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 an 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-Base 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.
See recipes below. Here are the products we offer for the Casein formulas:
2 1/2 oz. (80g) Casein Powder9 fl. oz. (apr. 250ml) cold water1 oz. (32g)Crystalline Borax9 fl. oz. (apr. 250ml) hot water
5 Parts of Casein w/ 9 Parts Cold Water2 Parts Crystalline Borax w/ 9 Parts Hot Water
Casein Glue (see above): 9 Parts
Chalk (French Chalk): 4 PartsZinc White (or Titanium) Pigment: 4 Parts
Casein Gesso makes an excellent ground to use for any type of paint; it is particularly good for Casein paints.
40 Grams of Casein Powder125cc. Cold Water33 grams Slaked Lime Putty