“Bertha Wright, niece of the Wright brothers, daughter of Lorin Wright,
age five”, - January 1901
Photographers: Wilbur and Orville Wright
(digital file from original) - 1 negative : glass, dry plate ; 4 x 5
in.
The process:
Gelatin (a protein obtained from animals that is transparent
and odorless, and used in a number of food processes as well as photography) is
mixed with either bromide or chloride along with silver nitrate which produces silver
bromide or silver chloride. This slightly acidic suspension has a milky white appearance.
The suspension is heated and then cooled until it becomes firm enough to be cut
into strands (known as noodles). The strands are washed to remove residue,
before being returned to a liquid state by applying heat. The liquid
suspension, known as gelatin silver halide emulsion is then coated on the base
material, in this case a glass plate (page 247 in Lavédrine has a couple of great pictures of the process of
making dry plates). Once the plates are dried they can be packaged and
sold for use at the photographer’s leisure. After exposure the plates are then
developed, fixed, and washed. (Lavédrine & Ritzenthaler)
The key players and dates:
Robert Bingham had suggested the use of gelatin as a
photographic binder in 1850; however his idea did not take off at the time,
perhaps due to the success the wet collodion process was experiencing at the
time. Richard Leach Maddox, a British physician and photographer, is credited
with producing the first practical dry glass plate negative in 1871. While
Maddox’s process eliminated the need for photographers to travel with chemicals
and makeshift darkrooms and removed time constraints associated with the wet
plate process, the level of photosensitivity in these first dry plates was
lower than that of wet plates, resulting in longer exposure times. This issue
of long exposure times was solved in 1878 by Charles Bennett, when he discovered
that heating the gelatin silver halide emulsion for a couple of hours in a
processes known as ripening, increases the level of photosensitivity which
resulted in shorter exposure times and gave the dry plate process the boost it
needed to overtake the wet plate in popularity.
In 1879, John Carbutt of Philadelphia offered dry plate
negatives for sale in the United States and was soon followed by others
including George Eastman. Eastman patented both a method and apparatus to coat
plates and set up production and sale of dry plates in Rochester, New York in
1880.
(Check out http://www.eastmanhouse.org/collections/eastman/biography.php
and http://www.pbs.org/wgbh/amex/eastman/peopleevents/pande18.html
for more about George Eastman and his contributions to photography in the 19th
century and beyond).
In addition to Eastman in the United States, dry plates were
also manufactured and sold by Lumiere (France), Agfa (Germany), and Ilford
(UK).
Dry plates decreased in popularity in the early 1920s as gelatin
coated paper negatives and rolled film processes were invented and perfected.
(Lavédrine,
Ritzenthaler, http://www.cartage.org.lb/en/themes/Arts/photography/photproces/significproc/gelatin.htm,
http://archives.syr.edu/exhibits/glassplate_about.html,
& http://www.pbs.org/wgbh/amex/eastman/timeline/index_2.html)
Dry plate
characteristics:
-
Light sensitive silver halides are dispersed and
suspended in the gelatin emulsion supported by a glass plate base.
-
Made through a completely mechanical process.
-
Glass used is thinner, the edges are smoother, and
emulsion coats more evenly.
-
Standardized sizes [4x5, 5x7, 8x10, and 11x14].
-
Coloration of dry plates ranges from rich black
shadows and bright white highlights
-
Dry plate negatives can be made ahead of time
and do not need to be developed immediately following exposure.
(Ritzenthaler)
The importance of the dry plate in the larger continuum of
photography:
The dry plate processes offered photographers a photographic
medium with faster exposure times, a fuller range of black and whites, as well
as a level of convenience previously unknown to the photographic process. Furthermore,
the relative simplicity of the pre-sensitized medium as well as the ability to
produce the plates en masse through a
mechanized process opened photography to great numbers of amateur photographers.
The use of gelatin emulsion in the dry plate process also paved the way for
other gelatin-centered processes such as celluloid rolled film and gelatin
silver paper negatives. (Lavédrine
& Ritzenthaler)
Print sources:
Lavédrine,
Bertrand. "Glass silver negatives on glass (1878-1940)." In Photographs
of the past: process and preservation. Los Angeles: Getty Conservation
Institute, 2009. 244-251.
Ritzenthaler,
Mary Lynn, and Diane Vogt-O'Connor. Photographs: archival care and
management. Chicago: Society of American Archivists, 2006.
Other sources to check out:
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