Chrysotype

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Chrysotype (or gold print) is a photographic process invented by John Herschel in 1842. Named from the Greek for "gold", it uses colloidal gold to record images on paper.

Herschel's system involved coating paper with ferric citrate, exposing it to the sun in contact with an etching used as mask, then developing the print with a chloroaurate solution. This did not provide continuous-tone photographs.

The modern chemist and photographic historian Dr Mike Ware has experimented with a reinvention of the process giving more subtle tones.