Monday, February 25, 2013

Offset Printing

The proper name of the process of offset printing is offset lithography, though it is usually called offset printing; or just offset. Offset printing is the most popular kind of printing used these days. The offset printing is so common that almost 40 % of the printing jobs are done by the usage of offset printing. The presence of offset printing is almost felt in every industry. Offset printing is the method most widely used for commercial printing runs of about 1,000 to 100,000. Typically, the speed of printing is much faster than office copiers, and very high quality can be achieved. Examples of offset printings include: catalogues, brochures, books, magazines, newspapers, maps, cards, and stationery. When used in combination with the lithographic process, which is based on the repulsion of oil and water, the offset technique employs a flat (planographic) image carrier on which the image to be printed obtains ink from ink rollers, while the non-printing area attracts a water-based film (called "fountain solution"), keeping the non-printing areas ink-free.
Usually, artwork files prepared on a computer, are used to produce a printing plate. The plate
is fitted to an offset printing press. Ink is applied to the image on the plate and, as the press
rotates, the ink offsets to a rubber blanket on another cylinder. The ink is again offset from the
blanket to paper or other material.
The most common kind of offset printing is derived from the photo offset process, which involves using light-sensitive chemicals and photographic techniques to transfer images and type from original materials to printing plates. In current use, original materials may be an actual photographic print and typeset text. However, it is more common — with the prevalence of computers and digital images — that the source material exists only as data in a digital publishing system. Offset litho printing on to a web (reel) of paper is commonly used for printing of newspapers and magazines for high speed production. it cant print variable repeat in one machine.
Offset printing holds about 70% of the printing market. Other printing processes include:
gravure, letterpress, flexographic, intaglio, and silk screening.

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