Hypersensitization

hypersensitization [¦hī·pər‚sen·sə·tə′zā·shən]

(graphic arts)

Any of various techniques for increasing the sensitivity of a photographic plate; includes chemical treatments, removal of oxygen and water, baking, soaking in hydrogen gas, preflashing, and push development.

(immunology)

The process of producing hypersensitivity.

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Hypersensitization 

a method of increasing the speed of a silver halide photographic material by washing it in water, an aqueous or aqueous-ammonia solution of silver nitrate, or a solution of triethanolamine. Hypersensitization can increase sensitivity severalfold, especially in the case of infrachromatic materials. The possibilities of hypersensitization are quite limited, however, largely because it must be carried out immediately before exposure. The effect of hypersensitization is manifested more in the region of additional sensitivity of the photographic material (caused by the presence in the emulsion of molecules of a sensitizer-dye) than in the region of the material’s own sensitivity (caused by the properties of the silver halide itself); it also appears at long exposure times and for low illumination on the layer. The nature of hypersensitization consists first in reducing the concentration in the emulsion layer of bromine ions, which reduce the photosensitivity of the layer but heighten the selectivity of the developer, and second in removing from the surface of the silver halide crystals oxidized molecules of the sensitizer-dye that have been adsorbed by it.

IU. N. GOROKHOVSKII