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Alternative Photographic Processes - (Hand made photographic -emulsions and processes)

Processes - Ambrotype 1851-1890s

The wet collodion process produced a glass plate negative that was normally used for making one or more albumen prints. However, Scott Archer and Peter Fry discovered the ambrotype process. They found that a thin glass negative could become the photo itself, if it was viewed against a black background. These photos were sometimes known in Britain as collodion positives, but are now known by the name by which they were patented in the USA in 1854 - "ambrotypes".

There were two stages to producing an ambrotype: A. Create a wet collodion negative. See steps 1 to 8 of the Wet Collodion Process. B Present the negative against a dark background: 1. Selectively bleach the negative (if necessary) 2. Provide a black background, using shellac or velvet. 3. Mount in a case behind glass, as for daguerreotypes.

The Image The result was a unique image, consisting of a negative, usually underexposed, mounted against a dark background then mounted in a case. Unlike a daguerreotype, an ambrotype image can be seen when viewed from all angles. For this reason the process became popular, even though the finished result lacked the detail and tonal range of the daguerreotype. The image would be either normal or reversed (left to right) according to whether or not the emulsion side of the negative lay against the black backing.

Ambrotypes were often produced using one-eighth of a wholeplate (6.25 ins x 8.5 ins) sheet of glass. This gave images about 3.125 x 2.125 ins).

http://www.edinphoto.org.uk/1/1_early_photography_-_processes.htm

 

 

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