Silver gelatin

The gelatin silver process is the photographic process used with currently available black-and-white films and printing papers. A suspension of silver salts in gelatin is coated onto a support such as glass, flexible plastic or film, baryta paper, or resin-coated paper. These light-sensitive materials are stable under normal keeping conditions and are able to be exposed and processed even many years after their manufacture. This is in contrast to the collodion wet-plate process dominant from the 1850s–1880s, which had to be exposed and developed immediately after coating.

The gelatin silver process was introduced by Richard Leach Maddox in 1871 with subsequent considerable improvements in sensitivity obtained by Charles Harper Bennett in 1878.

Gelatin silver print paper was made as early as 1874 on a commercial basis, but it was poor quality because the dry-plate emulsion was coated onto the paper only as an afterthought. Coating machines for the production of continuous rolls of sensitized paper were in use by the mid-1880s, though widespread adoption of gelatin silver print materials did not occur until the 1890s. The earliest papers had no baryta layer, and it was not until the 1890s that baryta coating became a commercial operation, first in Germany, in 1894, and then taken up by Kodak by 1900.

Although the baryta layer plays an important part in the manufacture of smooth and glossy prints, the baryta paper of the 1890s did not produce the lustrous or glossy print surface that became the standard for fine art photography in the twentieth century. Matting agents, textured papers, and thin baryta layers that were not heavily calendering produced a low-gloss and textured appearance. The higher gloss papers first became popular in the 1920s and 30s as photography transitioned from pictorialism into modernism, photojournalism, and “straight” photography.

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