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Thursday 15 November 2012

Print Processes - Offset Lithography


**Refer to 'Commercial Print' blogpost.

Offset Lithography


http://www.dynodan.com/printing-process-explained/lithography-files/index.html

http://www.technologystudent.com/designpro/prtpro5.htm

Lithography is mainly used by commercial printers, printing companies that will print thousands of copies of the same item, in one production run. Lithography machines can print on both sides of paper/card and they rely on four basic colours; yellow, cyan (type of blue), magenta (type of red) and black. This is also known as the CYMK process.



1. The printing plate has the image to be printed, in relief, on its surface (the image stands out slightly from the printing plate surface).

2. The printing plate is kept dampened. Ink is applied to the plate but it is repelled from the dampened surfaces which are the non-image areas.
3. As the printing cylinder rotates the ink is transferred to the rubber blanket cylinder.
4. The ink, now on the rubber blanket cylinder, is pressed onto the paper or card as it is pulled through the machine. (The paper is trapped between the blanket cylinder and the impression cylinder - these pull the paper through the machine)

Offset Lithography...\\


The most popular printing method for small business marketing materials is offset lithography. This is a little guide to the process.

What is Offset Printing?

Offset lithography operates on a simple principle: ink and water don't mix. Image information (art and text) is put on thin metal plates which are dampened by water and ink by rollers on the press. The oil-based ink adheres to the image area, the water to the non-image area. The inked area is then transferred to a rubber cylinder or "blanket" and then onto the paper as it passes around the blanket. The process is called "offset" since the image doesn't go directly from the plates to the paper, but is offset or transferred to another surface as the intermediary.

Why is it called 4-Color Printing?

Offset commercial printing presses and inkjet desktop printers both use four basic ink colors: CMYK. Where inkjet printing puts all the different ink colors on the paper in one pass through the printer, in offset printing each color of ink is applied separately - one plate per color. Small dots of the four inks - cyan (blue), magenta, yellow, and black (K) - are deposited in specific patterns that make our eyes believe we are seeing a wide range of colors. That's why the standard offset printing process is often called 4-color process lithography or 4-color printing.
Offset printing can also use premixed inks in specific colors including metallic and fluorescent colors, called spot colors, to obtain hues outside the normal color range of process printing.

Why Use Offset Printing?

The advantages of traditional commercial offset printing are higher quality and the best cost-effectiveness for quantities over a few hundred, especially high volume quantities.
  • Low price per piece. The more you print, the less you pay per piece, since most of the cost is in the setup. With a commercial printer, any additional quantity costs only a few cents per sheet for the paper and ink.
  • Brilliant quality. Offset printing produces rich, accurate color and high-quality images and photographs, with sharp typefaces and fine details.
When you need 250 to 500 or more business cards, postcards, posters, glossy brochures, flyers or catalogs, offset printing is tough to beat for high-end quality at an affordable price. 4 color offset printing enables small businesses to compete with the "big guys" by providing professional-looking marketing materials.


The following literature provides a very detailed and descriptive account of all the print processes..

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