The images Curtis creates may be beautiful, but they hide an ugly truth: the walls, tunnels and other surfaces he uses for a canvas are layered in pollutants. As Greg Hanscom writes,
"Street artist Paul Curtis, better known as 'Moose,'...doesn't use spray paint or wallpaper paste -- the usual tools of this trade. Instead, he wields scrub brushes, old socks, cleaning fluid, and, when he's living large, a high-pressure hose. He creates images by cleaning shapes into filthy urban surfaces such as retaining walls, signs, and tunnels. People have called it 'reverse graffiti,' 'clean graffiti,' and 'negative space.'
He is fond of carving the forms of flowers and trees onto dirty surfaces, adding organic forms, as delicate as paper cutouts, to the hard edges of the urban landscape. 'The environmental message [in my art] is unavoidable,' he says. 'I'm writing in grime.'"