When you paint images not with spray cans or pigment, but instead by cleaning dirt and pollution from public places in artistic patterns - painting the image by removing dirt - this is reverse graffiti. This defaces no surface, and in fact starts to clean what a city should have cleaned to begin with. In order to remove the image, you don’t sandblast or get out the toxic cleaners. Instead you just finish cleaning the surface. The whole surface returns to its original bright clean color. Just like someone writing “Wash Me!” into the grime on a dirty car windshield might shame someone into actually washing their car just to get rid of the message - so reverse graffiti artists cause cities to clean where they should have already.

In São Paulo Brazil, artist Alexandre Orion:

In Paris, corporate reverse graffiti (for the Electronic Arts game Burnout, but through a beautifully designed guerrilla campaign at Kah Ra Shin):

Related books: Graffiti Brasil and Street World: Urban Culture and Art from Five Continents.

Travel to Brazil or France (Travelocity).