Sequence viewing > Index - Alternative Photo Emulsions - Resource - ©
Photographic Processes - (Hand
made photographic -emulsions and processes)
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
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).
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