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. Nine thousand year old casein cave paintings have been discovered in Asia, and later, the medium was used by Byzantine, Roman and Renaissance artists including the Old Masters.
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. The velvety matte finish can also be buffed to a satin sheen or varnished to produce a resemblance to oils. Over time, casein pigments become resistant to moisture and as history has proven, the medium has a durability and permanence which has easily stood the test of time.
Casein differs from other media, yet it shares many of the same characteristics, which make it a very versatile medium that lends itself to many techniques. Casein has the wash capabilities of watercolor, the smooth opacity of tempera and gouache, and the richer textures of oils and acrylics. Brushes dipped in casein keep their finesse, producing clear, crisp lines. Unlike oils, casein is a clean, water-soluble medium requiring no strong solvents. And because it dries quickly, it's possible to lay on a glaze and move onto the next stage within a few hours instead of waiting for days, or even months, for oil glazes over oil to dry. In comparison to watercolors, the main advantage of casein is that it's easily correctable. It can be removed with a cloth, brush or eraser.