The gelatin silver process is the most commonly used chemical process in black-and-white photography, and is the fundamental chemical process for modern analog color photography. As such, films and printing papers available for analog photography rarely rely on any other chemical process to record an image. 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. The "dry plate" gelatin process was an improvement on the collodion wet-plate process dominant from the 1850s–1880s, which had to be exposed and developed immediately after coating.
History
Gelatine was used to copy the images of Daguerreotypes by 1845 and Alphonse Louis Poitevin wrote about positive proofs of negatives on dry gelatine plates in 1850.
In the 1860s, the dry plate collodion process (with gelatin or albumen) was described as advantageous for outdoor photography, especially when a large amount of shots in different places were required, or when there was little time. Negatives taken during summer outings could wait until the long winter evenings to be developed, fixed and printed. Exposure times were long compared to the wet process, but that required much more time to prepare a plate before exposure, to develop, fix and wash the negative soon after, with chemicals and a portable dark room that had to be dragged around and installed.
The introduction of the gelatin silver process is commonly attributed to Richard Leach Maddox, author of the 1871 article An Experiment with Gelatino-Bromide.
In 1873, Charles Harper Bennett discovered a method of hardening the emulsion, making it more resistant to friction. In 1878, Bennett discovered that by prolonged heating, the sensitivity of the emulsion could be greatly increased. While dry plate processes could previous only be used with long exposures, Bennett's plates attributed much to instantaneous photography turning into a very common practice.
George Eastman developed a machine to coat glass plates in 1879 and founded the Eastman Film and Dry Plate Company in 1881.
William de Wiveleslie Abney and Josef Maria Eder improved the formula with silver chloride.
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.
Research over the last 125 years has led to current materials that exhibit low grain and high sensitivity to light.
Timeline
1874 – First commercial production of gelatin developing out paper (DOP) 1885 – Coating machines first used in gelatin DOP manufacture for manufacture of continuous rolls 1894 – Baryta layer added to commercial gelatin DOP manufacture 1920s – Increasing popularity of glossy and semi-gloss papers 1960s – Color photography eclipses black and white for the first time