The collodion technique was invented by Frederic Archer in 1851 and is one of the first negative techniques. The image is created on glass or metal plates covered with a layer of collodion (a solution of guncotton, ether and ethanol). The plates are sensitized in silver nitrate before taking the photo. As a result, photosensitive silver halides are created in the collodion.
The name “wet plate” comes from the fact that the entire process – from preparing the plate, through photographing and developing – must be performed while the collodion layer is wet. Depending on the temperature and humidity, the photographer has from 15 to 30 minutes. This necessitates having a photographic darkroom nearby.