One night, during the course of changing the blade in the box-cutter, I left the old one on the edge of my workbench. (That's me- Safety Sally!) After spilling some water, I was cleaning and saw a ghost image of the blade where it had been laying. We figured it had something to do with the oil used to treat the blade. It looked awesome, as it was the same color as the real thing. For some reason, a few weeks later I attacked it with sharpies. Wish I would have left it alone though, the trompe l'oeil effect even freaked me out. Sometimes if I was brushing my desk off in a hurry, I'd see it and think, "Ahhhh, I almost cut myself!" before realizing it was the ghost blade.