Shrinkie shapes

Follow these instructions to find out about the amazing shrinking properties of some plastics.

You will need

  • plastic container with the number 6 inside the recycling symbol. This could be a yoghurt container or take-away container
  • sandpaper
  • coloured pencils
  • oven
  • scissors
  • hole punch (optional).

What to do

  1. Make sure you choose a piece of plastic with the number 6 inside the recycling symbol

    Clean your container and cut it into pieces that you can draw on.
  2. Rub the sandpaper on one side of the plastic to roughen the surface. This will help you to draw on the plastic with the coloured pencils.
  3. Draw your picture or shapes in coloured pencil on the roughened plastic.
  4. Cut around your shapes.
  5. If you want to make your shrinkie shapes into a necklace, punch a hole in them using a hole punch.
  6. Heat your oven to 180 degrees Celcius.
  7. Place the shrinkies in the oven for one minute. Turn the ventilation fan on and let fresh air into the kitchen while the oven is on.
  8. The plastic will shrink to three-quarters its original size and will become thicker.

What's happening

There are many different types of plastics. Plastics are made from synthetic (not natural) materials; the word ‘plastic’ means something that can be shaped or moulded.

Plastic with the number six on it is polystyrene, which is made from petroleum. Polystyrene is not biodegradable, meaning that nothing will eat it and break it down, not even bacteria.

When discarded polystyrene ends up in landfill it will stay there unchanged for quite a long time. Some local councils recycle polystyrene and turn it into clothes pegs, coat hangers, office accessories, spools, rulers or CD boxes.

Polystyrene is made up of polymers. Polymers are groups of molecules that are linked together in a massive chain. When thousands of small ‘styrene’ units are linked together into long chains, they form polystyrene.

Polystyrene is a thermoplastic, which means that when it’s heated it will soften and can be shaped, but will return to its original form when it cools down again. When you heat polystyrene at 180 degrees Celsius, its polymer chains become warped and scrunched and the plastic will shrink.


Each type of plastic is given a number that tells you what it is made of and whether it can be recycled. Most local councils recycle plastics up to the number six.

Australia produces and uses more than 1.3 million tonnes of plastic each year. Making something from recycled plastic uses only 30 per cent of the energy it would take to make it from new plastic, so placing your plastic in the recycling bin instead of the rubbish bin is definitely a good idea.


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