Cold Water Paints: Casein

Cold water paints are related both to whitewash and to calcimine; to the former because they contain quicklime, and to the latter because they contain a glue-like cementing material. The cement is casein which is obtained from milk. Milk consists of water, sugar, casein, and fat (butter), the last three in about equal proportions. When the butter is removed the casein may be precipitated, purified, and dried, and it is on the market as a white powder, soluble in a solution of any alkali in water. In the early days of cold-water paints borax was used; but this was a failure, because the compound formed by it and casein was not altogether insoluble when dry.

Now the casein is mixed with lime; when water is added to this mixture the casein first dissolves in the lime-water, then it combines chemically with more lime, and this lime and casein compound, when dry, is insoluble and is a cement of considerable strength. As the paint is put up in dry form, it is a powder containing, like kalsomine, whiting and coloring matter, and the proper amount of casein and powdered quicklime, the latter two taking the place of the glue in kalsomine.

Next Page: Casein Cement.