Graffiti is an ongoing problem in our school district. Do you know of any effective cleaning methods that can remove graffiti without damaging the brick or concrete block?

Vandals use hundreds of different materials: spray paints, lipstick, felt-tip markers, crayons, etc. No one cleaner is effective on all of them. As with any cleaning problem, it is best to begin with the gentlest method. Common removal methods are steam cleaning with strong detergents, high-pressure water blasting, scrubbing with commercially available graffiti removers, and dry or wet sandblasting. Unfortunately, the most effective graffiti removers often do the most damage to the brick or concrete block. Because most masonry materials are very absorptive, markings from many spray paints and permanent felt-tip markers penetrate deeply into masonry surfaces. Perhaps the best strategy to prevent graffiti from damaging masonry surfaces is to coat them before graffiti is applied. Many effective coatings are commercially available. They consist of silicones, acrylics, urethanes, and other substances. Several different graffiti-resistant coatings are discussed in the NCMA-TEK 100.Graffiti-resistant coatings should produce a film that:
  1. is transparent
  2. adheres well to the masonry substrate
  3. exhibits no tackiness to collect dirt
  4. does not change the appearance of the masonry
  5. does not crack, peel, or yellow when exposed to weather or sunlight
  6. has high water-vapor transmissivity so the film breathes (water vapor or salts that collect behind the film could contribute to deterioration of the masonry)
  7. is thick enough to prevent absorption of the materials into the masonry and does not wear over time
  8. is easy to maintain and economical to apply

Also, the compound should have no effect on other materials in the wall, such as sealants and window surfaces.