What is offset printing?

What is offset printing?
Offset printing replaced expensive and labor intensive raised metal type in the printing process with a photographic based system that uses a flat rubber mat to transfer an image onto paper. It was the predominant system for commercial printing from about 1960 into the beginning of the 21st century. It is currently losing ground to digital computer based systems that rely on colored toners to create an image.Offset printing works because of hydrophobia, oil and water don't mix. A photographic image in created on a flat metal printing plate that has a grainy surface that holds liquids well. The 'image area' on that plate has a coating that is receptive to oil-based printing inks while the uncoated areas tend to accept water and repel ink. Roller systems on an offset press supply measured amounts of ink and water to that plate allowing an image to form on it's flat surface. Other rollers transfer the image from the metal plate to a cylinder covered with a flat rubber mat called a 'blanket.' Finally, paper is delivered past the blanket cylinder and squeezed slightly against it by a third 'impression' cylinder. The ink transfers from the blanket to the paper and you have printed!In offset printing, the colors and appearance of the objects on all the printed materials are the same. For example, not one color is lighter or darker compared to the other copy. So this means that the finish printed products are consistent.