Casein - An Overlooked Medium
We have recently been re-exploring our casein paints, wanting to understand more clearly the basics of this lesser-used water-based pigment often referred to as "milk paint".
Casein is an ancient type of milk-based, water-soluble, opaque paint which has been found in prehistoric cave paintings. Archaeology Magazine has reported that researchers in the Sibudu Cave in South Africa have discovered residue on a stone tool that contains powdered ochre mixed with milk to create paint. The tool dates to 49,000 years ago. Ochre paints have been discovered dating from 125,000 years ago, but this discovery is the first to find milk proteins mixed with the powdered ochre. Casein was commonly used during the age of Pharaohs in Egypt and can be found on ancient Egyptian and Chinese artifacts. Its original primary function was as an adhesive, but when combined with powdered pigments, it became an important, commonly used paint.
Casein can be thinned with water for washes or used straight from the tube for thicker, more opaque impasto passages. Adding a bit of white with water brightens the transparency of colors. Extra emulsion can be used as a paint medium to change the sheen from flat to eggshell. Casein can even be buffed to a satiny sheen when thoroughly dry, which takes about two weeks for thick paintings. As with watercolor or gouache, it can be used on paper or any surface that accepts water-based paint, but, because dry casein is brittle, it is best to paint on a surface which is rigid. It can also be varnished, but varnish will deepen the colors.
Brushes may be difficult to completely clean after using casein. Even though it washes up with water, any paint residue not cleaned out of the brush will harden. Casein paint can be used with watercolor, acrylic and gouache. It can be corrected with a damp cloth or, if dry, with a weak mixture of ammonia and water. The ability to correct, or change is a major difference from gouache. Color shifting occurs as the pigments dry, so doing test swatches is advised.
One contemporary artist using casein paints is Mary Nagel Klein. She has also published a book about the medium. See our interview with her here - Voice of Experience: Mary Nagel Klein.
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