A printing plate used in offset lithography that has been pretreated with a light-sensitive coating. Presensitized Plates,as the name suggests already have a coating of light-sensitive material on them before being used, so they can be directly be exposed. PS Plates,as they are also known as, can be both positive or negative working depending upon the type of light-sensitive coating used on the plates. See Plate: Offset Lithography.
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