Invention / Key Elements of the Process
In 1871, the British Journal of Photography published Dr. Richard Leach Maddox’s description of how he created an emulsion made of gelatin, cadmium bromide and silver nitrate. The chemicals reacted to form silver bromide crystals suspended in the gelatin. The emulsion was spread on a thin layer of glass and allowed to dry, creating a gelatin dry plate.
Others quickly improved upon Maddox’s findings, particularly Charles Bennett, who pioneered the process of “ripening,”--heating the emulsion at 90 degrees Farenheit to increase the plate’s light sensitivity--making the gelatin dry plate process commercially viable in 1878.
The advent of the gelatin dry plate in the late 1870s revolutionized photography by making it more convenient in several ways:
Rapid exposure time of one second or less (no more eight hour photo sessions!).
Unlike wet collodian negatives, which necessitated exposure almost immediately after they were prepared, gelatin dry plates could be pre-made and stored for later use.
Once exposed, the negatives could be stored for long periods before being developed, freeing photographers from the cumbersome processes of preparing plates and developing negatives out in the field.
Steps of the gelatin dry plate processs
Pour the plate: between 1873 and 1878, plates were poured by hand; they were later mass produced by machine. The emulsion was warmed so it could be poured evenly onto the glass. The plate could not be touched while drying, which was a lengthy process.
Expose: Exposure time was one second or less.
Develop: Initially, the latent image was developed using inorganic agents (for example, ferrous oxalate, a metallic salt). Later, a variety of phenol (a.k.a.carbolic acid, an organic compound) derivatives were used.
Fix: Once developed, the gelatin binder was hardened with a potassium or chrome alum solution and fixed with sodium thiosulfate (“hypo” in photographer slang.)
Wash: The plates were washed thoroughly to remove the hypo complexes formed during fixing.
Intensify (optional): Underexposed images could be intensified using mercuric-ammonium chloride, mercuric iodide, cuprous bromide, or silver or chromium ions.
Varnish: Varnishes were used in the early days of gelatin plates (rarely after 1890) to protect them from the environment and prevent contamination with salts present in the printing papers. Shellac, copal, gum sandarac and celluloid were among the varnishes used.
Typical ways in which it was used
Because of the convenience of using gelatin dry plates, its uses were apparently endless. Examples I found of gelatin dry print negative photography while researching this report include:
Documentary photography
Sports photography
Nature Photography
Portraits
Nighttime photography
Important photographers associated with gelatin dry plate negatives:
British street photographer Paul Martin, who captured late 19th century and early 20th century urban life in a casual style. (photography, a cultural history)
Social documentary photographer Jacob Riis, who photographed the impoverished inhabitants of New York City’s tenements in the late 1800s.
Edward L. Wilson, an American photographer and editor of The Philadelphia Photographer. In 1882 Wilson traveled to the Middle East to take photographs using gelatin dry plates prepared in Philadelphia. He developed the photos upon returning to the city.
Identifying and dating gelatin dry plate negatives
Common use: 1880-1925
Could be mistaken with its predecessor, collodion glass plate
Deterioration can cause image tone to appear yellowish or orange
Emulsion side has matte surface; glass surface is high gloss
Range of standard sizes
Common sizes: 4 x 5, 5 x 7, 5 x 8, 8 x 10, 10 x 12, 11 x 14
Quarter size plate -- 3 1/4 x 4 1/4 inches
Half plate (American), stereo plate, or cabinet plate -- 4 1/4 x 6 1/2 inches
Half plate (English) -- 4 3/4 x 6 1/2 inches
Whole plate -- 6 1/2 x 8 1/2 inches (graphics atlas)
Mass produced, so high degree of uniformity in plates
Precisely cut edges of uniform thickness, usually 2 mm or less
Even coating of gelatin layer across plate
Tonality: neutral gray to black color
Preservation concerns:
Breakability of glass support: should be stored in individual envelopes made for long-term preservation and custom sized boxes that support and protect plates from movement.
Temperature of storage area should be not more than 68 degrees Farenheit; with relative humidity between 20-40 percent
Silver image deterioration due to poor storage environment and materials can result image fading, image discoloration, a bluish metallic sheen in reflected light, and a yellowish sheen in transmitted light.
Emulsion deterioration caused by deterioration of the glass support or poor storage conditions (i.e. drastic changes in relative humidity), can results in the lifting or flaking of the emulsion, usually from the edges, or appear as centric rings.
Mold is also a concern because of the gelatin, especially when relative humidity is elevated.
Glass decomposition is a risk when plates are exposed to relative humidity that is too high or extremely low.
Bibliography
Riis, J.A. How the Other Half Lives. D. Leviatin, Ed.) (Second). Bedford/St. Martin's.
Image Permanence Institute (IPI). (2015). Gelatin Dry Plate. Graphics Atlas. Rochester Institute of Technology. Retrieved from http://www.graphicsatlas.org/identification/?process_id=303.
Marien, Mary Warner. (2006). Photography: A Cultural History. Lawrence King Publishing.
Newhall, Beaumont. (1982). The History of Photography: From 1839 to the Present. Little, Brown and Company.
Wiedemer, N. (2014). Working Methods: The Howard D. Beach Photography Studio of Gelatin Dry Plate Negatives. Museum Studies Theses.
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