Please excuse the typographical error in the title of this post. Due to an obscure computer error, it cannot be changed. The title should have read: Shrinky Dinks are made of clear #6 plastic (polystyrene)! This is the plastic used to make those clear clamshell sandwich containers. Apparently (according to this website), the stuff is just like Shrinky Dinks. Color on it with Sharpies, then throw it in the oven, and voila! Shrinky stuff. (More careful details on the aforementioned website). I'm going to be watching for clear #6 plastic everywhere now. Free shrinky dinks? Excellent! Sign me up!
PS: This kind of reminds me of dropping syrofoam cups into the deep-fryer at McD's. They'd shrink right down, leaving a delicious poison residue on any Filet-o-Fish cooked up in that vat. I'm further reminded of the amazon sculptures which could be created with large blocks of styrofoam drizzled with acetone. Very cool, and only a few fumes were released.