Gelatin-silver process

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 acetate film or fiber-based or resin coated paper and allowed to dry (hence the term dry plate). These materials remain stable for months and years unlike the 'wet plate' materials that preceded them. The Gelatin-Silver process was introduced by R. L. Maddox in 1871 with subsequent considerable improvements in sensitivity obtained by Charles Harper Bennet in 1878. Intense research in the last 125 years has led to current materials that exhibit low grain and high sensitivity to light. When small crystals (called grains) of silver salts such as silver bromide and silver chloride are exposed to light, a few atoms of free metallic silver are liberated. These free silver atoms form the latent image. This latent image is relatively stable and will persist for some months without degradation provided the film... full article at wikipedia