Recipe: Casein: About Borax-Casein-Glue

Casein powder needs to be soaked thoroughly (overnight, if possible). After soaking it must be hydrolyzed with specially suited alkalis.

The hydrolyzing agents determine to a large extent to what purpose the casein glue can be used. The extraordinarily permanent lime-casein, made with lime putty or clear lime water, has already received its well-deserved praise in reference of materials for mural painting.

For the purpose of easel painting, however, borax casein has proved the best one, although theoretically it may appear that ammonium casein is better, because all alkaline residues evaporate after complete hydrolyzation. It has been found in practice, however, that liquid casein retains its ammonia residue for a long time, losing its viscous consistency after three days and decomposing relatively quickly.

Strong alkalis, such as soda (sodium carbonate) or potash (potassium carbonate), should not be used to hydrolyze casein intended for painting.

Borax (sodium tetraborate), on the other hand, is a weak alkali that has proved useful in practice, but mainly in easel painting, where weather-resistance is no factor. Crystalline borax containing water of crystallization, the kind available through the retail trade, should be used when making casein medium. The anhydrous variety should be avoided.