Recipe: Lime Casein Tempera

The word Tempera comes from Latin „temperare“ and means “to make mild” or “to control” which is probably referring to the fact that tempera paint combines materials which are usually unmixable. Mixing agents or emulsifier are used in order to blend resin, oil and water-dilutable colors without the use of odorous solvents. Tempera paint can be used for nuanced art work since it is hardly runny. The dry paint is water-resistant.

Processing

Soak 75 grams of powdered casein in 125 milliliters of water in a bucket or a mortar. If possible, let the mixture rest in a warm place for a couple of hours until it forms a soft mud. Afterwards, the casein will then have soaked up the water completely. Usually one prepares the casein-water-mixture one night before and allows it to soak overnight. This way, you can be sure that the swelling process will be finished by morning.

Step 1#431: Soak 75 grams of powdered casein in 125 milliliters of water in a bucket or a mortar. If possible, let the mixture rest in a warm place for a couple of hours until it forms a soft mud. Afterwards, the casein will then have soaked up the water completely. Usually one prepares the casein-water-mixture one night before and allows it to soak overnight. This way, you can be sure that the swelling process will be finished by morning.

The casein mud is then opened up by adding 50 grams of Pit Lime resulting in a very nice viscous casein glue of smooth texture. However, this casein glue made from powdered casein tends to gel if it is not used immediately. The total volume of the mixture should be 1 liter which is achieved by filling with water 5 minutes after mixing in the pit lime (7,5% casein glue solution). Add 150 milliliters of linseed oil varnish with a mixer or a whisk (in little portions) until the mixture forms a smooth emulsion.

Step 2#512: The casein mud is then opened up by adding 50 grams of Pit Lime resulting in a very nice viscous casein glue of smooth texture. However, this casein glue made from powdered casein tends to gel if it is not used immediately. The total volume of the mixture should be 1 liter which is achieved by filling with water 5 minutes after mixing in the pit lime (7,5% casein glue solution). Add 150 milliliters of linseed oil varnish with a mixer or a whisk (in little portions) until the mixture forms a smooth emulsion.

Prepare your paints by making, pigments and water into a thick lump-free paste. Mix the color paste with the casein glue emulsion with a mixing ratio of about 2:3. Since the casein glue is made using an alkaline revealing medium and thus reacts alkaline itself, you should use alkali-resistant pigments only. A trial painting or a test coat will show whether or not the paint contains enough binding medium: If the painted surface shows chalking (that is the formation of fine powder on the surface of the paint film) when it is dry, you need to add more casein emulsion. If the paint is brittle and shows cracks on the surface, the binding is too strong and you need to add more color paste to the mixture. Casein paint dries quickly to a hard finish and easily shows cracks and spalling. This is why, casein paint requires only small amounts of binding medium.

Step 3#862: Prepare your paints by making, pigments and water into a thick lump-free paste. Mix the color paste with the casein glue emulsion with a mixing ratio of about 2:3. Since the casein glue is made using an alkaline revealing medium and thus reacts alkaline itself, you should use alkali-resistant pigments only. A trial painting or a test coat will show whether or not the paint contains enough binding medium: If the painted surface shows chalking (that is the formation of fine powder on the surface of the paint film) when it is dry, you need to add more casein emulsion. If the paint is brittle and shows cracks on the surface, the binding is too strong and you need to add more color paste to the mixture. Casein paint dries quickly to a hard finish and easily shows cracks and spalling. This is why, casein paint requires only small amounts of binding medium.