Calotype
The Calotype is a photograph made from a paper negative, The original process for making paper negatives in the camera was patented by the Englishman William Henry Fox Talbot in 1841.
The basic process employed any stout paper brushed over with a solution of silver iodide and potassium iodide and allowed to dry. Before use, the paper was treated with a solution consisting of silver nitrate, acetic acid and gallic acid crystals. The paper could then be exposed in the camera either wet or after drying.
After exposure, development was carried out in a silver nitrate and gallic acid solution similar to that used prior to exposure. It was then rinsed, fixed in a potassium bromide solution, washed and dried. The printing time of the resultant paper negative could be shortened by soaking it in oil to make it more translucent.
The image which results is a negative of the photographed subject. This negative is inserted within the framework of a pane and is used as a board which can be reproduced many times, unlike a daguerreotype. The fibrous opacity of the paper, however, reduced the quality of the image.
p4A.com acknowledges the assistance of Bryan Ginns of Stereographica for providing much of the information used in this note. www.stereographica.com.