With the invention of the image setter, print shops can now print directly from their computer to film...
The plates that are used today are usually
plastic or aluminum. The plates are created with a brushed, or rough,
texture and then brushed with a smooth emulsion which is photosensitive.
A photographic negative is exposed to light on the plate, creating a
positive image on the emulsion. Chemicals are then used to remove any
unexposed emulsion. This plate is then placed on a drum and treated with
water, which only adheres to the areas without emulsion. A roller then
applies ink which only sticks to the positive parts of the image which
have been fixed by the emulsion. A rubber coated drum is then rolled
over the plate to both remove the water and pick up the ink. This ink is
then transferred only the printing medium. This method is called offset
printing because the image is transferred (“offset”) onto the rubber
drum prior to being place on the printing medium.
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