Paul "Moose" Curtis: I've never found that easy way of explaining what I do. I tell people that I make pictures by cleaning. I have this weird thing about dirt. I just look around for it all the time. I'm a professor of dirt. I create a contrast so where it's dirty and where it's clean, you can see these things like they're black and white.
Tonight we're making a mural that's about 140 feet long. It's downtown San Francisco, Broadway Tunnel. It's really dirty. It's like a massive canvas. All the images are of indigenous plants from California that you may find in the area where that tunnel is now maybe 500 years ago.
It was born one day, working as a kitchen porter in a restaurant. I've been cleaning pots and pans. And I was sitting there, and I saw a little dirty mark on the wall. And I got my cloth out, and I just wiped over this little dirty mark but I left a bigger clean mark where I'd clean over this dark. And then I was like, "What am I going to do?" So I tried to like diffuse it a little bit so you... and in the end, I had to clean the whole wall and it looked really weird. And when I'd cleaned the whole wall, I thought, "I'd have to clean the whole restaurant now," and I think I realized the power of it.
You know, I'm not the world's biggest environmentalist, but it's impossible for me not to toe the environmental line. The whole core of what I do is based around drawing and pollution and writing in nature. Nature's voice, if you like, is written in dirt like it would be written in blood. But however much the environment thing is around home to people, seeing how dirty a wall is by cleaning it in this way, it kind of gets people immediately. They go up and they look at it and they think it's spray paint or something and then it's just a cold realization that the world is really, really dirty.There may be small errors in this transcript.