Home science: milk plastic
Plastic can be environmentally friendly – if it’s made from milk!
Warning! Only under adult supervision.
- glass of warm milk;
- white vinegar;
- food coloring;
- silicone ice molds.
Add four tablespoons of vinegar to a glass of warm milk (about 45 °C / 113 °F). White lumps of milk protein begin to form. Filter the protein out by pouring the liquid through a funnel with gauze. Take the protein and carefully squeeze out any excess moisture. Divide the resulting mass into two equal parts. Add a different food coloring to each half. Fill some silicone ice molds with the colorful mass and leave to dry for two days. You’ve made solid multicolored figurines! You can play with them or even use them to draw on asphalt or on a chalkboard!
Milk protein consists of casein and whey protein. Casein is evenly distributed throughout milk in the form of very, very small particles, which give the liquid its white color. With the application of heat and addition of acid, these particles clump together and combine with the whey protein to form a white mass of very large molecules. When this mass dries, it hardens like plastic. The moisture loss also causes the mass to decrease in size. The process yields a hard but rather fragile material, which you can draw with just like a crayon.
A similar experiment is included in the “Chemistry of materials” set from the MEL Chemistry subscription.