The Reverse Graffiti Project

This a short documentary about a technique called "reverse graffiti" or "clean tagging". The artist, "Moose" is the pioneer of this technique and uses natural methods and natural cleaners to create a large scale mural in San Francisco by cleaning pollution and dirt from the walls of the Broadway Tunnel. The film was directed by acclaimed documentarian Doug Pray who recently directed the full length film "Surfwise". Take a look ! I think it's quite interesting. More content can be found here.(Thanks a lot for telling me about it !)