The Printing Process
Printing is a process for reproducing text and images, typically with ink on paper using a printing press. It is often carried out as a large-scale industrial process, and is an essential part of publishing and transaction printing.
There are nine main types of printing processes:
- offset lithography
- engraving - think fine stationery
- thermography - raised printing, used in stationery
- reprographics - copying and duplicating
- digital printing - limited now, but the technology is exploding
- letterpress - the original Guttenberg process (hardly done anymore)
- screen - used for T-shirts and billboards
- flexography - usually used on packaging, such as can labels
- gravure - used for huge runs of magazines and direct-mail catalogs
Offset lithography is the workhorse of printing. Almost every commercial printer does it. But the quality of the final product is often due to the guidance, expertise and equipment provided by the printer.
Offset lithography works on a very simple principle: ink and water don't mix. Images (words and art) are put on plates (see the next section for more on this), which are dampened first by water, then ink. The ink adheres to the image area, the water to the non-image area. Then the image is transferred to a rubber blanket, and from the rubber blanket to paper. That's why the process is called "offset" -- the image does not go directly to the paper from the plates, as it does in gravure printing.
Consumer and some commercial printers are designed for low-volume, short-turnaround print jobs; requiring virtually no setup time to achieve a hard copy of a given document. However, printers are generally slow devices (30 pages per minute is considered fast, and many inexpensive consumer printers are far slower than that), and the cost per page is actually relatively high. However, this is offset by the on-demand convenience and project management costs being more controllable compared to an out-sourced solution. The printing press remains the machine of choice for high-volume, professional publishing. However, as printers have improved in quality and performance, many jobs which used to be done by professional print shops are now done by users on local printers; see desktop publishing. Local printers are also increasingly taking over the process of photofinishing as digital photo printers become commonplace.