When is cleaning walls a crime? When you're doing it to T ber of street artists around the c create art, ob them elves through a practice r world have started expressing "clean me" messages known as reverse graffiti. Inspired by the they find that you see written the back of some messages dirty and them with images or it's using cleaning or e hose way, dirt same principle: the image is made by cleaning away the Each artist has an individual style, artists share our cities. common aim to draw attention to po opepatesv Paul Curtis, better known as Moose, around Leeds and has been commissioned by a number of companies to make reverse graffiti ads. Brazilian artist Alexandre Orion turned one of Sao Paulo's traffic tunnels into an amazing mu by scraping away the dirt. Made up of a series of white skulls, the mural reminds drivers of the effect their ion is having on the planet. "Every driver sits in the comfort of a car, but they don't give any consideration to t price their comfort has for the environment and consequently for themselves, says Orion.