Glue from milk
Heat a pint (half a liter) of skim milk and six tablespoons (90 ml) of vinegar slowly, stirring constantly. When it begins to curdle, remove from heat. Continue stirring until the curdling stops. Let sit until the curds have all settled to the bottom. Either strain the curds or pour off the liquid until they are dry. Add 1/4 cup (60 ml) of water and a tablespoon (15 ml) of baking soda (borax also will work). When the bubbling stops, you have made glue.
- skim milk
- non-metallic pan (enameled o.k.)
- baking soda
What is happening is that the milk solids are being separated from the liquid. These solids, the curds, dry to form a hard plastic like substance called casein, which also acts as an adhesive. The vinegar functions to curdle the solids so that they can be separated, and the soda neutralizes any acid that is left.