Home science: milk plastic

Plastic can be environmentally friendly – if it’s made from milk!

Warn­ing! Only un­der adult su­per­vi­sion.


  • glass of warm milk;
  • ther­mome­ter;
  • fun­nel;
  • gauze;
  • white vine­gar;
  • ta­ble­spoon;
  • food col­or­ing;
  • sil­i­cone ice molds.

Step-by-step in­struc­tions

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!

Sci­en­tif­ic de­scrip­tion

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.