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photographs
5.2 Types of Photographs

Gary Albright
Conservator in Private Practice

Monique Fischer
Senior Photograph Conservator
Northeast Document Conservation Center

Definitions

POP (printing-out paper): A photographic paper which forms a visible image directly from the reaction of light on light-sensitive materials. POP prints are warm in tone, tending towards a brown, purple, or reddish color. They are almost always made in contact with a negative.

DOP (developing-out paper): A photographic paper which forms a visible image through the use of a chemical developer to reveal the latent image made by exposure to light. DOP prints are cool in color -- blue, neutral, or black -- unless they have been toned. They may be either contact-printed or enlarged from a negative.

Coated paper: A support which has an emulsion layer on its surface consisting of either albumen, gelatin, or collodion. This layer holds the light-sensitive photographic salts. A three layer structure has as its third layer barium sulfate, (aka bryta layer). This layer occurs between the paper and the image layer.

Uncoated paper: A paper support without any emulsion layer. The image often appears to be within the paper.

Distinguishing Characteristics

The following are the most important features used to identify a type of photograph:

Positive or negative
Nature of support material
Texture, surface quality
Color, tone
Characteristics of deterioration

Photoprints (Direct Positives)

Support Materials	Technique	Date	Identifying Features
Silver-plated sheet of copper	Daguerreotype	1839 – c. 1860	Mirror surface; positive-negative nature; usually housed in a miniature case made of wood covered with leather, paper, cloth or mother of pearl; and/or made of thermoplastic material. Tarnish can form on support.
Glass	Ambrotype	1851 – c. 1880	Milky gray highlights; various black backings, occasionally use ruby glass; usually housed in a miniature case. (See daguerreotype for description.)
Iron, coated with a black varnish ("Japanned surface") containing raw linseed oil, asphaltum and pigments	Tintype, ferrotype, melainotype	1854 – c. 1930s	Milky gray highlights, lack of contrast in image. Rust can form.

Photoprints (From a Negative)

Support Materials	Technique	Date	Identifying Features
Uncoated Paper (1-layer structure)	Salted paper print	1840 – c. 1860	POP, matte surface; paper fibers visible; often faded to pale yellow, especially at the edges; sometimes varnished.
	Platinotype Palladiotype	1880 – c. 1930 1916 – c. 1930	Gray-black color, matte surface; paper fibers visible; rich, velvety texture; popular with art photographers; very stable images, no fading or silvering; paper often very acidic and discolored.
	Cyanotype (blue-print)	c. 1880 – c. 1910 still used	Brilliant blue color, matte surface; invented in 1842 but not used until 1880s; paper fibers visible.
Coated Paper (2-layer structure)	Albumen print	1851 – c. 1900s	POP, semi-glossy surface; thin paper support, usually on heavy mount; a crackle pattern can often be seen in dark highlights; usually yellowed in highlights; paper fibers visible through albumen coating.
	Carbon print	1860 – present	Used extensively for reproductions of works of art, also used as tip-ins for books. Subtle image relief; paper fibers visible in highlights; no fading or yellowing; may get large cracks in dark areas; may be any color.
	Woodburytype (Photoglypty)	1866 – c. 1900	Same characteristics as carbon prints. Woodburytypes are not photographic, but photomechanical. Mainly used for book illustration and large edition publications; often labeled.
Coated Paper (3-layer structure)	Collodion print	1888 – c. 1910 Glossy: late 1880s–1920s Matte: 1894 – 1920s	POP, glossy surface (sepia, purple color) or matte surface (gold or platinum toned, black color), very stable image, rarely faded; easily abraded; usually mounted; paper fibers not visible. Glossy collodion prints often exhibit a subtle rainbow effect on their surface when viewed under fluorescent lights.
	Gelatin POP print (silver chloride)	c. 1880 – c. 1910	POP warmer in tonality than a gelatin DOP; usually very glossy; often faded to yellow; paper fibers not visible.
	Gelatin DOP print (silver bromide)	c. 1880 – present	DOP appears black and white unless image deterioration has occurred; matte, glossy or textured; may be toned to various warm shades; often exhibits silvering; may fade; paper fibers not visible.

Photo Negatives

Support Materials	Technique	Date	Identifying Features
Paper	Calotype	1840 – c. 1855	Rare, usually waxed or oiled.
Paper	Eastman paper negative	1885 – c. 1895	Rare, usually in poor condition; small format.
Glass	Collodion wet plate	1851 – c. 1880	Plate coated by hand; edges often ground; uneven coating at the edges; varnished.
Glass	Gelatin dry plate	c. 1880 – c. 1975	Plate is machine coated; cut edges; even coating at edges; occasionally varnished.
Gelatin	Eastman American film	1884 – c. 1890	Rare; looks like plastic; brittle, uneven edges; used for Kodak No. 1 (2-1/2" diameter), Kodak No. 2 (3-1/2" diameter)
Plastic	Cellulose nitrate(sheet film)	1913 – 1939	"NITRATE" marked on edge; very flammable; small clipping sinks in trichloroethylene; degraded products smell very acrid; becomes yellow, brittle, sticky.
	Cellulose acetate,diacetate, triacetate, etc.	1925 – present	"SAFETY" marked on edge; burns with difficulty; clipping floats in trichloroethylene; degraded products smell of acetic acid (vinegar); channels form between base and emulsion as the negative deteriorates.
	Polyester	c. 1965 – present	When viewed between polarizing filters, the film is identified by interference patterns (rainbow colors);1 may include edge printing "SAFETY."

See preservation leaflet “A Short Guide to Film Base Photographic Materials: Identification, Care, and Duplication.”