When I first heard about the Desert Museum exhibit hosted by the International Society of Scratchboard Artists, I thought immediately of the artboards I used to play with when I was a kid: Use a sharp point to scratch the ink off of a black board and reveal a rainbow of color underneath. I think I remember doing scratchboard when I was a kid, I tell Paul Hopman, a Tucson artist who is exhibiting work at the event. We all did, he says. The lucky ones, anyway. It s literally the oldest art in the world. You know what a petroglyph is?