Quote Originally Posted by gmikol View Post

The families of chemicals discussed here (diazos and azides) are capable of polymerizing a great number of things, including gelatin, and are most likely capable of doing so with gum and casein, though I don't know of anyone who has made those efforts.

USPatent 3,721,557, which discusses light-sensitive color transfer sheets, specifically mentions the ability of diazos and azides to polymerize casein as well as other hydrophilic polymers such as gelatin.

The Patent also lists a number of compounds (in addition to Hardner #3) which have this capability. It also provides an extensive list of color pigments which can be used to make the color sheets.