Graffiti artists deface many valuable edifices

Sep 11, 2009 06:38 GMT  ·  By
A polymer coating designed to protect historic buildings from graffiti: its water-vapor permeability allows the building to breathe, despite the protective coating
   A polymer coating designed to protect historic buildings from graffiti: its water-vapor permeability allows the building to breathe, despite the protective coating

In most of the world's largest cities, there is bound to be a vibrant culture of street artists, who use paint, markers and wheat paste to leave their mark on the streets. But, at times, these drawings are done on old, historic buildings, defacing them, as the artists do not distinguish between common buildings and the more important ones. To counteract this trend, German researchers at the Fraunhofer-Gesellschaft Institute for Applied Polymer Research IAP, in Potsdam, have developed a new type of polymer coating that protects buildings, while allowing them to breath at the same time.

As most old buildings are made of natural stone or brickwork, which are porous materials, it's very difficult to remove the aerosol paint from these surfaces without using caustic agents. These chemicals do a lot of damage to the layers underneath, and can affect the construction adversely. But the new polymer designed at Fraunhofer is water-vapor permeable, which means that it allows the surface underneath to breath, while at the same time protecting it from spray-paint vapors.

“There are conflicting requirements for this kind of polymer coating – it mustn't seal the pores, because it is important that there should be a continuous exchange of air between the building and the external environment, and at the same time it has to prevent the spray paint from penetrating the pores. The coating needs to be sufficiently resistant to withstand both weathering and mechanical cleaning,” Fraunhofer Institute for Applied Polymer Research IAP research group leader, Professor Andre Laschewsky explains.

“Moreover, since we're dealing with historic landmarks, it must be possible to completely remove the coating from the walls if required, to restore them to their original condition with little effort and without damaging the structure,” he adds. Existing graffiti “defenses” already rely on polymers that are hydrophobic, which means that water cannot adhere to them. But the pores in these polymers are always closed, so any surface beneath cannot breathe. Additionally, these layers are very difficult to remove, which means that they are not very effective for conservation purposes.

“Our innovative polymer film seals the pores in the substrate, so that graffiti paint doesn't penetrate. But its micro-porous structure also creates a hydrophobic barrier that allows water vapor to escape from the building while at the same time preventing the infiltration of rainwater,” the expert concludes.