Casein is a milk-product based paint which may be thinned with water. An extremely versatile medium, caseins may be applied in any manner, from impasto to thin watercolor washes. They are water soluble, but become insoluble with time and exposure.
Caseins dry quickly to a natural matte finish, making them unexcelled for reproduction. They can also be brought to a satin sheen simply by buffing with a soft cloth. If a gloss finish is desired, casein paintings can be varnished.
Caseins may be used on most surfaces, but because of the inflexibility of the binder, they should not be applied to canvas in heavy impastos. Colors are brilliant, permanent and intermixable.