Bases & Emulsions
Most photographs have a base and a light-sensitive emulsion. The base supports the
emulsion. Bases can be many materials but usually are metal, glass, film or paper.
Emulsions can be created from many materials and the light-sensitive materials they
contain comprise different chemicals. Most emulsions are either albumen, collodion,
or gelatin and the most common light-sensitive materials are silver salts.
Considered to be the first successful and practical photographic process, daguerreotypes
were named for their inventor, J. L. M. Daguerre, in 1839. They were most popular between
1839 and the late 1850s with some dating into the 1860s. To create a daguerreotype, a
copper plate (the base) was coated with silver and then cleaned and finely polished. This
mirror-like polished plate was placed in a small box and exposed to iodine vapors for five
to thirty minutes. The result was a film on the plate's surface composed of silver iodide
(the emulsion). The sensitized plate was placed in a camera and exposed to light for five
to seventy minutes. After 1840 the exposure time was reduced to between five and forty
seconds due to improved lenses and more sensitive plates. The exposed plate was removed from
the camera and placed in another box where it was exposed to the fumes of heated mercury. When
the mercury vapors had brought out the image, the plate was removed, immersed in a solution of
distilled water and common salt or hyposulphide of soda, and dried over a flame. By 1841, toning
in a bath of gold chloride protected the emulsion, enhanced image contrast, and warmed the image's
hue. Images were commonly colored by hand and placed under glass in cases.
Each daguerreotype is unique. It is a direct positive, laterally reversed image with no negative.
Daguerreotypes were made in a variety of sizes from a whole plate (8 ½ x 6 ½ in.) to a sixteenth
plate (1 3/8 x 1 5/8 in.) The most common sizes are quarter plates (3 1/4 x 4 1/4 in.) and sixth
plates (2 3/4 x 3 1/4 in.).
First produced by James A. Cutting in 1854, ambrotypes were an application of the wet collodion
emulsion process developed by Frederick Scott Archer in 1848. They were most popular in the mid
1850s, but were available between 1854 and 1881. To create an ambrotype a well-cleaned and polished
plate of glass was sensitized by pouring collodion mixed with potassium iodide or bromide evenly
over the surface. Collodion is a mixture of gun cotton (purified cotton with nitric and sulfuric
acid), ether, and alcohol. The sensitized plate was then soaked in a silver nitrate solution, placed
in a holder, underexposed in a camera, and developed while still wet. After development the plate was
often bleached. Because a faint negative image was produced, the plate was backed by a black material
such as cloth, paper, metal, varnish or paint. The black backing showed through mostly where the
negative image was thinnest. Sometimes a dark purple, blue or red glass plate was used making it
unnecessary to use a backing.
Each ambrotype is unique. It is a direct positive, non-laterally reversed image. Much cheaper than
daguerreotypes, ambrotypes were cased and oftentimes mistakenly identified as daguerreotypes. To
distinguish between the two, ambrotypes appear as positives at all angles of illumination while
daguerreotypes appear positive only at certain angles.
Developed by Hamilton L. Smith in 1856, tintypes were another application of the wet collodion
emulsion process developed by Frederick Scott Archer in 1848. They were popular mostly in the
United States beginning just prior to the Civil War and continuing into the 20th century. To create
a tintype, a thin sheet of iron lacquered in black or chocolate brown was sensitized by pouring
collodion mixed with potassium bromide evenly over the surface. The sensitized iron sheet was then
soaked in a silver nitrate solution, placed in a holder, exposed in a camera, and developed while
still wet. Most tintypes were varnished to protect the surface and placed in paper mats. Many
early examples were cased.
Each tintype is unique. When multiple identical images are found, they were probably made with a
multi-lens camera. It is a direct positive, laterally reversed image. More durable and less expensive
than daguerreotypes and ambrotypes, tintypes (or more properly, ferrotypes) were frequently mailed to
friends and relatives. They were made in a great variety of sizes but the most common format was
2 ½ x 3 ½ in.
Albumen Prints & Wet Plate Collodion Negatives
In order to understand the production of albumen prints, which were often mounted on different
sized card stock and generically called card photographs, one must understand the production of
wet collodion negatives. The major mode of photography shifted from direct positives (daguerreotypes,
ambrotypes, and tintypes) to the negative/positive process using wet collodion negatives and albumen
prints when the collodion negative came into extensive use by 1860 and into the 1880s.
A glass plate was coated with a thin layer of liquid collodion mixed with a dissolved iodide or
bromide salt. After the coating set, the plate was immersed in a solution of silver nitrate thus
forming silver iodide or silver bromide in the collodion pores. All before the plate dried out
within five to fifteen minutes, the photographer exposed the plate in the camera, developed it with
pyrogallic acid, and fixed the image with potassium cyanide or sodium thiosulphate (hypo).
According to photo historian, James Reilly, albumen prints from wet collodion negatives comprise
approximately 80 percent of the extant prints in nineteenth-century historical collections in the
United States. Albumen (egg whites) was beaten and mixed with sodium or ammonium chloride to create
the emulsion which was applied by flotation to the very thin base paper. Stored until it was time to
use, the paper was then sensitized by flotation on a solution of silver nitrate and acetic acid. After
drying, the sensitized paper was placed in contact with the negative and exposed in a printing frame
in the sun until the image appeared. It was then washed in water, toned with gold chloride, fixed
with hypo, and given a final wash. The toning gave the image a rich purple-brown color. Trimmed to
the edge to minimize the expense of gold toner, the very thin albumen prints were susceptible to
tearing or curling. Consequently, the prints were mounted on cards, either of standard commercial
size or a size to accommodate the photographer's format.
Card photographs were the most popular way to present nineteenth-century photography. Prints of many
different types of processes were mounted on various sized cards. They include cartes de visite, cabinet
cards, and stereographs. Often having printed information about the photographer or studio that is useful
for dating and identifying images, card photographs might also exhibit captions and identifying information
by their owners.
Cartes de Visite & Cabinet Cards
Introduced in the United States in 1859 and made into the 1900s, the carte de visite (CDV) was a popular
format on which to present albumen prints. A special camera with four, eight, or more lenses was used
to make as many images as possible of a single or different poses on a single glass plate. A contact
print was made and the individual photographs were mounted onto cards measuring 2 ½ x 4 1/4 in. When
interest in the small portraits of the CDVs waned, studios produced photographs and cards in larger
sizes: Cabinet, 4 ½ x 6 1/4 in.; Victoria, 3 1/4 x 5 in.; Promenade, 4 x 7 in.; Boudoir,
5 1/4 x 8 ½ in.; Imperial, 6 7/8 x 9 7/8 in.; Panel, 8 1/4 x 4 in. Cabinet photographs were
introduced in the United States in 1866 and were popular to around 1900.
Daguerreotypes, ambrotypes, and albumen prints were among the many different processes used to
produce stereographs. Stereographs were formed of two images placed side by side. The images were
most commonly produced with cameras that had two lenses side by side, 2 ½ in. apart, and exposed
simultaneously. The lenses were spaced to approximate the view a person would have with each eye
receiving a slightly different image. Viewed through a stereoscope, stereographs, measuring
4 ½ x 7 in., created a three-dimensional effect. Paper prints from wet collodion negatives were
the most convenient way of producing card stereographs (stereo cards). Stereographs were popular
in the United States between 1859 and the 1920s.
Young boy with gun and powderhorn,
circa 1890, Whitehurst, Daguerreotype, b&w, 3.25 x 3.75 in., Accesssion #: 2003.081,
Photographic Study Collection
Ambrotype in case of leather work,
circa 1860, Ambrotype, b&w, 3.25 x 3 1/8 in., Accession #: 2002.041, Photographic Study Collection.
Western frontiersman in buckskin costume with gun ,
circa 1890, Tintype, b&w, 6.5 x 4.25 in., Accession #: 2003.273, Photographic Study Collection
Civil War Town (possibly Bonsall photo),
circa 1863, I.H. Bonsall, photographer, Wet collodion negative, b&w, 6.5 x 8.5 in.,
Accession #: 2000.005.5.33, Robert E. Cunningham Collection
Mountain man Seth Kinman in bear chair ,
circa 1875, Matthew B. Brady, photographer, Washington, D.C., Carte de visite, b&w,
3.5 x 2.25 in., Accession #: 2003.088, Photographic Study Collection
"A Dandy Shot, Jim, See Where the Bullet Blazed Him." Elk Hunt, Montana, U.S.A.,
1903, Meadville, PA, Keystone View Company, Stereograph, b&w, 3.5x7 in., Accession #: 2004.317,
Photographic Study Collection