Modern offset lithography relies on supple aluminium, polyester, mylar or paper plates to work with the photographic process. The imaging process begins when the rough surfaced plate is covered in a photosensitive emulsion, a negative image is then placed in contact with the plate and exposed to ultra-violet light which develops so that the emulsion reveals the postive of the negative image. Another technique includes the use of a platesetter which uses lasers to transfer the image directly from a computer.
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