What is a Stereograph?
The Miriam and Ira D. Wallach Division of Art, Prints and Photographs: Photography Collection, The New York Public Library.(1875).Black Dutchman. Retrieved from http://digitalcollections.nypl.org/items/510d47e1-4c3f-a3d9-e040-e00a18064a99
A Stereograph is a pair of photographic images on a single support that, when viewed through a special pair of lenses named, stereoscope, gives the appearance of a single image as having depth and solidity - a three dimensional effect. The standard format of a stereograph is a pair of photographs mounted next to each other on a piece of stiff card. The photographs are not exactly the same, even though both images are taken at the same time. The camera simulates the separation between the eyes and generates images with a slight lateral shift. The distance between the two lenses is 2 1/2 inches (6.3 cm) exactly as the distance between the centers of two human eyes.
The photographs are usually albumen prints and are glued against a colorful paper and around the margins the card bears the name of the photographer’s and/or publisher’s name(s) and a title. The same information is often also included on the back portion of the card.
An albumen print was made by floating a sheet of thin paper on a bath of egg whites containing salt, which have been whisked, allowed to subside, and filtered. This produced a smooth surface, the pores of the paper having been filled by the albumen. After drying, the albumanized paper was sensitized by floating it on a bath of silver nitrate solution or by brushing it on the same solution. The paper was again dried, but this time in the dark.