What is collodion wet-plate photography?

In 1847 Louis Menard discovered collodion, a clear flexible film originally used for dressing wounds. Photographers had been looking for a way to hold light sensitive materials on glass plates, and collodion was the answer. Fredrick Scott Archer published the first article describing the collodion wet-plate process in 1851. Images could now be made on glass, and multiple copies could be made from the same negative. Positive images could also be made clear or dark black or ruby glass. These images are called ambrotypes.
     In 1856, the Melainotype or Ferrotype process was patented, and positive images could now be made on Japanned sheets of soft iron plate. This process would later be referred to by the public as the tintype process.
     The invention of the dry plate process in the 1870's was the end of wet plate. No longer was a darkroom full of chemicals necessary when taking photographs in the field. Images could be made on these dry plates and developed later on at the photographers earliest convenience. Due to the extreme detail in a wet-plate negative, plates were still made through the 1940's for copy and scientific work, only being replaced by modern technical films. Today collodion is still used: as a medical dressing just as Louis Menard intended back in 1847.

Equipment

All this equipment must be taken on location to create a wet plate image:
-camera, tripod, portable dark room or tent
-chemistry including salted collodion, developer, hypo or fixer, varnish and water
-assorted glass bottles, graduates, porcelain trays, glass funnels, buckets, plate boxes, plate rack
-oil lamp for drying plates and heating varnish for sealing plates
-clear or dark clean polished glass plates or coated iron plates cut to size.

The process:

A clean glass or metal plate is quickly coated with "salted" collodion. Salted collodion is a mixture of collodion, ether, 190 proof alcohol, iodides and bromides. The tacky plate is taken into the darkroom and placed into a bath of silver nitrate. This silver bath and the salted collodion emulsion combine to create a light sensitive surface on the plate.
    After three minutes, while still in the darkroom, the plate is withdrawn from the silver bath and placed into a plate holder.
     The photographer's sitter is waiting patently as the photographer prepares the plate. As the photographer returns from the darkroom, the plate holder is then placed into the camera which has been pre-focused on the subject.
    An exposure is made, ranging from  five to thirty seconds or more. This is due to the very slow sensitivity of the emulsion and the amount of light necessary. Outdoor portraits generally require a 4-7 second exposure.
   The plate is returned to the darkroom for development. Developer is poured over the plate while the photographer holds the plate in his hands. The plate is washed and then placed into a bath of fixer to make the plate permanent and safe to view in the daylight.
     The plate is washed again, dried, and an amber bead varnish is applied to the surface of the plate to keep the ultra thin layer of silver and collodion from peeling from the plate.
    It takes about an hour to create a wet plate image. The plate must remain tacky wet during  most of the photographic process, hence the name "wet plate." If the photographer dawdles, especially during the coating, sensitizing, photographing and developing processes, the plate will dry and become useless.
     During the Civil War photographers on both sides of the conflict had to deal with bumpy roads in horse-drawn wagons, hazardous and sometimes unavailable chemistry, fragile glass plates, bad weather and the ravages of war while making images. It is amazing that so many quality photographs were made considering the circumstances.