Gum Bichromate Prints
Gum printing makes water-soluble pigments, such as gouache and watercolors, photographic, producing prints of subtle and wide-ranging colors on paper or fabric. Mixing gum arabic, paint, and a solution of ammonium or potassium bichromate as the light sensitizer, you can create a single or multicolored image ranging from continuous-tone to high-contrast. Gum printing also can be combined with traditional printmaking processes such as etching and drypoint, or with other photoprintmaking techniques from this book. Unlike Van Dyke, cyanotype, and palladium, gum printing creates an actual physical buildup on top of, rather than an absorption into, the substrate. Because the emulsion is delicate, your patience and a willingness to experiment are essential.