Was first introduced in 1851 by the Englishman, Frederick Scott Archer. By the 1860, it had become the universal photographic method employed by virtually all photographers here and abroad. The wet-plate process continued to be the state of the art till about 1880 when manufactured gelatin dry plates came into wide spread use.
It is called wet-plate because the plate, be it glass for negatives, ambrotypes or metal for tintypes, cannot be allowed to dry during the entire procedure. Once the plate has been coated with clear volatile, viscose collodion solution, it must be immediately sensitized, exposed in the camera, developed, fixed and rinsed before the plate dries. The plate loses sensitivity and usefulness once the it begins to dry. The whole wet-plate process must be performed for each plate taken. There is no shooting of pictures now and developing them later. In a sense the wet-plate photographer makes their own film and processes it on the spot. Thus, it is an absolute necessity that have a darkroom very close at hand. Within it the photographer can work under amber-red light as wet plates are sensitive to blue light.