Offset printing is the most popular technique for commercial printing. It has been around since the 20th century, helping businesses produce stationery, leaflets, brochures, magazines, and cards in bulk. Also called offset lithography, commercial offset printing is also used for labelling packages such as boxes or cartons.
What is offset printing?
This printing technique is called ‘offset’ because it does not transfer ink directly onto paper like other printing methods do. Instead of going from plate to paper in two steps, ink is transferred first to a rubber cylinder and then printed on paper. The three-step offset method reduces wear and tear on the lithographic printing plate, thus prolonging its lifespan.
An offset printer includes three cylinders:
- Plate cylinder
- Offset blanket cylinder
- Impression cylinder
In offset printing, the image area and the non-image area co-exist on the same flat surface.
Offset lithography works on the principle of oil and water separation. The plates have been treated to make image areas attract ink and non-image areas attract water to repel the ink. When water and ink are applied by the rollers to the plate, the oil-based ink sticks to the image while water sticking to the non-image area repels it.
Some offset printing presses use a silicone layer that repels ink instead of water. These systems are called ‘dry’ or ‘waterless’ offset presses.