Casein (kay'seen) is a quick-drying, aqueous medium using a milk-based binding agent, and is one of the most durable mediums known to man.
Known for their versatility and array of capabilities, casein paints can be used to create a variety of effects from the rich opaques of oil to thin watercolor washes. Because casein has an exceptional integrity of color and always dries to a perfect matte finish, it is unexcelled for art reproduction.
Helpful Tips for Caseins
Choose a rigid, non-oily surface for your work
Establish correct drawing and value patterns with a thin underpainting
Dilute caseins with water to make washes & transparent glazes
Casein colors, especially reds, oranges, and yellows, tend to shift after drying
Lighten colors by adding more water or brighten them by adding powdered pigment
To correct an overly dark area, cover it with a more opaque layer of a lighter color
When working on a gessoed panel, correct any errors with an eraser or a 1:9 ammonia and water mixture