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February 7 - February 13, 2011

What is the best way to remove graffiti from the surface of historic stone masonry on a church while preserving the appearance properties of the substrate?

Selected Answers

From David Lawson of Eagle Specialized Coatings on February 9, 2011:
Sooner is always better than later so as to prevent as much pigment saturation into the substrate as possible. Soft cleaning techniques are also advisable when it is a sensitive substrate. Abrassive techniques can damage the substrate beyond repair. We use a biodegradable cleaner that is manufactured by Superior Products Int. II that dissolves some of the toughest pigments such as engine enamels. Depending on the length of time it has set into the substrate a poultice may be the best approach, where an absorbant material saturated with your cleaner is held over the area to be cleaned to soften the pigments. If you can make the cleaner into a paste it will be easier to hold over vertical areas for a longer period of time. Once the pigments have been released from the substrate the surface can be wiped down with clean rags or if possible rinsed away with water.

From Jerry LeCompte of mmlj on February 9, 2011:
Graffiti removal is not the real challenge. For instance the City of Chicago has been removing graffiti by soda blasting for nearly 20 years. “Preserving the appearance properties of the substrate” is very subjective. For instance, if you want a clean-looking finish it’s not a problem. This is what you generally get when soda blasting. If you want to retain the same weathered aged appearance you are more apt to be out of luck. However, SodaBlast Systems, LLC. may have some updated information on this.

From VCBud Jenkins of CSCS on February 7, 2011:
Since some paint removers have acid which will etch the stone, beware of using them without first testing a small spot somewhere safe. I would try soaking rags in lacquer thinner and encapsulating them in plastic against the graffiti until it softened, then use 3500 psi hot-water pressure washer to blast the graffiti off. Some air quality districts will not allow lacquer thinner to be used for cleaning so a compliant cleaning solution would have to be used in that case.

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Tagged categories: Graffiti removal; Historic Preservation; Maintenance + Renovation; Masonry

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