The offset printing process is ink-based - similar to house paint in a can. It is a more human-dependant technology requiring multiple steps and phases. As with digital printing, presses and set-ups range in scope.
The Process: Offset printing is based on the principle that ink and water do not mix - instead, they repel each other. Artwork is photochemically transferred to thin metal (or paper) plates. Once wrapped around a cylinder within the press, these plates are dampened first by water, then ink. Ink from ink-coated rollers adheres to the image area. Conversely, the non-printing area attracts a film of water from water rollers. The image is then transferred (or 'offset') to a smooth rubber blanket, and further ‘offset’ from the rubber blanket to the paper, which is fed into the press through a conveyor-like system.
Although the equipment and set-up/running costs are relatively high due to tasks like inking the press, monitoring water and ink, checking for accurate image ‘registration,’ maintaining proper ink coverage, cleaning the press, etc., the actual printing process is relatively inexpensive. The time required for pre-press work, film and plate making, proofing, and setting up in preparation for a job are all one-time charges. We suggest you make arrangements with your print shop to save your film and plates in order to avoid those set-up charges in future runs.