Gum bichromate

Gum bichromate is a 19th-century photographic printing process based on the light sensitivity of dichromates. It is capable of rendering painterly images from photographic negatives. Gum printing is traditionally a multi-layered printing process, but satisfactory results may be obtained from a single pass. Any color can be used for gum printing, so natural-color photographs are also possible by using this technique in layers.