Casein is a colloid derived from milk. For those already versed in gum printing, casein printing is done much in the same way: a colloid is mixed with a light-sensitive dichromate and watercolor, brushed onto paper and exposed under a negative to UV light. Where the light hits the most the casein hardens the most. Where the light hits the least the casein and pigment wash away in a simple water bath, thus an image emerges. For each print this exposure and development process is done multiple times, particularly for a tri color print. Which requires a red, yellow and blue exposure to complete it. This kit contains Potassium Dichromate, Ammonium Caseinate, and Sodium Benzoate along with red,yellow and blue watercolors enough to make approximately 20, 8x10 tri-color gum prints.
You can find more information on Casein printing and other alternatives in Christina Z Andersons new book
"Gum Printing and other amazing Contact Printing Processes"