Offset printing is one of the most widely used types of printing today. The offset printing process typically employs principles from rotary printing and lithography. There are usually a printing plate cylinder, a rubber-wrapped blanket cylinder, and an impression cylinder. The printing plate is the first to be exposed to ink. The printing plate then transfers (offsets) the image to the rubber on the blanket cylinder. The printing surface (typically paper) is held against the blanket cylinder by the impression cylinder, and the image is transferred to the paper.
Web Fed
The more common form of offset printing is what is referred to as web fed printing. This is where large rolls of paper (webs) are set up to continuously feed paper into the machine.
Sheet Fed
A second, less common form of offset printing is sheet fed printing. In this type, paper is fed into the press one piece at a time for printing.
Printing Plates
The printing plates are specially treated to achieve a readable image. The image surfaces are designed to repel water and to attract ink, while the non-image surfaces are treated to do the opposite. This method finds its root in lithographic printing.
Applications
Offset printing is used for a variety of commercial printing purposes including newspapers, magazines, and brochures.
Enviroment
While it remains a popular format for printing, offset printing uses a number of potent chemicals that make it a potential environmental hazard if improperly handled.
