Casein & Milk Paint Recipe

Casein is the protein extracted from milk and the binder in the paint commonly known as "Milk Paint". Casein is one of the first binders ever used by mankind. Casein can be painted on a variety of surfaces, including wood and plaster. Which ever surface used, it must be a rigid one as casein is too brittle to paint on a flexible surface (such as canvas).

Casein is one of the natural components of milk. Casein is made from precipitated milk, which is then reconverted into glutinous casein glue with the aid of alkali. There are three types of alkali that can be used to convert the casein into a binder: lime, ammonium carbonate and borax.

Lime Casein: is produced by combining the soaked casein with either a powdered or slaked lime. This type of casein is an excellent option for porous surfaces such as plastered walls and raw wood and the binder is durable enough to be used outdoors. Lime Casein is limited by the fact that the binder needs to be used within hours of production and the resulting casein glue still retains a caustic pH balance which means that only alkali proof pigments (see fresco pigments) should be used. Most commercially available milk paints are lime casein.

Ammonium Carbonate Casein: similar to Lime Casein in durability and alkali pigments limitations and also needs to be used immediately after production.

Borax Casein: The most versatile of the three different casein, because it can be prepared and stored for weeks after production and the resulting glue is a pH neutral binder which allows for the use of all pigments. Borax Casein is an excellent binder for fine art applications on wooden panels and can be used for interior walls that are not exposed to moisture (bathrooms & kitchens). Borax Casein is an emulsifier which means that an oil, such as linseed oil, can be added to the glue. This addition makes the binder suitable for outdoor use, but still allows the resulting binder to be thinned and cleaned with water.

Sinopia now also offers prepared  Casein Milk Paint and Tinting Bases in a variety of forms. We offer a prepared Casein Gesso in both White and Black, Casein Milk Paint Base which can be tinted with our pigments, and a palette of Artisanal Milk Paint.

Borax Casein Recipe
ingredients by weight:

2 1/2 oz. (80g) Casein Powder
9 fl. oz. (apr. 250ml) cold water
1 oz. (32g)Crystalline Borax
9 fl. oz. (apr. 250ml) hot water volume

5 Parts of Casein w/ 9 Parts Cold Water
2 Parts Crystalline Borax w/ 9 Parts Hot Water

  1. Soak Casein powder in cold water in a covered container overnight.
  2. Dissolve Borax Powder in hot water.
  3. Add Borax Solution to the Casein Solution and stir.
  4. Hydrolysis will start right away and must be completed before the next step (wait approx. 2 hours until no more swelled casein particles can be seen and the yellowish mass is evenly translucent)
  5. Heat the solution in a double boiler until it becomes liquid (140° F).
  6. Once the solution has cooled, it will return to a syrupy consistency and is ready to be used as a pigment binder.
  7. Important: thin resulting mixture with water in a 1:1 ratio. The full strength glue is too strong and will crack after application.
As with all water-based media, the chosen pigment has to be wetted first. This is achieved by adding small amounts of water to the dry pigment. Then using a palette knife or spatula, the water is worked into the pigment until it retains a paste consistency. The casein solution is then added TO the color paste sparingly. The casein to pigment ratio can not be described in exact proportions. The amount of pigment varies according to desired opacity. The amount of binder (casein solution) varies according to pigment. Before use, apply small amounts to a piece of cardboard to make sure that there is a sufficient amount of binder. If the pigment comes off after a gentle rubbing, add more casein solution. Once pigment and binder have been combined to desired consistency, the resulting paint can be thinned with water.

Borax Casein Gesso Recipe

Casein Glue (see above): 9 Parts
Chalk (French Chalk): 4 Parts
Zinc White (or Titanium) Pigment: 4 Parts

  1. Combine Chalk and Pigment.
  2. Slowly add mixture to Casein Glue.
  3. Mix until smooth.
  4. Strain gesso through cheese cloth to ensure that there are no lumps. (optional)
  5. Apply in thin layers to a panel that has been sized with Casein Glue.

Casein Gesso makes an excellent ground to use for any type of paint; it is particularly good for Casein paints.

Lime Casein Recipe

40 Grams of Casein Powder
125cc. Cold Water
33 grams Slaked Lime Putty

  1. Soak Casein Powder in cold water in a covered container overnight.
  2. Remove excess water from casein by squeezing the soaked casein through a cloth.
  3. Thoroughly mix Casein and Slaked Lime together in a mortar and pestle.
  4. To prevent lumps, grind the soaked casein prior to being added to the lime. (optional)
  5. Within a minute the hydrolyzation will be complete.
  6. Immediately following hydrolyzation, dilute mixture with water to a brushable consistency. The volume of water should not exceed the volume of the casein-lime mixture. This binder is then ready to use with alkali fast (see fresco pigments) pigments.
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