Aka. Gold Printing.

The name comes from a Greek word for gold. This process is analogous to the CYANOTYPE process and was communicated to the Royal Photographic Society by Sir John Herschel in 1842. A sheet of paper was immersed in a solution of ferricitrate and dried in the dark. The paper was then exposed to light under a negative until a very faint image was obtained. Development took place by brushing a neutral solution of gold, i.e., chloroaurateIII over the exposed paper. The print then turned a purple tint.

In recent years (ca. 1987) Mike Ware in the UK has had a fresh look at the chemistry behind the original process and has come up with an improved version. (Nadeau, Encyclopedia, p. xxx.).