First of all, the image is split into CMYK (Cyan, Magenta, Yellow and Black). Next, each colour is etched onto a press plate and mounted on a drum called the plate cylinder.
The plate cylinder is first passed through water rollers so that the etched part of the plate is dampened and then through ink rollers which stick to all the parts of the plate that are dry.
Next, the drum stamps onto the blanket (offset) cylinder and sheets of paper are passed between this cylinder and the impression cylinder. By using an offset cylinder, a clearer finish is possible than just printing straight from the plate cylinder.
The paper then passes through all the CMYK colours before being stacked up on the delivery pile, separated with a powder to stop them sticking together as they dry.
- Produces a high-quality finish
- More printed the cheaper it gets
- Expensive to set up initially