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Identifying the type of photograph is a difficult task. You may wish to consult George Gilbert, Photography: the Early Years or James M. Reilly, Care and Identification of 19th-Century Photographic Prints, or other books in the library.
Albumen: 1855- ca.1920
A printing paper using albumen (egg white) as the medium for the active chemicals. The albumen content of the emulsion provided a distinctive and characteristic gloss, and most of the common developing baths lent a warm toned brownish hue to the image. Early albumen prints were generally done on papers that were 18 by 22 inches before they were trimmed to working size.
Ambrotypes: 1855- ca.1865
The ambrotype process was in use from 1855 to about 1865 but enjoyed its greatest popularity in the late 1850s. A negative image on glass (The glass is called a "support" and it is so1metimes colored). The back of the glass may have a black varnish or the supporting case will have a black fabric to "reverse" the image. Like daguerreotypes, most ambrotypes were put in cases. Ambrotypes can be identified by the fact that their images appear negative when examined by light transmitted through the glass. The ambrotype normally appears as a postive image no matter what the angle of view, whereas, daguerreotypes switch from postive to negative depending upon the angle of viewing.
Cabinet Cards: 1866 - ca.1920
A card, usually 6" x 4" inches with an albumen photograph glued to the card.
Cartes-De-Visite: 1860- ca.1900
Mostly small albumen prints glued to cards about 2.5" x 4.5". "Mosiac cards" are many portraits combined on one card. "Cardomania" was popular from 1860 through 1900.
Daguerreotype: 1840- ca.1860
The "dag" has a mirror-like surface - they switch from postive to negative depending on the angle at which they are held. Dags usually are in cases. They were popular mostly from 1840 to 1860.
Lantern Slides: ca.1880’s- ca.1920’s
Positive images on glass which are sometime colored. Be sure not to confuse these with glass plate negatives. In use approximately mid 1880’s-1920’s.
Lithographs (and related graphic processes):
Images created by the planographic printing process. This includes lithography, photolithography, offset printing and other process. Images from books, magazines, public relations brochures, etc. are included in this group. The images created by these processes are not technically photographs, however they do contain images akin to the photograph which are of historical value.
Negatives:
Negatives are reverse images that are used to make "positive prints" Negatives may be paper, glass, nitrate celluose, or other material.
Postcards: ca.1900 - present
Postcards can either be lithographs (or a related planographic process) or photographs.
Salt Paper: 1840- ca.1900
An image which was developed on treated paper. After 1840, this process was used throughout the nineteenth century. Salt paper images usually have a "warm," or "soft" hue in their appearance. This process is also known as a "Talbotype." "calotype," or "salt print."
Slides:
35 mm transparency film, often color, and in a paper-based or plastic mount. Should be placed in polypropylene slide sleeve pages.
Stereoviews: ca.1850-1925
Stereoviews, or stereographs, as they are otherwise known, are almost identical side-by-side images of a single scene, viewed simultaneously through an optical device. Popular from ca. 1850 - ca. 1925.
Tintype: 1856- ca.1930
The image is on a thin sheet of blackened (japanned) iron. The tintype is also known as a ferrotype and melainotype. The tintype was used approximately between 1856 and 1930, mostly in use, however 1860-1890.
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