I love using old modeling clay for printmaking. I give the students small pieces and have them roll it into a ball, then form it into a square. I place all kinds of "junk" on the tables such as old marker tops, tooth picks, buttons, paperclips, etc. (anything that will make an interesting impression) and have them press them in the clay making a design. Then they dip their "stamp" into different colors of paint and print patterns on their paper. Each student rinses the paint off their clay and place it on a paper towel to dry. I then put all the little balls back into the large coffee can I store them in. I've had the same clay for 6 years now...Crayola.