science · 14 March 1839 · 185 years ago
In 1839, Sir John Herschel referred to “photography” in a lecture to the Royal Society—possibly the first use of the word. Following Henry Fox Talbot's publication of his invention of what became known as the Calotype process, a number of scientific men made their own investigations, including not only Herschel but also Berard, Robert Hunt and Draper. Herschel used the name Chrysotype (from the Greek word for gold) for his process. It used paper washed in a solution of ammonio-citrate of iron and brought out the image with a solution of soda or chloride of gold, or with nitrate of silver, and fixing it in the first case by washing it with iodide of potassium and in the second, with hyposulphite of soda. It had technical difficulties in controlling the contrast, colour and fogging of the image.
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