Photographic Media The following are descriptions of some of the photographic formats of the original images from the Print and Picture Collection that have been digitized for this project.
|Select a media type:
Invented in 1850 by Louis-Desiré Blanquart-Evrard, the albumen
process used paper coated with a mixture of egg whites and ammonium chloride.
This was the first type of paper that could be prepared and stored well
before use, making its manufacture possible. Photographers could purchase
it in reams and sensitize it in a bath of silver nitrate when it was needed.
To make the print, a collodion negative was placed in direct contact with
the sensitized paper and exposed to direct sunlight for anywhere from
ten to thirty minutes. The tone and hue could be changed by stopping the
process at different times. Albumen prints were almost always toned with
gold chloride. Prints can range from reddish to purplish brown. Albumen
prints almost always show some deterioration through the appearance of
yellow highlights. The albumen print was the most common type of photograph
until the 1890s.
The cyanotype process was invented by John Herschel in 1842 and is based
on the principal that iron salts are sensitive to light. The paper was
brushed with ferric ammonium citrate and potassium ferricyanide and dried
in a dark place. The object to be reproduced was then placed upon the
sheet in direct sunlight. Sometimes the object was a negative, but often
a plant specimen was used. After about fifteen minutes, a white impression
formed where the light had not penetrated, leaving a blue background.
The paper was washed in water, and the oxidation formed a bright blue.
A variation of this process was used to duplicate architects' drawings.
The platinum print process is based on chemical reactions caused by the
sensitivity of iron salts to light, which produced an image consisting
of pure platinum. It is one of the most stable and permanent types of
photographs with a richness and tone superior to other processes. It was
invented in 1873 by William Willis, who refined it over the course of
five years, eventually making the platinum papers commercially available
through his company. Platinum prints were popular until the 1920s, when
platinum became prohibitively expensive.
Gelatin Silver Prints
Gelatin silver prints are photographs printed on paper coated with gelatin
containing silver salts. They generally displaced albumen prints in popularity
by 1895 because they were more stable, did not yellow, and were simpler
and quicker to produce. A modified version of the process is still in
use today. Photographers of the 1880s and afterward did not have to coat
their own papers because a variety of these papers were available from
commercial sources. Gelatin silver prints generally have a high surface
gloss. The tone depends on the type of silver salts used and the process.
A stereograph is a pair of photographic images of the same object, presented
on a single sheet, each at a slightly different angle. They were made
by using a dual lens camera, or two cameras side by side. Stereographs
were mainly albumen prints, but were produced by every photographic process
available during the 19th century. The images were viewed through a stereoscope,
a binocular-like device that produced a three dimensional effect. Stereographs
were introduced at the Crystal Palace Exhibition in London in 1851. These
photographs were produced purely for amusement, and a stereoscope was
a common fixture in parlors well into the twentieth century. In 1854 one
of the first commercial stereographic businesses was started in Philadelphia
by the Langenheim brothers.
|Sources and Further Reading
Baldwin, Gordon. Looking at Photographs: a Guide to Technical Terms.
Malibu, CA: The J. Paul Getty Museum, 1991.
Mace, O. Henry. Collector's Guide to Early Photographs. Radnor, PA: Wallace-Homestead
Book Company, 1990.