I'm taking a printmaking class, non toxic litho, at the Manhattan Graphics Center. This week we got introduced to polyester plate lithography. It uses a sheet of paper-like polyester that has lots and lots of tiny holes giving it a porus surface that holds water. The printing matrix is made by drawing on the sheet with waterproof media like crayons, ballpoint, pen, sharpie, etc. Drawing blocks these microscopic holes and makes that area repel water. The paper is then dampened with a mix of water and gum Arabic.