Casein Pigment Prints
This process, which utilizes curdled milk to bind the component materials, was patented in 1908 as a technique to use with other photo-printmaking methods, such as Van Dyke brown printing (see Chapter 8). Used by itself, however, casein printing can yield as subtly graded, colorful results as the watercolor paints that make up part of the emulsion. The translucency of each color coating permits a new hue in a new layer of emulsion to change the pigment color underneath. One of the least expensive of the hand-applied emulsions, casein printing is closely related to gum bichromate printing (see Chapter 9), and a reading of that chapter is recommended.