<P> The isoelectric point of casein is 4.6 . Since milk's pH is 6.6, casein has a negative charge in milk . The purified protein is water - insoluble . While it is also insoluble in neutral salt solutions, it is readily dispersible in dilute alkalis and in salt solutions such as aqueous sodium oxalate and sodium acetate . </P> <P> The enzyme trypsin can hydrolyze a phosphate - containing peptone . It is used to form a type of organic adhesive . </P> <P> Casein paint is a fast - drying, water - soluble medium used by artists . Casein paint has been used since ancient Egyptian times as a form of tempera paint, and was widely used by commercial illustrators as the material of choice until the late 1960s when, with the advent of acrylic paint, casein became less popular . It is still widely used by scene painters, although acrylic has made inroads in that field as well . </P> <P> Casein - based glues, formulated from casein, water, hydrated lime and sodium hydroxide were popular for woodworking, including for aircraft, as late as the de Havilland Albatross airliner . Casein glue is also used in transformer manufacturing (specifically transformer board) due to its oil permeability . While largely replaced with synthetic resins, casein - based glues still have a use in certain niche applications, such as laminating fireproof doors and the labeling of bottles. . The popular Elmer's School Glue was originally made from Casein because it was non-toxic and would wash out of clothing . </P>

Study of quantity of casein present in milk wikipedia