Derived from milk, casein paint dates all the way back to Asian cave paintings.
It is durable, fast-drying, and water-soluble and was widely used in ancient Egypt as tempera paint and by commercial illustrators and muralists in the twentieth century. Many oil painters also use it as an underpainting.
- Casein powder
- Earth & Mineral Pigments
- Mix 2 Tbsp. casein powder with 5 oz. water (distilled water is best), and let sit overnight.
- Discard the water that accumulates on the surface.
- Mix 1 Tbsp. borax with 4 oz. hot water and stir until dissolved.
- Add casein/water mixture to borax water and stir until smooth.
- Reheat this mixture - preferably in a double boiler - until about 180 degrees (82 degrees Celsius). Stir while heating - about 15 min. Let cool.
- Mix a spoonful of the casein binder with pigment in a glass bowl/jar or on your palette (see Note).
- Paint on wood, paper, or any rigid support. Thin with water.
Note: Many have found best results by "pre-wetting" the pigment first with water. Scoop out of pile of pigment on your palette, add small amounts of water and mix with a palette knife until it becomes a thick paste. Then add in small amounts of casein binder to desired consistency.
How much pigment do I add? The answer is different for every pigment. Test your mixed paint by applying it on a piece of cardboard. If some of the pigment rubs off after an hour, you need to add more binder. If it cracks, reduce the binder content by adding more pigment and water.
What is the shelf life? The shelf life of mixed casein paint is indefinite if stored in a cool, dry location. The un-used Casein binder should be stored in the refrigerator. Warm to room temperature before use. Keeps for 2–3 weeks.
Pro tip (optional): Prime your painting surface with a "Casein Gesso". First brush diluted casein binder onto the surface. Then mix "Impasto Medium" (limestone powder) and titanium dioxide pigment with the casein binder. Apply.