Silver dye-bleach


“Probably the first use of the catalytic property of silver was in 1889, when E. Howard Farmer disclosed the action of a silver image upon strong dichromate solutions (Eng. P. 17773/89). When a plate or film, containing a silver image, is immersed in a 20 per cent solution of ammonium, sodium, or potassium dichromate, the gelatin immediately surrounding the silver grains becomes tanned, the silver itself remaining apparently unaffected. As Farmer described the action, the dichromate and gelatin react under the influence of the catalyst silver, so that chromium salts are formed. These combine with the gelatin to form a tanned form of that colloid. The action is extremely rapid. We will discuss this reaction in greater detail in a later chapter, when the subject of Wash-Off Relief is taken up.

In 1897 R. E. Liesegang disclosed another somewhat similar action, this time with ammonium persulphate (Phot. Archiv., Vol. 32 (1897), p. 161), but now instead of forming a tanned image, there is formed an image of soft gelatin. The action of persulphate was to soften the gelatin in situ with the silver. An improvement in this procedure was introduced the following year by M. Andresen (Ger. P. 103516). He found that hydrogen peroxide, especially in the presence of the halogen acids, greatly accelerated this action. The further development of both this and the Farmer disclosure, appears to have been restricted to the preparation of matrices, and we will leave until we come to that subject the more detailed discussion of these reactions. Now we are merely interested in the fact that even before the turn of the twentieth century, the catalytic action of the metallic image was already noted.”

(Friedman, Joseph Solomon (1945): History of Color Photography. Boston: The American Photographic Publishing Company, p. 405.)

Original Technical Papers and Primary Sources

Liesegang, Raphaël E. (1889) In: Photographisches Archiv, p. 328. (According to Friedman 1945: 405)

Liesegang, Raphaël E. (1897) In: Photographisches Archiv, 32, 1897, p. 161. (According to Heymer 1935: 178)

Secondary Sources

Friedman, Joseph Solomon (1945): History of Color Photography. Boston: The American Photographic Publishing Company, p. 405. View Quote

Heymer, Gerd (1935): Farbenfilme nach dem Silberbleichverfahren. In: Veröffentlichungen des wissenschaftlichen Zentral-Laboratoriums der photographischen Abteilung Agfa, 4, 1935, pp. 177-186, on p. 178. (in German)View Quote

Pénichon, Sylvie (2013): Twentieth Century Colour Photographs. The complete guide to processes, identification & preservation. London, Los Angeles: Thames & Hudson, on p. 211 View Quote and on p. 224. View Quote

Schultze, Werner (1953): Farbenphotographie und Farbenfilm. Wissenschaftliche Grundlagen und technische Gestaltung. Berlin/Göttingen/Heidelberg: Springer, pp. 92-95. (in German) View Quote