The wet-collodion process is early photographic technique invented in 1851. It involves adding soluble iodide and/or bromide to a solution of collodion and coating a glass plate with the mixture. The plate is then immersed in a solution of silver nitrate to form light sensitive silver salts. The plate, while still wet, is exposed in the camera. Immediate processing of the exposed plate is then necessary because, after the collodion film had dried, it becomes waterproof and the developing solution can no longer penetrate it. While difficult to master and labor intensive, the process is valued and practiced to this day for the level of detail and clarity it allows.