Collodion Process

The collodion process is an early photographic process, invented by Frederic Scott Archer. It was introduced in the 1850s and by the end of that decade it had almost entirely replaced the first practical photographic process, the daguerreotype. During the 1880s the collodion process, in turn, was largely replaced by gelatin dry plates—glass plates with a photographic emulsion of silver halides suspended in gelatin. The dry gelatin emulsion was not only more convenient but could be made much more sensitive, greatly reducing exposure times.

"Collodion process" is usually taken to be synonymous with the "collodion wet plate process", a very inconvenient form which required the photographic material to be coated, sensitized, exposed and developed within the span of about fifteen minutes, necessitating a portable darkroom for use in the field. Although collodion was normally used in this wet form, the material could also be used in humid ("preserved") or dry form, but at the cost of greatly increased exposure time, making these forms unsuitable for the usual work of most professional photographers—portraiture. Their use was therefore confined to landscape photography and other special applications where minutes-long exposure times were tolerable.

Collodion processes were capable of recording microscopically fine detail, so their use for some special purposes continued long after the advent of the gelatin dry plate. The wet plate collodion process was still in use in the printing industry in the 1960s for line and tone work (mostly printed material involving black type against a white background) as for large work it was much cheaper than gelatin film. One collodion process, the tintype, was still in limited use for casual portraiture by some itinerant and amusement park photographers as late as the 1930s, by which time tintypes were already regarded as quaintly old-fashioned.

The collodion process is said to have been invented, almost simultaneously, by Frederick Scott Archer and Gustave Le Gray in about 1850. During the subsequent decades of its popularity, many photographers and experimenters refined or varied the process.