Invented in 1956 by Pierre Cordier, the chemigram combines the physics of painting (varnish, wax, oil) and the chemistry of photography (photosensitive emulsion, developer, fixer); without a camera, without an enlarger, and in full light.
Cordier discovered that a resist would hold back the chemical effects of developer and fixer on black and white photographic paper. Back and forth between developer and fixer, the resist begins to react to the chemistry slowly exposing the paper to developer or fixer creating black, white or some color in-between
Factors such as the type of paper, the strength of the chemistry, the type of resist, the length of time exposed to light, the order and length of time in the chemistry etc. impact the original image thereby creating intricate patterns that are unique and one-off.