1487
and modifying its “glutinous” consistency so that it would
remain viscous. A how-to-manual noted that “it is hardly
necessary to caution the student when using Gun Cotton,
as he is aware of its explosive nature; a single spark of fi re
in it might cause serious consequences.” The collodion
solution was then poured onto a glass plate and the trick
was to evenly distribute the viscous solution on the plate
surface allowing the collodion to “set” but not become
completely dry. The photographer moved into a darkroom
(or dark tent) to dip the plate in a silver solution, and load
into a negative holder. After the plate was exposed, the
photographer immediately returned to the darkroom to
develop and fi x the image before the collodion emulsion
would dry and harden.
The ambrotype, like the daguerreotype, is a unique
image. Photographers created a negative image (the
darkest areas were transparent, and the lighter areas had
a greater density of silver) by under exposing the plate in
the camera or under developing it in the fi nal processing.
A dark background was necessary to transform the im-
age from a negative to positive before it was presented in
a case to the patron. A variety of backings provided dark
tones that brought out the image details and create the
positive image: velvet fabric, black paper or “japanned
black” paint either painted on the back of the case or
the glass base of the image. Some photographers used
opaque surfaces including ruby red glass, and leather as
the base surface to prepare a wet collodion image. The
images on leather were known as pannotypes. A more
sophisticated process used by some studios in large
cities, was the relieveotype process invented in 185 by
Thomas C. Lawrence. In order to make the portrait stand
out, the photographer removed the background and only
blackened the area of the fi gure. The plate was backed
with glass and a white background, to provide a greater
illusion of depth.WET COLLODION POSITIVE PROCESSES
Pierson, Pierre Louis. Napoleon III and
the Prince Imperial.
The J. Paul Getty Museum, Los Angeles
© The J. Paul Getty Museum.