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Calotype Negative: By then a new process had been made public for producing negatives on glass coated with light-sensitive collodion. It was not patented, and professional portraitists thought that they were at last freed from having to pay for the right to photograph. But Talbot felt that the new collodion process itself was an infringement for, like the calotype, it was a negative-positive system, and although the negative support was glass instead of paper, the image was developed in pyrogallic acid, which he considered identical to his "gallo-nitrate of silver" solution. He sued William Henry Sylvester, who operated a London studio under the name "Martin Laroche," for working the new collodion process without a calotype license, and took him to court in 1854.
Although Talbot had taken out a French patent, he does not appear to have enforced it, and the calotype was widely used in France, especially for the documentation of architecture under the auspices of the government.
Frenchmen made two important technical improvements on Talbot's basic calotype process.
The imperfection of the calotype negative because of the fibrous texture of paper had early suggested the use of glass as an alternative support for the light-sensitive material. To attach the silver salts to glass various substances had been tried, even the gluey slime exuded by snails, until partial success came with the use of egg white. These albumen plates—invented in 1847 by Claude Felix Abel Niepce de St. Victor, a cousin of Niepce—gave excellent negatives, of a brilliance and fineness of detail approaching that of the daguerreotype. |
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