38 PRESERVATION 

BRIEFS 

Removing Graffiti from Historic Masonry 

Martin E. Weaver 

U.S. Department of the Interior 

National Park Service 

Cultural Resources 

Preservation Assistance 

In Cooperation with the 

New York Landmarks Conservancy 

Figure 1. Many stones resemble others, and even concrete can sometimes be mistaken for stone. The stone trim on the Old Merchant's (Seabun) 

TredwelI) House (1832), in Greenwich Village, New York City, is 

documented as Vermont marble. After establishing the stone type, cleaning methods should be tested in a discrete location in order to determine the most 

effective means of removing the graffiti without damaging the stone. More than one kind of removal technique may be required when both stone and 

brick require cleaning. Photo: Mark A. Weber 

Removing graffiti as soon as it appears is the key to its 

elimination-and recurrence. Thus, the intent of this 

Preservation Brief is to help owners and managers of historic 

masonry structures find the best way to remove exterior, 

surface-applied graffiti* quickly, effectively, and safely. The 

Brief will discuss the variety of materials used to apply 

graffiti, and offer guidance on how to remove graffiti from 

all types of historic masonry without harming either the 

surface or the substrate. Suggestions will also be given 

regarding the use of physical barriers to protect masonry 

surfaces from graffiti, and the application of barrier coatings 

to facilitate graffiti removal. Building managers and owners 

of historic properties will be advised on the importance of 

being prepared for rapid graffiti removal by testing different 

cleaning techniques in advance in order to select the most 

appropriate and sensitive cleaning technique. Health and 

safety and environmental concerns are addressed, as well as 

regulatory matters. Removing graffiti without causing 

damage to historic masonry is a job for trained maintenance 

crews, and in some cases, professional conservators, and 

generally should not be attempted by untrained workers, 

property owners or building managers. Although the focus 

of this Preservation Brief is on historic masonry, the same 

guidance may be applied equally to removing graffiti from 

non-historic masonry. 

Identifying the Graffiti and the Masonry 

Successful graffiti removal from historic masonry depends 

on achieving a balance between breaking the bond between 

the graffiti and the masonry surface without damaging the 

masonry. This generally requires knowledge both of the 

materials used to make the graffiti and the masonry on 

which the graffiti has been executed, as well as knowledge 

of cleaning methods and materials (Fig. 1). Without this, 

masonry surfaces can be badly disfigured or damaged 

during graffiti removal. 

Graffiti. Most graffiti is made with spray paints. Although 

a number of solvents and paint strippers are capable of 

dissolving or breaking down these paints, some may 

permanently discolor or stain the masonry surface if not 

used correctly. As a result, the remaining paint may become 
2 

more difficult, or even impossible, to remove. Poorly 

thought-out and generally hasty attempts to remove graffiti 

using harsh chemicals or abrasives can also cause 

permanent damage to the masonry that may be worse than 

the graffiti (Fig. 2). 

The ability to identify the graffiti material is an important 

step in successful removal. Numerous kinds of spray paint 

(polyurethanes, lacquers, and enamels), and brush-applied 

paints (oils and synthetic resins such as vinyls, acrylics, 

acetates, methacrylates, or alkyds), as well as permanent 

felt markers are the materials most often used to make 

graffiti. But other materials are also used for graffiti, 

including water-soluble felt markers, ballpoint pens, chalk, 

graphite and colored pencils, pastels, wax and oil crayons, 

liquid shoe polish, and lipstick (Fig. 3). The range of 

materials adopted by graffitists continues to expand. 

Figure 2. Harsh , but ineffective, graffiti removal methods have resulted in 

permanent damage to granite walls at the General Grant National 

Memorial in New York City. Photo: Judith M. Jacob 

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I f \ LYe .; 

b 

Paints are composed of pigments that provide color and 

hiding power; binder that holds the pigments together and 

to the substrate; and a solvent that allows the 

pigment/ binder mixture to flow. Some spray paints and 

markers may contain dyes instead of pigments. Paints are 

applied wet. Generally, as the solvent evaporates, the 

binder solidifies. The greater the solvent content of the 

paint, the greater the flow rate, and thus, the greater the 

ability of the paint to penetrate into masonry pores 

The two primary components contained in most graffiti 

materials-pigment or dye, and binder-may simply 

remain on the masonry surface, or penetrate into the 

masonry to varying depths depending on a number of 

factors, including the surface tension of the substrate and 

viscosity of the solvent or vehicle. Thus, even the total 

removal of the pigment or the binder may leave residues of 

the other component actually in, or below, the surface of the 

stone. Residual stains, or graffiti "ghosts," such as those 

from any kind of red paint or the fine black pigments used 

in spray paints, may be particularly difficult to remove (Fig. 

4). With painted graffiti, it is helpful to establish how long 

it has been on the surface. For most paints that have been 

on the surface for several weeks or months, hardening 

processes are likely to be complete or well-advanced; the 

solubility of the paint is proportionately reduced and it will 

be more difficult to remove. 

.... '1 I-h.J;~ I<;.;,'r 

I '" IL ". E:rlr 

Figure 3 (a-d). A wide 

variety of materials is 

used to make sllrfaceapplied graffiti on masonry, including 

(a) chalk, (b) felt-tip 

marker, (c) felt-tip 

marker combined with 

crayon, alld (d) felt-tip 

marker and spray 

paint all concrete. Photos: (a) Anne 

Grimmer, (b) Frallces Gale, (c) Martin 

Weaver, (d ) Anile 

Grimmer. 
Figure 4 (a-b). After cleaning with an alkaline paint remover, remnants or ghosts of black spray-painted graffiti are still visible and may require poulticing, while the blue paint has been almost completely removed. 

Photos: Mark A. Weber. 

Masonry. The historic masonry substrate must also be 

identified. As used here, the term masonry encompasses all 

types of natural stones; manufactured clay materials, 

including brick and terra cotta; and cementitious materials, 

such as cast stone, concrete and mortar. The common factor 

among masonry materials is that they are porous, to a 

greater or lesser extent, and sensitive to abrasion. After 

identifying the masonry, its condition, including fragility, 

porosity and permeability, must also be assessed prior to 

beginning graffiti removal. For example, a smooth, newlypolished granite surface is comparatively easy to clean 

because it is relatively impermeable and paint vehicles tend 

to stay on the surface rather than penetrate into microscopic 

pores. A very smooth, polished surface also has no pits or 

crevices that will retain particles of pigment or binder. In 

contrast, weathered marble or limestone may be extremely 

porous and permeable, with a rough surface on which 

particles of pigment can easily lodge. The fragility of such a 

surface can make it impossible to clean the surface even 

with a bristle brush without risking severe surface loss. A 

difference in surface texture or finish may also be the reason 

that a particular cleaning agent will work in one situation 

but not another. 

Some types of masonry may react adversely to contact with 

the various cleaning agents required to break or dissolve 

the bond between the graffiti and the masonry surface. 

Thus, for purposes of cleaning, masonry types are often 

categorized according to whether they are acid-sensitive, 

non-acid sensitive, or alkali-sensitive. Acid-sensitive stones 

consisting of carbonate materials may be damaged or even 

destroyed by contact with acids. Although, in many 

instances, acidic cleaning compounds are not effective for 

graffiti removal and generally should not be used for this 

purpose, it is useful to know that some acid-sensitive 

materials include: stones such as limestone, marble, 

travertine, calcareous sandstones and shales; most polished 

stones; and glazed architectural terra cotta and glazed brick. 

Non-acid sensitive masonry materials include slate, granite, 

unglazed architectural terra cotta and unglazed brick. 

Alkali-sensitive stones may contain silicates, or ferrous, 

soluble iron compounds that can react with alkalis or water 

to form severe staining. Alkali-sensitive stones include some 

granites, Indiana limestone, and many types of sandstone, 

especially those that are green or grey in color. Glazed and 

polished surfaces tend to be damaged by both strong acids 

and strong alkalis. 

Graffiti Removal Methods and Materials 

A variety of treatments are available from which to choose 

the most appropriate method of graffiti removal that will 

not damage the surface of historic masonry. Removal 

techniques, which are chosen according to the type of 

graffiti and the masonry, range from simply erasing 

pencilled graffiti with soft erasers, or removing chalked 

graffiti with soft brushes, to poulticing with water (with or 

without detergents), poulticing with organic solvents or 

alkali-based paint removers, or applying bleach to remove 

painted graffiti. In very limited situations, it may mean 

using very delicate and controlled abrasive means. 

Successful graffiti removal often requires a combination of 

cleaning materials and methods. 

Poulticing 

The most effective method of removing graffiti from 

masonry usually involves the use of a poultice. A poultice 

consists of an absorbent material or powder-inert clays such 

as kaolin or sepiolite, diatomaceous earth (fuller's earth); or 

cellulose products such as fluff puIp celluIose or shredded 

paper-mixed with a cleaning solution (a liquid reagent such 

as water, organic solvent, paint stripper or bleach) to form a 

paste or slurry. The purpose of a poultice is twofold: it 

enables a cleaning solution to be kept in contact with the 

stained area as long as possible, while allowing the cleaning 

solution to pull the staining material out of the substrate via 

the poultice without redepositing it in, or restaining, the 

masonry. A poultice is often covered with a plastic sheet to 

retard evaporation (Fig. 5). With some extremely porous 

types of stone, such as marble, although a poultice may 

remove a stain from one side of the stone, stains can pass 

completely through the stone and be redeposited on the 

other side of the masonry slab. Thus, caution should always 

be exercised in stain and graffiti removal. 

Water and Detergent. Graffiti removal from historic 

masonry should always begin with the gentlest means 

possible. In some instances, this means low-pressure water 

washing. Fresh graffiti- one or two days old-made with 

water-soluble markers may sometimes be removed with 

water, possibly aided by a neutral or non-ionic detergent. 

3 
4 

Figure 5. (a) Here, a commercially-manufactured poultice is being 

applied to the graffiti ghost that remains on this limestone building after an initial treatment with paint remover; (b) a plastic sheet has been taped over the poultice to slow dowll the rate of evaporatioll of the solvents con tained in the poultice. Photos: Ken Lustbadel'. 

(Non-ionic detergents which do not ionize in solution, do 

not deposit a solid, visible residue.) Ammonia can also be 

effective in removing fresh graffiti. Any detergent should 

be approached with caution and tested before using 

because most commercial laundry detergents are not 

neutral and contain substances which may leave 

undesirable residues on masonry materials. Usually, the 

water and detergent should be mixed with an absorbent 

material and applied in the form of a poultice. Although 

water washing is often likely to be the gentlest cleaning 

method for historic masonry, it may not be as effective for 

removing graffiti because many graffiti materials are not 

soluble in water. 

Organic Solvents and Paint Removers. Most graffiti can be 

removed without damaging the masonry with proprietary 

graffiti-removal products and commercial paint strippers 

containing organic solvents. But, these products should 

always be tested and used in accordance with 

manufacturer's instructions included in the product 

literature. Normally, solvents should be used in a poultice 

form to prevent them from penetrating into the substrate, 

and permanently discoloring or staining the masonry. A 

number of paint-removers are manufactured as thick gels 

or pastes that cling to the surface, and some commercial 

paint-removal products include a tough fiber-reinforced 

paper or cloth backing that retards evaporation and also 

facilitates neat and clean removal of the used stripper. The 

advantage of using organic solvents is that they evaporate 

completely, leaving no residual material in the masonry. 

However, organic solvents may present a severe health 

hazard, and workers using them must wear adequate 

protection. "Off-the-shelf" aerosol graffiti removers 

generally should not be used because the dissolved paint 

being removed may run down the wall "staining" a 

previously clean area; or pigments may also be 

redistributed by the rinsing and scrubbing recommended 

by the product manufacturer (Fig. 6). 

Alkaline Compounds. Alkaline compounds may be used 

to remove some oils and greases, and waxes from non-aLkali 

sensitive masonry. Like organic solvents, alkaline 

compounds should generally be used in conjunction with a 

poultice when removing graffiti. The use of alkaline 

compounds should always be followed by a weak acid 

Figure 6. Although all aerosol graffiti remover has taken off much of the 

graffiti, it has left Ilew stains where it dripped down the masonry surface. Photo: Kell Lustbader. 
wash and a water rinse in order to neutraliz~r remove--

all the alkaline residues from the masonry. Strong alkalies 

(pH13-14), such as sodium hydroxide-based paint removers 

(caustic soda or lye), generally should not be used as they 

can cause efflorescence and staining on masonry surfaces, if 

not properly neutralized. Potassium and other hydroxide 

paint removers may react with iron compounds in some 

masonry, particularly Indiana limestone, to form dark 

brown (rust-colored), or black ferric hydroxide stains, 

which are very difficult to remove. 

Bleaches. Alkali-based bleaches such as calcium 

hypochlorite can sometimes be used very successfully in a 

poultice to bleach or decolorize certain dyes contained in 

some paints and inks that cannot readily be removed by 

other means. 

Mechanical or Abrasive Methods. Mechanical treatments 

include dry or wet blasting, using abrasive grits, such as 

sand, dolomite powder, aluminum oxide, ground-walnut 

shells, sodium bicarbonate (baking soda), and others; highpressure water washing; and mechanical sanding or 

grinding. All of these abrasive methods will cause damage 

to masonry and, in most instances, should never be 

considered as a method of removing graffiti from historic 

masonry. Abrasive methods used mistakenly by untrained 

workers to remove graffiti usually result in etching the 

outline of the graffiti permanently into the masonry (Fig. 7). 

Some historic masonry materials can be easily damaged by 

pressure washing even at low or moderate pressures 000-

400 psi). Occasionally, however, under very controlled 

circumstances, a micro-abrasive technique may be 

appropriate for removing graffiti from delicate masonry 

surfaces, if used at low pressures of 35-40 psi with fine 

abrasives. This treatment, which must be done very slowly 

and carefully to avoid damaging the masonry, should be 

tested first, and undertaken only by a professional 

conservator. Another exception, even though it is not 

strictly an abrasive treatment, is using a razor blade as a 

first step to remove spray paint or felt-tip marker from 

polished granite. However, this too, should be undertaken 

only by a professional conservator, and only on polished 

granite, which is very hard and generally impervious to 

scratches. 

Laser Cleaning. Although not in general use as a cleaning 

technique, laser technology offers great promise in the 

future as a non-damaging method of graffiti removal. 

Testing 

Before selecting a removal method, all cleaning materials 

and techniques for removing graffiti from a historic 

masonry building should be tested on mock-ups or areas of 

the resource that are not highly visible, but which are 

representative of typical conditions. Visual observation 

should be supplemented by the use of a magnifying glass, 

and spot tests should be carried out with various solvents to 

help identify the specific graffiti medium, which will aid in 

its removal. More complex testing using laboratory 

equipment and more scientific analytical processes may 

sometimes be necessary in complex situations. Sample 

areas that represent the desired degree of "cleanliness" 

should be approved in writing by client, architect, 

conservator or other appropriate authority. The materials 

and all the other data necessary to reproduce the desired 

Figure 7 (a-b). The first time this spray-painted graffiti appeared it was 

removed abrasively. As a result, the graffiti was permanently etched into 

the limestone and cal1not be concealed even by the pigmented barrier 

coating painted over it later. The barrier coating did, however, facilitate 

110n-abrasive removal of graffiti the next time it was applied. 

Photos: Anne Grimmer. 

cleaning results should be meticulously recorded and the 

accepted sample area preserved for reference until the end 

of the job. The existence of a "clean" sample for comparison 

and a signed agreement can avoid unpleasant surprises, 

misunderstandings, and perhaps legal acti~ns. 

When a type of graffiti appears for the first time that was 

executed with a material not immediately recognizable and 

for which no countermeasures have been developed, tests 

may need to be carried out by an architectural conservator 

to identify the material and to determine effective removal 

treatments. Agencies with large inventories of graffitiprone buildings and structures should watch for graffiti 

made with new materials and experiment with different 

cleaning methods in order to be prepared when it appears. 

Such early action can save large sums of money in the long 

term. (See "Development of a Treatment Plan.") 

5 
6 

Development of a Treatment Plan 

For managers or owners of historic masonry buildings, 

or agencies responsible for large inventories of graffitiprone properties, including parks, highway and 

railroad bridges and viaducts, bus, train and subway 

stations, and cemeteries, the development of a 

treatment plan may be the first step toward an effective 

graffiti-removal program. It is becoming increasingly 

common for large or important historic properties to 

have regular maintenance and disaster plans that 

include graffiti removal. 

When feasible, a separate treatment plan should be 

prepared for each structure. However, if this is not 

possible, it is advisable to prepare a variety of 

treatment plans for specific masonry types. Plans 

should be prepared to cover all types of masonry that 

fall under one jurisdiction, management or ownership 

that are potential targets for graffiti. 

Guidance contained in treatment plans should be based 

on the results of carefully controlled testing to remove a 

wide variety of common graffiti materials safely, and 

without damaging the various types of masonry. 

Individual treatment plans should address all parts of 

the building or structure that could be disfigured by 

graffiti, and any features too fragile to be cleaned by 

anyone other than a conservator should be noted on 

the plan. 

A treatment plan is essentially a cleaning 

specification, but it should also include information 

on the following: 

• the types and conditions of masonry likely to be 

targeted by graffiti; 

• methods, materials and techniques known to work 

most successfully in the removal of specific types 

of graffiti from the surface of each type of masonry; 

• sources for materials; 

• a list of contractors with expertise in graffiti 

removal, including names, telephone numbers, 

information on emergency access to the property, 

and storage location of materials; 

• graffiti-removal methods which may be harmful to 

the masonry surface; 

• contractors or consultants who are not acceptable 

and should not be considered for graffiti removal; 

• scaffolding, pumps, or safety equipment that might 

be required, where it is available, and costs 

involved; and 

• health and safety concerns regarding specific 

removal treatments, product literature and 

Material Safety Data Sheets (MSDS). 

Health and Safety Considerations 

Most of the chemicals used for graffiti removal are dangerous 

to workers, as well as to others who may be in the vicinity. 

Organic solvents are toxic by ingestion, inhalation, and skin 

contact. Material Safety Data Sheets (MSDS), available from 

the product manufacturer for all paint-removal products, 

should always be consulted and followed. Identification of 

hazardous components and checking with chemical reference 

works will help assure that the least hazardous, but most 

effective, products are selected. 

Generally speaking, it is a sensible policy to carry out all 

graffiti removal in well-ventilated conditions. Some 

solvents can be used only outdoors, and sometimes forced 

ventilation may be necessary even there, requiring workers 

to use air-fed respiratory equipment to avoid wind-blown 

fumes. Smoking, eating or drinking must not be allowed 

when cleaning is in progress. 

Some materials used for graffiti removal are so corrosive 

that accidental contact can cause serious, permanent 

scarring and painful injuries. Wearing appropriate 

protective clothing must be strictly enforced. Mandatory 

personal protective equipment (PPE) normally includes face 

shields or safety glasses; long, chemical-resistant gloves; 

face masks with respirators for organic solvents; and 

possibly, full protective clothing with an independent 

air supply. 

All smoking and open flames should be rigorously 

excluded from work areas; many solvents are flammable or 

highly explosive in vapor or liquid form when mixed with 

air. Solvent residue, used swabs, cloths, overalls and all 

other solvent-contaminated items should be safely and 

legally disposed of, or properly stored-even overnightaway from potential sources of fire. Electrical equipment 

may require explosion-proof fittings when used with 

certain solvents. 

When electric pumps and pressure-spraying equipment are 

used, it is especially important that all necessary 

precautions be taken to avoid electric shock. Water sprays 

and puddles on the ground present a potentially dangerous 

situation, if they come into contact with temporary wiring 

at worksites where graffiti is being removed. Such hazards 

must be carefully monitored and controlled. 

As with any construction project, attention should always 

be directed toward the general safety of the workers and 

passers-by, but also toward possible damage to the resource 

itself that might result from careless placement of ladders, 

or scaffolding. Chemicals used for masonry cleaning can 

also damage adjacent metals, glass, and painted surfaces, as 

well as vegetation (Fig. 8). Product manufacturers' 

instructions should always be closely followed to avoid 

such inadvertent "collateral" damage. 

Environmental Considerations 

To protect against environmental contamination, including 

the formation of unwanted ozone at ground level and 

damage to the ozone layer in the earth's outer atmosphere, 

legislation has been enacted in some states making it illegal 

to use even moderate quantities of some solvents - voLatiLe 

organic compounds (VOCs) contained in paint removers. In 

response to this legislation, many new products are being 

developed that do not contain VOCs. 
After completing graffiti removal, the disposal of chemical 

products and rinsing effluent must be taken into account. 

Arrangement for disposal of the cleaning waste should be 

made prior to beginning graffiti removal, especially if it is a 

project of considerable size. In many places it is illegal to 

discharge solvents and/or paint residues into sewers or 

storm drains. The owner or manager of a historic property, 

or in some cases the individual or firm doing the cleaning 

or graffiti removal, is responsible for being informed of, and 

complying with, relevant laws and regulations. Under 

provisions of the National Historic Preservation Act of 1966, 

as amended, approval may be required from a state or 

federal preservation agency before any work can be 

undertaken on buildings or structures listed in or eligible 

for listing in the National Register of Historic Places, if such 

a project involves federal funding or licensing. Many state 

and local historic district commissions and review boards 

have their own regulations that require approval for 

cleaning or graffiti removal work that is undertaken on 

landmarks or properties in locally designated historic 

districts. 

Barrier Coatings 

Anti-graffiti or barrier coatings are intended to facilitate the 

removal of graffiti from porous as well as non-porous 

surfaces. These coatings are most commonly transparent, 

but may also be pigmented. They are available in a variety 

of formulations designed to serve different needs. The use 

of barrier coatings to protect graffiti-prone historic masonry 

surfaces may seem to be an easy preventive solution to a 

persistent graffiti problem. However, for the most part, 

these coatings are not the panacea that some advertising 

might suggest. Some of them simply do not work, and 

others may cause physical or aesthetic changes or damage 

to the masonry. 

Transparent Coatings. Transparent coatings serve as a 

barrier between the masonry surface and graffiti, 

preventing graffiti from penetrating into the masonry. 

They are also intended to make graffiti removal easier since 

most graffiti does not adhere well to them. Generally, 

graffiti applied over transparent barrier coatings can be 

removed with low-pressure water and a detergent, or with 

a solvent. 

There are basically two kinds of transparent barrier 

coatings: temporary and permanent. Temporary, or 

"sacrificial" coatings are removed when graffiti is removed 

and then must be reapplied. Permanent transparent barrier 

coatings are more resistant to the water or solvents used to 

remove graffiti, and remain on the masonry surface when 

graffiti is removed (although this type of coating also must 

usually be reapplied after several cleanings). A third type 

of transparent barrier coating combines temporary and 

permanent coatings, based on a two-part system. A waterbased acrylic sealer is first applied to the masonry surface, 

after which a sacrificial layer consisting of a polyethylene 

wax emulsion or dispersion coat is applied over the sealer. 

When graffiti is removed, the sealer coat remains on the 

masonry, but the sacrificial coat dissolves and is removed 

with the graffiti, and thus must be reapplied. (With this 

two-part system, even the first coat will eventually wear off 

after multiple cleanings, and must also be reapplied.) 

Unfortunately, in application, there are a number of 

negative aspects of transparent barrier coatings that 

generally prevent their being recommended for use on 

historic masonry. First, clear coatings may alter the color of 

the masonry surface and add a gloss that may be highly 

visible, or apparent only in certain lighting conditions or 

when it rains. Second, clear coatings may reduce the watervapor permeability of the masonry, thereby contributing to 

possible water-related deterioration. Third, the coating 

may discolor and change over time. Exposure to ultraviolet light can cause a coating to yellow; dirt build-up may 

darken the treated surface; and some coatings acquire a 

sheen when rubbed or brushed against. Such changes are 

especially noticeable when only a portion of the building 

has been coated. Furthermore, if coatings are not 

maintained on a regular basis, usually through periodic 

removal and reapplication, many coatings tend to fail. 

What often results is an uneven, "patchy" look to the 

masonry that can have a very negative impact on the 

character of the historic building (Fig. 9). 

Despite these potential drawbacks, there may be some 

instances in which the graffiti problem or frequency of 

occurrence is so severe that application of a transparent 

barrier coating on historic masonry may be worth 

considering. Some water-based polysaccharide coatings, 

and silicone and silicone-based coatings have been used 

with success on masonry structures. They are essentially 

Criteria to Consider Before Selecting 

a Barrier Coating as the Primary 

Protective Means of 

Combating Graffiti 

What to look for in a Barrier Coating: 

• Water-vapor permeable, or "breathable". 

• "Invisible" without gloss or sheen, when applied to 

masonry. 

• No change in appearance from uncoated areas when 

masonry is wet. 

• Does not discolor or attract dirt. 

• Weathers evenly. 

Questions to Ask: 

• Will the coating last long enough to offset its cost? 

• Will the application and reapplication of the coating 

be cost effective? 

• Will the coating be effective against more than one 

type of graffiti? 

• Can the coating be completely and thoroughly 

removed, so that, if necessary, paint, or another 

coating will adhere to the masonry surface? 

• Will the building ever need to be repointed or 

patched? A barrier coating may make this difficult 

or even impossible. 

Before Application: 

• Seek advice of an architectural conservator. 

• Test coating on an inconspicuous area of masonry, or 

study the success/ failure of the coating in other 

locations where it has been used. 

7 
8 

Figure 8. The cast-iron railing and light fixtures on this stone stoop have been wrapped with plastic sheeting to protect them from damage by chemicals being 

used to remove the graffiti. Photo: Mark A. Weber. 

Figure 9. These photographs illustrate some of the problems inherent in clear 

barrier coatings. (a) The transparent coating applied to the lower portion of 

this granite entranceway has darkened it, thus changing the character of the 

historic masonry. (b) But it is not nearly so obvious or damaging to the building's historic character as the thick and shiny clear coating applied here 

which resembles a plastic sheathing over the brick. Scratches are highly 

visible and a surface haze indicates that the coating has begun to deteriorate. 

(c) This transparent coating is peeling and has failed completely; 110t only is 

it an eyesore, but it may also be hard to remove from the brick. Photos: (a-b) 

Mark A. Weber, (c) Martin E. Weaver. 
invisible, and do not change the natural appearance of the 

masonry. Although less durable than solvent-borne 

coatings, they are water-vapor permeable (breathable), and 

may be reapplied to the masonry surface immediately after 

removing graffiti, while the surface is still damp. 

However, extreme caution must be exercised before 

applying a transparent barrier coating. Experimental test 

applications should always be tried first on discrete areas 

that are not highly visible, and the treated areas evaluated 

over a period of time. Laboratory test results on the 

performance of coatings applied to samples of like masonry 

types may be useful to some extent. But because the tests 

are carried out in a controlled environment, they may not 

be as accurate or reliable as tests actually carried out on-site 

where the factors of weather and pollution are the same as 

those at the location where the coating will be used. If 

circumstances warrant, and the use of a barrier coating is 

determined necessary, an architectural conservator should 

evaluate the test performance of a variety of coatings before 

selecting one to be applied to historic masonry. Because of 

the potential for disfigurement, owners of landmarkdesignated buildings are required by some preservation 

review boards and landmark commissions to obtain 

approval before they apply a barrier coating. 

Pigmented Coatings. A pigmented barrier coating may be 

used on masonry as a permanent, preventive barrier 

coating, or as a temporary means of concealing graffiti until 

it can be removed. 

Like a transparent barrier coating, a pigmented barrier coating 

facilitates the removal of graffiti because graffiti does not 

adhere well to it. Pigmented barrier coatings that are watervapor permeable may sometimes be used as a permanent 

barrier coating on non-historic masonry where there is 

frequent recurrence of graffiti, and when constant surveillance 

is not possible (Fig. 10). Although there are some instances in 

which pigmented barrier coatings may be appropriate on 

painted historic masonry, they are not recommended for 

unpainted historic masonry because they will change the 

appearance of the masonry. There is also another kind of 

pigmented coating that is specially formulated to be used as a 

temporary measure to conceal graffiti that cannot be removed 

right away. This temporary, vapor-permeable paint is 

removed when the graffiti is removed. 

Pigmented coatings are also not generally recommended as 

a permanent measure to cover up graffiti. Some graffiti 

materials, particularly felt markers, bleed through the 

coating; and repeated applications of the coating or paint 

can result in a heavy paint build-up on a masonry surface. 

Another disadvantage of using paint or a pigmented 

coating to hide graffiti is that it usually appears as an 

obvious patch on unpainted masonry and tends to attract 

more graffiti unless the paint can be applied in a discrete, 

and well-defined area (Fig. 11). If incompatible with either 

the masonry or the graffiti, such a coating may peel off the 

masonry surface in an unsightly manner. Like transparent 

coatings, pigmented coatings may be difficult or impossible 

to remove completely once their performance or 

appearance is no longer satisfactory (Fig. 12). 

Preventing and Controlling Graffiti 

Experience shows that prompt removal of graffiti is one of 

the most effective measures against its recurrence. Graffiti 

that is not removed quickly tends to attract more graffiti. 

Often motivated by a need to have their work seen, 

graffitists tend to be discouraged from repeating their 

efforts in a location where their work is quickly removed. 

Figure 10 (a) It may be appropriate to cOl1sider the applicatiol1 of a barrier 

coating in order to facilitate removal il1 some out-of-the-way 10catiol1s where ftl ll-time security is not possible, sHch as this stairway and bridge 

underpass next to the C&O Canal. (b) Overpainting graffiti on the stone wall at the left has not been successful; it has resulted il1 highlighting the 

defaced stones, thereby attracting more graffiti. Photos: Al1ne Grimmer. 

9 
10 

Figure 11. (a) The first floor of this 

Iimestol1e storefrol1t was pail1ted il1 al1 

effort to cover graffiti. However, because 

the pail1t is poorly matched to the color 

of the buildil1g stol1e, it is highly visible 

al1d 110W acts as a "magl1et" for l1ew 

graffiti. (b) Similarly, the lowest 

horizol1tal bal1d 011 this stol1e buildil1g, 

overpail1ted to cover graffiti, has also 

attracted more graffiti. Photos: (a) Mark 

A. Weber, (b) Martil1 E. Weaver 

Apart from removal, effective graffiti-prevention measures 

can be considered under two headings. The first consists of 

physical measures involving maintenance, lighting, 

security and the erection of barriers on or around the 

property itself. The second focuses on community 

awareness programs that include neighborhood patrols, 

community service programs and educational programs in 

the schools. 

Maintenance and Security. Neglect invites vandalism, 

whereas a well-maintained property encourages civic 

pride. Thus, careful attention should be given to 

establishing regular maintenance programs which do not 

allow properties to reach a point of obvious deterioration 

or abandonment. Cyclical maintenance also makes good 

sense economically. 

Graffiti is less likely to occur if graffitists can be clearly 

seen. It is often recommended that accessible, graffitiprone areas be illuminated with floodlighting or spotlights. 

Graffiti may also be reduced or prevented by the presence 

of security guards, park rangers or police officers, or by the 

visible presence of surveillance cameras. Publicity about 

arrests and punitive measures against the graffitists, and 

the general vigilance of the security system may also reduce 

graffiti. 

If they are historically appropriate and compatible with the 

historic property, soft barriers in the form of low, pOSSibly 

thorny, shrubs and bushes or other forms of landscaping 

and planting may be effective deterrents. Such plantings 

can make it difficult to reach the property by any route 

other than the approved secure one. Hard barriers 

provided by fences and transparent screens or shields, such 

as clear acrylic or other polycarbonate sheets, may also 

afford some degree of protection. But these can have a 

negative aesthetic impact on the property's appearance, 

particularly if the barriers themselves become disfigured 

by graffiti. 

Community Awareness. Community action and education 

often play an important role in a successful anti-graffiti 

program. Neighborhood watches can effectively deter 

graffitists, and can help police and other security agencies in 
the detection and prevention of graffiti. Intensive public 

campaigns against graffiti, including presentations in schools, 

developing programs to foster community pride, and 

sentencing offenders to remove graffiti in their own 

community can also be useful. Publicity concerning arrests of 

graffitists can be a useful preventive tool. (But, on the other 

a 

hand, frequent newspaper coverage of graffiti outbreaks or 

even of new community efforts at deterring graffiti can 

sometimes have the opposite effect by challenging the 

"creativity" of graffitists.) Community groups trained in 

proper cleaning techniques can also assist property owners in 

prompt and non-damaging graffiti removal. 

Figure 12. (a) Graffiti that was overpainted has been exposed here as a result of the coating's failure. The uneven edges where the overpainting has peeled 

away will make inconspicuous touch-up difficult. (b) The unsightliness of graffiti bleeding through layers of cracked and peeling paint makes an obvious 

point that using a pigmented coating was not an appropriate maintenance technique for this stone sculpture base. Photos: (a) Martin E. Weaver, (b) Judith 

M. Jacob. 
12 

Tips for Successful Graffiti Removal 

- It is important to pre-wet the masonry 

surface when using an alkaline paint 

remover; it is also advisable to pre-wet the 

masonry surrounding a graffitied area to 

dilute the effect of any cleaning agents that 

might be inadvertently splashed or spilled on 

the unsoiled surface. Do not wet the area to 

be cleaned if the cleaning agent is solventbased or incompatible with water. 

- Always rinse the cleaning agent off the 

masonry surface starting at the bottom and 

moving up. This prevents the cleaning agent 

from running down and staining a lower 

surface. 

- Air temperature can be a factor in graffiti 

removal. Most paint removers do not work 

when the air temperature is either very cold 

or very hot. This may sometimes explain 

why a method that worked in one instance 

may not be effective again in another, similar 

situation. 

- Variations within the same type of stone, 

such as bedding planes, density, finish, or 

degree of weathering, may explain why some 

areas of the same stone sometimes clean 

better that others. 

- Even if advance testing has been done and a 

treatment plan exists, at least some on-thespot testing will probably be necessary. 

- Mortar joints react differently from masonry 

units, and may require a different cleaning 

material and/ or method to be cleaned 

effectively. 

- Graffiti removal may result in an obviously 

"clean" spot. Always clean the entire 

masonry unit that is bounded by mortar 

joints (but not the joints themselves, unless 

necessary). The prominence of the clean spot 

may be minimized by fanning the cleaning 

out from the spot, and "feathering" it by 

gradually reducing the strength or 

thoroughness of the cleaning. 

- If it is not possible to completely remove all 

traces of graffiti without removing some of 

the masonry surface, it may be preferable to 

leave the masonry alone. Some graffiti 

ghosts become less noticeable with time due 

to fading of the dyes used in paints and 

markers. Sometimes it may be possible to 

conceal more obvious graffiti ghosts with 

carefully-matched paint. 

- After graffiti removal, the masonry surface 

should always be tested with pH strips to 

make sure all the cleaning materials have 

been completely removed. Non-staining pH 

strips, available from chemical supply 

companies, will indicate whether acids or 

alkalis remain on the masonry surface. 

- Although alkaline paint removers are 

sometimes ineffective on modern 

formulations of aerosol paints, they can 

work well in removing multi-layered graffiti 

because they last longer. 

- What removes graffiti in one instance may 

not always work again even in what appears 

to be an identical situation. 

- More than one cleaning material and 

technique may be required to clean a heavily 

graffitied area if different materials were 

used to make the graffiti. For example, 

shapes are often outlined with broad-tip felt 

markers and then filled in with spray paint. 

- Effective graffiti removal often depends on 

trial-and-error testing, as well as a 

knowledge of masonry materials, graffiti 

materials and cleaning techniques. 
Suggestions for Removing Graffiti from Historic Masonry 

Graffiti Removal Method Health and Safety Cautions 

Pencil 1. Erase with non-abrasive pencil eraser. None. 

2. Wash with water and non-ionic detergent. 

3. Rinse with water. 

Chalk/ Pastel 1. Brush off with bristle brush. None. 

(not wax or oil-base) 2. Wash with water and non-ionic detergent. 

3. Rinse with water. 

Paint 1. Poultice with paint remover*, organic +See cautions below for NMP, solvents 

Spray (aerosol) solvent, or petroleum-based compound**. and petroleum-based compounds. 

Non-spray paint 2. Rinse with water, denatured alcohol or 

mineral spirits. Wear proper respirator, gloves 

3. Wash with water and non-ionic detergent. and eye protection. 

4. Rinse with water. 

Permanent (felt-tip) 1. Wash with water and non-ionic +See cautions below for NMP, solvents 

Marker detergent, if necessary. and petroleum-based compounds. 

2. Poultice with bleach***, 

paint remover*, organic solvent Bleach is corrosive, causes chemical 

or petroleum-based compound**. burns, and forms toxic gases (chlorine). 

3. Wash with water and non-ionic detergent. Wear proper respirator, gloves 

4. Rinse with water. and eye protection. 

Water Soluble 1. Wash with water and non-ionic detergent. Bleach is corrosive, causes chemical 

(felt-tip) Marker 2. Poultice with bleach***. burns, and forms toxic gases (chlorine). 

3. Wash with water and non-ionic detergent. Wear proper respirator, gloves 

4. Rinse with water. and eye protection. 

Ballpoint Pen 1. Erase with non-abrasive pencil eraser. +See cautions below for NMP, solvents 

2. Poultice with organic solvent and petroleum-based compounds. 

or petroleum-based compound**. Wear proper respirator, gloves 

3. Wash with water and non-ionic detergent. and eye protection. 

4. Rinse with water. 

Crayon 1. Poultice with denatured alcohol, paint +See cautions below for NMP, solvents 

Lipstick remover* or organic solvent**. and petroleum-based compounds. 

Shoe Polish 2. Wash with water and non-ionic detergent. Wear proper respirator, gloves 

3. Rinse with water . and eye protection. 

.. Paint Remover based on N-methyl-2-pyrrolidone (NMP). 

** Organic Solvent such as acetone, lacquer-thinner, or petroleum-based compound such as dimethyl adipate. 

*** Bleach such as calcium hypochlorite. 

+ N-methyl-2-pyrrolidone (NMP) is mildly toxic and may have adverse reproductive effects. 

Solvents and petroleum-based compounds have toxic vapors, are flammable, and require well-ventilated conditions. 

These are suggestions to assist in graffiti removal. Methods should always be tested first under the supervision and guidance of an 

architectural conservator. 

13 
14 

Summary 

Although rapid graffiti removal is the most effective 

weapon in eliminating graffiti and preventing its recurrence 

in the same location, hasty, untested removal attempts can 

disfigure and cause harm to historic masonry. Thus, it is 

important that the owner or manager of a historic masonry 

building or structure be prepared with a plan to ensure the 

prompt removal of graffiti when it occurs. Regularly 

scheduled maintenance and cleaning programs to eliminate 

graffiti from historic masonry properties may be assisted by 

the installation of physical barriers, security systems and 

Selected Reading 

American Geological Institute. AGI Glossary of Geology and 

Related Sciences. Washington, D.C: American Geological 

Institute, 1960. 

Ashurst, Nicola. Cleaning Historic Buildings. Vol. I: 

Substrates, Soiling and Investigations; Vol. II: Cleaning 

Materials and Processes. London: Donhead Publishing Ltd., 

1994. 

"Chemistry Leaves Its Mark on Graffiti." Chemical 

Marketing Reporter. November 14, 1993. 

Ehrenkrantz & Eckstut Architects, P.C Technical Tips: 

Removing Graffiti. New York: New York Landmarks 

Conservancy, n.d. (1994). 

Graffiti Removal Manual. Providence, RI: Keep Providence 

Beautiful, September 1986. 

Grimmer, Anne E. Keeping it Clean: Removing Exterior Dirt, 

Paint, Stains and Graffiti from Historic Masonry Buildings. 

Washington, D.C: Preservation Assistance Division, 

National Park Service, U.s. Department of the Interior, 1988. 

Lewis, Richard J. Hazardous Chemicals Desk Reference. 

Second Edition. New York: Van Nostrand Reinhold, 1991. 

NIOSH Pocket Guide to Chemical Hazards. Washington, D.C: 

National Institute for Occupational Safety and Health, 

Centers for Disease Control and Prevention, Public Health 

Service, U.S. Department of Health and Human Services, 

June 1994. 

lighting, as well as increased community involvement. 

Successful graffiti removal from historic masonry requires 

knowledge of a variety of cleaning methods and materials, 

and an awareness that what works to remove graffiti from 

one kind of masonry surface may not remove it from 

another. By testing different cleaning methods in advance, 

treatment plans will be available, when needed, to provide 

guidance for safe and sensitive graffiti removal from 

historic masonry. 

Reisner, Robert. Graffiti: Two Thousand Years of Wall 

Writing. Chicago: Cowles Book Company, 1971. 

Science for Conservators: Conservation Teaching Series. The 

Conservation Unit of the Museums and Galleries 

Commission. 3 volumes. New York: Routledge, A 

Division of Routledge, Chapman and Hall, Inc., 1992. 

Torraca, Giorgio. Porous Building Materials. Rome: 

ICC ROM, 1988. 

Torraca, Giorgio. Solubility and Solvents for Conservation 

Problems. Rome: ICC ROM, 1990. 

Weaver, Martin E. Conserving Buildings: A Guide to 

Techniques and Materials. New York: John Wiley & Sons, 

Inc., 1993. 

Whitford, Maurice J. Getting Rid of Graffiti: A practical guide 

to graffiti removal and anti-graffiti protection. New York: Van 

Nostrand Reinhold, Inc., 1992. 

Wollbrinck, Thomas. "The Composition of Proprietary 

Paint Strippers." Journal of the American Institute for 

Conservation. Vol. 32 (1993), pp. 43-57. 

Young, Daniel J. How to Comply with the OSHA Hazard 

Communication Standard: A Guide to Compliance with OSHA 

Worker Right-to-Know Regulations. New York: Van 

Nostrand Reinhold, 1989. 

,., u.s. GOVERNMENT PRINTING OFFICE: 1995 387-091/20004 
Acknowledgements 

This Preservation Brief was developed under a cooperative 

agreement between the New York Landmarks Conservancy 

and the National Park Service. Mark A. Weber, Director, 

Technical Services Center, served as project coordinator for 

the Conservancy. The author, Martin E. Weaver, is the 

Director of the Center for Preservation Research at 

Columbia University. He is an internationally recognized 

expert in the conservation of architectural and cultural 

resources, a noted lecturer, and author of Conserving 

Buildings: A Guide to Techniques and Materials, as well as 

numerous articles on the subject. 

Anne E. Grimmer, Senior Architectural Historian, 

Technical Preservation Services, Preservation Assistance 

Division, National Park Service, coordinated the 

development of this Preservation Brief and served as 

Technical Editor. Technical review of this publication by 

the following is gratefully acknowledged: Frances Gale, 

Training Coordinator, National Center for Preservation 

Technology and Training, National Park Service, 

Natchitoches, LA; Judith M. Jacob, Architectural 

Conservator, Building Conservation Branch, Northeast 

Cultural Resources Center, National Park Service, NY, NY; 

Andrea Mones-O'Hara, Regional Historic Preservation 

ISSN: 0885 7016 

'The word grnffito Igrnffiti, plural) - is derived from the old Italian diminutive of 

graffio - to scratch, and the Latin grnphire - to write. Grnffiti in contemporary 

usage has come to mean an inscription, drawings, or markings, Except in very 

formal or technica l appli ca tions, graffiti is generally considered a "mass" noun 

and paired with a Singular verb, 

Officer, National Capital Region, General Services 

Administration, Washington, DC; Nicolas F. Veloz, 

Conservator of Outdoor Sculpture and Monuments, 

National Capital Area Office, National Park Service, 

Washington, DC; and Michael J. Auer, Timothy Buehner, 

Charles E. Fisher, and especially Kay D, Weeks, Technical 

Preservation Services, Preservation Assistance Division, 

National Park Service, Washington, DC. 

This publication has been prepared pursuant to the 

National Historic Preservation Act of 1966, as amended, 

which directs the Secretary of the Interior to develop and 

make available information concerning historic properties. 

Comments on the usefulness of this publication may be 

directed to: Technical Preservation Services, Preservation 

Assistance Division, Center for Cultural Resource 

Stewardship and Partnerships, National Park Service, P.O. 

Box 37127, Washington, DC 20013-7127, or Technical 

Services Center, New York Landmarks Conservancy, 141 

Fifth A venue, NY, NY 10010. This publication is not 

copyrighted and can be reproduced without penalty. 

Normal procedures for credit to the author, the National 

Park Service, and the New York Landmarks Conservancy 

are appreciated. 

October 1995 

Cover Photograph: Sandstone gatepost, Springfield Armory National 

Historic Site, Springfield, Massachusetts. Photo: Judith M, facob , 

15