A Graffiti ‘Shield’!
Posted by Science Oxford on August 19, 2009 | comments
Although, there are already several anti-graffiti paints out on the market this innovative new salt mixture claims to be a huge improvement.
Read on to find out more:
Visit this page »Graffiti mars many a historic landmark, but it can only be erased—if at all—using caustic solutions that risk damaging the underlying surface.
A new “breathable” wall coating, though, offers efficient, all-round protection against attacks by spraycan hooligans, researchers claim.
It takes seconds to spray on graffiti, but hours or weeks to remove, especially from the porous natural stone or brickwork that characterize the majority of historic monuments. The paint seeps deep into the pores and can become unremoveable even with a pressure hose or powerful cleansing solvents.
Often nothing will do the trick short of chemicals that eat away at a venerable wall.
Some anti-graffiti coatings have already been on the market for several years. They create a water-repellent seal that shuts the pores. That helps keep the paint from sticking to the surface, so that it easily comes off.
But these coatings also seal out air and lock in moisture, according to André Laschewsky, a researcher with the Fraunhofer Institute for Applied Polymer Research in Potsdam, Germany. That, he said, leaves the surface vulnerable to mold or the development of unsightly salt deposits. Moreover, he added, these coatings are themselves hard to remove, and thus flout a principle dear to conservationists—that any changes to a historic monument should be reversible.
The trouble, Laschewsky said, is that a successful coating must meet “conflicting requirements.” It mustn’t seal the surface entirely, yet it has to keep the paint from getting in. It needs to resist weathering and wiping down, yet be easily removeable when it’s necessary.
As part of a European Union-sponsored project, Laschewsky and colleagues with the Polish Academy of Sciences developed a polymer coating that they claim satisfies these demands. Polymers are a large class of compounds consisting of large molecules made up of smaller repeating units, as in plastics.
The newly created polymer film seals the pores on a building surface so as to block the unwanted paint, Laschewsky explained. At the same time, the new coating has its own, much smaller “micro-pores,” which create a water-repellent barrier that allows air to reach the building.
The coating is removeable using a salt solution that modifies its chemical composition and allows it to be washed off, he added. In a project coordinated by the Labein Foundation, a nonprofit research center in Bilboa, Spain, and the German Federal Institute for Materials Research and Testing, Laschewsky and partners coated samples of ancient stone and brick and repeatedly covered them with graffiti—which, they said, completely washed off each time.
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