Tintype HistoryIn 1851, Frederick Scott Archer introduced a wet plate process, sometimes referred to as the collodion process after the carrier material used. The process is simple: a bromide, iodide, or chloride is dissolved in a solution of collodion and ether. This mixture is poured on an anodized black aluminum plate, which is allowed to sit until the coating gels. The plate is then placed in a silver nitrate solution, which converts the iodide, bromide, or chloride to silver iodide, bromide or chloride. Once the reaction is complete, the plate is removed from the silver nitrate solution and exposed in a large format camera while still wet. The plate loses sensitivity as it dries, requiring it to be coated and sensitized immediately before use. It must also be developed while still moist, using a solution of ferrous sulfate, acetic acid and alcohol in water. As the developer is poured onto the plate, the image begins to appear as a negative. The plate is then rinsed and placed in a fix bath, where the image is converted from a negative to a positive image.