Chrysotype

Chrysotype (also known as a chripotype 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 process
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.

In 2006, 164 years after Herschel's work with gold printing, photographers Liam Lawless and Robert Wolfgang Schramm published a formula based on Herschel's process.

Processes based on ziatype
Following the introduction of Richard Sullivan's ziatype process in 1997, which uses ammonium ferric oxalate to print out palladium images, many photographers began experimenting successfully with substituting gold for some or all of the palladium. Image quality decays rapidly as the printer approaches 100% gold in a ziatype print.

Puckett's process
Richard Puckett, an American photographer, announced in the March/April 2012 issue of View Camera magazine a chrysotype process that uses ascorbate with ammonium ferric oxalate to print out on dry paper, with no hydration, fine-grained, continuous tone gold images. Puckett presented the process at the 2013 APIS (Alternative Photography International Symposium) in Santa Fe, New Mexico. Originally the process was named the Texas Chrystoype; following a major revision of the formula in 2017, Puckett renamed the process the Chrysotype Supreme.

Literature
The modern chemist and photographic historian Mike Ware published the first books covering the subject of chrysotype in 2006, The Chrysotype Manual: the science and practice of photographic printing in gold and Gold in Photography: the history and art of chrysotype.