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William Henry Fox Talbot and the Calotype
Transcript of William Henry Fox Talbot and the Calotype
Calotype or talbotype is an early photographic process introduced in 1841 by William Henry Fox Talbot, using paper coated with silver iodide. The term calotype comes from the Greek καλό for 'good', and τύπος for 'impression'. It can be regarded as a direct forerunner of modern photography with its use of both a negative and a positive
However, the term actually calotype only refers to the negative of the image; not both the negative and positive of an image, which is a common misconception. http://www.rleggat.com/photohistory/history/calotype.html The Process A piece of paper was brushed with weak salt solution, dried, then brushed with a weak silver nitrate solution, dried, making silver chloride in the paper. This made it sensitive to light, and the paper was now ready for exposure. This might take half an hour, giving a print-out image. It was fixed in strong salt solution - potassium iodide of hypo. The following year Fox Talbot succeeded in improving the "photogenic drawing" process, renaming it the calotype. He discovered that if he added gallic acid, the paper became more sensitive to light, and it was no longer necessary to expose until the image became visible. With further treatment of gallic acid and silver nitrate, the latent image would be developed. The Calotype process was not as popular as its rival one, the Daguerreotype. Reasons:
its popularity was to a great extent arrested by patent restrictions;
the materials were less sensitive to light, therefore requiring longer exposures;
the imperfections of the paper reduced the quality of the final print; Calotypes did not have the sharp definition of daguerreotypes.
the process itself took longer, as it required two stages (making the negative and then the positive);
the prints tended to fade. However, there were advantages the Calotype had over the daguerreotype it provided the means of making an unlimited number of prints from one negative;
retouching could be done on either negative or print;
prints on paper were easier to examine, and far less delicate;
the calotype had warmer tones. Resources http://www.rleggat.com/photohistory/history/talbot.htm "Mousetrap" Camera