Wet Plate Collodion

Wet plate collodion, also called the collodion process, is a nineteenth century photographic technique in which a glass or metal plate is coated with a solution of collodion, a syrupy nitrocellulose compound, mixed with light-sensitive silver salts, then exposed in a camera and developed while the collodion coating is still wet and tacky, since the process loses its sensitivity within minutes of drying. This tight time constraint required photographers to carry a full portable darkroom, whether a tent or a dedicated wagon, wherever they worked, coating, exposing and developing each plate on location within roughly ten to fifteen minutes. Introduced in 1851 by Frederick Scott Archer, the process largely displaced the daguerreotype and paper calotype negatives within a decade, thanks to its shorter exposure times and its ability to produce a sharp glass negative from which unlimited paper prints could be made, and it remained the dominant photographic technique through the 1860s and 1870s, used extensively by war photographers including Roger Fenton and Mathew Brady's studio.