Photolithography is the chemical and optical process used to manufacture plates for offset printing. A flat aluminum plate coated with a photosensitive polymer is placed in a vacuum frame beneath a piece of high-contrast film. Ultraviolet light hardens the exposed areas of the polymer to make them accept oil-based ink, while the unexposed areas are washed away to expose the water-receptive metal base.
We use photolithography for all our commercial runs, but we still keep a small letterpress for specialty invitations.
Related terms
Photo-offset
A lithographic printing process that uses photographically produced plates to transfer images to a rubber blanket.
Lithographic
Pertaining to a printing process based on the chemical repulsion of oil and water.
Plate
A flat, flexible sheet of metal or polymer that carries the image to be printed.