Processes: Offset Lithography

The most widely used printing process, offset uses the principle that oil repels water and keeps image and non-image areas on the same plane on the same plate. The plate is chemically treated on the image areas to be ink receptive and water repellent. The non-image areas are treated to be water receptive and ink repellant. The plate is placed on a cylinder and first contacts rollers of water, then the inked rollers. The image areas are now full of ink, the non-image areas are saturated with water. The image is transferred (or offset) from the plate to a rubber cylinder and then from the rubber cylinder to the combined board or paper.

You can recognize offset printing by a smooth print without embossing, an ink ring or serrated edges.

PRO - The main advantage is that offset produces a clearer impression with excellent photograph and graphic reproduction. It can be used on a wide variety of paper sizes and surfaces with both smooth and rough finishes. On combined board it is best used with flutes of size E, F or smaller. In addition, less ink is required for equal coverage, drying is speeded, and smudging and set-off are reduced.

CON - Not cost-effective for smaller runs.

COST - $$$$

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