Collodion

Collodion is a transparent, viscous fluid formed by dissolving pyroxylin or guncotton (a sort of cellulose nitrate formed by treating cotton or wood with sulfuric and nitric acid) in ether and alcohol. It becomes a photographic print binder when light-sensitive silver halides are added to it. Collodion made its first appearance in photography as the binder for the wet collodion negative process invented by F. Scott Archer in 1851. Due to collodion's inherent brittleness, plasticizers such as castor oil or glycerin were often added. Collodion printing-out papers were in use from ca. 1885 to 1930.