Presentation at the Annual APT meeting in Victoria Canada, 2011.

1. A comparison of cleaning methods
for graffiti removal from masonry
materials
B Y M A R Y F. S T R I E G E L , E R I C G U I D R Y, M O L LY
M C G AT H , A N D C AT H E R I N E A R C E N E A U X
N AT I O N A L C E N T E R F O R P R E S E R VAT I O N
TECHNOLOGY AND TRAINING

2. What are important factors to consider before
removing graffiti?

3. Graffiti or Art?
The Polish city of Lodz is making huge waves in the street art world. Under the
patronage of Mayor Hanna Zdanowska … In MyModern Met website 9/29/2011

4. Gentlest Means Possible:
Do no harm

5. Type of graffiti materials
 Markers
 Spray paints
 Others

6. Weathering factors
 Sunlight = UV cross-
linking or fading
 Temperature
 Humidity
“Graffiti peeling – yellow” by Greig Christie, August 12, 2005. Flickr. Accessed 10/09/2011.

7. How do we evaluate graffiti removal methods?
NCPTT study

8. What are people using to remove graffiti?
 Survey of Professionals: requests to conservators
and preservation professionals in the field
 20 responses received
 Most used chemical cleaners
 Organic Solvents: Acetone, MEK, Xylene
 Solvent poultices
 Solvent Gels
 Commercial Products
 Solvent based
 Hydroxide based
 Peel Away products

9. Selection of masonry types
 Marble
 Red, Low Fired Brick
 Beige, Modern Brick

10. Selection of Graffiti materials
 Type: Rust-oleum Enamel
 Color: Red, Black

11. Choice of cleaning systems
 Peel Away 1®
 Wipe Out Porous Surface Graffiti Remover®
 Sure Klean® Fast Acting Stripper
 Laser Cleaning

12. Peel Away 1®
 A poultice like paste
containing caustic
cleaners
 Active Ingredients
 Calcium Hydroxide
 Magnesium Hydroxide
 Sodium Hydroxide
 pH = 13
 Requires a separate
neutralizing solution

13. Wipe Out Porous Surface Graffiti Remover®
 Basic gel
 Active Ingredients
 75% proprietary
ingredient
 1-5% Monoethanolamine
 1-10 % Potassium
Hydroxide
 1-5% Nonylphenol
Ethoxylate
 pH = 11-12

14. Sure Klean® Fast Acting Stripper
 Solvent-based gel
 Active Ingredients:
 Dichloromethane
 Amine
 Methyl Alcohol
 Xylene
 Alcohol
 pH = NA
 Major handling and
environmental issues

15. Laser Cleaning
 Remove material from a
solid surface in a
controlled fashion
 Active Ingredients = NA
 pH = NA
 Expensive equipment
 Time intensive

16. Sample
Preparation
. .Cutting and
coring samples. .

17. . . .Painting
samples with red
and black stars. . .

18. . . .Artificial weather exposure chamber. . .

19. Testing
Methods
. . .Colorimetry. . .

20. Laser profilometry

21. Visual appearance ranking

22. Results: Color change
Percent Change in L Value
0.600
0.500
0.400
Peel Away
0.300 Laser
Stripper
Wipeout
0.200
0.100
0.000
H-B Red H-B Black L-B Black M Red M Black

23. Laser Profilometry: Texture change

24. Improvement of Visual Appearance
Percent Ranked #1 in Visual Appearance Survey
100
90
80 Poultice
70
60 Laser
50
40
Stripper
30
20
Gel
10
0
H-F Brick Red H-F Brick Black L-F Brick Red L-F Brick Black Marble Red Marble Black

25. What have we learned?
Of the products tested:
 Peel Away was most efficient for removing paint and the
least physical damage to the surface, but it was difficult
to remove from some surfaces
 Sure Klean Fast Acting Stripper was a gel that limited
penetration into the material. It was a poor performer
overall.
 Wipe Out was difficult to control during application and
caused the relocation of pigment. It performed well on
the high fired yellow brick.
 Laser ablation required a great deal of pre-experimental
examination to be effective.

26. Where do we go from here?
 Limited study established methods for evaluating
graffiti removers
 A greater range of products must be tested, with an
emphasis on cleaners that are:
 Environmentally friendly
 Effective at removing a range of materials
 Safe for the cultural resource, the environment, and the user