a water-base paint made with casein (which is a protein precipitated from milk)

A paint much like opaque watercolor in which casein, a milk glue, is its binder. Casein is a white, tasteless, odorless protein precipitated from milk by rennin. Casein is the basis of cheese, and is used to make plastics, adhesives, and foods, as well as paint. Casein paint can be used on paper or board for light impasto, for underpainting, wall decoration, etc. Casein paint is too inflexible for use on canvas. It dries quickly with a waterproof surface, and may be varnished.

An old-fashioned paint made by mixing pigments with milk solids. It is seldom used today except on furniture where a faded look is desired.