Making Casein Plastic

Heating milk and mixing it with vinegar causes the protein casein to separate and form curds. These curds can be dried and kneaded into a moldable bioplastic that hardens over time, demonstrating polymer formation.

1. Heat 1 cup of full cream milk in a microwave-safe container until steaming but not boiling.
2. Add 4 teaspoons of white vinegar to a mug or bowl, then pour the hot milk into it.
3. Stir gently until white curds begin to separate from the liquid.
4. Use a spoon to transfer the curds onto layered paper towels.
5. Pat the curds dry thoroughly with more paper towels.
6. Knead the dried curds together until they form a soft, dough-like mass.
7. Shape the plastic by hand, with cookie cutters, or by adding decorations such as food coloring or glitter.
8. Leave the creation on a paper towel to dry for about 48 hours until it hardens.

Make plastic from milk! Nanogirl's Great Science Adventures - Dr Michelle Dickinson:

Turn Milk Into Plastic! | STEM Activity - Science Buddies:

📄 How to Turn Milk Into Plastic - Street Science: https://streetscience.com.au/turn-milk-into-plastic/

• Add food coloring, glitter, or small beads for decoration.
• Shape the bioplastic using molds or cookie cutters.
• Test different types of milk (skim, whole, non-dairy alternatives) and compare the results.

• Handle hot milk carefully to avoid burns.
• Supervise children when using the microwave or stove.
• Dispose of leftover liquid properly; do not pour large amounts down the sink.

• Why does adding vinegar cause the milk to form curds? (The acid lowers the pH, causing casein proteins to unfold and clump together.)
• What is the role of casein in forming the plastic? (Casein acts as a monomer that links into polymer chains, creating a solid plastic.)
• How does this bioplastic compare to commercial plastics? (It is biodegradable and less durable, while commercial plastics are stronger and longer-lasting.)
• Could this method be used to make useful products on a large scale? (Historically, casein plastics were used, but today synthetic polymers are more practical and efficient.)