Colodión

Colodión, also known as collodion, is a type of photographic emulsion that was widely used in the mid-19th century. It consists of a mixture of nitrate of silver (AgNO3) and collodion, a solution of cellulose nitrate in ether and alcohol. The collodion acts as a binder, suspending the silver nitrate in a thin, flexible layer on a glass plate or paper.

The process of creating a colodión photograph involves several steps. First, the glass plate is sensitized by dipping it into a solution of silver nitrate. The plate is then coated with collodion, which hardens upon exposure to air. The coated plate is then exposed to light, which causes a chemical reaction that forms a latent image on the emulsion. The exposed plate is developed by immersing it in a solution of sodium thiosulfate, which reduces the exposed silver nitrate to metallic silver, making the image visible.

Colodión photography was popular due to its simplicity and the ability to produce high-quality images. However, it was also dangerous due to the use of highly flammable and toxic chemicals. The process was largely abandoned in the late 19th century with the advent of safer and more convenient photographic techniques, such as wet plate and dry plate processes. Despite its decline, colodión photography has experienced a resurgence in recent years among photographers and collectors interested in historic techniques.