Wet plate collodion process was invented in 1850 and was one of the first major photographic process invented after the Daguerrotype was patented in 1839. Wet plate collodion which is the process used to make tintypes (on metal) or ambrotypes (on glass) became the popular photographic process through the American Civil War into the 1880's, at which point dry plates were developed and manufactured.
Wet plate collodion begins with either a metal or a glass substrate. The photographer coats the substrate in collodion which is a type of liquid cotton used in the Crimean and American Civil Wars by surgeons to adhere wounds. The coated substrate is dipped in a bath of silver nitrate creating a light sensitive film on the surface of the plate. Because the photographer is creating the emulsion on the plate a darkroom is required on site of the shoot. The plate is loaded into a film holder which goes in the back of a camera. The plate is exposed to the subject through a lens, typically requiring a long exposure. After the exposure has been made the plate is developed and fixed by the photographer allowing the image to appear on the plate almost immediately. The plate is then rinsed and varnished and becomes an archival artifact to be cherished for generations.
Since wet plate collodion reads only blue and ultraviolet wavelengths and it is by nature a slow photographic process it tends to render a profound and authentic portrait of the sitter.