Submitted by Al …
(Adapted from The Encyclopedia of Photography ©1963)
In the calotype process, a negative is produced on paper by means of silver nitrate and gallic acid. From this negative an almost unlimited number of prints can be made.
This paper process of photography was invented by the Englishman, William Henry Fox Talbot, in 1835, his experiments having paralleled in time, those of Daguerre. It derives its name from the Greek ‘kalos’ meaning beautiful and ‘typos’ meaning image. Sometimes this process is called talbotype in honour of its inventor.
In the calotype process, the paper was first coated with salt and then with a silver nitrate solution. In this sensitized condition, it was exposed for five or ten minutes in the camera. The resulting negative was then fixed in salt and dried. It was usually made transparent after that by being passed through a bath of molten wax. Later, Fox Talbot perfected the calotype. Potassium iodide was substituted for the common salt and gallic acid added to the sensitive silver nitrate solution as well. Then, the negative having a latent image, had to be developed in silver nitrate and gallic acid. Prints were then fixed, the resulting photographs being usually of a red or brownish colour.
The calotype process attained great popularity in the 1840s and represented the first practical example of the positive-negative concept. The daguerreotype, for a few decades more popular than the calotype, gradually began to give way to its rival in commercial supremacy. Although calotypes were grainy and it was difficult to get the paper negatives to lie flat, the images could at least be duplicated. In the case of the daguerreotype, each was unique in itself since there was no separate negative. Refinements in the calotype eventually resulted in glass plates, and finally, the film of today. The calotype process is somewhat similar to the modern ‘paper negative process’.
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