A type of printing plate used in offset lithography, in contrast to a subtractive plate, in which light shined through a photographic negative hardens and renders insoluble the image areas on the plate, the non-image areas remaining soluble. The coating in the non-image areas then needs to be removed—or subtracted—from the surface of the plate following exposure. Additive plates require the addition of a special image-strengthening material to the image areas to keep them durable. See Plate: Offset Lithography.
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