B Y M A RY F. S T R I E G E L , E R I C G U I D RY, 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 RVAT I O N T E C H N O L O G Y A N D T R A I N I N G

A comparison of cleaning methods for graffiti removal from masonry

materials

What are important factors to consider before removing graffiti?

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

Gentlest Means Possible: Do no harm

Type of graffiti materials

MarkersSpray paintsOthers

Weathering factors

Sunlight = UV cross-linking or fading

TemperatureHumidity

“Graffiti peeling – yellow” by Greig Christie, August 12, 2005. Flickr. Accessed 10/09/2011.

How do we evaluate graffiti removal methods? NCPTT study

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

Selection of masonry types

MarbleRed, Low Fired BrickBeige, Modern Brick

Selection of Graffiti materials

Type: Rust-oleum EnamelColor: Red, Black

Choice of cleaning systems

Peel Away 1®Wipe Out Porous Surface Graffiti Remover®Sure Klean® Fast Acting StripperLaser Cleaning

Peel Away 1®

A poultice like paste containing caustic cleaners

Active Ingredients Calcium Hydroxide Magnesium Hydroxide Sodium Hydroxide

pH = 13Requires a separate

neutralizing solution

Wipe Out Porous Surface Graffiti Remover®

Basic gelActive Ingredients

75% proprietary ingredient

1-5% Monoethanolamine

1-10 % Potassium Hydroxide

1-5% Nonylphenol Ethoxylate

pH = 11-12

Sure Klean® Fast Acting Stripper

Solvent-based gelActive Ingredients:

Dichloromethane Amine Methyl Alcohol Xylene Alcohol

pH = NAMajor handling and

environmental issues

Laser Cleaning

Remove material from a solid surface in a controlled fashion

Active Ingredients = NA

pH = NAExpensive equipmentTime intensive

. .Cutting and coring samples. .

Sample Preparation

. . .Painting samples with red

and black stars. . .

. . .Artificial weather exposure chamber. . .

. . .Colorimetry. . .

Testing Methods

Laser profilometry

Visual appearance ranking

Results: Color change

H-B Red H-B Black L-B Black M Red M Black0.000

0.100

0.200

0.300

0.400

0.500

0.600

Percent Change in L Value

Peel AwayLaserStripperWipeout

Laser Profilometry: Texture change

Improvement of Visual Appearance

0

10

20

30

40

50

60

70

80

90

100

Poultice

Laser

Stripper

Gel

H-F Brick Red H-F Brick Black L-F Brick Red L-F Brick Black Marble Red Marble Black

Percent Ranked #1 in Visual Appearance Survey

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.

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