Gemini Press

Offset printing

Offset printing is the most commonly used method of printing today. The main reason for its success is that ink and water don’t mix and therefore allow for a clean transfer of ink from plate to blanket.

Offset printing is a simple process involving the use of three cylinders. The first cylinder is called the plate cylinder and sits under the press’s ink duct and this allows a steady flow of ink onto the plate. The image on the plate is created right side up, this image is then transferred or “offset” onto the offset cylinder as a reverse image of the artwork. The offset cylinder is mounted with a rubber blanket to create a smooth impression and increase the durability of the plate. Finally the image is then transferred from the blanket to the paper. The third cylinder, known as the impression cylinder provides a hard backing which allows the blanket to press a strong, solid impression onto the paper. The image once again has been reversed and reads right side up.

This process is used to print multiple colours on one sheet by having different units on a press filled with different colours, for example, Cyan, Magenta, Yellow and black. These four colours are the basis for all four colour process jobs.

Offset printing has a consistently high quality output which produces sharp clean images.  Plates can be produced easily and fitted simply, increasing the production time of your press. A very popular benefit to offset printing is the possibility to adjust ink levels on press; this can be done by adjusting the metal blade which controls the ink flow to the fountain rollers which are situated above the plate cylinder. Having this flexibility on press means a minder can add or remove ink on specific areas of the plate and therefore adjust the colours of an image. The key benefit of offset printing is, for the majority of run lengths, it is the cheapest method of producing high quality printing in a short period of time.