Wet collodion process
A nineteenth-century photographic process in which a glass plate coated with collodion is sensitized, exposed, and developed while still wet.
Collodion: A solution of nitrocellulose in ether and alcohol that forms a thin film as its solvents evaporate. This film holds light-sensitive salts on the glass plate.
Frederick Scott Archer: An English sculptor and photographer who introduced the collodion photographic process in 1851. His published method made wet collodion widely available to photographers.
Civil War photography: Photographic documentation of the American Civil War, produced largely with collodion plates and paper prints. Wet-plate photographers recorded camps, battlefields, and soldiers during the war.
Gelatin dry plate: A glass photographic plate coated with a light-sensitive gelatin emulsion that could be stored before exposure. Dry gelatin plates retained high detail without requiring immediate coating and development.
Silver halide: A light-sensitive compound of silver and a halogen, including silver chloride, bromide, and iodide. Silver halides in the wet coating record the image when exposed.
Louis Daguerre: A French artist and inventor who developed the daguerreotype, an early photographic process announced in 1839. The daguerreotype was a major predecessor, but made unique images on silvered copper.
Roger Fenton: A British photographer whose 1855 photographs of the Crimean War were among the first extensive war photographs. His field work shows the logistical demands of making wet plates during wartime.
Photographic negative: An image in which light and dark values are reversed, used to produce positive photographs. Wet collodion's glass negatives made multiple positive prints possible.
Ambrotype: A positive-looking photograph made on an underexposed collodion negative on glass, viewed against a dark backing. It turns a wet-plate negative into a direct positive image.
William Henry Fox Talbot: An English scientist and inventor who developed the calotype, a paper-negative photographic process. The calotype established negative-to-positive photography, but produced less detail than glass negatives.