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In the mid-XIX century, two photographic processes coexist. The Daguerrotype remains the most used but it is tedious and not reproducible. The Calotype offerts a good alternative but the quality of the images is poor compared with the Daguerre's process.

In 1851, the English sculptor Frederick Scott Archer (1813 – 1857) and his collaborator Peter Fry have the idea to replace the salted paper used for calotypes by a glass plate poured with collodion and sensitized (Wet plate). This process provides a negative image on a glass plate.

Later on, the American James Ambrose Cutting (1814 – 1867) discover that when placing this negative image on a dark surface, emulsion on the top, it is possible to see the positive image. He improves the process and patented it for the USA in 1854 under the designation of Ambrotype (from the greek Ambrotos). This process was also known as "Collodion Positif » in France and « Verrotype » in Great Britain.

The Ambrotype is in fact a collodion glass plate which has been voluntarily underexposed or lightened using a chemical process. Dropping this negative picture on a dark paper, or painting its non-emulsioned side with a black varnish or a red one (Ambrotype Ruby), makes the positive image appearing. This one does not shimmer as a Daguerreotype and the process is faster and cheaper. The only issue remains the fact that no copy of the picture is possible.


United states, c.1860, 1/6 plate

American family #1, Mother and Daughter.






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