This can result from the presence of sulphur in the atmosphere, but it is most often due to inadequate processing that leaves behind residual processing chemicals (fixers) in the print. Sulfiding-This is the formation of silver sulfide when silver reacts with sources of sulphur. Silver images exhibit several characteristic types of deterioration: Dyes were often used for hand coloring, or to tint layers of the image or support, and often become very unstable as they age. Carbon prints, woodburytypes, and gum bichromate prints all use inorganic pigments, and have excellent stability. Iron slats, used to create cyanotypes, are far less stable, which causes the prints to fade when exposed to light or alkaline materials. Platinum was used to create paltinotypes, which are silver-gray in color and quite stable. Several other image-forming materials were used as different processes developed through the 19th century. Differences in appearance in the different types of prints are due to differences in the physical form of the silver particles. The most important was metallic silver, which was used in most 19th century photographic prints (including salted paper prints and albumen prints) and is still used in modern black and white prints. Image-Forming MaterialsĪs photographic techniques developed, a number of different light-sensitive materials were used to form the image. It is then washed to remove residual fixer.
The image is "fixed" in order to remove excess light-sensitive material and stop the darkening process. This forms either a direct visible image (known as printing out) or a latent image, which can be developed using a chemical developer (known as developing out).
To produce a photographic image, light-sensitive materials such as silver salts are applied to a support made of paper, cloth, plastic, or metal, and exposed to light. Photographs are composite objects, consisting of a base (also called a support), a binder, and an image-forming substance. You must also become familiar with problems related to their physical and chemical composition.
#Silver gelatin print and prints difference how to#
In order to care properly for photographic collections, you must understand how photographs are made and learn how to identify their various types. Extensive technical and aesthetic changes have affected photography since 1839, when Louis Daguerre developed a practical method for creating permanent images.Įach photographic process has unique characteristics that affect its deterioration, storage, and handling.
Conservation Services for Private and Family Collections.Conservation Services for Cultural Institutions and Government Agencies.
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