character of the Oil House 

(such as the windows) 

 Restores important character defining 

features such as the multi-pane, wood 

windows and shutter assemblies that 

were present prior to 1967. 

 Returns the interior of the Oil House 

to its 1920s appearance by removing 

wall and floor finishes installed during 

the recent past that are not in keeping 

with the historic character of the 

building. 



This approach has the following 

disadvantages: 

Lighthouse 

 Removes tangible evidence of 

modifications made during final the 

USCG and NPS eras. 
Ultimate Treatment and Use 

National Park Service 99 

 Potentially removes VRB-25 optic 

installed by USCG in 1996. 

Oil House 

 Potentially removes tangible evidence 

of modification made during the 

USCG and NPS eras. 

 Potentially removes the south 

addition to the Oil House constructed 

in 1982. 
100 Dry Tortugas Lighthouse HSR 
National Park Service 101 

Alternatives for Treatment 

and Use 

Use 

The Dry Tortugas Lighthouse was designed 

for a single purpose: to elevate and house a 

beacon that would warn mariners of 

hazardous sailing conditions. It continues to 

be used for this same purpose today. 

The architecture of the Lighthouse is efficient, 

responding solely to this narrow function. The 

structure contains only three spaces, the stair 

tower, the Watch Room and the Lantern. 

Potential to adapt the structure for alternative 

uses, other than interpretation, is therefore 

limited. 

The Oil House and its additions currently 

house utility-related equipment and panels. 

The interior spaces of the original two-story 

Oil House are used only minimally for this 

purpose. Therefore opportunity exists for 

restoring the interior only for interpretative 

programming. Given that the surviving 

historic fabric generally dates from the 1920s, 

when the building was converted to a Radio 

Beacon House, this would be the most logical 

period on which to focus. 

Alternatively, increased use and visitation to 

the site will likely require the upgrade or 

expansion of existing utility systems, and 

possibly the addition of more equipment. With 

this said it may be prudent to reserve these 

currently underutilized spaces to 

accommodate future needs. 

Treatment 

The proposed ultimate treatment 

recommends restoring certain features 

(primarily the windows) of the Lighthouse to 

their pre-1967 appearance. This would be 

done in order to remove fabric from the recent 

past that diminishes rather than enhances the 

historic character of the resource. This 

approach also supports the potential 

reinstallation of the second-order bivalve lens 

removed in 1986. 

An alternative treatment approach would be to 

preserve all existing fabric, including that from 

the recent past, regardless of its aesthetic 

character. 
102 Dry Tortugas Lighthouse HSR 
National Park Service 103 

Recommendations for 

Treatment and Use 

Dry Tortugas Lighthouse 

Masonry 

An assessment of the Lighthouse conducted in 

1984 by National Park Service personnel 

identified the deterioration of the 

Lighthouse’s mortar joints as a condition 

requiring treatment. The conditions observed 

today match precisely those described in the 

assessment. Both the exterior and interior 

mortar joints of the Lighthouse are eroding or 

becoming friable and falling from the wall as 

fine sand or powder. This condition varies in 

severity from approximately 1

/8” to 1” loss of 

mortar depth, and seems to affect the head 

joints more than the bed joints. On a positive 

note, the mortar that remains is stable, very 

hard, and well bonded. Although this 

condition is not currently jeopardizing the 

stability of the structure, there are areas of 

severe mortar loss, particularly at the interior 

newel where, if left to progress, may in the 

short term result in bricks becoming loose or 

possibly falling from the wall. 

Although the processes causing this condition 

are not entirely known, the movement of 

moisture through the wall or possibly surface 

condensation are probable contributing 

factors. Based on the previous deteriorated 

condition of the Lantern and past problems 

with the Watch Room gallery floor, it is likely 

that moisture is presently, or has in the past, 

been able to enter the wall system at the top of 

the tower. 

Ideally a comprehensive program of 

repointing and repair should be conducted 

wherein the exterior and interior masonry 

walls of the tower are repaired in a single 

effort. This approach would be the most cost 

effective because of the significant costs 

associated with contractor mobilization and 

the erection of scaffolding. If funding 

limitations and sequencing require a phased 

approach, repair should be focused on those 

areas of the tower interior that are exhibiting 

the most severe deterioration. Phasing the 

exterior work is less practical because 

scaffolding would need to be erected to access 

the most deteriorated areas unless the exterior 

repairs are performed from a hanging 

scaffolding or basket as has been done in the 

past (which has its own limitations). 

Loss of mortar to a depth of more than 5

/8” is a 

general rule of thumb that can be used to 

determine which areas require treatment in 

the short term. This is not to say that 

individual spot repairs should be made at each 

and every location where the mortar has 

receded beyond this point, but rather that this 

measurement be used to identify broad areas 

that can be repointed in their entirety. 

Based on inspections made during the 

development of the HSR we estimate that 

approximately 35% of both the interior and 

exterior of the Lighthouse should be 

repointed as a priority. 

Recommendations for design development and 

masonry repair. 

 Verify construction of the masonry 

walls through boroscopic 

examination. 

 If necessary, make repairs to Watch 

Room gallery floor to prevent 

infiltration of moisture into tower 

masonry wall system. 

 Investigate the possibility of 

ventilating the interior voids of the 

masonry wall if found to be present 

during the boroscopic investigation. 
104 Dry Tortugas Lighthouse HSR 

 Identify areas of critical mortar loss 

both on the exterior and interior of 

the tower. The most severe loss of 

mortar on the exterior walls appeared 

to be confined to the top third of the 

tower. It may be necessary to dry 

brush the interior walls to remove 

mortar fall out so that the amount of 

mortar loss can be accurately 

measured. 

 Formulate repointing mortar to match 

the composition of the existing 

mortar. The results of the mortar 

analysis identified that the historic 

mortar is a mixture of one part natural 

cement to 1.5 parts local carbonate 

sand. 

 Repair corroded iron elements 

embedded within the masonry prior 

to conducting repointing. (See Watch 

Room recommendations below). 

 Conduct paint removal (see discussion 

below) 

 Repoint all exterior mortar joints 

within defined areas of the Lighthouse 

(to be more specifically identified 

during final design as described 

above), comprising approximately 

35% of the overall area. 

 Repoint all interior mortar joints 

within defined areas of the Lighthouse 

(to be more specifically identified 

during final design as described 

above), comprising, approximately, 

35% of the overall area. 

 Coordinate the extent of repointing 

with lead-containing paint removal 

and reapplication of finishes, 

described below. 

The hairline vertical cracking below the 

Watch Room floor plate is a condition that 

should be monitored. This phenomenon has 

been identified at numerous lighthouses and 

has been attributed to a variety of causes from 

lighting strikes, to wind loading, to stresses 

caused by the corrosion of embedded steel 

components, and thermal expansion and 

contraction. In some cases vertical cracking of 

the tower masonry was identified early in the 

history of the structure. It is unknown if the 

observed vertical cracking in this structure is 

active or dormant. The extreme build-up of 

finishes at the fifth and sixth levels suggest an 

effort to mask a recurring condition. 

Recommendation: Begin a program of crack 

monitoring and conduct further investigation 

once the painted finish has been removed. The 

use of deep penetration mortar may be a repair 

option that can be determined once the scope 

and severity of the condition is confirmed. 

Reapplying the Daymark and Interior Finish 

According to historic documentation, the 

existing painted finish of the tower was 

applied in 1967 following a program of 

sandblasting that removed all previous layers 

of finish. A 1984 analysis of the paint 

confirmed that only two layers remained on 

the tower and that the paint was a “lead-zinc 

based acrylic-polyvinyl acetate mixture.” 

Since this time weathering and deterioration 

have reduced the intensity of the daymark and 

started to expose the underlying brick. The 

reapplication of the daymark and interior 

finish are important not only because they are 

significant character-defining features of the 

structure but also because the applied finish 

will protect the masonry once repaired. 

Removing the existing paint prior to applying 

a new finish is an important consideration. 

Although it may or may not be necessary to 

remove the paint in order to achieve good 

adhesion, improving permeability and ridding 

the structure and the site of lead-based paint 

should remain a priority. Permeability of the 

existing finish is not a concern on the exterior 

where only a few weathered layers are present. 

It may be a concern however on the interior of 

the Lighthouse, at the upper levels, where 

there is significant paint build-up. 

In recent years the USCG has conducted 

surveys to determine the extent of lead 

contamination in the soils around the base of 

the Lighthouse. The lead contaminated soils 

have not been removed as of the date of this 

report. To avoid recontamination of abated 

soils during repair efforts, we recommend 

removing the lead-containing paint before 

repairing and refinishing the Lighthouse 

exterior. The limited availability of potable 
Recommendations for Treatment and Use 

National Park Service 105 

Figure 90. Undated view of the Lighthouse 

showing four-over-four double-hung 

windows and wood shutters. 

Figure 91. Pre-1967 image showing fourover-four, double hung windows with 

shutters. 

water and the logistics of collecting and 

transporting the hazardous paint remnants 

from the island should be given careful 

consideration when developing a program for 

removal. If the decision is made not to remove 

the existing paint, an adhesion test should be 

performed before applying a new finish. 

As part of the current study, paint samples 

were taken from that portion of the exterior 

wall of the Lighthouse that is protected within 

the Concrete Passageway. Analysis revealed a 

range of paint layers applied over the original 

finish of the structure since it was first painted 

in the 1870s. The earliest layers of finish 

appear to be a lime wash followed by layers of 

paint. Because the Watch Room gallery was 

not accessible at the time of inspection, the 

upper portion of the tower was not sampled. It 

is likely that the original black finish would 

have been achieved using paint or a carbon 

black loaded lime wash. The key factors in 

selecting a finish for the Lighthouse exterior 

will be compatibility with the historic 

masonry, breathability, durability and 

maintenance requirements. 

Recommendation: Remove existing interior 

and exterior finishes, and, after repair and 

repointing of the masonry, renew the daymark 

and interior finishes. It is recommended that a 

lime wash be applied to the tower interior and 

exterior using traditional renders (both black 

and white) such as the mineral coatings and 

renders by Keim. These would provide a 

breathable coating that would be compatible 

with the historic masonry and have an 

expected longevity measured in decades, as 

opposed to a fraction of that for ordinary 

paints. 

Windows 

The USCG installed the existing tower 

windows in the early 1980s to replace 

aluminum awning windows installed 

approximately 15 years earlier. (Prior to 1967, 

the windows were four-over-four, double 

hung sash with wood shutters. Moving back 

through time from this point, historic images 

and drawings suggest that several generations 

of multi-light sash were installed in the tower.) 
106 Dry Tortugas Lighthouse HSR 

Figure 92. Close-up of window and shutters 

present in Lighthouse prior to 1967. 

The replacement windows installed in the 

1980s were described at the time as “heavy 

duty” units designed to better withstand the 

high winds and severe climatic conditions of 

the region. No attempt was made to replicate 

the four-light, double-hung windows that 

were present in the tower throughout much of 

twentieth century, nor did the replacement 

units incorporate the wood shutters that had 

been present on the windows from the 1870s 

through to 1967. 

The existing bronze anodized aluminum 

windows in the tower are experiencing 

significant condition problems. All of the units 

have become loose or unseated from their 

frames and several are missing panes. One unit 

has been removed and replaced with a plexiglass insert. 

Recommendation: Given the harshness of the 

local environment, selecting a durable 

weather-resistant and maintainable 

replacement window is of primary 

importance. A wood replacement window 

would most closely match the historic 

condition. However, the desired level of 

durability is simply not available from 

standard wood window manufacturers and 

therefore only a custom fabricated, custom 

finished window unit constructed of a 

weather- and termite-resistant durable 

species, such as teak, would be appropriate. A 

similarly durable species should be used for 

replacement shutters. 

Alternatively it is recommended that the 

existing windows be replaced with new 

fluoropolymer coated aluminum units having 

profiles and sightlines in keeping with the pre1967 four-over-four double-hung wood units. 

The aluminum units should also be selected 

with quality and durability as the primary 

criterion. The windows and shutters in the 

tower should be painted white and the 

window and shutter at the Watch Room level 

should be painted black (see Figure 90). 

Tower Door 

The existing tower door is not original and 

was likely installed in an effort to “make do” 

with that which was available. The paint 

analysis reveals that the door frame has several 

more layers of paint than the door, and 

therefore likely predates installation of the 

door. However, the 30 to 35 layers of paint on 

both the door and door frame suggest that 

they have both been in place for some time or 

that they could have been moved from 

another location. Assuming repainting 

occurred at 2-3 year intervals the door and 

frame were installed circa 1910 – 1940. 

Only the mortise lock and the interior 

escutcheon plate remain on the tower door 

and no documentation could be located 

showing the door with a full complement of 

hardware. Paint ghosting suggests that there 

was once an exterior escutcheon and it is likely 

that the door included a handle set. It is 

recommended that these items be replicated 

and installed to improve security and 

operability. 

The existing mortise lock may provide 

additional information about the age of the 

door. Often these components contain 

manufacturer information and serial or model 

numbers that can be used to date the 

hardware. 

Stairs 

We recommend that the two failed stair treads 

that are being temporarily stabilized be 
Recommendations for Treatment and Use 

National Park Service 107 

replaced with matching treads. This will 

require the removal of a small amount of 

masonry at the exterior wall and newel. A 

source for acquiring blue slate slabs that match 

the dimensions of the original treads should be 

identified. We did not observe any other 

weakened or broken treads. 

We recommend that the stair rail installed in 

1967 be repaired where the anchors have 

failed. This may require fabrication of new 

anchors and sections of rail. 

Watch Room 

There are several condition issues impacting 

the Watch Room that require attention. The 

most critical is the significant (1

/4” wide) 

vertical crack that extends through the Watch 

Room wall along its east elevation. Similar 

conditions were identified during the 1984 

assessment and linked to the probable 

corrosion of tie rods that were extended down 

through the masonry wall as part of the repairs 

made following the 1873 hurricane and again 

in the 1930s. The corrosion and resulting 

expansion of these embedded elements 

imposes stresses on the masonry that cause 

cracking of the wall. It is anticipated that if this 

issue is not addressed the condition will 

worsen and accelerate. The 1984 study 

recommended that the tie rods be exposed, 

inspected and treated with an anti-corrosive 

coating, but it is unknown if these repairs were 

implemented. 

Recommendation: Given that the significant 

crack on the east elevation extends through 

the wall to the exterior, it is serving as a 

pathway for water to infiltrate the structure. If 

left unchecked, this moisture will continue to 

corrode the iron elements in the Watch Room 

and, if filtering down into the masonry of the 

tower, will continue to deteriorate the bricks 

and mortar. We recommend that at a 

minimum the crack on the east wall be further 

explored to determine its origin and, if found 

to be associated with corrosion of the 

embedded anchor rods, that the rods be 

exposed through the removal of masonry and 

treated. 

The existing stucco finish applied to the 

Watch Room walls was not analyzed as part of 

the current investigation. However, it appears 

to be a Portland cement based mixture. The 

stucco is extremely hard and grey in color. The 

finish exhibits wide-spread hairline cracking. 

Although hairline cracking of the stucco was 

observed universally throughout the Watch 

Room, no other obvious signs that individual 

anchor rods are imposing stresses on the 

masonry were noted. 

Removal of the existing stucco would allow 

close inspection of the underlying masonry; 

but removing the Portland cement-based 

finish may result in considerable damage to 

the historic brick. We recommend that the 

existing stucco be left intact and repaired as 

required unless extensive removal of the 

existing stucco is necessary to facilitate 

masonry repair. 

If the stucco is removed, reapplication of the 

stucco finish should take place using a 

formulation that is based on historic 

precedent and more compatible with the 

historic masonry. The stucco finish coat 

should have integral color so as to eliminate 

frequent repainting. 

Another issue impacting the Watch Room is 

the corrosion of the sill plate and I-beams

supporting the floor plate. Significant 

corrosion of the I-beams at their ends was 

noted during inspection. It appears that 

adequate cross section remains, but this 

condition should be treated as a priority. 

Further corrosion and expansion of these 

embedded iron elements will quickly result in 

damage to the historic masonry and greatly 

increase the cost of future repair. 

Recommendation: As is the case with the 

corroded anchors in the Watch Room walls, 

treatment should include removal of the 

masonry around these elements to expose 

those surfaces embedded in the walls, blast 

cleaning of the iron to remove the built-up 

corrosion, and then application of an 

appropriate anti-corrosion coating. A zincrich primer and two coats of catalyzed epoxy 

should be applied to other interior areas 

where metals are experiencing corrosion. In 

locations where the corroding metal is 

exposed to sunlight, such as the Lantern 

gallery floor plates, a urethane or fluorourethane should be applied as the final coat. 

The arched iron door that provides access to 

the Watch Room gallery was removed and 
108 Dry Tortugas Lighthouse HSR 

replaced with a plywood insert during the 

recent Lantern repair project. The door had 

experienced severe corrosion at its base and 

had broken free from its hinges. According to 

the contractor that removed the door, repair is 

not feasible. The door, which is being stored at 

the Everglades National Park collections 

facility, was inspected as part of the current 

investigation. The bottom third of the door is 

severely deteriorated and the hinges broken. 

Repair would require splicing new material on 

the bottom portion of the door and casting 

new iron to repair the fractured hinges. A 

repair approach may not be practicable. 

Recommendation: The Watch Room door is a 

significant character-defining feature. It is 

recommended that a replica of the historic 

door be fabricated and installed. 

The exterior walls of the Watch Room are 

painted stucco. The painted finish of the walls 

is fading and peeling exposing the lightcolored stucco beneath. The stucco is also 

experiencing cracking throughout much of its 

surface. Removal of at least some of the stucco 

may be necessary to investigate and repair the 

large crack and embedded elements. If it is 

found that the exterior stucco is also Portland 

cement based, the same treatment approach 

recommended for the interior should be 

applied to the exterior. As a means to reduce 

maintenance, we recommend a stucco system 

with integral black coloring. In conjunction 

with these repairs, it is further recommended 

that the circular vents in the Watch Room 

walls be made operable to promote adequate 

ventilation of the Watch Room and Lantern. 

Finally, both the Watch Room and Lantern 

gallery railings are experiencing corrosion, 

primarily at their connection points. Neither 

of the non-historic railings, which were 

installed in 1985, is compliant with applicable 

codes. If it is the intention of the National Park 

Service to allow visitor access to the Watch 

Room gallery (The Lantern-level gallery is 

only accessible by exterior-mounted ladder) 

modification of the railing may be required 

given the existing condition constitutes a 

“distinct life safety hazard”. Design of a new 

railing or guard that complies with the IBC for 

strength and attachment, height (42”) and 

opening limitations would impact the visual 

character of the Lantern. Therefore design 

options should be explored that address lifesafety concerns while at the same time 

maintain the historic character of the Lantern. 

Options for addressing opening limitations 

may be to preserve the main supports and use 

a small diameter intermediate baluster or mesh 

screen to span between balusters. Given the 

exposed location, a glazed panel option would 

not be practical. If the Watch Room or 

Lantern galleries are not to be opened to the 

public, we recommend that connection 

deterioration be repaired and corrosion be 

arrested with zinc-rich/epoxy/urethane 

coatings mentioned previously. At all times, 

proper safety precautions should be taken 

when accessing the galleries for maintenance, 

repair or other purposes. 

Lantern 

The recent repair and reconstruction of the 

Lantern roof did not fully replicate the historic 

condition. Due to limited funding, a reduced 

scope of work was implemented that 

eliminated reconstruction of the roof edge and 

integral gutter system and replication of the 

vent ball and lighting rod. The historic vent 

ball and lightning rod removed from the roof 

during the repair project are severely 

deteriorated and cannot be reinstalled. These 

important historic features should be 

replicated and installed to complete the 

accurate reconstruction of the Lantern roof. 

We recommend that the Lantern roof repair 

project be completed, including roof edge, 

gutter, vent ball, and lightning rod. 

Also associated with this project was the descaling and repainting of iron components of 

the Lantern structure. Many of the iron 

headers were deformed and weakened by 

severe corrosion. Although these members 

were de-scaled and painted as part of the 

recent repairs, it may be necessary to replace 

corroded headers with newly cast members. 

The contractor that completed the roof repair 

has recommended that all of the headers be 

replaced although only 6-8 have been severely 

deformed by corrosion. It should be noted 

that replacement of these components will be 

a labor intensive operation as the headers are 

incorporated into an interconnected 

“knuckle” where the vertical bar columns, 
Recommendations for Treatment and Use 

National Park Service 109 

headers, roof rafters and gutter supports all 

come together. Repair of these headers should 

not be conducted in isolation but should be 

completed as part of a comprehensive project 

that includes completion of the copper roof. 

Replacement of the headers will require 

removal of a number of copper roof panels. 

Special attention needs to be paid to the 

isolation of dissimilar metals when conducting 

repairs to the Lantern’s structural 

components. 

Recommendation: It is recommended that the 

corroded and deformed headers be removed, 

and new headers be recast and installed. 

The gallery and roof access ladder installed in 

1978 is experiencing significant corrosion, 

especially at its connections. Given that a 1967 

date is proposed for making treatment 

decisions, it is recommended that the access 

ladder be removed. During the recent 

restoration of the Lantern roof, a hatch was 

installed thus reducing the need for the ladder 

to provide roof access. A small ladder, more in 

keeping with the historic condition could be 

fabricated to provide a means of access 

between the Watch Room and Lantern 

galleries. 

The Lantern gallery floor plates are 

experiencing moderate to severe pitting 

corrosion both in their field and at the joint 

between plates. These conditions do not 

appear to compromise structural integrity, but 

if left untreated will eventually lead to more 

significant deterioration and potentially costly 

repairs. In addition continued corrosion of the 

underside of the floor plates will stress and 

damage the masonry walls of the Watch 

Room. Treatment of the pitting corrosion 

generally includes blast cleaning the surface, 

and the applying a protective coating system 

(organic zinc primer, two coats of epoxy paint, 

and urethane topcoat). The underside of the 

floor plates requires this treatment promptly 

because it is here that the most significant 

corrosion is taking place and causing stress to 

the historic masonry at the top of the Watch 

Room walls. This same treatment should be 

applied to the lens pedestal components and 

Lantern stairs to remove and arrest surface 

corrosion. 

The proposed ultimate treatment allows for 

the future reinstallation of the second-order 

lens that was installed in the Lighthouse in 

1911 and removed in 1986. The return of this 

important character defining feature would 

greatly enhance the interpretive experience 

and historic character of the Lantern. We 

recommend that the feasibility of obtaining 

and reinstalling the second-order bi-valve lens 

be further investigated. 
110 Dry Tortugas Lighthouse HSR 

Figure 93. Pre-1969 image of Oil House showing wood-frame addition and shutters on the Oil House 

windows. 

Dry Tortugas Oil House 

Exterior Masonry Walls 

The masonry exterior of the Oil House shows 

no signs of significant deterioration. There 

remains numerous small iron anchors 

embedded in the masonry in various locations 

that if left to corrode may cause localized harm 

to the masonry. We recommend that the 

anchors be removed and the voids left in the 

masonry be pointed and painted. 

Documentation of the anchors and their 

location should be conducted before their 

removal. 

The painted finish of the exterior walls has 

been well maintained and also shows no signs 

of significant deterioration. Removal of the 

existing exterior paint may not be necessary 

(since it is currently serviceable), but the finish 

likely contains lead and therefore 

consideration should be given to its removal. 

Removal of the paint would allow close 

inspection of the underlying masonry. 

Roof 

The roof of the Oil House is performing well 

and therefore its replacement is not necessary 

at this time. Composition shingles or possibly 

asbestos shingles, similar in appearance to 

those currently installed on the building can 

be seen in the pre-1969 image below (Figure 

92). Therefore when replacement is necessary 

it is recommended that the composition 

shingles be reapplied. 

Windows and Doors 

Like the Lighthouse, the Oil House received 

new windows in 1967 and 1982. A single 

awning window remains from the 1967 

installation and the remainder of the windows 

are bronze aluminum awning units similar to 

those installed in the Lighthouse. The 

hardware on all of the existing windows is 

deteriorated or damaged and in most cases the 

windows are no longer operable. We 

recommend that the windows be replaced in 

the short term. 

Available documentation from the 1920s 

conversion of the Oil House shows four-overfour, double-hung windows installed at the 

time (see Figure 26). Consistent with the 

proposed ultimate treatment, we recommend 

that existing aluminum units be removed and 

four-over-four, fluoropolymer coated 
Recommendations for Treatment and Use 

National Park Service 111 

aluminum double-hung units be installed 

similar to the treatment prescribed for the 

Lighthouse. We also recommend that the 

vertical board shutters with “Z-bracing” that 

were present on the Oil House be replicated 

and installed as part of the window 

replacement (see Figure 93). 

No documentation exists that verifies when 

the existing door of the Oil House was 

installed. We recommend that the existing 

door be preserved and repaired as necessary. 

Oil House Interior 

Currently, the interior of the original Oil 

House structure is underutilized; therefore 

treatments may be contingent upon its 

ultimate use. If it is anticipated that the interior 

of the Oil House will be accessed as part of an 

interpretive program, we recommend that the 

existing faux wood paneling be removed to 

reveal the 1920s bead board wall finishes and 

the electrical panels be relocated to the south 

addition. This modification, as well as the 

installation of the four-over-four, doublehung windows would return the original 

portion of the Oil House to its pre-1967 

appearance. 

It is also recommended that if the building is 

interpreted that the existing vinyl tile flooring 

on the second floor be removed and 1” x 6” 

wood flooring be installed per the 1926 

architectural plans. 

Concrete Passageway (1927) 

The reinforced concrete passageway exhibits 

initial signs of deterioration. In a few areas the 

embedded reinforcing has begun to corrode, 

resulting in spalled concrete. This initial 

deterioration now provides a pathway for 

moisture to infiltrate the concrete and further 

corrode the embedded reinforcing. This 

condition will continue to worsen and 

accelerate if it is not addressed. The longevity 

of reinforced concrete structures in a marine 

environment was a concern when the 

passageway was first built in 1927 and 

continues to be a consideration today. Unless 

diligently maintained, it is likely that the 

structure will continue to succumb to the 

effects of the corroding and expanding 

reinforcing, resulting in deterioration similar 

to that occurring on the Dry Tortugas Boat 

House. 

The preservation of reinforced concrete 

structures in marine environments is a 

challenge that requires diligent attention and 

intensive maintenance. For these reasons it 

may not be practicable to preserve the existing 

structure in its current state for the long term. 

We recommend the following steps to repair 

the existing spalled concrete; 

 Confirm the integrity/water tightness 

of the Passageway roof by flooding it 

with water and looking for leaks 

through the concrete slab. If integrity 

of roof is compromised, replace roof. 

 chip away all loose concrete at 

spalled areas, 

 remove concrete to exposing all 

surfaces of the rebar, 

 square the edges of the concrete 

repair area, 

 clean rebar to a bright finish with 

wire brush, 

 paint rebar with corrosioninhibitor / bonding agent, 

 patch hole with special latex 

modified compound appropriate 

for use in marine environments. 

The interior and exterior painted finish of 

the passageway is deteriorated. We 

recommend that it be repainted following 

repair of the spalled concrete. This will 

provide another level of protection against 

moisture and salt infiltration. 

West Addition to Oil House (1935-1941) 

We recommend that the horizontal crack in 

the north and west walls be pointed and a 

crack monitor installed to determine if the 

structure is continuing to move. The crack 

does not appear to correspond with the 

location of internal reinforcing shown on the 

drawings and therefore may be the result of 
112 Dry Tortugas Lighthouse HSR 

foundation settlement. If it is found that the 

structure is continuing to settle, measures 

should be taken to stabilize the foundation. 

There is currently no window in the rough 

opening on the west elevation. It is 

recommended that a new window be 

fabricated and installed in this opening as 

indicated in the original architectural plans 

(four-over-four, double hung unit) and as 

proposed for the two-story portion of the Oil 

House. 

South Addition to Oil House (1982) 

The south addition to the Oil House currently 

houses equipment associated with the various 

critical utility systems. 

Given that a 1967 date is being used as a 

framework for making treatment decisions, 

technically the 1982 concrete-block addition 

should be removed and the gable-roof frame 

addition, present until 1969, be reconstructed. 

However unless the interpretive program calls 

for the precise restoration of the historic 

scene, this approach would not be 

recommended. 

It is recommended that the 1982 addition 

remain in place as long as it is needed to house 

utility equipment. 
National Park Service 113 

Sources of Information 

Bearss, Edwin C. Historic Structure Report, Historical 

Data Section, Fort Jefferson: 1846-1898 Fort 

Jefferson National Monument. 1983.

______. Shipwreck Study-The Dry Tortugas. 

Washington, DC: Eastern Service CenterOffice of History and Architecture, 

Department of the Interior, National Park 

Service, 1971. 

Calder, Dale R. and Lester D. Stephens. Seafaring 

Scientist: Alfred Goldsborough Mayor, Pioneer 

in Marine Biology, Columbia, South Carolina: 

University of South Carolina Press, 2006. 

Cipra, David L. Lighthouses, Lightships, and the Gulf of 

Mexico. Alexandria, Virginia: Cypress 

Communications, 1997. 

Dean, Love. Lighthouses of the Florida Keys. Sarasota, 

Florida: Pineapple Press, 1998. 

Ebert, James D. “Carnegie Institution of Washington 

and Marine Biology: Naples, Woods Hole, 

and Tortugas.” Washington, DC: Carnegie 

Institute of Washington, 1985. 

Florida Center for Instructional Technology, College 

of Education. “Florida’s Role in the Civil 

War: ‘Supplier of the Confederacy’.” 

University of South Florida. 

 http://fcit.usf.edu/Florida/cvl_war1.

htm. 

Holland, Jr., Francis R. America’s Lighthouses: Their 

Illustrated History Since 1776. Brattleboro, 

Vermont: Stephen Greene Press, 1972. 

Hurley, Neil E. Lighthouses of the Dry Tortugas, An 

Illustrated History. Aiea, Hawaii: Historic 

Lighthouse Publishers, 1998. 

Johnson, Stuart and Richard Ramsden. Rehabilitation 

Report and National Register Nomination for 

the United States Coast Guard Light Station 

Dry Tortugas Light Station, Loggerhead Key, 

Florida. National Park Service, 1984. 

Manucy, Albert. A Constructional History of Fort 

Jefferson 1846-1874. Atlanta, Georgia: 

National Park Service Southeast Region, 

1961. 

Organization and Duties of the Light-House Board and 

Regulations, Instructions, Circulars, and 

General Orders of the Light-House 

Establishment of the United States, 

Washington, DC: Government Printing 

Office, 1871. 

Tag, Thomas. “The Early Development of the Fresnel 

Lens.” U.S. Lighthouse Socieity, The Keeper’s 

Log, Summer, 2005. www.uslhs.org. 

______. “The Sautter Lens Works Producers of the 

Fresnel Lens—Parts 1 and 2” U.S. 

Lighthouse Society, The Keeper’s Log,

Summer, 2005. www.uslhs.org. 

U.S. Congress. Light-house and Appropriation Bill. 

Lighthouse Board. 32nd Congress, 1st sess., 

Statues at Large of the United States of 

America, 1789-1873. vol. 10, August, 1852. 

______. Light-house and Appropriation Bill. 34th

Congress, 1st sess., Statues at Large of the 

United States of America, 1789-1873. vol. 11, 

August, 1856. 

U.S. Lighthouse Board. Registers of Lighthouse 

Keepers, 1845-1912. National Archives and 

Records Administration Southeast Region, 

Morrow, Georgia. 

______.List of General Correspondence, 1791-1900. 

National Archives and Records 

Administration, Washington, DC. Record 

Group 26. NC-31. Series 38. 
114 Dry Tortugas Lighthouse HSR 

United States Coast Guard. Records Concerning 

Illuminating Apparatus, 1839-1960. National 

Archives and Records Administration, 

Washington, DC. Record Group 26. NC-31. 

Entry 59. 

______. Logbook of Lightstations. National Archives 

and Records Administration, Washington, 

DC. Record Group 26. NC-31. Entries 5, A1 

330E, A1 330M, A1 330T, A1 330S, A1 330Z, 

A1 330AF,159D-159I. 

______. Studies and Surveys. National Archives and 

Records Administration, Washington, DC. 

Record Group 26. NC-31. Entry A1 345. 

______. Boards of Survey (Real Property) Case Files. 

National Archives and Records 

Administration, Washington, DC. Record 

Group 26. NC-31. Entries A1 99 and 99a. 

______. Light Station Files. National Archives and 

Records Administration, Washington, DC. 

Record Group 26. NC-31. Entry 381. 

United States Department of Commerce. 

Recommendations as Aids to 

Navigation.National Archives and Records 

Administration, Washington, DC, Record 

Group 26 (These forms are filed within NC31. Entry 51. Boxes 408 and NC-31. Entries 

A1 99 and 99a and occasionally among other 

records. They are standard appropriation 

request forms.) 

United States Lighthouse Board. Dry Tortugas 

Clipping File. National Archives and 

Records Administration, Washington, DC. 

Record Group 26. NC-63. Entry 13. 

United States Bureau of Lighthouses. National 

Archives and Records Administration, 

Washington, DC. Record Group 

26. NC-31. Entry 51. Boxes 408 and 862. 
APPENDIX A 

Draft National Register Nomination 























APPENDIX B 

Materials Analysis 

Dry Tortugas Light Station

Materials Analysis

Dry Tortugas, Florida

August 2009

BUILDING CONSERVATION ASSOCIATES INC

Dry Tortugas Light Station

Materials Analysis

Dry Tortugas, Florida

Prepared For

Lord Aeck & Sargent Architecture

Ann Arbor, Michigan

Prepared By

Building Conservation Associates, Inc.

329 Race Street

Philadelphia, Pennsylvania 19106

CONTENTS

1.0 INTRODUCTION .........................................................................................1

2.0 METHODOLOGY...........................................................................................5

2.1 Finishes Analysis .................................................................................5

2.2 Mortar and Plaster Analysis ............................................................8

3.0 SUMMARY OF FINDINGS............................................................................9

3.1 Finishes Analysis ................................................................................9

3.2 Mortar and Plaster Analysis.............................................................18

4.0 CONCLUSIONS & RECOMMENDATIONS ...........................................23

4.1 Finishes ................................................................................................23

4.2 Mortar...................................................................................................31

APPENDICES

Appendix A: Sample Stratigraphies and Photomicrographs

Appendix B: Mortar and Plaster Analysis Report (Testwell, Inc. 2009)

Appendix C: Rehabilitation Report and National Register Nomination for the United Stated Coast 

Guard Light Station, Dry Tortugas Lighthouse, Loggerhead Key, Florida, 1984

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1.0 INTRODUCTION

At the request of Rob Yallop of Lord Aeck & Sargent Architecture (LAS), Building Conservation 

Associates, Inc. (BCA) prepared an analysis of select building materials removed from buildings 

associated with the Dry Tortugas Light Station, including the Dry Tortugas lighthouse. The light 

station is located in the Dry Tortugas National Park in Florida. The materials investigated as part of 

this study include mortar and paint finishes. The buildings investigated as part of this study include:

the lighthouse, original oil house, kitchen building, keeper’s residence and the south brick cistern. The 

primary goal of the materials analysis is to document the buildings’ original mortars and paint finishes 

for inclusion in a Historic Structure Report (HSR). A secondary goal is to provide recommendations 

for future restoration work based on the findings of the analysis. (Figures 1-5)

The report summarizes the findings of both the mortar analysis and the finishes study. Following the 

introductory information regarding the site and study methodology, the report discusses the findings 

of the research and then makes recommendations for appropriate restoration mortar mixes and 

paint colors. All mounted cross-sections have been labeled and permanently housed and will be 

archived at BCA’s Philadelphia office unless otherwise requested by the client.

All work required for the execution of this study was performed by Dorothy S. Krotzer, BCA 

Regional Director, with assistance from Testwell, Inc. for completion of the laboratory portion of the 

mortar analysis. Mortar and paint samples were taken from the site in March 2009 and laboratory 

analysis was performed in April and May 2009. 
DRY TORTUGAS LIGHT STATION. DRY TORTUGAS, FLORIDA. Page 2

Materials Analysis

BUILDING CONSERVATION ASSOCIATES INC August 2009

.

Figure 2. Oil house, March 

2009. Photograph by author.

Figure 1. Lighthouse, 

March 2009. Photograph by 

author.
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Materials Analysis

BUILDING CONSERVATION ASSOCIATES INC August 2009

Figure 3. Original kitchen building. March 2009. Photograph by author.

Figure 4. Keeper’s residence. March 2009. Photograph by author.
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Materials Analysis

BUILDING CONSERVATION ASSOCIATES INC August 2009

Figure 5. South brick cistern. March 2009. Photograph by author.
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BUILDING CONSERVATION ASSOCIATES INC August 2009

2.0 METHODOLOGY

Prior to the site visit and removal of samples, information related to the history of the Dry Tortugas 

Light Station provided by LAS was reviewed. Portions of the draft HSR, including historic images and 

information on the construction chronology and materials, were studied in order to gain a general 

understanding of the history of the site and any information related to the buildings’ paint finishes and 

masonry construction. The archival information included a 1984 Rehabilitation Report and National 

Register Nomination that contained paint and mortar analysis of the lighthouse. (Appendix C)

Once the relevant historical documentation was reviewed, a site visit was made and the buildings 

were physically examined for areas from which representative samples of mortar and paint finishes 

could be removed. Once these intact areas were identified, samples were removed. Mortar and 

plaster samples were removed using a small masonry chisel or five-in-one tool and a hammer. Paint 

samples were removed using a scalpel. A total of eleven mortar and plaster samples and sixteen finish 

samples were removed from the buildings and taken back to the laboratory for analysis. 

2.1 Finishes Analysis

All finish samples were initially examined in reflected light using a Nikon high-resolution 

stereomicroscope SMZ-1500 with variable magnification (16x-160x) to identify which samples would 

be embedded and sectioned for analysis. The selected samples were then mounted in a commercial 

polyester/methacrylate resin polymerized with a methyl ethyl ketone peroxide catalyst (Bioplast®). 

Embedded samples were sectioned on a Leco® VC-50 micro-saw for microscopic examination. The 

sectioned samples were dry-polished using a series of fine Micromesh® polishing cloths ranging from 

6,000 to 12,000 grit. Sectioned samples were observed under a Nikon 50i compound microscope in 

both visible light filtered through a daylight correction filter and ultraviolet light. The ultraviolet light 

was generated by a mercury illumination system filtered through a violet filter cube (EF4 V-2A 

Ex400/40 Dm430 Bar 450). Photomicrographs of representative samples were taken using a five 

megapixel Nikon DigiSight color digital camera system and are included in this report to illustrate 

specific observations.

All paint samples were viewed in cross-section and their paint layering sequences, or stratigraphies, 

recorded. These stratigraphies are included in Appendix A. Once the stratigraphies of every sample 

were deciphered, significant paint layers were identified and raw samples were manipulated in order 

to expose these layers for color matching purposes. Once the target layers were exposed, they were 

subjected to a bleaching process in order to reverse any yellowing that may have occurred over time. 

It is well documented that linseed oil-based paints (especially pale-colored paints) darken and yellow 

over time if not exposed to sunlight. This even affects oil-based finishes that have been covered with 
DRY TORTUGAS LIGHT STATION. DRY TORTUGAS, FLORIDA. Page 6

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BUILDING CONSERVATION ASSOCIATES INC August 2009

subsequent paint layers. In order to diminish this yellowing of paint layers, they were exposed to an 

ultraviolet light source for approximately two weeks.

Following the bleaching process, the exposed layers were subjected to a portable 

spectrophotometer, a GretagMacbeth X-Rite EyeOne®., in order to generate a CIE L*a*b* value for 

each sample. Then, each sample was visually matched to two different color systems, the 

standardized Munsell color system and the commercial Benjamin Moore paint palette. The 

spectrophotometer was then used to generate CIE L*a*b* values for each of the color matches. 

A color in the CIE L*a*b* system is defined according to three axes. The L*-axis (from 0 to 100)

is the light-dark axis. The a*-axis (from –100 to +100) is the green-red color axis. The b*-axis

(from –100 to +100) is the yellow-blue axis. Delta E is a measurement of the color difference

between the original paint surface color and the closest color matches that BCA has

identified. A perfect match would have a Delta E value of 0.00. Delta E equals the square root of

[(L*1 – L*2)2 + (a*1 – a*2)2 + (b*1 – b*2)2]. Where L*1, a*1, b*1 are the original paint surface values

and L*2, a*2, b*2 are the commercial paint values. Consequently, the lower the value of Delta E,

the closer the match. Although several commercial colors were tested for each element, only the 

closest match has been presented. All color matches are included in Section 4.1 of this report.

Finish samples were removed from the following locations:

LOKE.F.1 Oil house Exterior, east wall (now enclosed), finishes on 

brick.

LOKE.F.2 Passageway between oil 

house & lighthouse

Interior, south wall, finishes on concrete. For 

comparison with LOKE.F.1.

LOKE.F.3 Oil house Exterior, east wall (exposed), finishes on brick.

LOKE.F.4 Oil house Exterior, east wall (now enclosed), door frame, 

finishes on wood.

LOKE.F.5 South brick cistern Exterior, west wall, finishes on brick.

LOKE.F.6 Lighthouse Exterior, west elevation (now enclosed), 

finishes on brick. 

LOKE.F.7 Lighthouse Exterior, west wall (now enclosed), door 

frame, finishes on wood.

LOKE.F.8 Lighthouse Exterior, west wall (now enclosed), door to 

lighthouse, finishes on wood.

LOKE.F.9 Lighthouse Interior, ground floor level, finishes on brick.

LOKE.F.10 Kitchen building Exterior, east elevation, finishes on brick.

LOKE.F.11 Oil house Exterior, south elevation (now enclosed), 

finishes on brick.
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LOKE.F.12 Keeper’s residence Interior, hallway outside bathroom, original 

west wall (covered by drop ceiling), finishes on 

plaster.

LOKE.F.13 Keeper’s residence Interior, hallway outside bathroom, original 

west wall (covered by drop ceiling), original 

wood cornice, finishes on wood.

LOKE.F.14 Keeper’s residence Interior, bathroom, original west wall, finishes 

on plaster.

LOKE.F.15 Keeper’s residence Exterior, east elevation, front door frame, 

finishes on wood.

LOKE.F.16 Keeper’s residence Exterior, east elevation, front porch beam 

above columns, back face, finishes on wood.
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2.2 Mortar and Plaster Analysis

Cursory visual examination of the mortar samples was performed by D. Krotzer and subsequent 

laboratory analysis was executed by John Walsh of Testwell Laboratories, Inc. in Ossining, New 

York. John Walsh specializes in the analysis and identification of historic mortar materials. Testwell’s 

laboratory work included: petrographic examination; chemical analysis (gravimetric analysis and 

atomic absorption spectroscopy); statistical point counting (used instead of acid digestion to gain 

information on the quantity of aggregate since it is an acid-soluble carbonate sand); and water-soluble 

chloride analysis. The goal of Testwell’s analysis was to identify the binder and aggregate components 

of each mortar, as well as the original component ratio and any deterioration due to salt 

crystallization or hydration.

Although Testwell’s findings are discussed in Section 3.2 of this report, the full mortar analysis report 

has also been included in Appendix B.

Samples of brick mortar and plaster were removed from the following locations:

LOKE.M.1 Oil house Exterior, east elevation, mortar. Taken from 

protected wall now enclosed. Sample from 

interior of wall (from an area where a hole was 

cut through wall for a pipe).

LOKE.M.2 South brick cistern Exterior, east elevation, mortar.

LOKE.M.3 South brick cistern Interior, parging. Taken from upper portion of 

interior wall.

LOKE.M.4 Lighthouse Exterior, west elevation, mortar. Taken 

approx. 8-feet from ground.

LOKE.M.5 Lighthouse Exterior, west elevation, mortar. Taken from 

former exterior wall now enclosed, adjacent 

to entrance to lighthouse.

LOKE.M.6 Lighthouse Interior, mortar. Taken from wall at ground 

floor level.

LOKE.M.7 Lighthouse Interior, mortar. Taken from wall below watch 

level (supposedly rebuilt in 19th century).

LOKE.M.8 Oil house Interior, south wall, plaster. Taken from behind 

modern wood paneling and earlier beadboard 

wall; three-layer plaster system applied over 

brick.

LOKE.M.9 Kitchen building Exterior, north elevation, mortar. Sample from 

interior of wall.

LOKE.M.10 Keeper’s residence Exterior, west wall, mortar.

LOKE.M.11 Keeper’s residence Interior, bathroom, west wall, plaster. Twocoat plaster system.
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3.0 SUMMARY OF FINDINGS

3.1 Finishes Analysis

The paint finishes of five historic buildings at the Dry Tortugas Light Station were examined as part of 

this study. The majority of paint samples were removed from exterior brick and wood trim 

elements. However, samples of interior paint were also removed from the keeper’s residence and 

the lighthouse.

MASONRY

The exterior brick masonry surfaces of the oil house, south brick cistern and lower half of the 

lighthouse all seem to share a similar finish history. Each of these buildings has been painted a version 

of cream or white throughout its history, although the total number of layers varies. In addition, the 

earliest finish appears to be a white lime wash, followed by paint finishes (presumably oil-based) that 

are also white/cream in color. The brick masonry of the kitchen building was examined and found to 

only have four layers of modern white paint. The upper portion of the lighthouse (currently painted 

black) was not accessible at the time of the field investigation.

Although the brick masonry of the oil house, kitchen building, lighthouse and south brick cistern is 

currently painted, historic documentation indicates that originally the brick on these buildings was left 

unpainted. An undated historic photograph shows both the kitchen building and the oil house as 

exposed brick structures. (Figure 6) Although the date of this photograph is unknown, it must predate 1892 because a photograph taken circa 1892 clearly shows the oil house painted. (Figure 7) In 

the same circa 1892 photograph, the brickwork of the kitchen building, barely visible through the 

palm trees, remains unpainted. In addition, there are several written descriptions of the lighthouse 

dating from 1858 that refer to it as being a “natural color brick” or as a “brick-color tower.”1

Physical evidence confirms the historical documentation. The surface of the brick in samples 

removed from these buildings appears somewhat weathered and uneven, suggesting it was worn by 

exposure to the elements before being painted. The only structure that may have always been 

painted was the south brick cistern. As evidenced in Figure 9 the sample removed from the 

brickwork of the cistern shows a relatively clean brick surface, suggesting it has always been 

protected from the weather. (Figures 8-9)

 1 “Loggerhead Key Lighthouse, Dry Tortugas, Florida.” Printed October 21, 1993. PP. 1-2
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Figure 6. Historic image showing the oil house and kitchen building as unpainted brick masonry buildings. 

The Lighthouse has been painted black and white but the oil house is not yet painted, dating this photograph 

to some time between 1870 and 1892.

Figure 7. Historic image showing the 

lighthouse, oil house and old keeper’s 

residence circa 1892. Note that the oil 

house has been painted white in this 

photograph. Photograph courtesy of LAS.
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Figure 8. Oil house. Photomicrograph of painted exterior brick showing 

numerous layers of cream and white-colored paint. (40x magnification, visible 

light).

Figure 9. South brick cistern. Photomicrograph of earliest finish applied to brick 

wall of cistern. Note first layer is more translucent than the others and appears to 

be a limewash. Also, the surface of the brick is relatively unsoiled. (100x 

magnification, visible light).
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Although archival documentation indicates that the lighthouse was not originally painted, records 

document that it has been painted black and white at least since 1875, when an inspection log states

that “The black portion of the tower has been painted, and the remainder whitewashed.”2

Interestingly, this reference illustrates the use of two different types of paint finishes on the brick 

structures of the Dry Tortugas Light Station, a practice that may have been applied to not only the 

lighthouse but to the other buildings as well. For the lighthouse, it would have been necessary for the 

black finish to be a paint (presumably oil) instead of a lime wash, as achieving a truly black-colored 

lime wash would have been difficult if not impossible. 

A Rehabilitation Report and National Register Nomination on the Dry Tortugas lighthouse from 1984 

included materials analysis of the paint by Law Engineering Testing Company. One paint sample from 

the lighthouse was provided for analysis. Although the location of the sample was not indicated, it is 

assumed that the sample was removed from the exterior of the lighthouse. According to the 1984 

report, the paint sample consisted of two paint layers, both found to be an acrylic-polyvinyl acetate 

mixture with lead and zinc-based pigments. A recent in situ examination of the lighthouse exterior 

for this report confirms the presence of only a few layers of modern white paint on the exposed 

portion of the lighthouse exterior. This number of paint layers is far fewer than the approximately 30 

paint layers documented for the paint sample removed from a protected area of the lighthouse 

exterior (from a wall inside the connector building) as part of the current study. This discrepancy in 

number of paint layers can most likely be attributed to the fact that the exterior of the lighthouse 

was sandblasted in 1967. The blasting would have removed any early coatings, explaining why the 

sample examined in 1984 had only two paint layers and why the recent in situ investigation revealed 

only a few paint layers on the exposed portion of the lighthouse exterior. The paint sample removed 

from the protected area inside the connector is more representative of the complete finish history of 

the lighthouse exterior and provides insight into the building’s earliest finishes.

WOODWORK & METALWORK

The exterior woodwork of the four buildings (oil house, lighthouse, kitchen building and keeper’s 

residence) was also examined. The exterior door and doorframe of the lighthouse, currently 

enclosed by the link to the original oil house, contain between 30-35 layers of paint. The doorframe 

contains more paint layers than the door, suggesting it may pre-date the door. The earliest paint 

layers on the frame are cream-colored paint. After these, the frame was painted various shades of 

grays approximately 30 times. The door contains slightly fewer layers (approximately 30), all of which 

are various shades of gray. The doorframe of the original oil house was also painted numerous times 

(approximately 40 paint layers). The earliest finish is a medium gray. Subsequent layers are 

predominantly gray with a few creams later in the sequence. The wood trim of the kitchen building 

 2 LAS, Draft Historic Structure Report (HSR), “Background” section.
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contains only a few layers of modern paint, indicating the woodwork is relatively modern or that it 

has been stripped. (Figures 10-11)

The historic photographs provide some insight into the color palette of the exterior woodwork of 

these buildings. In both photographs, the window sash and frames of all of the buildings appear to be 

a pale color (likely white or cream) and the shutters are a dark color. However, at the time of this 

study, there was no access to historic windows in these buildings, as many have been replaced with 

modern units and the shutters have been removed. This prevented a positive identification of the 

actual color of the pale paint visible in the photographs. 

In the historic images shown in Figures 6 and 7, the doors of the buildings are typically open in the 

photographs, preventing the color of the doors from being seen; they could have been painted the 

light color of the windows or the dark color of the shutters. As discussed above, the physical 

evidence indicates that the door frame (and possibly the door) of the lighthouse was originally 

painted white, followed by numerous layers of gray paint. It is not know when the transition from 

white to gray occurred for the lighthouse. By contrast, the door frame of the original oil house was 

always painted gray. Again, there is no photographic evidence to corroborate either of these 

observations.

There is, however, written historic documentation regarding paint for the metalwork and woodwork 

of the lighthouse. In an 1862 document entitled “Instructions and Directions for Light-House and 

Light-Vessel Keepers of the United States”, paint colors and paint types are carefully specified for the 

interior and exterior metal and wood work of the lighthouse. All paint is linseed-oil based and 

generally glossy in sheen. The interior of the lighthouse lantern is to be painted white, while the 

exterior is to be painted black or red. Black seems to be the most prevalent color called for, 

although there are also references to “lead”, “gray”, “yellow”, “straw”, “brick”, “oak wood” and 

“Portland stone.” In addition, all ironwork is supposed to be primed with red lead.3 Although the 

metal components of the lighthouse were not examined as part of this study, the colors found on the 

existing woodwork (white and gray) are in keeping with the colors specified in 1862.

The exterior woodwork of the keeper’s residence was originally painted white, a conclusion based 

on both physical and archival documentation. Samples removed from the front porch trim show 11 

layers of white and cream paint. In addition, historic photographs of the house show white-colored 

trim and the preliminary specifications for the building that date to 1917 state that all woodwork was 

to be painted white. (Figure 12) The original hurricane blinds, which appear a dark color in the 

historic photographs, do not remain on the building and could therefore not be sampled to confirm 

 3

 Instructions and Directions for Light-House and Light-Vessel Keepers of the United States, 4th edition, 1862. 

Pages 106-110.
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Figure 10. Oil house. Photomicrograph of a paint sample removed from the exterior 

door of the oil house showing numerous layers of gray paint applied to the frame over 

time. (100x magnification, visible light).

Figure 11. Lighthouse. Photomicrograph of a paint sample removed from the 

exterior door frame of the lighthouse showing a similar range of gray paint colors as 

the sample above, although the earliest paint color was cream. (40x magnification, 

visible light).
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their original color. However, the preliminary specifications state that they are to be painted green. 

(Figure 13)

Select interior finishes of the keeper’s residence were also examined. Samples were removed from 

the plaster walls of the hallway and bathroom and the wood cornice of the hallway. The walls of both 

the hall and bathroom were painted a pale gray-green originally and the cornice was painted white, 

after having been sealed with a clear coat. The preliminary specifications call for the wood to be 

sealed with shellac and for a three-coat paint system (1 primer and 2 finish coats), all white in color. 

While the sealer layer and three-coat system seems to have been employed, the color varied from 

that included in the specification. (Figure 14)
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Figure 12. Historic image showing the exterior of the keeper’s residence. Note light-colored trim on most 

exterior woodwork with the exception of the hurricane blinds.

Figure 13. Keeper’s residence. Photomicrograph of a paint sample removed from the exterior 

porch trim contains only cream and white-colored paint. (100x magnification, visible light).
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Figure 14. Keeper’s residence. Photomicrograph of a sample of paint removed from 

the plaster wall’s of the bathroom. Note original three-layer paint system of two 

primers topped by a pale gray-green. (100x magnification, visible light).
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3.2 Mortar & Plaster Analysis

MORTAR

Laboratory analysis indicates that the majority of mortars used historically at the Dry Tortugas Light 

Station are composed of natural cement and local carbonate sand. Lime, which would have been 

added to the mortars as a gauging material to improve workability, was not documented in any of the 

historic mortars analyzed as part of this study. The natural cement and sand mortars were found at 

the lighthouse, the oil house, the original kitchen building and the south brick cistern. In addition, 

samples of mortar removed from four different locations within the lighthouse, including the portion 

of brick masonry directly below the watch room floor plate, were as natural cement and carbonate 

sand mortars that ware virtually indistinguishable from one another. The similarity of these mortars 

makes it difficult to draw any conclusions about the date of installation or type of mortars used for 

the numerous repair campaigns made to the lighthouse, which were documented in extensive 

written material. However, the physical evidence suggests that, although there were numerous 

repairs campaigns, the same mortar mix and ingredients were used consistently for the majority of 

the re-pointing campaigns in the 19th century. (Figure 15)

The natural cements in these mortars were identified as American natural cements, typical of those 

manufactured in Rosendale, New York or Louisville, Kentucky. The sand in all mortar samples was 

identified as a natural carbonate sand containing coral and shell fragments, presumably the same sand 

found along the shore of Loggerhead Key. The sand is fairly narrowly-graded, with the bulk of the 

material falling between a No. 16 and a No. 30 sieve. Given the remote location of the key, use of 

materials at hand such as beach sand for the construction of these buildings would have been 

practical as well as commonplace.

Establishing original component proportions for these mortars was challenging due to the acidsoluble carbonate sand. Instead of dissolving the binder through chemical means and extracting the 

insoluble sand, a different approach involving microscopical point-counting of sand and binder 

components and bulk chemical analysis of representative mortar samples had to be preformed. Using 

this non-traditional two-tiered approach revealed that the original binder to aggregate ratio of the 

Dry Tortugas Light Station mortar samples is approximately 1 part natural cement to 1.5 parts sand, 

by volume. This is a fairly typical mix for historic natural cement mortars. A more in-depth discussion 

of the methodology used to determine this ratio is discussed in Appendix B.

A natural cement is defined as an eminently hydraulic lime that is typically derived from the burning

of highly impure limestone. It is these impurities that give the lime the characteristic of hydraulicity, 

or the ability to set by reaction with water (no air is needed, unlike with pure high calcium limes). 

Natural cements differ from Portland cements, which were produced later, in that the latter are 

artificially produced. Portland cements of the 19th century were made by grinding together chalk and 
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clay and then heating the mixture at high temperatures to produce a simulated natural cement. Both 

natural and Portland cements can have quite high strength and durability. Natural cement based 

mortars were quite common in the mid to late 19th century and would have been readily available 

when these buildings were constructed. 4

The use of natural cement and carbonate sand mortars is, of course, not surprising given what we 

know about the construction of nearby Fort Jefferson, which dates to roughly the same period and is 

associated with the same builders. In fact, Captain H.G. Wright, who oversaw the construction of 

Fort Jefferson, wrote a proposal to the Light House Board for the construction of the Dry Tortugas 

lighthouse in which he calls specifically for the use of cement mortars with no lime. Writing in 1855, 

he states: “I am disposed to believe that the mortar for both brickwork and concrete should be 

made of cement and sand without any admixture of lime, and in the proportion of two parts of the 

latter to one of the former in powder.”5 Note that the ratio Wright calls for is quite close to that 

documented in the current lab analysis.

Although Wright does not specifically call for “natural cement”, there was no other commercially 

available cement in the United States until Portland cement was introduced in the 1870s. So, the 

mortar Wright was specifying was indeed meant to be a natural cement based mortar. There were 

many subsequent repair campaigns that involved re-pointing weathered brick joints as well as 

significant reconstruction of a portion of the masonry below the lighthouse lantern in 1875. Natural 

cement mortars were specified for some of the re-pointing repairs, namely those made to the 

lighthouse in 1868.

The Rehabilitation Report from 1984 also included chemical analysis of a mortar sample taken from the 

Dry Tortugas lighthouse. The results of this report conflict with the findings presented here. The 

report identified the mortar sample as a lime-based mortar with a small percentage of Portland 

cement and possibly gypsum as the binder mix, and fine silica sand and shell fragments as the 

aggregate. Because the aggregate contains calcium carbonate-based shell fragments, the acid in the 

chemical analysis will dissolve the aggregate as well as the binder, and will therefore not provide an 

accurate reflection of the mortar proportions. In addition, it also may cause the binder to be 

misidentified as lime. The author of the 1984 report does note that because of the shell content of 

the mortar, precise identification of the binder to aggregate ratio is impossible, but they still provide 

an approximate ratio of 1part cement, 3 parts lime and 12 parts sand.

 4

 Eckel, Edwin C. Cements, Limes and Plasters. Reprinted Third Edition. Dorset: Donhead Publishing, 2005. Page 

242.
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Figure 15. Lighthouse. Area of historic mortar removed for analysis. Note 

characteristic carbonate sand inclusions.

 5

 LAS, Draft Historic Structure Report (HSR), “Background” section. [Reference: Dry Tortugas Light Station 

clipping file, Appendix no. 17, H.G. Wright, Capitan of Engineers, Fort Jefferson, FL, letter to Lieutenant T.A. 

Jenkins, U.S.N., secretary, Light-house Board, Washington, D.C., September 23, 1855, Record Group 26, NA.]

Figure 16. Oil house. Area of early 

plaster, discovered behind later wall 

finishes, removed for analysis.
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The only mortar analyzed as part of this study that did not contain natural cement was the mortar 

removed from the exterior brickwork of the keeper’s residence, which dates from 1922-23. This 

mortar is composed exclusively of Portland cement and the same local carbonate sand; no lime was 

detected in this mortar either. The estimated cement to sand ratio, by volume, is 1 part cement to 

2.4 parts sand.

Archival research supports the use of Portland cement and local sand in the construction of the 

keeper’s residence. The 1920 specifications for the construction call for mortar to be composed of 

“1 part [Portland] cement and 2-1/2 parts sand. Hydrated lime not to exceed 10% by volume of the 

cement shall be used for tempering.”6 Although the mortar specifications were written for concrete 

block and not brick, the information can certainly be applied to the brick. In fact, the ingredients and 

proportions documented in the current lab analysis are almost identical to those included in the 1920 

specifications.

The mortars were also examined for the presence of any deterioration due to salt crystallization or 

salt hydration. This examination was performed petrographically, looking for signs of microcracking, 

and chemically, looking for elevated levels of water-soluble alkali salts (sodium, potassium and 

chloride). In general, most mortar samples exhibit “good microstructural integrity”, with no evidence 

of deterioration from salts. Although some minor sulfate deposits and chlorides were detected, they 

are not related to any significant cracking distress. In addition, the presence of alkali salts is most 

likely due to the original mortar mix and the use of unwashed sands, an not from subsequent 

deposits of salt from the environment.

PLASTER

Interior plaster of two of the historic buildings was also examined. In the oil house, a sample of a 

three-coat plaster system, discovered behind a layer of modern wood paneling and a bead board 

wall, was removed for analysis. The plaster is composed of: a lime and carbonate sand scratch coat 

gauged with natural cement, a natural cement and carbonate sand brown coat, and a lime-based finish 

coat that is gauged with gypsum (no sand). Although it is unclear when this plaster dates from, it is 

possible that it is original to the building and dates to the 1850s. The sand used in the scratch and 

brown coats is the same as that used in the brick mortar of the same building, a local carbonate sand.

(Figure 16)

The other interior plaster examined for this study was removed from the keeper’s residence, and 

presumably dates to the original 1922-23 period of construction. The plaster is a two-coat system, 

with gypsum and sand-based scratch coat and a gypsum-based finish coat gauged with lime. The 

brown coat is consistent with a Keene’s cement mixture. Keene’s cement is a slow-setting, hard-

 6

 1920 specification, page 3.
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finish plaster produced by burning very pure gypsum at high temperatures and treating the material 

with alum or other chemicals during the manufacturing process.7 The current lab findings indicate 

that a different plaster was used than what was originally specified. The preliminary specifications for 

the keeper’s residence, which date to 1920, call for the use of cement and lime plaster and not 

gypsum. However, the finish plaster was to be “cement plaster equal to the US Gypsums Co’s 

Adamant’”, a fire-resistant type of early drywall.

For a more in depth discussion of the specific findings of the mortar and plaster analysis performed 

as part of this study, including detailed characterization of the aggregate and binder as well as 

annotated photomicrographs, refer to Appendix B.

 7

 Edwin C. Eckel. Cements, Limes and Plasters: Their Materials, Manufacture and Properties. Michigan: Donhead 

Publishing Co. 2005 (originally published 1905), 78.
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4.0 CONCLUSIONS AND RECOMMENDATIONS

4.1 Finishes

MASONRY

The recommendation for an appropriate paint finish for the masonry of the historic buildings at the 

Dry Tortugas Light Station is fairly straightforward. The white finish on the brick masonry portions of 

the lighthouse, oil house, south brick cistern and kitchen building should be maintained (note that the 

masonry portions of the keeper’s residence were never painted). Even though archival and physical 

evidence indicates that these buildings were not originally painted (possibly with the exception of the 

cistern), a white finish was applied early enough in their history that it can be considered historically 

significant. For instance, the oil house was painted white by circa 1892 and the lighthouse was painted 

with its current black and white scheme by 1875. In the case of the lighthouse, not only is the black 

and white paint scheme historic, but it also defines the lighthouse’s appearance and its identity. In 

addition to being historically appropriate, the use of a finish on the brick masonry of these buildings 

also affords a level of protection for the brick substrate by protecting it from wind and moisture that 

would no doubt take a toll on the surface of the brick over time, possibly eroding away the fire skin 

and making the brick even more susceptible to weathering. 

Although the brick of these buildings should be maintained white, the type of finish used to achieve 

this white color should be carefully considered. Archival evidence indicates that both limewash and 

oil paints were used historically on the buildings at the Dry Tortugas Light Station, although where 

each of these finishes was used is not always made clear. Physical evidence, however, suggests that 

white limewash was used on the brick portions of these buildings, with the exception of the black 

paint on the top half of the lighthouse, and oil paint was used on the wood elements. The use of 

limewash on masonry structures was commonplace throughout history and into the early 20th

century. It was an inexpensive and readily available finish. From a preservation perspective, limewash 

is a perfect finish for masonry substrates because it forms a good bond, it is moisture-permeable and 

it resists biological growth. It could also be renewed both easily and cheaply. 

The majority of the white finishes currently on the brick buildings at the Dry Tortugas Light Station 

appear to be modern acrylic- or oil-based paints. While the color of the finish is appropriate, the 

finish type is not. These modern finishes, which in some cases appear to be trapping moisture in the 

wall, should be removed and white limewash applied instead. Of course, care should be taken to 

carefully remove the modern paint layers in a way that does not damage the brick substrate (this 

would exclude the use of many abrasive blasting techniques). In addition, the existing paint should be 

tested to determine any lead content prior to removal. The materials analysis included in the 1984 

rehabilitation report cites that the paint on the exterior of the lighthouse is an acrylic-polyvinyl 

acetate mixture with lead and zinc-based pigments. It is likely this paint still remains on the lighthouse 
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and that other buildings of the light station were painted with the same lead-based paint. Further

testing would be required to identify lead content in any of the paint coatings on the buildings.

Once the modern coatings are successfully removed from the brick masonry, the limewash will bond 

well to the brick, the mortar and any traces of earlier limewash. The limewash will allow any 

moisture present in the brick walls to escape without compromising the limewash finish (as opposed 

to the less permeable modern paints which can fail when moisture gets trapped behind them). 

Performing a mock-up of such a finish is strongly advised in order to assess the longevity of this type 

of finish in the environmental conditions associated with the island.

The only masonry surface that should not get painted with a lime wash is the top half of the day 

mark, which is painted black. Achieving a truly black limewash is difficult if not impossible, so some 

other type of finish will have to be used in this location. Although oil paints were most likely used 

historically, a better paint may be currently available. Modern paints such as those based on 

potassium silicate or even some highly permeable acrylic paints designed for historic masonry should 

be considered for the lighthouse.

WOODWORK & METALWORK

Recommendations for appropriate restoration finishes for the woodwork and metalwork of the oil 

house, lighthouse and keeper’s residence are included in the chart below; no paint colors are 

provided for the kitchen building because no historic paint was found on the wood trim of this 

building. Wherever surviving physical evidence remains, a color match to the historic paint color is 

provided. Color matches are made to both the Munsell and Benjamin Moore color systems. 

However, in cases where there is no longer any physical paint evidence or access to a particular 

element was not permitted during the study, recommendations for appropriate restoration colors 

are provided but are based solely on archival information (written or photographic). In the latter 

case, a general recommendation is provided but a specific color match is not. The basis for each 

color match is provided in the “Source” column of the chart below.

The recommended restoration paint colors are provided below. Specific color matches have been 

made to both the standardized Munsell color system and the commercial Benjamin Moore paint 

palette. CIE L*a*b values for the actual color as well as the color matches are also provided so that 

the difference between the actual color and the matches can be determined. Please note that, 

although there was subtle variation in the color of the limewashes on the different buildings, a single 

color match to the limewash is provided.

It should also be mentioned that the recommended colors for the lighthouse and oil house door trim 

(which are based on physical evidence) may represent original paint colors that were on the buildings 

when the brick masonry was exposed and not once the brick was painted white. Unfortunately, it is 
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not possible to determine the paint color on the wood door trim when the brick was first painted 

white.

Any attempt to reproduce the following pages, including printing from the electronic version of the 

report, will distort the color of the provided chips. Only the actual color chip or notation should be 

used for paint replication purposes.





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4.2 Mortar

Analysis of the brick mortars of the buildings at the Dry Tortugas Light Station indicates that the 

original mortars were composed of natural cement. Such mortars were typical for the period, 

especially for maritime construction. The mortar has generally held up well through the years, even 

in the harsh environment of wind and salt-laden sea air; although exceptions can be seen at the 

lighthouse, where the mortar is friable in many areas and paint loss occurs regularly at the mortar 

joints. However, as previously discussed, this deterioration is most likely a factor of moisture 

permeating through the wall and inappropriate paint films and not failure of the original material. A 

more comprehensive evaluation of this aspect of the masonry construction falls outside of the scope 

of this research.

For future re-pointing campaigns, it is important that the correct mortar be used. It may also be 

prudent to replace existing repair campaigns with a more appropriate mortar. Mortars based on 

large amounts of Portland cement are typically too strong and dense to be used in combination with 

the type of low-fired brick found on most of these buildings. Although, the keeper’s residence, which 

was built later, is an exception, as it is constructed of high-fired modern brick and Portland cement 

mortar. In general, the use of a high calcium or hydraulic lime mortar would also be inappropriate for 

these buildings. Therefore, the recommended restoration mortar for the historic buildings at the Dry 

Tortugas Light Station is as follows:

Lighthouse, Oil House, Kitchen Building & South Brick Cistern

Binder: natural cement 

Sand: natural carbonate sand (to match existing)

Component Ratio (binder: sand): 1:1.5

Keeper’s Residence

Binder: Portland cement

Sand: natural carbonate sand (to match existing)

Component Ratio (binder: sand): 1:3 (note this mix is slightly less binder-rich than the original)

APPENDIX A.

PHOTOMICROGRAPHS AND STRATIGRAPHIES

* bold indicates a finish layer and not a primer

SAMPLE NO: LOKE.F.1 (40x, Visible Light)

LOCATION: Oil House, exterior, east elevation now enclosed, finishes on brick.

LAYER* COLOR NOTES

Substrate Brick Surface looks weathered and soiled, suggests exposure 

prior to painting

1 Cream All finishes look like paint, missing early limewash layer 

visible in LOKE.F.9

2 Off-white

3 Off-white

4 Cream

5 Cream

6 Cream

7 Off-white

8 Cream

9 Off-white

10 Off-white

11 Off-white Current finish
* bold indicates a finish layer and not a primer

SAMPLE NO: LOKE.F.2 (100x, Visible Light)

LOCATION: Passageway between Oil House & Lighthouse, south wall, finishes on concrete.

LAYER* COLOR NOTES

Substrate Concrete

1 Off-white

2 Cream

3 Cream

4 Off-white

5 Off-white Modern paint

6 Off-white Current finish
* bold indicates a finish layer and not a primer

SAMPLE NO: LOKE.F.3 (40x, Visible Light)

LOCATION: Oil House, exterior, east elevationl, finishes on brick.

LAYER* COLOR NOTES

Substrate Brick Fracture at surface suggests weathering prior to painting

1 Cream

2 Cream

3 Cream

4 Cream

5 Cream

6 Cream

7 Cream

8 Cream

9 Cream

10 Cream/tan Translucent 

11 White

12 Off-white

13 Off-white

14 Off-white

15 White Current finish
SAMPLE NO: LOKE.F.4 (100x, Visible Light, only earliest layers visible in photo)

LOCATION: Oil House, exterior, east elevation, door frame, finishes on wood.

LAYER* COLOR NOTES

Substrate Wood

1 Pale gray

2 Pale gray

3 Pale gray

4 Gray-green Translucent 

5 Pale gray

6 Pale gray

7 Pale gray

8 Pale gray

9 Medium gray

10 Pale gray

11 Medium gray

12 Medium gray

13 Medium gray

14 Pale gray

15 Medium gray

16 Off-white
* bold indicates a finish layer and not a primer

17 Gray-green

18 Gray-green

19 Light gray-green

20 Pale gray

21 Off-white/ pale gray

22 Pale gray

23 Pale gray

24 Dark gray

25 Cream 

26 Off-white Remaining paints look more modern

27 Dark gray

28 Gray 

29 Blue-gray

30 White 

31 Dark gray

32 Cream

33 Cream

34 Cream

35 Cream

36 Cream

37 Cream

38 Cream

39 Gray

40 Olive green

41 Dark gray

42 White 

43 Dark gray

44 Dark gray

45 Dark gray

46 Light Gray

47 Gray Current finish
* bold indicates a finish layer and not a primer

SAMPLE NO: LOKE.F.5 (100x, Visible Light)

LOCATION: Cistern, west elevation, finishes on brick.

LAYER* COLOR NOTES

Substrate Brick (missing in photo) No sign of weathering of brick surface, suggests brick was 

always finished

1 Off-white Translucent, white wash

2 Off-white Translucent, white wash

3 Off-white

4 Off-white Modern paint

5 White

6 White Current finish
SAMPLE NO: LOKE.F.6 (40x, Visible Light)

LOCATION: Lighthouse, exterior, north wall now enclosed adjacent to door, finishes on brick.

LAYER* COLOR NOTES

Substrate Brick Surface looks soiled

1 Tan Thin, translucent, lime wash

2 Cream

3 Tan Translucent 

4 Cream

5 Tan

6 Cream

7 Buff

8 Cream

9 White

10 Cream

11 Cream

12 Cream

13 Cream

14 Cream

15 Cream

16 Cream
17 Cream

18 Cream

19 Cream

20 [fracture]

21 White 

22 Light Green

23 Blue

24 Light Green

25 Blue

26 Dark Blue

27 Dark Blue

28 Gray

29 Gray

-blue

30 White Current finish
SAMPLE NO: LOKE.F.7 (40x, Visible Light)

LOCATION: Lighthouse, exterior, west wall now enclosed, door frame, finishes on wood.

LAYER* COLOR NOTES

Substrate Wood

1 Cream

2 Off-white

3 Off-white

4 Cream

5 Off-white 

6 Cream Translucent 

7 Off-white

8 Cream

9 Off-white

10 Dark green-gray Translucent 

11 Blue-gray

12 Dark blue-gray

13 Gray

14 Blue-gray

15 Light blue-gray

16 Light blue-gray

17 White 

18 Light blue-gray
* bold indicates a finish layer and not a primer

19 Light blue-gray

20 Blue-gray

21 Blue-gray

22 Dark blue-gray

23 Light blue-gray

24 Gray

25 Light gray

26 Gray

27 Blue-gray

28 Blue-gray

29 Blue-gray

30 Blue-gray

31 Blue-gray

32 Blue-gray

33 Blue-gray

34 Gray Thin 

35 Dark blue-gray

36 Blue-gray

37 White 

38 White 

39 Blue-gray

40 Light blue-gray

41 Gray Current finish
SAMPLE NO: LOKE.F.8 (100x, Visible Light, only earliest layers visible in photo)

LOCATION: Lighthouse, exterior, west wall now enclosed, door, finishes on wood.

LAYER* COLOR NOTES

Substrate Wood (not visible in photo)

1 Cream

2 Light gray

3 Light gray

4 Gray

5 Gray

6 Blue-gray

7 Gray

8 Blue-gray

9 Blue-gray

10 Blue-gray

11 Blue-gray

12 Light blue-gray

13 Light blue-gray

14 Dark blue-gray

15 Blue-gray

16 Blue-gray

17 White 

18 Blue-green
* bold indicates a finish layer and not a primer

19 Light blue-green

20 Blue-green

21 Blue-gray

22 Blue-gray

23 Blue-gray

24 Light blue-gray

25 Light blue-gray

26 Light green

27 Dark blue

28 Blue-gray

29 Light blue-gray

30 Gray Current finish
* bold indicates a finish layer and not a primer

SAMPLE NO: LOKE.F.9 (40x, Visible Light)

LOCATION: Oil House, exterior, east wall, finishes on brick.

LAYER* COLOR NOTES

Substrate Brick Surface looks weathered

1 Cream Translucent, limewash

2 Cream Remaining layers look like paint

3 Cream

4 Cream Translucent material at surface

5 Cream

6 Off-white

7 Cream

8 Cream

9 Cream

10 White Translucent 

11 Cream

12 White Current Finish
* bold indicates a finish layer and not a primer

SAMPLE NO: LOKE.F.10 (40x, Visible Light)

LOCATION: Kitchen Building, exterior, east elevation, finishes on brick.

LAYER* COLOR NOTES

Substrate Brick/Mortar

1 White All layers are modern paint

2 White

3 White

4 White

5 White Current Finish
SAMPLE NO: LOKE.F.11 (40x, Visible Light)

LOCATION: Oil House, exterior, south elevation now enclosed, finishes on brick.

LAYER* COLOR NOTES

Substrate Brick Surface is weathered, suggests exposure

1 Cream/tan Translucent, lime wash (partial layer)

2 Cream

3 Cream

4 Cream

5 Light cream

6 Cream

7 Cream

8 Cream

9 Cream

10 Cream

11 Cream

12 Cream

13 White

14 Off-white

15 White

16 Gray

17 Light gray

18 Light gray/off-white
* bold indicates a finish layer and not a primer

19 Off-white

20 Cream

21 Off-white

22 Light gray/off-white

23 Off-white

24 Green

25 Gray

26 Dark blue-gray

27 Light green

28 Green

29 Peach

30 White Current finish
* bold indicates a finish layer and not a primer

SAMPLE NO: LOKE.F.12 (100x, Visible Light)

LOCATION: Keeper’s Dwelling, interior, hallway outside bathroom, west wall, finishes on plaster.

LAYER* COLOR NOTES

Substrate Plaster

1 Cream

2 White

3 Cream

4 Light green

5 Light green

6 White

7 Medium blue

8 Warm yellow

9 Medium green

10 Cream

11 White 

12 Cream

13 Light gray/beige

14 White 

15 Cream

16 White Current finish
* bold indicates a finish layer and not a primer

SAMPLE NO: LOKE.F.13 (200x, Visible Light)

LOCATION: Keeper’s Dwelling, interior, hallway outside bathroom, cornice, finishes on wood.

LAYER* COLOR NOTES

Substrate Wood Sealed with clear coat

1 Cream

2 White

3 Cream

4 White

5 Cream

6 White

7 Cream Current finish
* bold indicates a finish layer and not a primer

SAMPLE NO: LOKE.F.14 (100x, Visible Light)

LOCATION: Keeper’s Dwelling, interior, bathroom, west wall, finishes on plaster.

LAYER* COLOR NOTES

Substrate Plaster

1 Cream

2 White

3 Light Green

4 Light Gray

5 Gray

6 Blue

7 Warm cream

8 White

9 Light blue 

10 White

11 Light blue Current finish (behind drywall)
* bold indicates a finish layer and not a primer

SAMPLE NO: LOKE.F.15 (100x, Visible Light)

LOCATION: Keeper’s Dwelling, exterior, east elevation, front door surround, finishes on wood.

LAYER* COLOR NOTES

Substrate Wood Surface distressed, looks stripped, missing earliest finish?

1 Dark green Soaked into pores of wood at surface

2 Cream 

3 White Thin 

4 Gray-green

5 White 

6 Dark red Thin 

7 Dark gray 

8 Dark red Disrupted, weathered

9 White

10 White Current finish 
* bold indicates a finish layer and not a primer

SAMPLE NO: LOKE.F.16 (40x, Visible Light)

LOCATION: Keeper’s Dwelling, exterior, east elevation, porch soffit (rear face), finishes on wood.

LAYER* COLOR NOTES

Substrate Wood

1 White

2 Cream Translucent 

3 White 

4 Cream

5 Off-white

6 Cream 

7 Cream

8 White

9 Cream 

10 White

11 White Current finish 

APPENDIX B.

MORTAR AND PLASTER ANALYSIS REPORT

(TESTWELL, INC. 2009)

TESTWELL, INC. 

Building Conservation Associates, Inc.; Loggerhead Key Light Station 

Report #: OPCL011/PGE-001 

Page 2 of 53 

Table of Contents 

1. Introduction 3 

2. Methods of Examination 3 

3. Petrographic Findings 4 

4. Point-Count Analyses 17 

5. Chemical Analyses 18 

5.1 Chemical Analysis Results 18 

5.2 Calculated Components 20 

6. Discussion and Conclusions 22 

6.1 Mortar Materials 22 

6.2 LOKE.M.10 Materials 24 

6.3 LOKE.M.8 Materials 24 

6.4 LOKE.M.11 Materials 25 

6.5 Cracking Distress and Salt Crystallization 26 

Appendix I: Photographs and Photomicrographs 27 
TESTWELL, INC. 

Building Conservation Associates, Inc.; Loggerhead Key Light Station 

Report #: OPCL011/PGE-001 

Page 3 of 53 

 

1. Introduction 

On March 27, 2009, Testwell received eleven mortar and plaster samples from Ms. Dorothy Krotzer of Building 

Conservation Associates, Inc. reported to have been sampled from various structures at the Loggerhead Key Light Station in 

the Dry Tortugas National Park, FL (Figs. 1 through 4). Samples are identified by the client as follows: 

Sample No. Building Description 

LOKE.M.1 Oil House Exterior, east elevation mortar. Taken from protected wall now enclosed. Sample 

from interior of wall (from an area where a hole was cut through wall for a pipe). 

LOKE.M.2 Brick Cistern Exterior, east elevation mortar. 

LOKE.M.3 Brick Cistern Interior, parging. Taken from upper portion of interior wall. 

LOKE.M.4 Lighthouse Exterior, west elevation, mortar. Taken approximately 8-feet from ground. 

LOKE.M.5 Lighthouse Exterior, west elevation, mortar. Taken from former exterior wall now enclosed, 

adjacent to entrance to lighthouse. 

LOKE.M.6 Lighthouse Interior, mortar. Taken from wall at ground floor level. 

LOKE.M.7 Lighthouse Interior, mortar. Taken from wall below watch level (supposedly rebuilt in 19th 

century). 

LOKE.M.8 Oil House Interior, south wall, plaster. Taken from behind modern wood paneling and earlier 

beadboard wall; three-layer plaster system applied over brick. 

LOKE.M.9 Kitchen Building Exterior, north elevation, mortar. Sample from interior of wall. 

LOKE.M.10 Keeper’s Dwelling Exterior, west wall, mortar. 

LOKE.M.11 Keeper’s Dwelling Interior, bathroom, west wall, plaster. Two-coat plaster system. 

At the client’s request, all samples are examined petrographically in order to identify material constituents and assess the 

degree of microcracking and associated mineral deposition. Aside from some of the plaster coats, all samples are also 

analyzed chemically in order to provide information regarding original binder chemistries and estimate original component 

proportions. Water-soluble chloride analysis is also requested for the four lighthouse mortar samples in order to provide 

information regarding possible salt crystallization or hydration distress. Finally, statistical point-count analysis is performed 

on three strategically chosen samples in order to provide a cross-check of the material proportion estimates generated from 

the chemical analyses. 

2. Methods of Examination 

The petrographic examination is conducted in accordance with the standard practices contained within ASTM C 1324: 

Standard Test Method for Examination and Analysis of Hardened Masonry Mortar. Data collection is performed by a 

degreed geologist who by nature of his/her education is qualified to operate the analytical equipment employed. Analysis 

and interpretation is performed or directed by a supervising petrographer who satisfies the qualifications as specified in 

Section 3 of ASTM C 856. 

Chemical analysis was conducted via a modification of the procedures outlined in ASTM C 1324: Standard Test Method for 

Examination and Analysis of Hardened Masonry Mortar. Water, carbon dioxide and aggregate weight percentages are 

determined gravimetrically. Oxide weight percentages are determined by atomic absorption spectroscopy. 

Statistical point counting was conducted in general accordance with the procedures outlined in ASTM C 457: Standard Test 

Method for Microscopical Determination of Parameters of the Air-Void System in Hardened Concrete. Sample sizes do not 

satisfy the minimum requirements outlined in the method and results are used as an approximate cross-check for other more 

quantitative methods. 

Water-soluble chloride analysis was performed in accordance with ASTM C 1218: Standard Test Method for Water-Soluble 

Chloride in Mortar and Concrete. 
TESTWELL, INC. 

Building Conservation Associates, Inc.; Loggerhead Key Light Station 

Report #: OPCL011/PGE-001 

Page 4 of 53 

3. Petrographic Findings 

SAMPLE ID LOKE.M.1 (Oil House) 

GENERAL APPEARANCE 

Sample Type/Dimensions Multiple, irregular, mortar fragments weighing 17.91g. 

Surfaces One piece has two parallel sides that may be a joint surface. Approximately 0.5” thick. 

Hardness / Friability Moderately hard and non-friable. 

Appearance Luster on freshly exposed surfaces is dull. Fresh paste color is light gray (Munsell color designation approximately 

2.5Y 7/2). 

Cracks, Deposits, Etc., Cracking cannot be assessed due to the fragmental nature of the sample. No mineral deposits are observed. There is a 

low abundance of coal fragments detected. 

AGGREGATE 

Lithology and Mode Carbonate natural sand consisting of shell fragments and porous coral fragments. Low abundance of opaques are also 

detected. 

Appearance Viewed on weathered surfaces the sand is white in some cases and with a pale yellow hue (Munsell color code 

approximately N9 to 5Y 8/1). The luster is slightly reflective to dull. 

Size and Gradation The sand is medium-grained and somewhat narrowly graded. The nominal top size is estimated at the No. 16 sieve 

with most material estimated to pass. Peak abundance is estimated between the No. 16 and No. 30 sieve and few fines 

are present below No. 50. 

Shape Subrounded in shape on average. Aspect ratios are subequant to subelongate. 

Distribution Homogeneous and somewhat randomly oriented though there is a somewhat preferential alignment of more elongate 

grains parallel or subparallel to the bed. 

Other No cracking, coatings, or chemical reactions are detected. 

BINDER MATRIX 

Hardened Binder Dense and homogeneous cementitious matrix with moderate to moderately high capillary porosity on average. No 

significant calcium hydroxide as a cementitious hydrate is detected and the paste is almost completely carbonated. 

Residual Hydraulic Grains Natural cement relicts are found in moderate to moderately high abundance. These are fine to medium grained and 

generally carbonated in cross polarized light. Microtextures are varied but include typical calcined dolomite rhombs 

with rims of iron-bearing ferrite and distributed grains of partially combined quartz silt. Rimmed quartz silt is also 

commonly found as isolated grains within the paste matrix. No significant clinkered material is detected but there are 

traces of inert aluminate clusters. 

Residual Lime Grains None detected. 

Residual Pozzolans None detected. 

Pigments None detected. 

AIR-VOID SYSTEM 

Estimated Air Content Estimated at 4% - 6% 

Consolidation / Distribution The mortar is well consolidated and the air distribution is homogeneous. 

Size / Shape Voids are generally less than 1 mm in dimension. Voids are rounded and subspherical to irregular in shape on average. 

Secondary Deposits No secondary deposits are positively identified. 

AGGREGATE INTERFACES 

Details Sand grains are well coated with binder. No variation in binder characteristics are found adjacent to aggregate. No 

cracking or secondary mineral deposits are found at aggregate interfaces. In honed section, interfaces are moderately 

soft when scratched with a steel pick but do not exhibit any significant friability. 

SECONDARY REACTIONS 

Carbonation In thin section, all portions of the sample exhibit virtually full carbonation. 

Other No other evidence for chemical reaction is found within the bulk of the material. 

CRACKING 

Details Trace microcracking is found along one edge of the sample in thin section. Otherwise, no significant macroscopic or 

microscopic cracking is detected. 
TESTWELL, INC. 

Building Conservation Associates, Inc.; Loggerhead Key Light Station 

Report #: OPCL011/PGE-001 

Page 5 of 53 

SAMPLE ID LOKE.M.2 (Brick Cistern) 

GENERAL APPEARANCE 

Sample Type/Dimensions Multiple, irregular, mortar fragments weighing 26.79 g. 

Surfaces One piece has two parallel sides that may be a joint surface. Approximately 0.5” thick. 

Hardness / Friability Moderately hard and non-friable. 

Appearance Luster on freshly exposed surfaces is dull with some waxy areas where there are cement streaks. Fresh paste color is 

light gray (Munsell color designation approximately 2.5Y 7/2). 

Cracks, Deposits, Etc., Cracking cannot be assessed due to the fragmental nature of the sample. There is an adherent veneer of a white coating 

on many pieces. Sand grains are exposed below this wash indicating prior weathering. Low abundance of coal 

fragments are detected. 

AGGREGATE 

Lithology and Mode Carbonate natural sand consisting of shell fragments and porous coral fragments. Low abundance of opaques are also 

detected. 

Appearance Viewed on weathered surfaces the sand is white in some cases and with a pale yellow hue (Munsell color code 

approximately N9 to 5Y 8/1). The luster is slightly reflective to dull. 

Size and Gradation The sand is medium-grained and somewhat narrowly graded. The nominal top size is estimated at the No. 16 sieve. 

Peak abundance is estimated between the No. 16 and No. 30 sieve and few fines are present below No. 50.

Shape Subrounded in shape on average. Aspect ratios are subequant to subelongate. 

Distribution Homogeneous and somewhat randomly oriented. Preferential alignment of more elongate grains are not obvious. 

Other No cracking, coatings, or chemical reactions are detected. 

BINDER MATRIX 

Hardened Binder Dense and homogeneous cementitious matrix with moderate to moderately high capillary porosity on average. No 

significant calcium hydroxide as a cementitious hydrate is detected and the paste is almost completely carbonated. 

Residual Hydraulic Grains Natural cement relicts are found in moderate abundance. These are fine to medium grained and generally carbonated in 

cross polarized light. Microtextures are varied but include typical calcined dolomite rhombs with rims of iron-bearing 

ferrite and distributed grains of partially combined quartz silt. Rimmed quartz silt is also commonly found as isolated 

grains within the paste matrix. No significant clinkered material is detected but there are traces of inert aluminate 

clusters. 

Residual Lime Grains None detected. 

Residual Pozzolans None detected. 

Pigments None detected. 

AIR-VOID SYSTEM 

Estimated Air Content Estimated at 3% - 5% 

Consolidation / Distribution The mortar is well consolidated and the air distribution is homogeneous. 

Size / Shape Voids are generally less than 1 mm in dimension. Voids are rounded and subspherical to irregular in shape on average. 

Secondary Deposits No secondary deposits are positively identified. 

AGGREGATE INTERFACES 

Details Sand grains are well coated with binder. No variation in binder characteristics are found adjacent to aggregate. Minor 

abundance of microcracking found around aggregate paste interfaces. No secondary mineral deposits are found at 

aggregate interfaces. In honed section, interfaces are moderately soft when scratched with a steel pick but do not 

exhibit any significant friability. 

SECONDARY REACTIONS 

Carbonation In thin section, all portions of the sample exhibit virtually full carbonation. 

Other No other evidence for chemical reaction is found within the bulk of the material. 

CRACKING 

Details Minor abundance of polygonal microcracking found passing through the paste and around aggregate paste interfaces. 

Some green-colored organic material is observed within cracks. No other significant macroscopic or microscopic 

cracking is detected. 
TESTWELL, INC. 

Building Conservation Associates, Inc.; Loggerhead Key Light Station 

Report #: OPCL011/PGE-001 

Page 6 of 53 

SAMPLE ID LOKE.M.3 (Brick Cistern) 

GENERAL APPEARANCE 

Sample Type/Dimensions Multiple, irregular, parging mortar fragments weighing 97.83 g. 

Surfaces Approximately 0.25” - 0.5” in thickness. 

Hardness / Friability Moderately hard and non-friable. 

Appearance Luster on freshly exposed surfaces is dull. Fresh paste color is light brownish gray (Munsell color designation 

approximately 10YR 6/2). 

Cracks, Deposits, Etc., No significant cracking is detected in hand sample. Paste is in positive relief over the aggregate at the microscopic 

scale along the exposed surface. There is a low abundance of coal fragments detected. No mineral deposits are 

observed. 

AGGREGATE 

Lithology and Mode Carbonate natural sand consisting of shell fragments and porous coral fragments. Low abundance of opaques are also 

detected. 

Appearance Viewed on weathered surfaces the sand is white in some cases and with a pale yellow hue (Munsell color code 

approximately N9 to N8). The luster is slightly reflective to dull. 

Size and Gradation The sand is medium-grained and somewhat narrowly graded. The nominal top size is estimated at the No. 16 sieve. 

Peak abundance is estimated between the No. 16 and No. 30 sieve and few fines are present below No. 50.

Shape Subrounded in shape on average. Aspect ratios are subequant to subelongate. 

Distribution Homogeneous and somewhat randomly oriented though there is a somewhat preferential alignment of more elongate 

grains parallel or subparallel to the bed. 

Other No cracking, coatings, or chemical reactions are detected. 

BINDER MATRIX 

Hardened Binder Dense and homogeneous cementitious matrix with moderate to moderately high capillary porosity on average. The 

paste has a very slightly clumpy texture. No significant calcium hydroxide as a cementitious hydrate is detected and the 

paste is almost completely carbonated. 

Residual Hydraulic Grains Natural cement relicts are found in moderate abundance. These are fine to medium grained and generally carbonated in 

cross polarized light. Microtextures are varied but include typical calcined dolomite rhombs with rims of iron-bearing 

ferrite and distributed grains of partially combined quartz silt. Rimmed quartz silt is also commonly found as isolated 

grains within the paste matrix. No significant clinkered material is detected but there are traces of inert aluminate 

clusters. 

Residual Lime Grains None detected. 

Residual Pozzolans None detected. 

Pigments None detected. 

AIR-VOID SYSTEM 

Estimated Air Content Estimated at 5% - 7% 

Consolidation / Distribution The mortar is well consolidated and the air distribution is homogeneous. 

Size / Shape Voids are generally less than 1 mm in dimension. Voids are subrounded and subspherical to irregular in shape on 

average. 

Secondary Deposits Most voids are free of secondary deposits with only traces of sparry carbonate detected. 

AGGREGATE INTERFACES 

Details Sand grains are relatively well coated with binder. No variation in binder characteristics are found adjacent to 

aggregate. Moderate abundance of small discontinuous polygonal cracking found along aggregate paste interfaces. 

Secondary mineral deposits are found at aggregate interfaces in trace abundance as sparry carbonate. In honed section, 

interfaces are moderately soft when scratched with a steel pick but do not exhibit any significant friability. 

SECONDARY REACTIONS 

Carbonation In thin section, all portions of the sample exhibit virtually full carbonation. 

Other No other evidence for chemical reaction is found within the bulk of the material. 

CRACKING 

Details Microscopic discontinuous hairline polygonal cracking detected in moderate abundance throughout the thin section. No 

other significant macroscopic or microscopic cracking is detected. 
TESTWELL, INC. 

Building Conservation Associates, Inc.; Loggerhead Key Light Station 

Report #: OPCL011/PGE-001 

Page 7 of 53 

SAMPLE ID LOKE.M.4 (Lighthouse) 

GENERAL APPEARANCE 

Sample Type/Dimensions Multiple, irregular, mortar fragments weighing 24.14 g. 

Surfaces One piece has two parallel sides that may be a joint surface. Approximately 0.5” thick. 

Hardness / Friability Moderately hard and non-friable. 

Appearance Luster on freshly exposed surfaces is dull. Fresh paste color is light gray (Munsell color designation approximately 

2.5Y 7/2). 

Cracks, Deposits, Etc., Cracking cannot be assessed due to the fragmental nature of the sample. There is an adherent veneer of a white 

powdery coating on many pieces. There is a low abundance of coal fragments detected. 

AGGREGATE 

Lithology and Mode Carbonate natural sand consisting of shell fragments and porous coral fragments. Low abundance of opaques are also 

detected. One chalcedony grain detected may belong to the cement. 

Appearance Viewed on weathered surfaces the sand is white in some cases and with a pale yellow hue (Munsell color code 

approximately N9 to 5Y 8/1). The luster is slightly reflective to dull. 

Size and Gradation The sand is medium-grained and somewhat narrowly graded. The nominal top size is estimated at the No. 16 sieve 

with most material estimated to pass. Peak abundance is estimated between the No. 16 and No. 30 sieve and few fines 

are present below No. 50. 

Shape Subrounded in shape on average. Aspect ratios are subequant to subelongate. 

Distribution Homogeneous and somewhat randomly oriented though there is a somewhat preferential alignment of more elongate 

grains parallel or subparallel to the bed. 

Other No cracking, coatings, or chemical reactions are detected. 

BINDER MATRIX 

Hardened Binder Dense and homogeneous cementitious matrix with moderate capillary porosity on average. No significant calcium 

hydroxide as a cementitious hydrate is detected and the paste is mostly carbonated though some areas remain isotropic. 

Residual Hydraulic Grains Natural cement relicts are found in varied abundance with some mortar pieces exhibiting a high abundance. These are 

variously sized grains and are generally carbonated in cross polarized light. Microtextures are varied but include typical 

calcined dolomite rhombs with rims of iron-bearing ferrite and distributed grains of partially combined quartz silt. 

Rimmed quartz silt is also commonly found as isolated grains within the paste matrix. No significant clinkered material 

is detected but there are traces of inert aluminate clusters. 

Residual Lime Grains None detected. 

Residual Pozzolans None detected. 

Pigments None detected. 

AIR-VOID SYSTEM 

Estimated Air Content Estimated at 4% - 6% 

Consolidation / Distribution The mortar is well consolidated and the air distribution is homogeneous. 

Size / Shape Voids are generally less than 1 mm in dimension. Voids are irregular in shape on average. 

Secondary Deposits No secondary deposits are positively identified. 

AGGREGATE INTERFACES 

Details Sand grains are well coated with binder. No variation in binder characteristics are found adjacent to aggregate. No 

cracking or secondary mineral deposits are found at aggregate interfaces. In honed section, interfaces are moderately 

soft when scratched with a steel pick but do not exhibit any significant friability. 

SECONDARY REACTIONS 

Carbonation In thin section, most portions of the sample exhibit virtually full carbonation. 

Other No other evidence for chemical reaction is found within the bulk of the material. 

CRACKING 

Details No significant macroscopic or microscopic cracking is detected. 

MISCELLANEOUS 

Details Opaque finishes are detected above a discontinuous microscopic veneer of depleted material in some areas of the 

perimeter. 
TESTWELL, INC. 

Building Conservation Associates, Inc.; Loggerhead Key Light Station 

Report #: OPCL011/PGE-001 

Page 8 of 53 

SAMPLE ID LOKE.M.5 (Lighthouse) 

GENERAL APPEARANCE 

Sample Type/Dimensions Multiple, irregular, mortar fragments weighing 28.28 g. 

Surfaces All pieces exhibit irregular surfaces. 

Hardness / Friability Moderately hard and non-friable. 

Appearance Luster on freshly exposed surfaces is dull. Fresh paste color is light gray (Munsell color designation approximately 

2.5Y 7/2). 

Cracks, Deposits, Etc., Cracking cannot be assessed due to the fragmental nature of the sample. There is an adherent veneer of a white 

powdery coating on many pieces and a minor amount of adherent brick residue. There is a low abundance of coal 

fragments detected. 

AGGREGATE 

Lithology and Mode Carbonate natural sand consisting of shell fragments and porous coral fragments. Low abundance of opaques are also 

detected. 

Appearance Viewed on weathered surfaces the sand is white in some cases and with a pale yellow hue (Munsell color code 

approximately N9 to 5Y 8/1). The luster is slightly reflective to dull. 

Size and Gradation The sand is medium-grained and somewhat narrowly graded. The nominal top size is estimated at the No. 16 sieve 

with most material estimated to pass. Peak abundance is estimated between the No. 16 and No. 50 sieve and 

moderately low amount of fines are present below No. 50. 

Shape Subrounded in shape on average. Aspect ratios are subequant to subelongate. 

Distribution Homogeneous and somewhat randomly oriented though there is a somewhat preferential alignment of more elongate 

grains parallel or subparallel to the bed. 

Other No cracking, coatings, or chemical reactions are detected. 

BINDER MATRIX 

Hardened Binder Dense and homogeneous cementitious matrix with moderate to moderately high capillary porosity on average. No 

significant calcium hydroxide as a cementitious hydrate is detected and the paste is almost completely carbonated. 

Residual Hydraulic Grains Natural cement relicts are found in moderately low abundance. These are fine to medium grained and generally 

carbonated in cross polarized light. Microtextures are varied but include typical calcined dolomite rhombs with rims of 

iron-bearing ferrite and distributed grains of partially combined quartz silt. Rimmed quartz silt is also commonly found 

as isolated grains within the paste matrix. No significant clinkered material is detected but there are traces of inert 

aluminate clusters. 

Residual Lime Grains None detected. 

Residual Pozzolans None detected. 

Pigments None detected. 

AIR-VOID SYSTEM 

Estimated Air Content Estimated at 4% - 6% 

Consolidation / Distribution The mortar is well consolidated and the air distribution is homogeneous. 

Size / Shape Voids are generally less than 1 mm in dimension. Voids are irregular in shape on average. 

Secondary Deposits Most voids are free of secondary deposits. 

AGGREGATE INTERFACES 

Details Sand grains are well coated with binder. Zones of possible bleed water channels are found around some aggregate paste 

interfaces. Trace, small discontinuous cracks are found subparallel to the surface and passing around aggregates 

interfaces. No secondary mineral deposits are found at aggregate interfaces. In honed section, interfaces are moderately 

soft when scratched with a steel pick but do not exhibit any significant friability. 

SECONDARY REACTIONS 

Carbonation In thin section, all portions of the sample exhibit virtually full carbonation. 

Other Traces of very fine grained deposits are found only within one microcrack surface and these have characteristics 

consistent with either sulfates or chlorites. 

CRACKING 

Details Small discontinuous cracks are found subparallel to the surface and passing around aggregates interfaces. Otherwise no

significant macroscopic or microscopic cracking is detected. 

MISCELLANEOUS 

Details A layer of lime wash is detected that is well bonded to the mortar. Lime wash appears to have two distinct layers. 

There is an opaque finish found above the lime wash. 
TESTWELL, INC. 

Building Conservation Associates, Inc.; Loggerhead Key Light Station 

Report #: OPCL011/PGE-001 

Page 9 of 53 

SAMPLE ID LOKE.M.6 (Lighthouse) 

GENERAL APPEARANCE 

Sample Type/Dimensions Multiple, irregular, mortar fragments weighing 59.75 g. 

Surfaces One piece has two parallel sides that may be a joint surface. Approximately 0.5” thick. 

Hardness / Friability Moderately hard and non-friable. 

Appearance Luster on freshly exposed surfaces is dull. Fresh paste color is light gray (Munsell color designation approximately 

10YR 7/2). 

Cracks, Deposits, Etc., Cracking cannot be assessed due to the fragmental nature of the sample. There is an adherent veneer of a white 

powdery coating on many pieces and a minor amount of adherent brick residue. There is a low abundance of coal 

fragments detected. 

AGGREGATE 

Lithology and Mode Carbonate natural sand consisting of shell fragments and porous coral fragments. Low abundance of opaques are also 

detected. 

Appearance Viewed on weathered surfaces the sand is white in some cases and with a pale yellow hue (Munsell color code 

approximately N9 to 5Y 8/1). The luster is slightly reflective to dull. 

Size and Gradation The sand is medium-grained and somewhat narrowly graded. The nominal top size is estimated at the No. 8 sieve with 

all material estimated to pass. Peak abundance is estimated between the No. 16 and No. 30 sieve and few fines are 

present below No. 50. 

Shape Subrounded in shape on average. Aspect ratios are subequant to subelongate. 

Distribution Homogeneous and somewhat randomly oriented though there is a somewhat preferential alignment of more elongate 

grains parallel or subparallel to the bed. 

Other No cracking, coatings, or chemical reactions are detected. 

BINDER MATRIX 

Hardened Binder Dense and homogeneous cementitious matrix with moderate capillary porosity on average. No significant calcium 

hydroxide as a cementitious hydrate is detected and the paste is almost completely carbonated. 

Residual Hydraulic Grains Natural cement relicts are found in moderate to moderately high abundance. These are variously sized grains and are 

generally carbonated in cross polarized light. Microtextures are varied but include typical calcined dolomite rhombs 

with rims of iron-bearing ferrite and distributed grains of partially combined quartz silt. Rimmed quartz silt is also 

found as isolated grains within the paste matrix. No significant clinkered material is detected but there are traces of 

inert aluminate clusters. 

Residual Lime Grains None detected. 

Residual Pozzolans None detected. 

Pigments None detected. 

AIR-VOID SYSTEM 

Estimated Air Content Estimated at 6% - 8% 

Consolidation / Distribution The mortar is well consolidated and the air distribution is homogeneous. 

Size / Shape Voids are generally less than or equal to 1 mm in dimension. Voids are rounded and subspherical to irregular in shape 

on average. 

Secondary Deposits Most voids are free of secondary deposits. 

AGGREGATE INTERFACES 

Details Sand grains are well coated with binder. No variation in binder characteristics are found adjacent to aggregate. No 

cracking or secondary mineral deposits are found at aggregate interfaces. In honed section, interfaces are moderately 

soft when scratched with a steel pick but do not exhibit any significant friability. 

SECONDARY REACTIONS 

Carbonation In thin section, all portions of the sample exhibit virtually full carbonation. 

Other A microscopically thin lining of isotropic, low relief secondary deposits tends to line the exterior surfaces of many of 

the mortar pieces. Some are also found within voids just adjacent to the surface but never in the interior. 

CRACKING 

Details No significant macroscopic or microscopic cracking is detected. 
TESTWELL, INC. 

Building Conservation Associates, Inc.; Loggerhead Key Light Station 

Report #: OPCL011/PGE-001 

Page 10 of 53 

SAMPLE ID LOKE.M.7 (Lighthouse) 

GENERAL APPEARANCE 

Sample Type/Dimensions Multiple, irregular, mortar fragments weighing 42.36 g. 

Surfaces All pieces exhibit irregular surfaces. 

Hardness / Friability Moderately hard and non-friable. 

Appearance Luster on freshly exposed surfaces is dull. Fresh paste color is light gray (Munsell color designation approximately 

10YR 7/2). 

Cracks, Deposits, Etc., Cracking cannot be assessed due to the fragmental nature of the sample. No mineral deposits are observed. There is a 

low abundance of coal fragments detected. 

AGGREGATE 

Lithology and Mode Carbonate natural sand consisting of shell fragments and porous coral fragments. Low abundance of opaques are also 

detected. 

Appearance Viewed on weathered surfaces the sand is white in some cases and with a pale yellow hue (Munsell color code 

approximately N9 to 5Y 8/1). The luster is slightly reflective to dull. 

Size and Gradation The sand is medium-grained and somewhat narrowly graded. The nominal top size is estimated at the No. 16 sieve. 

Peak abundance is estimated between the No. 16 and No. 30 sieve and few fines are present below No. 50. 

Shape Subrounded in shape on average. Aspect ratios are subequant to subelongate. 

Distribution Homogeneous and somewhat randomly oriented. Preferential alignment of more elongate grains is not obvious. 

Other No cracking, coatings, or chemical reactions are detected. 

BINDER MATRIX 

Hardened Binder Dense and homogeneous cementitious matrix with moderate capillary porosity on average. No significant calcium 

hydroxide as a cementitious hydrate is detected and the paste is almost completely carbonated. 

Residual Hydraulic Grains Natural cement relicts are found in moderate to moderately high abundance. These are variously sized grains and are 

generally carbonated in cross polarized light. Microtextures are varied but include typical calcined dolomite rhombs 

with rims of iron-bearing ferrite and distributed grains of partially combined quartz silt. Rimmed quartz silt is also 

commonly found as isolated grains within the paste matrix. No significant clinkered material is detected but there are 

traces of inert aluminate clusters. 

Residual Lime Grains None detected. 

Residual Pozzolans None detected. 

Pigments None detected. 

AIR-VOID SYSTEM 

Estimated Air Content Estimated at 3% - 5% 

Consolidation / Distribution The mortar is well consolidated and the air distribution is homogeneous. 

Size / Shape Voids are generally less than 1 mm in dimension. Voids are rounded and subspherical to irregular in shape on average. 

Secondary Deposits No secondary deposits are positively identified. 

AGGREGATE INTERFACES 

Details Sand grains are well coated with binder. No variation in binder characteristics are found adjacent to aggregate. No 

cracking or secondary mineral deposits are found at aggregate interfaces. In honed section, interfaces are moderately 

soft when scratched with a steel pick but do not exhibit any significant friability. 

SECONDARY REACTIONS 

Carbonation In thin section, all portions of the sample exhibit virtually full carbonation. 

Other No other evidence for chemical reaction is found within the bulk of the material. 

CRACKING 

Details No significant macroscopic or microscopic cracking is detected. 
TESTWELL, INC. 

Building Conservation Associates, Inc.; Loggerhead Key Light Station 

Report #: OPCL011/PGE-001 

Page 11 of 53 

SAMPLE ID LOKE.M.8 (Oil House) 

GENERAL APPEARANCE 

Sample Type/Dimensions The sample represents a complete cross section of a three coat plaster system. One large piece and several smaller 

pieces were received from the interior, south wall weighing 40.17 g. The nominal thickness of the whole sample is 

0.75”. Three distinct material types are detected. Thicknesses of the three general layers is as follows: 

Scratch coat: approximately 1/8” 

Brown coat: approximately 3/8” 

Finish coat: approximately 1/8” 

Surfaces Contact surfaces are more or less planar. The scratch and finish coats are partially adhered to the brown coat. The 

finish coat disbonds easily along a relatively clean surface. 

Hardness / Friability Scratch coat: Moderately soft and moderately non-friable. 

Brown coat: Hard and non-friable. 

Finish coat: Moderately soft and moderately friable.

Appearance Scratch coat: Dull luster and nearly white on fresh exposure (Munsell color code approximately 5Y 8/1). 

Brown coat: Opaque waxy luster and light gray on fresh exposure (Munsell color code approximately 10YR 7/2). 

Finish coat: Moderately dull luster and bright white on fresh exposure (Munsell color code approximately N9). 

Cracks, Deposits, Etc., No significant cracking is visible in the larger sample though incipient disbonds may be present at layer contacts. No 

mineral deposits are observed. There is a low abundance of coal fragments detected within the brown coat. 

SAMPLE ID LOKE.M.8 (Oil House plaster scratch coat) 

AGGREGATE 

Lithology and Mode Carbonate natural sand consisting of shell fragments and porous coral fragments. 

Appearance Viewed on weathered surfaces the sand is white in some cases and with a pale yellow hue (Munsell color code 

approximately N9). The luster is dull. 

Size and Gradation The sand is medium-grained and narrowly graded. The nominal top size is estimated at the No. 8 sieve with all material 

estimated to pass. A strong peak abundance is estimated between the No. 16 and No. 30 sieves and only a moderately 

low abundance of material is estimated to pass the No. 30 sieve.

Shape Subrounded in shape on average. Aspect ratios are subequant to subelongate. 

Distribution Homogeneous and somewhat randomly oriented. Preferential alignment of more elongate grains is not obvious. 

Other No cracking, coatings, or chemical reactions are detected. 

BINDER MATRIX 

Hardened Binder Homogeneous mildly hydraulic matrix with high capillary porosity on average and a moderate abundance of 

discontinuous polygonal microscopic cracks. 

Residual Hydraulic Grains Natural cement relicts are found in very low abundance. These are fine to medium grained and generally carbonated in 

cross polarized light. Microtextures are varied but include typical calcined dolomite rhombs with rims of iron-bearing 

ferrite and trace grains of partially combined quartz silt isolated within the paste matrix. 

Residual Lime Grains Low abundance of fine residual lime grains. Grains are fully carbonated with no internal relict rock textures or 

hydraulic inclusions. However, textures are difficult to assess due to a limited sample size. 

Residual Pozzolans None detected. 

Pigments None detected. 

AIR-VOID SYSTEM 

Estimated Air Content Estimated at 2% - 3% 

Consolidation / Distribution The plaster is well consolidated and the air distribution is homogeneous. 

Size / Shape Voids are generally less than 1 mm in dimension. Voids are rounded and subspherical in shape on average. 

Secondary Deposits No secondary deposits are positively identified. 

AGGREGATE INTERFACES 

Details Sand grains are well coated with binder. No variation in binder characteristics are found adjacent to aggregate. 

Discontinuous polygonal cracking is detected along some of the interfaces. Otherwise, no significant cracking or 

secondary mineral deposits are found at aggregate interfaces. In honed section, interfaces are soft when scratched with 

a steel pick. 

SECONDARY REACTIONS 

Carbonation In thin section, all portions of the sample exhibit virtually full carbonation. 

Other No other evidence for chemical reaction is found within the bulk of the material. 

CRACKING 

Details Discontinuous polygonal cracking. Otherwise, no significant macroscopic or microscopic cracking is detected. 
TESTWELL, INC. 

Building Conservation Associates, Inc.; Loggerhead Key Light Station 

Report #: OPCL011/PGE-001 

Page 12 of 53 

SAMPLE ID LOKE.M.8 (Oil House plaster brown coat) 

AGGREGATE 

Lithology and Mode Carbonate natural sand consisting of shell fragments and porous coral fragments. Low abundance of opaques are also 

detected. 

Appearance Viewed on weathered surfaces the sand is white in some cases and with a pale yellow hue (Munsell color code 

approximately N9 to 5Y 8/1). The luster is slightly reflective to dull. 

Size and Gradation The sand is medium-grained and narrowly graded. The nominal top size is estimated at the No. 8 sieve with all material 

estimated to pass. A strong peak abundance is estimated between the No. 16 and No. 30 sieves and only a moderately 

low abundance of material is estimated to pass the No. 30 sieve. 

Shape Subrounded in shape on average. Aspect ratios are subequant to subelongate. 

Distribution Homogeneous and somewhat randomly oriented though there is a somewhat preferential alignment of more elongate 

grains parallel or subparallel to the bed. 

Other No cracking, coatings, or chemical reactions are detected. 

BINDER MATRIX 

Hardened Binder Dense and homogeneous cementitious matrix with moderate capillary porosity on average. No significant calcium 

hydroxide as a cementitious hydrate is detected and the paste is almost completely carbonated. 

Residual Hydraulic Grains Natural cement relicts are found in moderate to moderately high abundance. These are fine to medium grained though 

fines are much more abundant and are generally carbonated in cross polarized light. Microtextures are varied but 

include typical calcined dolomite rhombs with rims of iron-bearing ferrite and distributed grains of partially combined 

quartz silt. Rimmed quartz silt is also commonly found in high abundance as isolated grains within the paste matrix. 

No significant clinkered material is detected but there are traces of inert aluminate clusters. 

Residual Lime Grains None detected. 

Residual Pozzolans None detected. 

Pigments None detected. 

AIR-VOID SYSTEM 

Estimated Air Content Estimated at 4% - 6% 

Consolidation / Distribution The mortar is well consolidated and the air distribution is homogeneous. 

Size / Shape Voids are generally less than 1 mm in dimension. Voids are rounded and subspherical to irregular in shape on average. 

Secondary Deposits No secondary deposits are positively identified. 

AGGREGATE INTERFACES 

Details Sand grains are well coated with binder. No variation in binder characteristics are found adjacent to aggregate. No 

cracking or secondary mineral deposits are found at aggregate interfaces. In honed section, interfaces are moderately 

soft when scratched with a steel pick but do not exhibit any significant friability. 

SECONDARY REACTIONS 

Carbonation In thin section, all portions of the sample exhibit virtually full carbonation. 

Other No other evidence for chemical reaction is found within the bulk of the material. 

CRACKING 

Details No significant macroscopic or microscopic cracking is detected. 

SAMPLE ID LOKE.M.8 (Oil House plaster finish coat) 

AGGREGATE 

Details No aggregate is present in the finish coat. 

BINDER MATRIX 

Hardened Binder Homogeneous mixed binder matrix with high capillary porosity and no significant microcracking. The matrix consists 

of a mixture of very fine grained, hydrated gypsum crystallites and fine mostly carbonated lime. 

Residual Hydraulic Grains None detected. 

Residual Lime Grains Residual lime grains are found in high abundance as fine- to medium grained particles. Most are fully carbonated 

though fully uncarbonated grains are also observed. Relict rock textures are rare and are difficult to interpret. 

However, these have the character of partially calcined silicate minerals. No evidence for significant hydraulic 

inclusions is observed. 

Residual Gypsiferous Grains Medium-grained gypsum relicts are relatively rare. Some of rehydrated to gypsum while some still represent 

unhydrated hemihydrate. Dead-burned anhydrite crystals are extremely rare. 

Residual Pozzolans None detected. 

Pigments None detected. 

AIR-VOID SYSTEM 

Estimated Air Content Estimated at 2% - 3% 

Consolidation / Distribution The plaster is well consolidated and the air distribution is homogeneous. 

Size / Shape Voids are generally less than 1 mm in dimension. Voids are irregular in shape on average. 

Secondary Deposits No significant secondary deposits are observed. 

SECONDARY REACTIONS 

Carbonation In thin section, all portions of the sample exhibit virtually full carbonation. 

Other No other evidence for chemical reaction is found within the bulk of the material. 

CRACKING 

Details No significant macroscopic or microscopic cracking is detected. 
TESTWELL, INC. 

Building Conservation Associates, Inc.; Loggerhead Key Light Station 

Report #: OPCL011/PGE-001 

Page 13 of 53 

SAMPLE ID LOKE.M.9 (Kitchen Building) 

GENERAL APPEARANCE 

Sample Type/Dimensions Multiple, irregular, mortar fragments weighing 28.75 g. 

Surfaces One piece has two parallel sides that may be a joint surface. Approximately 0.5” thick. 

Hardness / Friability Moderately hard and non-friable. 

Appearance Luster on freshly exposed surfaces is dull. Fresh paste color is light gray (Munsell color designation approximately 

2.5Y 7/2). 

Cracks, Deposits, Etc., Cracking cannot be assessed due to the fragmental nature of the sample. There is an adherent veneer of a white coating 

on many pieces. There is a low abundance of coal fragments detected. 

AGGREGATE 

Lithology and Mode Carbonate natural sand consisting of shell fragments and porous coral fragments. Low abundance of opaques are also 

detected. 

Appearance Viewed on weathered surfaces the sand is white in some cases and with a pale yellow hue (Munsell color code 

approximately N9 to 5Y 8/1). The luster is slightly reflective to dull. 

Size and Gradation The sand is medium-grained and somewhat narrowly graded. The nominal top size is estimated at the No. 16 sieve 

with most material estimated to pass. Peak abundance is estimated between the No. 16 and No. 30 sieve and few fines 

are present below No. 50. 

Shape Subrounded in shape on average. Aspect ratios are subequant to subelongate. 

Distribution Homogeneous and somewhat randomly oriented though there is a somewhat preferential alignment of more elongate 

grains parallel or subparallel to the bed. 

Other No cracking, coatings, or chemical reactions are detected. 

BINDER MATRIX 

Hardened Binder Dense and homogeneous cementitious matrix with a moderately high to high capillary porosity. No significant calcium 

hydroxide as a cementitious hydrate is detected and the paste is almost completely carbonated. 

Residual Hydraulic Grains Natural cement relicts are found in moderate abundance. These are medium grained and generally carbonated in cross 

polarized light. Microtextures are varied but include typical calcined dolomite rhombs with rims of iron-bearing ferrite 

and distributed grains of partially combined quartz silt. Rimmed quartz silt is also commonly found as isolated grains 

within the paste matrix. No significant clinkered material is detected but there are traces of inert aluminate clusters. 

Residual Lime Grains None detected. 

Residual Pozzolans None detected. 

Pigments None detected. 

AIR-VOID SYSTEM 

Estimated Air Content Estimated at 4% - 6% 

Consolidation / Distribution The mortar is well consolidated and the air distribution is homogeneous. 

Size / Shape Voids are generally less than 1 mm in dimension. Voids are rounded and subspherical to irregular in shape on average. 

Secondary Deposits No secondary deposits are positively identified. 

AGGREGATE INTERFACES 

Details Sand grains are well coated with binder. No variation in binder characteristics are found adjacent to aggregate. No 

cracking or secondary mineral deposits are found at aggregate interfaces. In honed section, interfaces are moderately 

soft when scratched with a steel pick but do not exhibit any significant friability. 

SECONDARY REACTIONS 

Carbonation In thin section, all portions of the sample exhibit virtually full carbonation. 

Other No other evidence for chemical reaction is found within the bulk of the material. 

CRACKING 

Details No significant macroscopic or microscopic cracking is detected. 
TESTWELL, INC. 

Building Conservation Associates, Inc.; Loggerhead Key Light Station 

Report #: OPCL011/PGE-001 

Page 14 of 53 

SAMPLE ID LOKE.M.10 (Keeper’s Dwelling) 

GENERAL APPEARANCE 

Sample Type/Dimensions Multiple, irregular, mortar fragments weighing 32.83 g. 

Surfaces One piece has two parallel sides that may be a joint surface. Approximately 0.5” thick. There are weathered areas with 

a type of biological growth present in low abundance. 

Hardness / Friability Moderately hard and non-friable. 

Appearance Luster on freshly exposed surfaces is mostly dull, however the mortar does exhibit streaking and high variation. Fresh 

paste color is very pale brown (Munsell color designation approximately 10YR 8/2). 

Cracks, Deposits, Etc., Cracking cannot be assessed due to the fragmental nature of the sample. No mineral deposits are observed. 

AGGREGATE 

Lithology and Mode Carbonate natural sand consisting of shell fragments and porous coral fragments. 

Appearance Viewed on weathered surfaces the sand is white in some cases and with a pale yellow hue (Munsell color code 

approximately N9 to 5Y 8/1). The luster is slightly reflective to dull. 

Size and Gradation The sand is medium-grained and somewhat narrowly graded. The nominal top size is estimated at the No. 16 sieve 

with most material estimated to pass. Peak abundance is estimated between the No. 16 and No. 50 sieve and few fines 

are present below No. 50. 

Shape Subrounded in shape on average. Aspect ratios are subequant to subelongate. 

Distribution Homogeneous and somewhat randomly oriented. Preferential alignment of more elongate grains is not obvious. 

Other No cracking, coatings, or chemical reactions are detected. 

BINDER MATRIX 

Hardened Binder Dense and homogeneous cementitious matrix with moderate to moderately high capillary porosity on average. No 

significant calcium hydroxide as a cementitious hydrate is detected and the paste is almost completely carbonated. 

Residual Hydraulic Grains Residual portland cement is detected in moderate abundance as medium grained belite agglomerates with interstitial 

ferrite. Virtually all grains are well hydrated and consist only of a ferrite “skeleton”. Alite forms are also detected 

within agglomerates in moderately low abundance. 

Residual Lime Grains None detected. 

Residual Pozzolans None detected. 

Pigments None detected. 

AIR-VOID SYSTEM 

Estimated Air Content Estimated at 3% - 5% 

Consolidation / Distribution The mortar is well consolidated and the air distribution is homogeneous. 

Size / Shape Voids are generally less than 1 mm in dimension. Voids are rounded and subspherical to irregular in shape on average. 

Secondary Deposits Some voids are lined with secondary deposits with optical characteristics consistent with gypsum. Otherwise most 

voids are free of secondary deposits. 

AGGREGATE INTERFACES 

Details Sand grains are well coated with binder. No variation in binder characteristics are found adjacent to aggregate. No 

cracking or secondary mineral deposits are found at aggregate interfaces. In honed section, interfaces are moderately 

hard when scratched with a steel pick and do not exhibit any significant friability. 

SECONDARY REACTIONS 

Carbonation In thin section, all portions of the sample exhibit virtually full carbonation. 

Other No other evidence for chemical reaction is found within the bulk of the material. 

CRACKING 

Details No significant macroscopic or microscopic cracking is detected. 
TESTWELL, INC. 

Building Conservation Associates, Inc.; Loggerhead Key Light Station 

Report #: OPCL011/PGE-001 

Page 15 of 53 

SAMPLE ID LOKE.M.11 (Keeper’s Dwelling) 

GENERAL APPEARANCE 

Sample Type/Dimensions The sample represents a complete cross section of a two coat plaster system. Several pieces were received from the 

interior bathroom, west wall weighing 30.60 g. The nominal thickness of the whole sample is approximately 0.5 

including brown coat and finish coat. The brown coat is well bonded to the finish coat. A layer of paint is also detected 

on the finish coat. Approximate thicknesses of the two coats is as follows: 

Brown Coat: 3/8” 

Finish Coat: 1/8” 

Surfaces The contact surface is mostly planar and the two coats well bonded. 

Hardness / Friability Brown coat: Moderately hard and moderately non-friable. 

Finish coat: Moderately hard and non-friable. 

Appearance Brown coat: Luster on freshly exposed surfaces is dull. Fresh paste color is nearly white with a yellowish 

cast (Munsell color designation approximately 5Y 8.5/1). 

Finish coat: Luster on freshly exposed surfaces is dull. Fresh paste color is white (Munsell color designation 

approximately N9). 

Cracks, Deposits, Etc., No significant cracking, efflorescence, or secondary mineral deposits are detected in hand sample. However, cracking 

is difficult to assess due to the fragmental nature of the sample. A moderately low abundance of light-colored fiber 

reinforcement is identified in the brown coat. 

SAMPLE ID LOKE.M.11 (Keeper’s Dwelling plaster brown coat) 

AGGREGATE 

Lithology and Mode Carbonate natural sand consisting of shell fragments and porous coral fragments. 

Appearance The sand is white in most cases and with a pale yellow hue (Munsell color code approximately N9 to 5Y 8/1). The 

luster is slightly reflective to dull. 

Size and Gradation The sand is medium-grained and somewhat narrowly graded. The nominal top size is estimated at the No. 16 sieve 

with most material estimated to pass. Peak abundance is estimated between the No. 16 and No. 50 sieve and few fines 

are present below No. 50. 

Shape Subrounded in shape on average. Aspect ratios are subequant to subelongate. 

Distribution Homogeneous and somewhat randomly oriented though there is a somewhat preferential alignment of more elongate 

grains parallel or subparallel to the bed. 

Other No cracking, coatings, or chemical reactions are detected. 

BINDER MATRIX 

Hardened Binder Homogeneous gypsiferous matrix with high capillary porosity on average. While the matrix consists of an interlocking 

network of fine-grained gypsum crystals, the texture is somewhat coarse. 

Residual Hydraulic Grains None detected. 

Residual Lime Grains None detected. 

Residual Gypsiferous Grains A high abundance of medium-grained gypsum residuals are detected and almost all are fully hydrated to coarser grained 

gypsum. Finer unhydrated hemihydrate crystals are less common. There is moderately low abundance of very finegrained, dead burned anhydrite. 

Residual Pozzolans None detected. 

Pigments None detected. 

AIR-VOID SYSTEM 

Estimated Air Content Estimated at 8% - 10% 

Consolidation / Distribution The plaster is well consolidated and the air distribution is homogeneous. 

Size / Shape Voids are generally less than or equal to 1 mm in dimension. Voids are subspherical in shape on average. 

Secondary Deposits No significant secondary deposits are detected. 

AGGREGATE INTERFACES 

Details Sand grains are well coated with binder. No variation in binder characteristics are found adjacent to aggregate. No 

cracking or secondary mineral deposits are found at aggregate interfaces. In honed section, interfaces are moderately 

soft when scratched with a steel pick but do not exhibit any significant friability. 

SECONDARY REACTIONS 

Carbonation No carbonation is detected. 

Other No other evidence for chemical reaction is found within the bulk of the material. 

CRACKING 

Details No significant macroscopic or microscopic cracking is detected. 
TESTWELL, INC. 

Building Conservation Associates, Inc.; Loggerhead Key Light Station 

Report #: OPCL011/PGE-001 

Page 16 of 53 

SAMPLE ID LOKE.M.11 (Keeper’s Dwelling plaster finish coat) 

AGGREGATE 

Details No aggregate is present in the finish coat. 

BINDER MATRIX 

Hardened Binder Homogeneous mostly gypsiferous matrix with high capillary porosity on average. The matrix consists of a network of 

ultrafine gypsum crystallites with a minor carbonated component. 

Residual Hydraulic Grains None detected. 

Residual Lime Grains Residual lime grains are found in very low abundance as fine-grained mostly carbonated particles. No internal rock 

textures or hydraulic inclusions are detected within lime grains. 

Residual Gypsiferous Grains A low abundance of fine-grained gypsum residuals are detected and almost all are fully hydrated to coarser grained 

gypsum. Finer unhydrated hemihydrate crystals and dead burned anhydrite are both relatively uncommon. 

Residual Pozzolans None detected. 

Pigments None detected. 

AIR-VOID SYSTEM 

Estimated Air Content Estimated at 2% - 4% 

Consolidation / Distribution The plaster is well consolidated and the air distribution is homogeneous. 

Size / Shape Voids are generally less than 1 mm in dimension. Voids are subspherical in shape on average. 

Secondary Deposits No significant secondary deposits are detected. 

SECONDARY REACTIONS 

Carbonation In thin section, the lime portions of the sample exhibit virtually full carbonation. 

Other No other evidence for chemical reaction is found within the bulk of the material. 

CRACKING 

Details No significant macroscopic or microscopic cracking is detected. 
TESTWELL, INC. 

Building Conservation Associates, Inc.; Loggerhead Key Light Station 

Report #: OPCL011/PGE-001 

Page 17 of 53 

4. Point-Count Analyses

Point-count analysis was performed using methods adapted from ASTM C 457. Honed cross sections of the materials were 

prepared for the analysis. Sample LOKE.M.3 was chosen as a robust cross-check sample as sufficient material was available 

for both chemical analysis and point-count analysis. LOKE.M.4 and LOKE.M.7 were chosen for point-count analysis as 

these represent natural cement mortar samples with extremes in binder to sand ratio estimated via chemical analysis. It 

should be noted that that surface area of these latter two prepared samples and the number of points counted is smaller than 

required to produce the accuracy reported by the test method. 

Table 4.1 - Point-Count Data

Sample ID LOKE.M.3 LOKE.M.4 LOKE.M.7 

Location Cistern 

Exterior

Lighthouse 

Exterior

Lighthouse 

Interior

Approximate surface area (in.2

) 1.9 0.9 0.4 

Sand points 252 72 116 

Paste points 342 108 194 

Air-void points 34 12 13 

Total points 628 192 323 

Table 4.2 - Solid Volume Percentages

Sample ID LOKE.M.3 LOKE.M.4 LOKE.M.7 

Location Cistern 

Exterior

Lighthouse 

Exterior

Lighthouse 

Interior

Sand 40.1 37.5 35.9 

Paste 54.5 56.3 60.0 

Air-voids 5.4 6.2 4.0 

Totals 100.0 100.0 99.9

Table 4.3 - Calculated Bulk Ratios

Sample ID LOKE.M.3 LOKE.M.4 LOKE.M.7 

Location Cistern 

Exterior

Lighthouse 

Exterior

Lighthouse 

Interior

Sand volume percentage 56 53 50 

Cement volume percentage 44 47 50 

Cement : Sand Ratio (by volume) 1 : 1.3 1 : 1.1 1 : 1.0 

Notes: 

1) Solid volume of sand is adjusted by considering the void ratio of the sand in damp, loose condition. Paste volume is adjusted downward to account for 

the volume increase resulting from hydration of the cement. Counted sand volumes are divided by 0.62 to account for void space and paste volumes 

divided by 1.05 to account for volume increase upon hydration. 

2) Adjusted bulk volumes are normalized to 100% as presented in this table. 

3) Cement to sand ratios represent the ratios of these normalized values. 
TESTWELL, INC. 

Building Conservation Associates, Inc.; Loggerhead Key Light Station 

Report #: OPCL011/PGE-001 

Page 18 of 53 

5. Chemical Analyses

The chemical preparations used on all samples with the exception of the finish coat plaster represent significant deviations 

from the standard procedures given in ASTM C 1324. The carbonate sand is exceptionally soluble in any acid capable of 

dissolving the binder and there is no effective way to separate the binder and sand effectively. Therefore, it was decided to 

fuse the sample into a glass, dissolve that in concentrated acid and measure the bulk chemistry of the entire sample. A 

separate acid digestion was performed in order to produce an insoluble residue. Instead of representing the sand, this residue

is used to examine the uncalcined inclusions within the natural cement binder. Water-soluble chloride was also measured for 

the Lighthouse samples and this was done in general accordance with ASTM C 1218. 

The analysis for the finish plaster also represents a deviation from ASTM C 1324 in that a hot acid digestion was used to 

bring all sulfate species into solution as well as all lime. These methods are more consistent with those of ASTM C 114 for 

the measurement of sulfates in cement. 

Table 5.1a: Chemical Analysis Results

SAMPLE ID LOKE.M.4 LOKE.M.5 LOKE.M.6 LOKE.M.7

Location Lighthouse 

Exterior 

Lighthouse 

Exterior 

Lighthouse 

Interior 

Lighthouse 

Interior 

Component (wgt. %) 

SiO2 7.06 8.63 8.34 10.26 

CaO 40.17 37.42 38.30 37.20 

MgO 6.97 7.65 7.18 5.63 

Al2O3 1.26 1.41 1.22 1.53 

Fe2O3 0.95 0.98 1.01 1.08 

Na2O 0.98 1.30 0.69 2.28 

K2O 0.08 0.38 0.65 1.01 

Cl 1.12 0.43 1.35 1.09 

Insoluble residue 1.35 3.09 2.53 5.26 

LOI %, to 110°C (Free water) 4.03 4.75 4.30 4.82 

LOI %, 110°C-550°C (Combined water) 8.48 9.75 8.32 10.04 

LOI %, 550°C-950°C (Carbon dioxide) 28.41 25.93 28.90 24.44 

Measured Totals 98.40 98.20 98.92 98.27 

Notes: 

1) The insoluble residue is not included in the totals calculation as it represents an intentional duplicate measurement. 

2) Chloride is also not included in the totals calculation nor is an adjustment made for the reduced oxygen that must accompany the alternate anion. 
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Table 5.1b: Chemical Analysis Results

SAMPLE ID LOKE.M.2 LOKE.M.3 LOKE.M.9 LOKE.M.10

Location Cistern 

Exterior 

Cistern 

Exterior 

Kitchen Bldg. 

Exterior 

Keeper’s 

Dwelling 

Component (wgt. %) 

SiO2 8.18 8.87 7.98 5.44 

CaO 42.03 40.07 40.24 45.67 

MgO 5.52 5.85 6.93 1.62 

Al2O3 1.71 1.58 1.40 1.27 

Fe2O3 1.07 1.07 1.31 0.68 

Na2O 0.34 0.31 0.35 0.36 

K2O 0.01 0.07 0.17 0.34 

Insoluble residue 2.33 3.09 2.90 0.72 

LOI %, to 110°C (Free water) 2.77 2.49 3.33 2.37 

LOI %, 110°C-550°C (Combined water) 5.27 4.19 7.67 6.19 

LOI %, 550°C-950°C (Carbon dioxide) 31.88 32.80 29.95 32.34 

Measured Totals 98.80 97.31 99.33 96.27 

Notes: 

1) The insoluble residue is not included in the totals calculation as it represents an intentional duplicate measurement. 

Table 5.1c: Chemical Analysis Results

SAMPLE ID LOKE.M.1 LOKE.M.8 LOKE.M.8

Location 

Oil House 

Exterior 

Oil House 

Plaster 

Brown Coat 

Oil House 

Plaster 

Finish Coat 

Component (wgt. %) 

SiO2 8.05 6.22 0.67 

CaO 40.05 41.20 45.20 

MgO 5.43 6.94 3.55 

Al2O3 1.83 1.33 0.15 

Fe2O3 1.09 1.13 0.14 

Na2O 1.18 0.61 0.79 

K2O 0.38 0.22 0.23 

SO3 n.d. n.d. 13.57 

Insoluble residue 2.70 4.03 0.00 

LOI %, to 110°C (Free water) 3.59 2.29 1.54 

LOI %, 110°C-550°C (Combined water) 7.60 9.01 7.70 

LOI %, 550°C-950°C (Carbon dioxide) 28.68 29.66 27.23 

Measured Totals 97.88 98.62 100.78 

Notes: 

1) The insoluble residue is not included in the totals calculation for the natural cement samples as it represents an intentional duplicate measurement. 
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Table 5.2a: Calculated Components

SAMPLE ID LOKE.M.4 LOKE.M.5 LOKE.M.6 LOKE.M.7

Location Lighthouse 

Exterior 

Lighthouse 

Exterior 

Lighthouse 

Interior 

Lighthouse 

Interior 

Component 

Portland cement (wgt. %) Not detected Not detected Not detected Not detected 

Natural cement (wgt. %) 32 41 39 47 

Lime expressed as dry hydrate (wgt. %) Not detected Not detected Not detected Not detected 

Hydraulic lime (wgt. %) Not detected Not detected Not detected Not detected 

Pozzolans (wgt. %) Not detected Not detected Not detected Not detected 

Mineral pigment (wgt. %) Not detected Not detected Not detected Not detected 

Sand (wgt. %) 68 59 61 53 

Binder : sand ratio (by volume) 1 : 2.0 1 : 1.4 1 : 1.5 1 : 1.1 

Table 5.2b: Calculated Components

SAMPLE ID LOKE.M.2 LOKE.M.3 LOKE.M.9 LOKE.M.10

Location Cistern 

Exterior 

Cistern 

Exterior 

Kitchen Bldg. 

Exterior 

Keeper’s 

Dwelling 

Component 

Portland cement (wgt. %) Not detected Not detected Not detected 33 

Natural cement (wgt. %) 35 39 36 Not detected 

Lime expressed as dry hydrate (wgt. %) Not detected Not detected Not detected Not detected 

Hydraulic lime (wgt. %) Not detected Not detected Not detected Not detected 

Pozzolans (wgt. %) Not detected Not detected Not detected Not detected 

Mineral pigment (wgt. %) Not detected Not detected Not detected Not detected 

Sand (wgt. %) 65 61 64 67 

Binder : sand ratio (by volume) 1 : 1.7 1 : 1.5 1 : 1.7 1 : 2.4 
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Table 5.2c: Calculated Components

SAMPLE ID LOKE.M.1 LOKE.M.8 LOKE.M.8

Location Oil House 

Exterior 

Oil House Plaster 

Brown Coat 

Oil House Plaster 

Finish Coat 

Component 

Portland cement (wgt. %) Not detected Not detected Not detected 

Natural cement (wgt. %) 36 28 Not detected 

Lime expressed as dry hydrate (wgt. %) Not detected Not detected 68 

Hydraulic lime (wgt. %) Not detected Not detected Not detected 

Gypsum as hemihydrate (wgt. %) Not detected Not detected 32 

Pozzolans (wgt. %) Not detected Not detected Not detected 

Mineral pigment (wgt. %) Not detected Not detected Not detected 

Sand (wgt. %) 64 72 Not detected 

Binder : sand ratio (by volume) 1 : 1.7 1 : 2.4 n/a 

Gypsum : lime ratio (by volume with lime as a hydrate) n/a n/a 1 : 0.2 

Gypsum : lime ratio (by volume with lime as a putty) n/a n/a 1 : 0.3 

Notes: 

1) For the natural cement mortars, parging, and plaster coats, the cement weight is calculated assuming an original cement silica content of 27% and 

calcium oxide content of 35%. Cement content is calculated assuming all measured silica is attributed to this average natural cement composition. 

Excess calcium is then attributed to the carbonate sand and the equivalent weight of calcium carbonate is calculated by molecular weight conversion. 

Both calculated weights are then normalized to 100%. Volumetric ratios are calculated assuming bulk densities for natural cement and damp loose 

sand of 75 lb./cu. ft. and 80 lb./cu. ft. respectively. 

2) For the portland cement mortar (LOKE.M.10), the cement weight is calculated assuming an original cement silica content of 21% and calcium oxide 

content of 63%. Cement content is calculated assuming all measured silica is attributed to this average cement composition. Excess calcium is then 

attributed to the carbonate sand and the equivalent weight of calcium carbonate is calculated by molecular weight conversion. Both calculated weights 

are then normalized to 100%. Volumetric ratios are calculated assuming bulk densities for portland cement and damp loose sand of 94 lb./cu. ft. and 

80 lb./cu. ft. respectively. 

3) For the Oil House plaster finish coat (LOKE.M.8), the gypsum weight as hemihydrate is calculated by assuming that all measured sulfate is attributed 

to this component. Sufficient calcium oxide is taken up to account for this calculated gypsum component. The remaining calcium oxide and all 

magnesium oxide is attributed to the lime component and the mass is calculated by molecular weight conversion for both calcian and magnesian lime 

species. All calculated weights are then normalized to 100%. Volumetric ratios are calculated assuming bulk densities for dry gypsum plaster and dry 

lime hydrate of 93.5 lb./cu. ft. and 40 lb./cu. ft. respectively. A separate calculation is presented considering lime as a putty rather than a dry hydrate. 

This assumes an approximate 40% loss in bulk volume to turn a volume of dry lime hydrate into a stiff putty by addition of water. 
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6. Discussion and Conclusions

6.1 Mortar Materials 

All mortar samples are identified as pure cement mortars containing a natural carbonate sand (Figs. 5 through 15). 

Additionally, the brown coat of the Oil House plaster sample LOKE.M.8 is very similar and is grouped in this discussion for 

convenience. No lime-type binders, pozzolans, or mineral pigments are identified in any of these samples. Original water to 

cement ratios are difficult to assess due to the advanced age of the materials. However, variations in the quantity of cement 

relicts, differences in capillary porosity, and differences in lightness of the cement paste indicate relative differences in water 

to cement ratios between the samples. For the most part, the lighthouse samples exhibit slightly lower capillary porosities 

suggestive of a lower original water to cement ratio (Figs. 8 and 9). Sample LOKE.M.10 (Keeper’s Dwelling) differs in that 

the binder is a portland rather than natural cement and this sample will be discussed separately. Therefore, this discussion 

includes samples LOKE.M.1 through LOKE.M.7 as well as LOKE.M.9 and the brown coat of LOKE.M.8. 

The cement in these samples are all identified as American natural cements typical of those manufactured in the more 

productive cement regions such as Rosendale, NY or Louisville, KY. All unhydrated cement relicts exhibit microstructural 

properties consistent with the low-temperature calcination of an argillaceous and partly ferruginous dolomitic limestone. 

Such textures include fine-grained, calcined carbonate rhombs surrounded by a rim of iron-bearing phase as well as partly 

burned quartz silt and sand grains surrounded by a rim of hydraulic product (Figs. 12 through 15). While some variation is 

observed across all samples, the general cement characteristics are grossly similar. Furthermore, the chemical analysis of all

samples indicates a magnesium component no less than half that of the silica component and usually much more than this. 

Such chemistries are characteristic of the American natural cements and this clearly distinguishes them from a European 

product. Minor fine-grained coal fragments are also detected in most samples and these are interpreted to be contaminants 

from the cement burning. 

While difficult to ascertain different placement vintages based on cement characteristics, there are some subtle variations 

observed both petrographically and chemically that appear to group cements into similar batches or sources. Three of the 

four lighthouse samples (all but LOKE.M.5) exhibit a greater variation in the grind of the cement. All other samples exhibit 

a fine to medium grind but these three contain unhydrated cement relicts that are found as large as several hundred microns in 

dimension (Fig. 12). It is tempting to interpret this coarseness as representative of an earlier vintage but this would be purely 

speculative. The very slight difference in the sand gradation in LOKE.M.5 (discussed below) in addition to slightly different 

cement characteristics could suggest that this sample is not contemporaneous with the other lighthouse samples. It is also 

noted that some variation exists within the fragments of sample LOKE.M.4 (Fig. 9). Some portions of this sample exhibit 

cement characteristics more similar to those of the Oil House plaster brown coat (LOKE.M.8) rather than those of the other 

lighthouse samples . The distinctive texture here is a much greater abundance of very fine-grained, partially calcined quartz 

silt grains dispersed as isolated cement residuals throughout the paste (Fig. 13). The acid-insoluble residues measured 

chemically for both samples is also the highest in these two samples and this is consistent with the petrographic observation. 

The cement in these two samples is clearly of a different quality than the others and this has implications in the estimation of 

sand to binder ratios as discussed below. What is not clear based on examination of the fragments is the reason that 

LOKE.M.4 appears to contain two different types of cement within one sample. 

The sand in all samples is virtually identical with only subtle differences in gradation (Figs. 5 through 11). The sand is 

identified as a natural carbonate sand containing coral and shell fragments similar to that making up the sediment of the Dry 

Tortugas. A local source is certainly expected given the isolated nature of the site. No obviously crushed particles or foreign 

siliceous sands are identified that might suggest some modification to the local source. While it would be impossible to 

separate the sand from the binder through acid digestion, it is fairly clear through low-powered examination of fresh surfaces 

that the sand is homogeneous in color ranging from nearly white to pale yellow with no significant variegation. The grains 

are rounded due to natural weathering processes but tend to be somewhat elongate due to the original shapes of the 

organisms. All samples exhibit a relatively narrow sand gradation. Generally, all grains are estimated to pass a No. 8 sieve,

most passing No. 16, with a minor to a moderately low amount of grains estimated to pass the No. 50 sieve. With some 

minor exception, the samples exhibit a sharp peak abundance of material between the No. 16 and No. 30 sieves. Such narrow 

gradations within this size range make geological sense in beach zones subject to regular wave action. While the site sand 

was not examined for this report, it is fully expected from a geological perspective that the local material would match the 

observed gradations without further processing. 

Several subtle differences are detected in the sand gradations but these are very minor when compared to the general pattern. 

Some samples contain a slightly higher abundance of material retained on the No. 16 sieve. These include samples 
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LOKE.M.2, M.3, M.6, M.7, M.8 and (brown coat). In two cases the nominal top size is estimated at the No. 8 rather than 

No. 16 sieve where it appears that more than 10% of the material is retained on No. 16. and these include samples LOKE.M.6 

and M.8. Some minor differences are also found in the fine end of the gradation. In most cases, minor material is estimated 

to pass the No. 50. A slightly higher abundance of fines is found in sample LOKE.M.5. The brown coat of sample 

LOKE.M.8 contains only a moderately low abundance of material estimated to pass the No. 30 sieve and is therefore even 

more narrowly graded. 

Generally speaking, all samples discussed in this section exhibit cement and sand components that are well mixed and 

distributed. Air contents tend to be low and the mortars are well consolidated. Hydration qualities of the cement are 

adequate with a homogeneous distribution of cementitious product. While some variation in original water to cement ratios 

are suggested by minor variations in capillary porosity (Figs. 8 through 11), all appear to have been mixed without an excess 

of water or significant retempering. 

Establishing original component proportions is challenging for this particular combination of sand and cement. Typically, a 

chemical methodology would be utilized whereby insoluble sand would be separated chemically for gravimetric 

measurement and the elemental chemistry of the dissolved binder component would be reverse engineered based on a fairly 

robust assumption of original binder chemistry. In this case, the sand is completely soluble and original natural cement 

chemistries are more variable than those of American portland cements or limes. Two analytical options are available to 

overcome these complications. The first is a microscopical point-counting of sand and binder components on polished slabs 

of the mortar. This method is insensitive to variations in the original binder chemistry and only measures paste and sand 

volume. The second is a complete fusion, or bulk chemical analysis of the mortar. Analysis of this chemistry requires an 

assumption of the original binder chemistry in order to partition the binder portion. This is followed by a calculation of the

sand based on the remaining calcium unaccounted for by the binder partitioning. The former method may be considered 

more robust but requires a relatively large sample in order to be statistically significant. As such large sized samples were 

not available, it was agreed in discussions with the client that the chemical analysis that requires a smaller sample would be 

performed on all samples. The point-count method is then performed on sample LOKE.M.3 as a large sample is available. 

Comparison of the independent results is then expected to inform how well the chemical analysis may estimate the 

proportions. Additional point-counts on less than adequate samples are then performed on mortar samples estimated to 

exhibit extremes of binder to sand ratios based on the chemistry. These are performed on sample LOKE.M.4 and 

LOKE.M.7. A summary of the estimates are given in the table below based on bulk volume. 

Sample ID Cement to sand ratio

by chemical analysis 

Cement to sand ratio

by point-count analysis 

LOKE.M.1 1 : 1.7 n.d. 

LOKE.M.2 1 : 1.7 n.d. 

LOKE.M.3 1 : 1.5 1 : 1.3 

LOKE.M.4 1 : 2.0 1 : 1.1 

LOKE.M.5 1 : 1.4 n.d. 

LOKE.M.6 1 : 1.5 n.d. 

LOKE.M.7 1 : 1.1 1 : 1.0 

LOKE.M.8 (brown coat) 1 : 2.4 n.d. 

LOKE.M.9 1 : 1.7 n.d. 

Some interesting features are revealed particularly in light of the qualitative petrographic observations. First, the independent 

methods result in good agreement for the binder to sand ratio in sample LOKE.M.3. This suggests that the assumption of 

original natural cement chemistry is relatively effective at estimating ratios from the bulk chemical analysis. Similar 

agreement is found in sample LOKE.M.7 even though the point-count sample is smaller than might be desired for statistical 

significance. Interestingly, the chemical analysis of samples LOKE.M.4 and M.8 result in a higher sand content calculation 

than the other mortars yet such variation is not evident by qualitative petrographic observations where all sand contents 

appear more or less similar. These are the two samples where the characteristics of the relict cement grains are distinctly 

different than the others in the suite with a high abundance of partially burned quartz silt. Point-count analysis of LOKE.M.4

suggests half the sand content as that estimated from the chemical analysis. It is interpreted that the original cement 

chemistry is different in these samples and the proportions estimated via the chemical analysis may represent an 

overestimation of sand content for these two. 
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Based on these analyses, it is interpreted that most binder to sand ratios are approximately 1 : 1.5 by volume. Samples 

LOKE.M.4 and LOKE.M.7 may be closer to 1 : 1. Such low sandings with narrow and relatively coarse sand gradations are 

considered typical of historical natural cement mortars. If in-kind replication is a priority, mix designs with these proportions 

and gradations may be considered viable. 

6.2 LOKE.M.10 Materials 

The exterior mortar of the Keeper’s dwelling (LOKE.M.10) appears identical to the other mortars based on visual 

characteristics and is also identified as a pure cement mortar (Figs. 6 and 10). However, the binder is identified as a pure 

portland cement with no lime additions identified. The distinctive low-magnesium, low insoluble residue values measured 

chemically are consistent with this qualitative identification. Cement relicts are identified petrographically as medium-sized

agglomerates of well-hydrated calcium silicates with interstitial ferrite (Fig. 14). The iron-bearing ferrite identifies the binder 

as an ordinary gray portland cement. The medium grind and homogeneity of calcium silicate size is consistent with cements 

produced in the early twentieth century and is considered consistent with the early 1920’s vintage reported by the client. 

The sand in this sample is identical in composition and only slightly different in gradation as that observed in the natural 

cement mortars discussed above. As with these, the sand is a natural carbonate sand consistent with the local source (Figs. 6 

and 10). The appearance of the sand is also homogenous and light-colored ranging from nearly white to pale yellow. The 

grains are rounded due to natural weathering processes but tend to be somewhat elongate due to the original shapes of the 

organisms. The gradation is still narrow with a nominal top size estimated at the No. 16 sieve but the peak abundance is 

estimated to be spread more evenly between the No. 16 and No. 50 sieves as compared to other samples in the suite. Still, 

there are relatively few fines in the sand estimated to pass the No. 50 sieve size. As with the other samples, this relatively

narrow gradation is considered geologically consistent with the local sediment. 

LOKE.M.10 exhibits cement and sand components that are well mixed and distributed. Air contents tend to be low and the 

mortar well consolidated. Hydration qualities of the cement are virtually complete with a homogeneous distribution of 

cementitious product. The original water to cement ratio is estimated to be moderate based on the observed capillary porosity 

and the mortar appears to have been mixed without an excess of water or significant retempering (Fig. 10). 

Chemical analysis was performed in order to estimate the original binder to sand ratios. In this case, an estimate based on 

chemical analysis is considered more robust as portland cement has a less variable chemistry than natural cement. Assuming 

a typical portland cement chemistry and bulk densities of cement and damp, loose sand, the binder to sand ratio is estimated 

at 1 : 2.4. The sand content is higher than that observed in the other natural cement mortars but this is considered consistent 

with historic practice. 

6.3 LOKE.M.8 Materials 

LOKE.M.8 is reported to represent an Oil House plaster sample and consists of a three-coat plaster system (Figs 16 through 

20). Substrate is not included with the sample. The sample includes a relatively soft and porous scratch coat identified as a

sanded, lime-based plaster gauged with natural cement, a relatively hard and dense brown coat identified as a sanded, pure 

natural cement plaster, and a fine-textured, unsanded finish coat consisting of lime gauged with gypsum. Generally speaking, 

these materials are considered consistent with a mid-nineteenth century vintage and certainly are inconsistent with twentieth 

century practice. The use of gypsum-based plaster as a gauging material is less well understood. While the use of calcined 

gypsum as a binder has a long history, the author is unaware of any American references to its use in the States prior to 

approximately 1880. 

The sand in the scratch and brown coats is more or less identical (Fig. 7). As discussed earlier for the brown coat, the 

aggregate is identified as a natural carbonate sand containing coral and shell fragments similar to that making up the sediment

of the Dry Tortugas. Visual examination indicates a homogeneous color ranging from nearly white to pale yellow with no 

significant variegation. Grains are rounded due to natural weathering processes but tend to be somewhat elongate due to the 

original shapes of the organisms. The gradation is quite narrow with a nominal top size estimated at the No. 8 sieve with all 

material estimated to pass. A strong peak abundance is estimated between the No. 16 and No. 30 sieves with only a 

moderately low abundance of material estimated to pass the No. 30 sieve. 
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The binder matrix in the scratch coat is characterized by a highly porous, carbonated paste, with a moderate abundance of 

microscopic shrinkage cracks. The paste matrix is typical of a high lime binder (Fig. 16). Larger relict lime grains are 

observed in low abundance and these exhibit homogeneous internal textures. Given the limited sample available for the 

scratch coat, it is not possible to speculate on the source of the lime. Furthermore, a chemical analysis could not be 

performed and no information is available for the lime chemistry. Natural cement grains identical to those of the brown coat 

are found in very low abundance (Fig. 17). The cement is estimated to represent a minor gauging affording only minimal 

hydraulic property to the scratch coat. While no quantitative estimate is offered, it is unlikely that the cement represents 

more than one tenth part of the lime by volume. The sanding is interpreted to be relatively low based on petrographic 

observations and the binder to sand ratio is probably less than 1 : 2 by volume. 

Due to the similarity of the brown coat to the natural cement mortars, more detail for this layer is provided above. The binder 

matrix is moderately dense and consists of a natural cement binder with no lime addition. The cement is identified as a 

magnesium natural cement consistent in texture with the more productive American manufactories. However, a higher 

abundance of calcined silt is observed than in any of the other mortar samples with the exception of portions of sample 

LOKE.M.4. Chemical analysis was performed on this sample and binder to sand ratio estimated at 1 : 2.4 by volume. 

However, based on arguments presented earlier, this is likely a significant overestimate due to a distinctly different chemistry 

for this cement. Petrographic similarity of this sample with those of the other mortar samples suggest that the actual ratio 

may be closer to 1 : 1.5. 

The finish coat matrix is fine-textured and porous (Fig. 19). An abundance of fine residual lime grains indicates the layer is

mostly lime based. Chemical analysis was performed on this layer. Even assuming that all magnesium is contained in the 

lime, a CaO/MgO weight ratio of 10 (an order of magnitude higher than an ideal dolomitic ratio of 1.4) suggests a high 

calcium rather than dolomitic lime. Traces of calcined silicate contaminants suggest a rock lime source but not enough 

material is observed petrographically to offer a definitive statement. Gypsum plaster is identified as a gauging material (Fig. 

20). Very few unhydrated gypsum relicts are identified. The rare abundance of coarser hemihydrate or finer dead-burned 

anhydrite suggests that the plaster was not a cement plaster or Keene’s cement but rather a fine finishing plaster such as 

Plaster-of-Paris. 

Chemical analysis was performed on the finish coat in order to estimate the lime to plaster proportions. Assuming the lime 

was added as a dry hydrate, the lime to plaster ratio is estimated at 1 : 0.2. It is unlikely that the lime was a prepackaged 

hydrate. However, a given volume of dry hydrate has a more constant weight ratio of constituent elements than a given 

volume of putty and the estimate may be considered more robust. Assuming a similar mass of hydrate loses approximately 

40% of its volume when mixed with water to the consistency of a stiff putty, the ratio is recalculated at 1 : 0.3 by volume. 

6.4 LOKE.M.11 Materials 

LOKE.M.11 is reported to represent an Keeper’s Dwelling plaster sample and consists of a two-coat plaster system (Figs. 21 

through 24). Substrate is not included with the sample. The sample includes a relatively hard but porous brown coat 

identified as a sanded, gypsum-based plaster and a relatively hard but porous, unsanded finish coat consisting of a finetextured gypsum gauged with lime. The use of gypsum materials rather than lime for interior plastering is considered 

consistent with the 1920’s vintage reported by the client. 

The brown coat contains a relatively coarse-textured and porous binder matrix composed of a network of fine-grained 

gypsum hydrate (Fig. 21). Coarser hydrated residuals are relatively common and unhydrated hemihydrate and fine-grained, 

dead-burned anhydrite are also present though in lower abundance (Fig. 22). A chemical analysis was not requested for this 

sample and further information regarding the plaster provenance cannot be provided. However, the microtexture of the coat 

clearly discounts a refined finishing plaster and the presence of the dead-burned gypsum (anhydrite) suggests that the plaster 

may have been a Keene’s cement. It should be noted that the term “cement” here does not refer to hydraulic calcium silicates 

and Keene’s cement represents a relatively pure calcium sulfate product. 

The sand in the brown coat is identical to that of the other samples in the suite and is most similar to the other Keeper’s 

Dwelling sample (LOKE.M.10) in gradation (Figs. 7 and 21). The aggregate is identified as a natural carbonate sand 

containing coral and shell fragments similar to that making up the local sediment. Visual examination indicates a 

homogeneous color ranging from nearly white to pale yellow with no significant variegation. Grains are rounded due to 

natural weathering processes but tend to be somewhat elongate due to the original shapes of the organisms. The gradation is 
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somewhat narrow with a nominal top size estimated at the No. 16 sieve. The peak abundance is estimated between the No. 

16 and No. 50 sieves with only a minor abundance of material estimated to pass the No. 50 sieve. 

The finish coat matrix is fine-textured and moderately porous. The paste matrix is dominated by a network of very-fine 

grained hydrated gypsum crystallites (Fig. 23). Very few unhydrated gypsum relicts are identified. The rare abundance of 

coarser hemihydrate or finer dead-burned anhydrite suggests that the plaster was not a cement plaster or Keene’s cement but 

rather a fine finishing plaster such as Plaster-of-Paris (Fig. 24). A very low abundance of carbonated lime grains are 

dispersed throughout the largely gypsum-based matrix. While a chemical analysis was not performed for this sample, the 

lime is interpreted to represent a minor gauging rather than a major component of the finish plaster. 

6.5 Cracking Distress and Salt Crystallization 

The client requested some discussion regarding the possible role of salts as a deleterious agent in the examined suite of 

samples. A combination of petrographic and chemical techniques are utilized in order to address this concern. 

First, it is noted that while some samples are provided in fragmental condition, very little internal microcracking is detected

in the majority of the samples (Fig. 25). Most exhibit good microstructural integrity. Some minor to moderate 

microcracking is detected in the cistern samples (LOKE.M.2 and M.3) and some minor microcracking is found in the 

Lighthouse sample LOKE.M.5. It should be stated that while minor salt deposits are detected within some of these cracks 

and other samples have chemistries suggestive of some soluble salt content, there is no evidence suggesting that any sample 

in the suite has undergone any deterioration related to either salt crystallization or salt hydration distress (Fig. 26). Minor 

sulfate deposits are observed petrographically in sample LOKE.M.5 as well as fine deposits likely to represent chloride salts 

based on their optical character. Similar salts consistent with chlorides are found as minor thin surface linings in sample 

LOKE.M.6. The greatest amount of secondary sulfate as gypsum is found within air-voids of sample LOKE.M.10. This is 

not surprising as this is the only sample containing a portland cement binder with hydrates more susceptible to secondary 

gypsum recrystallization. Even here however, the deposits are not related to any significant cracking distress. 

The alkali elements sodium and potassium were measured quantitatively for all samples analyzed chemically. These are 

somewhat elevated for most samples. Additionally, water-soluble chloride was measured for the four Lighthouse samples 

and these may also be considered slightly elevated in content. However, it is likely that the local carbonate sand was 

unwashed prior to mixing and was rich in soluble alkali salts (particularly chlorides). It is also noted that no natural 

freshwater sources are present in the Dry Tortugas and all freshwater would have to have been collected by cistern systems. 

Given the scarcity of freshwater, it is also likely that the mortars were mixed with saltwater. A greater proportion of the 

alkali content is more likely to be related to the original mix constituents rather than later contamination. It is interesting to 

note that the cistern samples (LOKE.M.2 and M.3) exhibit the lowest alkali contents. Given the application, these mortars 

and pargings likely had a greater exposure to freshwater through drinking water storage and the reduced alkali content may 

be related to leaching and dilution of original chloride salts. 

TESTWELL, INC.

John J. Walsh 

Senior Petrographer/ Geologist 

Samples will be discarded 30 days after the final report date unless otherwise instructed. This report is the confidential property of the 

client and any unauthorized reproduction is strictly prohibited. The interpretations and conclusions presented in this report are based on 

the samples provided.
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Appendix I: Photographs and Photomicrographs

Microscopic examination is performed on an Olympus BX-51 polarized/reflected light microscope and a Bausch and Lomb 

Stereozoom 7 stereoscopic reflected light microscope. Both microscopes are fitted with an Olympus DP-11 digital camera. 

The overlays presented in the photomicrographs (e.g., text, scale bars, and arrows) are prepared as layers in Adobe Photoshop 

and converted to the jpeg format. Digital processing is limited to those functions normally performed during standard print 

photography processing. Photographs intended to be visually compared are taken under the same exposure conditions 

whenever possible. 

The following abbreviations may be found in the figure captions and overlays and these are defined as follows: 

cm centimeters PPL Plane polarized light 

mm millimeters XPL Crossed polarized light 

m microns (1 micron = 1/1000 millimeter) 

mil 1/1000 inch 

Microscopical images are often non-intuitive to those not accustomed to the techniques employed. The following is offered 

as a brief explanation of the various views encountered in order that the reader may gain a better appreciation of what is 

being described. 

Reflected light images: These are simply magnified images of the surface as would be observed by the human eye. A 

variety of surface preparations may be employed including polished and fractured surfaces. The reader should note the 

included scale bars as minor deficiencies may seem much more significant when magnified. 

Plane polarized light images (PPL): This imaging technique is most often employed in order to discern textural 

relationships and microstructure. To employ this technique, samples are milled (anywhere from 20 to 30 microns depending 

on the purpose) so as to allow light to be transmitted through the material. In many cases, Testwell also employs a technique 

whereby the material is impregnated with a low viscosity, blue-dyed epoxy. Anything appearing blue therefore represents 

some type of void space (e.g.; air voids, capillary pores, open cracks, etc.) Hydrated cement paste typically appears a light 

shade of brown in this view (with a blue hue when impregnated with the epoxy). With some exceptions, most aggregate 

materials are very light colored if not altogether white. Some particles will appear to stand out in higher relief than others. 

This is a function of the refractive power of different materials with respect to the mounting epoxy. 

Crossed polarized light images (XPL): This imaging technique is most often employed to distinguish components or 

highlight textural relationships between certain components not easily distinguished in plane polarized light. Using the same 

thin sections, this technique places the sample between two pieces of polarizing film in order to determine the crystal 

structure of the materials under consideration. Isotropic materials (e.g.; hydrated cement paste, pozzolans and other glasses,

many oxides, etc.) will not transmit light under crossed polars and therefore appear black. Non-isotropic crystals (e.g.; 

residual cement, calcium hydroxide, calcium carbonate, and most aggregate minerals) will appear colored. The colors are a 

function of the thickness, crystal structure, and orientation of the mineral. Many minerals will exhibit a range of colors due

to their orientation in the section. For example, quartz sand will appear black to white and every shade of gray in between. 

Color differences do not necessarily indicate material differences. When no other prompt is given in the figure caption, the 

reader should appeal to general shapes and morphological characteristics when considering the components being illustrated. 

Chemical treatments: Many chemical techniques (etches and stains typically) are used to isolate and enhance a variety of 

materials and structures. These techniques will often produce strongly colored images that distinguish components or 

chemical conditions. 
TESTWELL, INC. 

Building Conservation Associates, Inc.; Loggerhead Key Light Station 

Report #: OPCL011/PGE-001 

Page 28 of 53 

 

 

Figure 1: Photographs of the four Lighthouse mortar samples as received by Testwell for examination. 
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Figure 2: Photographs of mortar samples from the cistern, Kitchen Building and Keeper’s Dwelling as received by Testwell for 

examination. 
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Building Conservation Associates, Inc.; Loggerhead Key Light Station 

Report #: OPCL011/PGE-001 

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Figure 3: Photographs of the samples from the Oil House as received by Testwell for examination. Sample LOKE.M.8 is a plaster 

sample. A top view (top right) and rear view (bottom left) show the scratch coat (SC), brown coat (BC), and finish coat (FC) in this threecoat plaster. The last photograph presents a side view. 
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Figure 4: Photographs of the plaster sample from the Keeper’s Dwelling as received by Testwell for examination. The bottom 

photograph presents a side view of the two-coat plaster with brown coat (BC) and finish coat (FC) visible. 
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Building Conservation Associates, Inc.; Loggerhead Key Light Station 

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Figure 5: Reflected light photomicrographs of honed cross sections of the Lighthouse mortar samples. Binder matrix is well compacted 

and consolidated around sand grains (S). The sand is light-colored and homogeneous and the same type of sand component is found in all 

samples. Gradations tend to be relatively narrow with all material estimated to pass a No. 8 sieve and little material found below the No. 

50 sieve. Blue coloration in some of the samples is due to the impregnation of a low-viscosity blue dyed epoxy. Several of the honed 

sections were prepared directly from residual thin section billets where total sample size is small. 
TESTWELL, INC. 

Building Conservation Associates, Inc.; Loggerhead Key Light Station 

Report #: OPCL011/PGE-001 

Page 33 of 53 

 

 

Figure 6: Reflected light photomicrographs of honed cross sections of mortar samples from the cistern, Kitchen Building and Keeper’s 

Dwelling. Binder matrix is well compacted and consolidated around sand grains (S). The sand is light-colored and homogeneous and the 

same type of sand component is found in all samples. Gradations tend to be relatively narrow with all material estimated to pass a No. 8 

sieve and little material found below the No. 50 sieve. Blue coloration in some of the samples is due to the impregnation of a low-viscosity 

blue dyed epoxy. Several of the honed sections were prepared directly from residual thin section billets where total sample size is small.
TESTWELL, INC. 

Building Conservation Associates, Inc.; Loggerhead Key Light Station 

Report #: OPCL011/PGE-001 

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Figure 7: Reflected light photomicrographs of honed cross sections of samples from the Oil House and sanded plaster coats. Binder 

matrix is well compacted and consolidated around sand grains (S). The sand is light-colored and homogeneous and the same type of sand 

component is found in all samples. Gradations tend to be relatively narrow with all material estimated to pass a No. 8 sieve and little 

material found below the No. 50 sieve. Blue coloration in some of the samples is due to the impregnation of a low-viscosity blue dyed 

epoxy. Several of the honed sections were prepared directly from residual thin section billets where total sample size is small.
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Building Conservation Associates, Inc.; Loggerhead Key Light Station 

Report #: OPCL011/PGE-001 

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Figure 8: PPL photomicrographs illustrating the overall microstructure of the Lighthouse mortar samples. Sample LOKE.M.4 is not 

shown here and is presented in the next figure. The hydraulic binder matrix (BM) is well developed. Porosities tend to be moderate for the 

Lighthouse samples and this is demonstrated by the relatively low absorption of blue-dyed epoxy used in the sample preparation. The sand 

(S) is well coated with binder and is identified as a soft, natural carbonate sand composed of a variety of coral and shell fragments. Airvoids (AV) are not abundant. 
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Figure 9: PPL photomicrographs illustrating the overall microstructure of Sample LOKE.M.4. Sample LOKE.M.4 is unusual in that two 

different microtextures are found within the same sample. The top image shows a binder matrix (BM) that has a higher porosity than the 

one in the image below. This is shown by the difference in absorption of blue-dyed epoxy used in the sample preparation. The binder 

matrix in the lower image also has a “grittier” character. This is interpreted to be due to a difference in the cement for this portion of the 

sample. The feature is shown in greater detail in Figure 13 below. The sand (S) has the same characteristics as that of the other Lighthouse 

samples. Air-voids (AV) are not abundant. 
TESTWELL, INC. 

Building Conservation Associates, Inc.; Loggerhead Key Light Station 

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Figure 10: PPL photomicrographs illustrating the overall microstructure of mortar samples from the cistern, Kitchen Building and 

Keeper’s Dwelling. The hydraulic binder matrix (BM) is well developed. Porosities tend to be moderate to moderately high for these 

samples and this is demonstrated by the moderate absorption of blue-dyed epoxy used in the sample preparation. Sample LOKE.M.9 has a 

high porosity in some areas of the sample. The sand (S) is well coated with binder and is identified as a soft, natural carbonate sand 

composed of a variety of coral and shell fragments. Air-voids (AV) are not abundant. 
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Figure 11: PPL photomicrographs illustrating the overall microstructure of the Oil House samples. The brown coat is shown for 

LOKE.M.8 as this material is more or less identical to that of the masonry mortar samples. The hydraulic binder matrix (BM) is well 

developed. Porosities tend to be moderately high for LOKE.M.1 and moderate for the brown coat of LOKE.M.8 samples and this is 

demonstrated by variations in the absorption of blue-dyed epoxy used in the sample preparation. The sand (S) is well coated with binder 

and is identified as a soft, natural carbonate sand composed of a variety of coral and shell fragments. The brown coat contains the coarsest 

sand of all examined samples and this is evident in this photomicrograph. Air-voids (AV) are not abundant in either sample. 
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Figure 12: PPL photomicrographs illustrating binder residuals in the Lighthouse mortar samples. All are identified as natural cement 

relicts (NC). Typical textures within these grains include calcined dolomite rhombs surrounded by an iron-rich hydraulic product and 

partially burned quartz silt grains evenly dispersed throughout the particles. These textures are characteristic of magnesium-rich American 

cements of the nineteenth century. With the exception of sample LOKE.M.5, the Lighthouse samples tend to have more variably-sized 

cement relicts with coarse grains not uncommon. This is different than other samples in the suite and may suggest a different cement batch 

or source for these three mortars. 
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Figure 13: PPL photomicrographs illustrating distinctive cement microtextures in portions of LOKE.M.4 and all of the brown coat in 

LOKE.M.8. The arrows exhibit isolated fine silt grains dispersed throughout the paste matrix. These are not a component of the sand as 

closer inspection reveals fine calcination rims around these grains. Such calcined quartz silt is a common component of natural cements 

and in fact, these are found in all the natural cement mortars examined for this report. However, the abundance is distinctively high in 

these two samples suggesting a different cement batch or source. 
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Figure 14: PPL photomicrographs illustrating binder residuals in mortar samples from the cistern, Kitchen Building and Keeper’s 

Dwelling. All but those in LOKE.M.10 (Keeper’s Dwelling) are identified as natural cement relicts (NC). Typical textures within these 

grains include calcined dolomite rhombs surrounded by an iron-rich hydraulic product and partially burned quartz silt grains evenly 

dispersed throughout the particles. These textures are characteristic of magnesium-rich American cements of the nineteenth century. 

Residual cement tends to fine- to medium-grained. The residual binder in LOKE.M.10 is identified as an ordinary gray portland cement 

(PC). The grain shown here contains rounded “ghosts” of fully hydrated calcium silicate with interstitial iron-bearing cement phases. The 

grind and consistency of the cement is characteristic of early twentieth century portlands. 
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Figure 15: PPL photomicrographs illustrating binder residuals in some of the Oil House samples. The brown coat is shown for 

LOKE.M.8 as this material is more or less identical to that of the masonry mortar samples. All are identified as natural cement relicts 

(NC). Typical textures within these grains include calcined dolomite rhombs surrounded by an iron-rich hydraulic product and partially 

burned quartz silt grains evenly dispersed throughout the particles. These textures are characteristic of magnesium-rich American cements 

of the nineteenth century. Residual cement tends to fine- to medium-grained. 
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Figure 16: PPL photomicrograph illustrating the overall microstructure of the scratch coat in sample LOKE.M.8. The binder matrix 

(BM) has a high capillary porosity as indicated by the high absorption of blue-dyed epoxy used in the sample preparation. Fine shrinkage 

cracks are also detected within the matrix and these two features are characteristics of high-lime binder matrices. The sand (S) is the same 

soft, natural carbonate sand found in the mortar samples. Air-voids (AV) are moderately abundant. 
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Figure 17: Photomicrographs illustrating binder residuals in the scratch coat in sample LOKE.M.8. (Top) XPL image. A lime grain 

(LG) is shown. The internal texture of the lime is homogeneous and little evidence is provided that might suggest the provenance of the 

lime. (Bottom) PPL image. A natural cement relict is shown (NC). These have the same characteristics as other cements in the sample 

suite. The cement is present in low abundance and is estimated to represent a minor gauging of an otherwise non-hydraulic lime plaster. 
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Figure 18: PPL photomicrograph illustrating the contact between the scratch coat (SC) and brown coat (BC) in LOKE.M.8. While 

natural cement (NC) is present in both, the difference in binder texture between a lime plaster gauged with cement (left) and a pure cement 

plaster (right) is quite apparent and difficult to mistake. Other details of the brown coat are presented above and are not repeated here. 
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Figure 19: PPL photomicrograph illustrating the overall microstructure of the finish coat in sample LOKE.M.8. The binder matrix (BM) 

has a high capillary porosity as indicated by the high absorption of blue-dyed epoxy used in the sample preparation. The layer is unsanded 

and all grains observed here are part of the binder. 
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Figure 20: Photomicrographs illustrating binder residuals in the finish coat in sample LOKE.M.8. (Top) XPL image. Lime grains (LG) 

are found in high abundance. Chemical analysis indicates that the finish is principally a lime plaster with a moderate gypsum gauging. 

The darker appearance of the grain at left indicates that it has not carbonated. The brighter grain at right is carbonated as are most observed 

residuals. (Bottom left) A gypsum residual (G) represents a grain of originally unhydrated hemihydrate that has hydrated to coarser 

grained gypsum. (Bottom right) This gypsum residual (GR) contains residual unhydrated hemihydrate. Both types of residual are 

relatively rare in this fine-textured plaster coat. 
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Figure 21: PPL photomicrographs illustrating the overall microstructure of the brown coat in sample LOKE.M.11. (Top) The binder 

matrix (BM) has a high capillary porosity as indicated by the high absorption of blue-dyed epoxy used in the sample preparation. The sand 

(S) is the same soft, natural carbonate sand found in the mortar samples. Air-voids (AV) are moderately abundant. (Bottom) The matrix is 

defined by a network of fine hydrated gypsum crystals. Still, the texture is somewhat coarse when compared to the finish coat (Fig. 23 

below) and the plaster in this coat may have been a Keene’s cement. 
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Figure 22: XPL photomicrographs illustrating binder residuals in the brown coat of sample LOKE.M.11. Gypsum residuals (G) represent 

grains of originally unhydrated hemihydrate that has hydrated to coarser grained gypsum. The arrow indicates a fine crystal of deadburned anhydrite. This type of inclusion is typical of Keene’s cement and would not be abundant in a Plaster-of-Paris. 
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Figure 23: PPL photomicrographs illustrating the overall microstructure of the finish coat in sample LOKE.M.11. (Top) The binder 

matrix (BM) has a high capillary porosity as indicated by the high absorption of blue-dyed epoxy used in the sample preparation. The layer 

is unsanded and all grains observed here are part of the binder. (Bottom) The matrix is defined by a network of fine hydrated gypsum 

crystals. Even in this higher magnification image, the texture is difficult to see and the finish coat plaster is much finer textured. 
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Figure 24: Photomicrographs illustrating binder residuals in the finish coat in sample LOKE.M.11. (Top) XPL image. Gypsum 

residuals (G) represent grains of originally unhydrated hemihydrate that have hydrated to coarser grained gypsum. The arrow indicates an 

unhydrated hemihydrate residual. Both types of residual are relatively rare in this fine-textured plaster coat. (Bottom) A carbonated lime 

grain is shown (LG). While chemical analysis was not performed on this sample, the lime is interpreted to represent a very minor gauging 

based on its observed abundance. 
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Figure 25: PPL photomicrographs illustrating microcracks in the cistern samples and one of the Lighthouse samples (arrows). These are 

minor and no sample in the examined suite exhibits any significant cracking distress. 
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Figure 26: PPL photomicrographs illustrating the few secondary chemical deposits detected petrographically in the examined sample 

suite. No visible distress is associated with any of these deposits. (Top left) Isotropic mineral deposits consistent with chlorides (Cl) are 

found in low abundance in samples LOKE.M.5 and LOKE.M.6. (Top right) Fine secondary deposits consistent with sulfates (S) are quite 

rare. (Bottom) Some air-voids in the portland cement mortar of sample LOKE.M.10 contain linings of secondary gypsum but again, no 

associated distress is noted.
APPENDIX C.

REHABILITATION REPORT AND NATIONAL REGISTER NOMINATION 

FOR THE UNITED STATED COAST GUARD LIGHT STATION

DRY TORTUGAS LIGHTHOUSE, LOGGERHEAD KEY, FLORIDA

(1984)































As the nation’s principal conservation agency, the 

Department of the Interior has responsibility for most 

of our nationally owned public lands and natural 

resources. This includes fostering sound use of our 

land and water resources; protecting our fish, wildlife, 

and biological diversity; preserving the environmental 

and cultural values of our national parks and 

historical places; and providing for the enjoyment of 

life through outdoor recreation. The department 

assesses our energy and mineral resources and works 

to ensure that their development is in the best 

interests of all our people by encouraging stewardship 

and citizen participation in their care. The 

department also has a major responsibility for 

American Indian reservation communities and for 

people who live in island territories under U.S. 

administration. 

364/105054 August 2010