If you did not read part one…read it
Fast forward ahead to “modern” lithography. It is now sometimes called, Photolithography and sometimes referred to as Offset Printing, which we will clarify later.
It has evolved to a process whereby the typesetting and/or artwork (called copy) is supplied to the printer, Camera Ready, meaning that no further work is required before it goes to the camera. The copy is photographed and a negative is produced which is then stripped into a flat which is a light stopping paper sheet. The copy is opened to light and now goes to the plate maker.
The plate is an aluminum sheet and is light sensitive. It is now placed in a vacuum exposure frame with the flat in tight contact with it. A bright light is turned on and the plate is “burned” in the areas of the negative that transmit light. After exposure, the plate is wiped with a solution that desensitizes anything on the plate not exposed to light, leaving a positive image of the copy on the plate. The plate is now ready for the press.