One day it's a blank slate, the next morning it's emblazoned with someone's hasty "throw up". If isn't immediately buffed, the graffiti spreads like a virus in the night, until all available space is filled. Lately, the SFPD have been making their presence felt by parking their vehicles in the alley in front of the freshly painted pieces, obviously hoping to discourage vandalism. Yeah right. Within the next few days the wall is bound to be painted over enabling someone else to get their ups. Sure enough, they'll be back, like Sisyphus pushing a rock up a hill for eternity, the graffiti writers will continue to crush the freshly painted alley wall. How thick is the paint on this wall?