Recognize many attributed (although not always taken) to Mathew Brady, but certainly some Sullivan's, Gardners, and other Brady contemporaries. To see more go to this link
http://lcweb2.loc.gov/ammem/cwphtml/cwphome.htmlCan you imagine photography in the mid 1860's - Glass wet Plate collodion process.
Collodion, a thick and syrupy liquid, is made by dissolving nitrated cotton in a mixture of alcohol and ether. Collodion was used to hold light-sensitive salts to glass plates. Once the salts, such as potassium iodide, were in the mixture of collodion, the liquid was poured onto the plate. Allowing the alcohol and ether to evaporate, a thin film containing the necessary iodides was left on the plate. The plate still had to be sensitized. The plate was placed in a bath of silver nitrate. This formed a light sensitive compound of silver iodide on the surface of the plate.
Once sensitized, the plate was exposed in the camera before the collodion began to set and dry. If the plate dried before development,it i would have had practically no sensitivity and would be therefore useless. After exposure in the camera, the plate was quickly returned to the darkroom. Using an acidic solution of ferrous sulfate, the plate was developed, then rinsed and fixed in a mild solution of potassium cyanide, or hypo.
All this was done in wagons and tents. Not done by popping into the Walgreens on the corner for one-hour processing - and saying nothing about today's digital images. After having been transported hundreds, possibly thousands of miles back and forth to Washington DC over what could barely be called roads. Those glass plates are fragile and the image (negative) easily scratched. Amazing any survived. I own a few glass plates from the general era, but none of the war - I have printed one or two - almost a spiritual experience.
