Gelatin
Daylight-gelatin-silver prints
Gelatin developing-out paper
Gelatin
Dry gelatin emulsions
were first introduced in the late 1880s. The advantage of gelatin emulsions is
that it could be manufactured in advance, the photographer could make his
picture without any preparations like in previous processes. Gelatin emulsions
were first used on glass plates but later on also on paper and film. Gelatin is
very stable but becomes vulnerable when it is wet or too dry. When wet the
gelatin swells and eventually will break up, when dehydrated the emulsion
hardens, may crack and be lifted from the support layer.
Daylight-gelatin-silver prints (late 1880s -
1920s), were made on printing-out paper. Printing-out paper was
designed to produce an image by exposing the paper to (day)light. There is no
need to develop the print in a developing solution. After the image appears you
only need to fix and wash the paper. These were mostly contact prints and
needed a rather long exposure time, in contrast with developing-out paper. The
image tone ranges from reddish brown to purple.
Gelatin-silver-prints
are vulnerable to overall fading, especially loss of details in the highlights
and a shift of colour to yellow brown, mostly due to left-over chemicals from
the fixing solution. Toning, usually with gold chloride, protects the prints to
some extent against fading.
This image has suffered serious damage from exposure to light. This image was not toned and therefore more vulnerable. The photograph shows a woman in front of a mirror.
Gelatin developing-out paper needs a developing solution to make the image appear, in contrast with printing-out paper. Developing-out paper is primarly used for enlargements. Developing-out papers were available from 1873 onwards, but most popular from c. 1905 until about 1960.
Although this process is almost similar to modern development of
photographs, the images are as vulnerable as older processes. One of the most
common signs of image deterioration is silver mirroring, which is a kind of
metalic haze over the shadow areas. Another characteristic form of
deterioration is the yellowing and fading of the light image tones. After 1900
many images were toned with sulphur to get a sepia hue. These prints display
hardly any signs of fading or silver mirroring.
