'Stains is a boxed set of single sheets of paper, done in 1969, and it's like a little treasure chest of overlooked things. Stains have always been scorned I guess, and it evolved out of my concepts of painting. I've always painted with a skin on a support, like paint on a canvas. And finally I got sick of doing it, and staining something, letting a wet material sink down into the fabric of the support—in this case paper—was the effort here and was my interest. The idea of using something that stains rather than a paint that sits on the surface of a canvas was my discovery for myself at the time.

So there is everything from wine stains, coffee stains, L.A. tap water that's almost invisible—lots of 'em, lots of stains. I made a little laundry list of things that I think I wanted to see at that time, one was even sulfuric acid which eats a hole in the paper, and everything that I selected seemed to be right at the time.

When I produced this thing, I remember buying a large quantity of this 100% rag content paper, and I got a call from the US government because it is the same kind of paper that would be used in counterfeiting, so I had a short-lived problem there, proving that I was not doing anything nefarious' – Ed Ruscha