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gelatin - A binder from animal parts used as a support for the light-sensitive particles in certain emulsions.

genealogical (genealogy) - An account of the descent of a person, family, or group from an ancestor involving methodical search, fact finding, and record keeping.

gesso - A sizing material made up of a mixture of whiting and animal glue or gelatin. It must be applied warm after liquefying it in a double boiler. This is the gesso traditionally used by artists, gilders, and framers.

glass mounted slides - Sandwiching transparent slide films between thin glass to protect against dust and fingerprints. The glass is held in place within the slide mount. Some glass mounts consist of only a single piece of glass.

glass plate - A photographic exposure material consisting of a light-sensitive emulsion coated on a plate of glass. After exposure in a camera, the emulsion was then processed and usually dried on the glass and contact printed on light-sensitive paper. Cumbersome and fragile, technical advances replaced glass with clear films of acetates and polymers around the turn of the century. Some applications still exist for glass plates (astronomical photography), however digital imaging is replacing this use rapidly.

glassine - Translucent, smooth paper made by extensive beating and subsequent super-calendering. Most commonly used as protective wrappers. Basis weight: 12 to 90 lbs. Usually acidic and hygroscopic. Not recommended for photographic storage due to tendency of emulsion to permanently adhere to glassine under conditions of high humidity or moisture exposure.

glazing - Glass or other transparent material used for framing (also windows).

grain - In paper, the direction in which most of the fibers lie in a finished sheet of paper. Fibers flow parallel to the direction in which the paper travels on the paper machine during manufacture.

grain - In photography, the clusters of light-sensitive silver halides in a negative that are changed into black metallic silver by development. The grain becomes more apparent in a print when the negative is enlarged. Generally, the more sensitive (i.e., faster) films have more grain than less sensitive (i.e., slower) films.

grain long - Term used to designate that the grain of the paper is parallel to the longest measurement of a sheet of paper. The fibers are aligned parallel to the length of the sheet.

grain short - Opposite of grain long. Grain of the paper runs at right angles to the longest dimension of the sheet. Fiber alignment in grain short paper parallels the sheet's shortest dimension.

gravure - The major commercial application of the intaglio principle of printing, often used for photographic books and frontispieces.

gray scale - A strip of standard gray tones ranging from black to white, used to measure tonal range and contrast.

groundwood pulp - Pulp composed of "ground wood". Typically, newsprint, gray cardboard or brown corrugated board (box board). Regarded as non-archival and acidic, as the pulp is processed quickly and economically leaving most of the harmful impurities (mostly lignin) in the pulp.

gum bichromate - One of the antiquated non-silver photographic process using suspended color pigments and ammonium dichromate, as the light sensitive chemistry. Non-enlarging process-contact printing only. Usually requires multiple printing and registration techniques to build density for satisfactory image.