Homemade Shrinky Dinks®

Transparent polystyrene packaging such as those used to hold baked goods can be used to make plastic trinkets. (Not all clear packaging works. Polystyrene containers should have a number 6 inside the recycling triangle on the plastic.) When the plastic is heated, stretched-out polymer chains have enough energy to relax their orientations. As a result, thin flexible sheets of the clear polystyrene will shrink laterally, thicken, and become less flexible. Writing that was placed on the surface of the polystyrene with permanent markers will also shrink. This polymer behavior is the basis for Shrinky Dinks®, a craft/toy that was popular in the 1970s and 1980s, and can still be purchased today.

®Shrinky Dinks is the Registered Trademark of K & B Innovations, Inc.

 

ABOVE: The polystyrene "windows" on envelopes can be used to make Shrinky Dinks®. Before (LEFT) and after (RIGHT).

BELOW: Patterned polystyrene sheets before (LEFT) and after (RIGHT) being placed in an oven. Use a relatively low temperature (about 65 C) or they will melt rather than shrink! NOTE: Many but not all sheets of polystyrene will shrink and not all sheets will shrink equally in all lateral directions.

BELOW: Making clear polystyrene icicles. There is a significant burn risk here. A polystyrene sheet placed on aluminum foil in a toaster oven at 300 F or simply to "toast" mode will shrink fairly quickly (it is fun to watch - but don't leave them in the oven too long or they might melt). A narrow triangle of polystyrene container material, with a hole punched in the top, is shown at LEFT. The wrinkles usually flatten out upon heating. While the shrunken sheets are still hot, remove them from the oven, twist them quickly into a spiral shape, and hold until they have cooled, as shown at RIGHT. If the shape of the twist is unsatisfactory, placing the icicle back into the oven will untwist it. Again, there is a significant burn risk here. My wife loaned me her thimble to provide a measure of protection.

MORE BELOW: One can make interesting faces on polystyrene sheets, shrink them, and attach them to pom-poms. (Hot melt glue works much better than school glue for this.) Placing a magnet on the back enables the decoration to stick to a refrigerator door. The picture below includes a couple versions of moles (a popular mascot for chemists) and a tomato cartoon character that is popular in the Campbell household.