Preservation Note 21

Removal of Bird Repellent Gel from Masonry

Masonry

March-91

Masonry Restoration and Cleaning-04900

Removal of Bird Repellent Gel from Masonry

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The following cleaning specification is based on tests conducted by
Mesick Cohen Waite Architects on the Tweed Courthouse for the City of
New York in 1989.

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This specification describes the method which proved most successful in
removing repellent gel from marble at the Tweed Courthouse. Relative
success has been reported using similar materials and techniques at
other historic buildings. Briefly, the cleaning sequence involves
careful scraping to remove the bulk of the gel, followed by repeated
applications of solvents applied in liquid and poultice form to remove
the oily gel residue and staining.

The Tweed Courthouse study confirms that bird repellent gels cause
serious damage to masonry. Retention of water resulting from the
application of repellent gel to stone surfaces caused severe
deterioration in marble window hoods saturated with the product. Because
of the possibility of hidden stone damage, great care must be taken in
applying and removing cleaning chemicals, particularly during poultice
removal.

Instruct cleaning contractors to use a conservative rule of thumb: if
evidence of deterioration raises doubts about the ability of the stone
to withstand rinsing pressures and the mild abrasion of manual scrubbing
and scraping, remove cleaning products as gently as possible and cease
the cleaning procedure at that location.

In areas where the stone remains sound, each cleaning step may be
repeated several times, as long as there is no evidence of masonry
damage or discoloration resulting from cleaning products or procedures.

Because repellent gel products tend to get absorbed deeply into masonry
pores, it may not be possible to remove all of the oily residue in areas
where the masonry has been heavily saturated with gel. Be prepared to
accept an improved, if not perfect, stone appearance.

Hire only experienced contractors who specialize in cleaning historic
masonry buildings. Require contractors to demonstrate (with project
descriptions, photographs, and references) successful experience in all
specified cleaning techniques. Require specific experience in cleaning
exterior masonry stains on historic buildings of similar complexity and
similar materials (name all masonry types to be cleaned). See
Preservation Notebook No. 3, \"Bidder Competency Clause,\" for
competency specifications, editing guidelines, and a checklist for
evaluating bidder competency.

These specifications outline materials and methods for removing bird
repellent gel only. Specifications for general cleaning and removal of
other stains, if planned, must be added (consult the Building\'s
Historic Structure Report, available in the GSA-NCR Technical Resources
Library, 7th and D Streets, SW, Room, Washington, DC (202) 708-6278 for
additional masonry cleaning specifications).

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Section 04900

Masonry Cleaning of Bird Repellent Gels

\[EDITING INSTRUCTIONS APPEAR IN BOLD\]

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Part I. General

Part II. Materials

Part III. Execution

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PART 1: GENERAL

1-1 Description: Work in this section includes:

Removal of bird repellent gel from \[LIST EACH TYPE OF STONE AND ELEMENT
TO BE CLEANED\]:

Protection of pedestrian and vehicular traffic, adjacent materials and
buildings, and building occupants and contents from harm by cleaning
operations.

1-2 Quality Assurance

GENERAL OBJECTIVE: The objectives of stone cleaning are to remove bird
repellent gel \[ADD OTHER TYPES OF SOILING INCLUDED IN THE SCOPE OF WORK
FOR THIS CLEANING PROJECT, EG., GENERAL SOILING, COPPER STAINING,
BITUMINOUS DEPOSITS. ALGAE\] without damaging underlying material and to
give the stone a clean uniform appearance. Protection of the stone form
damage is the highest priority.

CONTRACTOR QUALIFICATIONS: This work must be done by a firm specializing
in the cleaning of historic masonry. Refer to the Competency of Bidder
Clause, Sections 00120 and 00900 for submission requirements.

In the event that the Contractor wishes to modify any cleaning method
specified, he must submit his proposal in writing to the Contracting
Officer\'s Representative (COR) for consideration. The COR may ask for
test samples before approval. Approval or rejection of the Contractor\'s
request will be at the COR\'s discretion. Any such changes shall be at
no additional cost to the Government.

1-3 Regulatory Requirements

Comply with municipal and Federal regulations governing cleaning,
chemical waste disposal, and scaffolding

1-4 Submittals

Protection Program: Prior to the execution of cleaning samples, submit
to the Contracting Officer\'s Representative a written description of
the methods and materials for protection of all surrounding materials
not to be cleaned.

Waste Water Collection and Removal: Prior to execution of cleaning
samples, submit to the Contracting Officer\'s Representative a written
description of methods of waste water and chemical collection and
removal.

Submit to the Contracting Officer\'s Representative in triplicate a
written description of the methods, materials, and equipment proposed
for use in cleaning each type of masonry specified. Submit actual
samples of each cleaning product to be used, along with manufacturer
certifications that chemical ingredients conform to those specified for
each cleaning procedure.

1-5 Sample Cleaning Panels

Clean a representative sample of approximately 10 square feet of stone
surface at locations selected by the Contracting Officer\'s
Representative, for each type of stone to be cleaned and each different
procedure to be performed, including scraping to remove gel bulk. The
samples accepted by the Contracting Officer will be marked and left
undisturbed to serve as standards for the entire job.

Sample cleaning procedures must be executed in the presence of the
Contracting Officer\'s Representative and must demonstrate the
Contractor\'s ability to perform each specified cleaning procedure
without harming masonry. Damage to masonry as a result of cleaning
operations may result in the technician\'s dismissal from the project.

Adjust cleaning materials and methodologies during test panel cleaning
as directed by the Contracting Officer\'s Representative.

Allow a minimum of seven calendar days after completing cleaning samples
to permit the Contracting Officer\'s Representative to study the sample
panels for negative reactions.

Do not proceed with cleaning until cleaning samples have been approved
in writing by the Contracting Officer.

Approved samples shall be marked and left unaltered for the duration of
the project. Approved samples shall be used as the standard for similar
work throughout the project.

1-6 Delivery, Storage and Handling

Deliver materials to the site in manufacture\'s original and unopened
containers and packaging, bearing labels as to the type of material,
brand name and manufacturer\'s name. Delivered materials shall be
identical to tested materials.

Store materials off the ground in a clean, dry location. Remove
materials which are damaged or otherwise not suitable for use from the
job site.

1-7 Job Conditions

Take all precautions necessary to protect surrounding materials on the
site, surfaces of the building not being cleaned. Adjacent buildings,
pedestrians and vehicles from coming in contact with cleaning chemicals,
overspray, or runoff.

Use polyethylene film, masking tape, and whatever means necessary to
protect plantings, automobiles, building occupants, and building
surfaces not being cleaned. Remove such coverings when masonry cleaning
operations have been completed at that area of the building.

Repair or replace with new stock, at no cost to the Government, to the
Contracting Officer\'s satisfaction, any materials or plantings damaged
by scaffolding, laborers, cleaning materials, or cleaning operations.

Prior to full scale cleaning, perform, in the presence of the
Contracting Officer\'s Representative, a site test of the protective
methods to prove that chemical damage to stone, glass, interior
finishes, and other surfaces not being cleaned will not occur.

Test all drains and other water removal systems to assure that they are
functioning properly prior to initiating cleaning operations. Notify the
Contracting Officer\'s Representative immediately of all blockages.
Repair drains if so directed by the Contracting Officer\'s
Representative. Do not begin cleaning until drains are in working order.

Provide a method to prevent solids such as stone or mortar residue from
entering drains or drain lines. Clean out drains or drain lines that
become blocked because of work performed under this Contract.

Follow manufacturer instructions regarding the safe storage and use of
all products and equipment. Remove all solvents, soiled rags,
applicators, and other flammable materials daily and dispose off- site
according to Federal and municipal regulations.

1-8 Environmental Conditions

No cleaning shall be executed when air or masonry surface temperature is
below 45 degrees F, unless adequate, approved means are provide for
maintaining a 45 degree temperature of the air and materials during, and
for 48 hours subsequent to, cleaning.

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PART 2: Materials

2-1 Cleaning Products

Repellent Gel Remover: solvent based, methylene chloride paint stripper
formulated for removal of paint, tar, and adhesives from stone, such as
Sure Klean 509 Paint Stripper, supplied by ProSoCo, Inc. (P.O. Box
171677, Kansas City, KS 66117 Local distributor: 201-754-4410), or
approved equal.

Oily Stain Remover: Solvent mixture of methylene chloride, ketone methyl
alcohol, and aromatic hydrocarbon, formulated for the removal of oily
stains from stone, such as Sure Klean T1012, supplied by ProSoCo, Inc.,
Kansas City, Kansas, or approved equal.

Poultice:

Blend the following to form a paste:

Sure Klean T1012, supplied by ProSoCo, Inc., Kansas City, Kansas, or
approved equal

Poultice clay containing soda ash (sodium carbonate), talc (magnesium
silicate hydrate), and fullers earth (magnesium aluminum silicate), as
supplied by ProSoCo, Inc., Kansas City, Kansas, or approved equal.

2-2 Rinse Water:

Clean, potable, and free of oils, acids, alkalis, and organic matter.

2-3 Tools

Gel Scraper (use for removal of gel residue \@l ): Sharp steel blade,
held at a shallow angle against surface to avoid damage to stone.

Poultice Scraper: Non metallic spatula

Brushes: Fiber bristle brushes (nonmetallic)

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PART 3: EXECUTION

3-1 Preparation

Examine masonry to be cleaned prior to installing protection and
executing sample panels. Notify Contracting Officer\'s Representative
(COR) immediately of any masonry damage observed. Use caution in
installing protection and undertaking cleaning in damaged areas. Clean
and rinse by gentlest means possible and follow COR\'s recommended
precautions to avoid further damage to deteriorated masonry.

Following approval of proposed protection scheme as outlined in 1-4,
install protection as described in 1-7.

Following approval of submitted materials and written description of
methods as stipulated under 1-4, execute sample panels as directed in
1-5.

Check drains as described in 1-7.

3-2 Removal of Bird Repellent Gel

Remove bulk of gel by carefully scraping masonry surface with a steel
blade. Hold blade at a shallow angle to avoid scratching or abrading
stone surface. Scratching or otherwise damaging masonry will result in
the cleaning technician\'s dismissal from the project.

Apply and remove solvent paint stripper, as directed by manufacturer, as
many times as necessary to remove surface coatings remaining after
scraping bulk of repellent gel.

3-2 Removal of Repellent Gel Stains

Apply Oily Stain Remover to dry stone in areas where gel stains remain
after removal of repellent gel.

Trowel apply poultice-solvent mixture immediately after application of
Oily Stain Remover. Apply poultice to a minimum thickness of 1/4 inch.

Cover the poultice with plastic film to keep it from drying out for a
minimum of 24 hours. Press film to poultice and tape or otherwise seal
the edges to exclude air.

Remove plastic cover and allow the poultice to dry thoroughly.

Remove poultice by scraping with a nonmetallic spatula. Wash the surface
thoroughly with fresh water.

Repeat steps A through E as necessary to obtain results matching
approved samples.