What is collodion photography?

Collodion is a viscous liquid, which is made by dissolving nitrocellulose in ether and alcohol. Archer invented the collodion photography method. First, collodion containing silver iodide was coated on the glass plate to spread it evenly on the whole glass surface. Immediately after that, it was immersed in silver nitrate solution to enhance sensitivity. The drier the collodion, the lower the sensitivity. Therefore, before the collodion is dry, put the wet glass negative into the camera for exposure, and then develop and fix it immediately. This method is also called "wet printing".