Shrinky Dinks


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Experiment Category: 


Participants will explore polymers as they create a craft by heating and shrinking recyclable plastic.

What You Need: 

  • Solid polystyrene (general purpose recyclable Plastic #6)
  • Tops of food containers work very well
  • Toaster oven
  • Markers (Dry Erase or Permanent)
  • Sandpaper
  • Hole punch
  • Spatula
  • Tongs
  • Oven mitt
  • Ribbon (optional)
  • Scissors

To Do and Observe: 

1. Preheat toaster oven to 350 degrees 2. Sandpaper one side of the plastic completely so that it can be drawn on. In its initial state, the plastic is too smooth, so the sandpaper creates a rough surface. 3. Sand any sharp edges of the plastic to avoid injury. 4. Draw any design on the rough surface using the markers. The more color you use and the larger the design, the more vibrant the final product will be. Use hole punch to make a hole in the plastic, at the top of the design. 5. Place the plastic on the metal tray in the oven and watch it SHRINK! It will start to melt and curl up, but eventually unfold itself into its initial form after it has finished shrinking. Total shrink time is approximately 3.5 minutes 6. Remove the plastic from the oven The plastic will be very hot so please use caution when handling. The use of an oven mitt is recommended. Place plastic on a dry hard surface and flatten it out with the spatula. 7. After it has cooled down, pull the ribbon through the hole and tie.

What's Going On: 

Plastic is composed of polymers in the form of a carbon chain. A polymer is a chemical compound or mixture of components formed by polymerization (a chemical reaction in which two or more small molecules combine to form larger molecules) and consisting essentially of repeating structural units. Polystyrene is an extremely versatile polymer. The polymer molecules are bonded together on a long chain. Heat excites them causing them to move around and come closer together, becoming more dense. This molecular activity causes the plastic to shrink.

Parent/Teacher Tips: 

Plastic can be cut into any shape children wish – the shape will be retained after shrinking. Finished product will be approximately 1/3 the size of the original piece of plastic. Children can measure the dimensions of their designs before and after shrinking and can determine what percentage of shrinkage it experienced.