Being a liquid made from animals and also a few plants, milk has some strange properties. For instance, there’s actually a way you can turn milk into plastic and in this experiment, we’re going to explore how! This is the Plastic Milk experiment, a fun and creative project for kids to try at home with an adult. You will need:

• Milk (with fat)
• White Vinegar
• Paper Towels
• A Mug
• A Teaspoon
• A Measuring Cup
• Cookie Cutters (optional)
• Food Dye (optional)
• Glitter (optional)

Method:

• Firstly, grab your milk and measuring cup and pour in 1 cups worth of milk. After that, put it in the microwave and heat until the milk is steaming!
• While your milk is brewing, prepare your mug and put in 4 teaspoons of white vinegar. When your milk has fully steamed, transfer over the contents to the mug with the vinegar in it.
• The next step is to use your spoon to stir everything inside the mug. After a few minutes stirring, you should notice flakes starting to emerge inside the mug – what has happened to the steamed milk? Place 4 sheets of paper towels on top of each other on a hard surface and dig out the milk flakes to put on them. (To make things easier, you can use a sieve to quickly gather the milk flakes.)
• Pull the corner ends of the paper towels towards each other and wrap the milk flakes within the sheets of the paper towels. This should soak up the excess liquids and giving the materials a squeeze will help the milk flakes stick together.
• Unwrap the paper towels and you should be left with a ball of milk turned plastic that you can shape and colour how you please. For example, you can choose to flatten the ball out and use your cookie cutter to make different shapes or add in food dye or glitter to add some flair to your blob of plastic. And that’s the Plastic Milk experiment!

The Science Bit: So… what happened to the milk to turn it into plastic? To find out, we need to learn about polymers! Milk contains molecules of a protein called casein. When milk is heated and combined with vinegar (or similar acids) the casein molecules inside the milk unfold and reorganize into a long chain. This chain structure is called a polymer. This polymer is considered a plastic because it can be shaped and molded. Or more precisely, the plastic we have made is called “casein plastic” or “milk plastic” because of the type of molecules the plastic is made from.