Wetplate process

An English sculptor and photographer, Fredrick Scott Archer, invented Collodion photography in 1851.
He experimented with collodion in the hope of producing a photographic positive on ordinary glass plates.
Collodion, a thick and syrupy liquid, is made by dissolving nitrated cotton in a mixture of alcohol and ether.
It was widely used by surgeons as a liquid bandage owing to its strength and adhesion.

In 1851, Archer used collodion to hold light-sensitive salts to his glass plates.
Once the salts, such as potassium iodide, were in the mixture of collodion, the viscous liquid was poured onto the plate.
Allowing the alcohol and ether to evaporate, a thin film containing the necessary iodides was left on the plate.
Ready for sensitizing, the plate was placed in a bath of silver nitrate.
This formed a light sensitive compound of silver iodide on the surface of the plate.

Once sensitized, the plate was exposed in the camera before the collodion began to set and dry.
If the plate dried before development,it would have had practically no sensitivity and would be therefore useless.
For this reason alone, the process Archer invented became known as "Wet Plate" collodion process.

After exposure in the camera, the plate was quickly returned to the darkroom.
Using an acidic solution of ferrous sulfate, the plate was developed, then rinsed and fixed in a mild solution of potassium cyanide, or hypo.

The wet plate photographers could now produce multiple images from a single negative or offer a collodion positive