Portraits, images of castles and churches and towns in Scotland, Italy, Belgium and Malta.
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The calotype process (from the Greek kalos meaning beautiful) was discovered by William Henry Fox Talbot at Lacock Abbey in Wiltshire (see photographs nos. 115-117 vol. two); Talbot’s friends coined the term Talbotype. The calotype process was novel in a number of ways. It can be regarded as a direct forerunner of modern photography with its use of both a negative and a positive; the paper negative was the earliest process to allow the manufacture of several prints and it was also the first paper process- its predecessor, the daguerreotype, primarily used for portraiture, was printed onto a silvered copper surface.
Camera for creating calotypes, circa 1843
The first stage in producing the negative paper was to iodise the paper. This was done by brushing silver-nitrate solution onto one side of a sheet of fine quality writing paper and drying it. Then in the dark, the paper was immersed in a potassium iodide solution and left to dry in the sunlight
The second stage was to sensitise the paper for the camera. The paper was coated with silver-nitrate and gallic acid, thus making it light-sensitive. It was left to sit for about thirty seconds and then dipped in water. It was then partially dried in the dark, often using blotting paper and was loaded damp into the camera. After an exposure of up to ten minutes, depending on the weather, time of day and intensity of the chemicals used, a latent image was formed.
To develop the image, the paper was again dipped in a bath of silver-nitrate, acetic and gallic acids, and washed over with a fixing liquid such as bromide of potassium.
Strictly speaking, the term calotype applied only to the negative – the positive prints were made by placing the negative on top of sensitised salted paper. This was then laid flat in a frame and exposed to daylight until a positive image appeared.
The calotype had warmer tones and was more durable than the daguerreotype, which was easily damaged by touching. The daguerreotype was also a fixed permanent image that could not be reproduced. However the calotype had a tendency to fade and could also be quite blurred because of imperfections in the paper. By the 1850s the calotype was going out of fashion as the albumen prints and collodion positives and negatives being produced were of finer quality than those of Talbot’s invention.
For a fuller description of the calotype process see Glasgow University, Special Collections, Calotype Process http://special.lib.gla.ac.uk/hillandadamson/calo.html