Glue Strength Comparison: Homemade Casein Glue and Commercial Glue
Casein is the principle protein of milk. It accounts for approximately one third of the non-aqueous (liquid) ingredients in cow’s milk, from which commercial casein is obtained. The casein protein can be used to make glue and is also used in the manufacturing of various goods, including fabrics, adhesives, plastics, and protective coatings.
In order to remove the casein from the milk, the product goes through a process called precipitation. Essentially, the milk is heated and acid (vinegar) is added. As the heating takes place, the casein content begins to shrink and expel moisture, producing clumpy white solid curds and liquid whey. The next step in extracting the casein involves separating the whey from the curd by filtering. After the separation, a baking soda solution is added to neutralize the acid. The curd is then subjected to pressure to further remove the water content. When the moisture content is reduced to an acceptable level, the curd is dried to form a hard, plastic-like protein substance which can act as an adhesive.
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