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What is Offset Lithography?

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  • Written By: Mary McMahon
  • Edited By: O. Wallace
  • Last Modified Date: 07 April 2014
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Offset lithography is a printing technique which is widely used around the world. Most books, newspapers, and magazines are printed using offset lithography, and this printing technique is widely regarded as the workhorse of printing, because it is fast, efficient, cheap, and relatively easy. The “offset” in the name refers to the fact that the ink is transferred to a separate surface before being applied to the paper.

The first step in offset lithography is making a plate with the image to be printed. If the image is in black and white, only a single plate is required, because the plate can simply be inked with black ink. Color images are produced using a four-color separation process, in which four different plates are made for the cyan, magenta, yellow, and key (black) inks; when the plates are printed, the colors blend together visually, creating a color image.

Plates in offset lithography are entirely flat, in contrast with the textured surfaces of engraved plates and movable type. They are made by creating a film negative of the image, placing it over a photo-sensitive plate, exposing it, and then developing it. Once the plate is made, it can be mounted in a press, and the real fun begins.

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This printing technique takes advantage of the fact that oil and water do not mix. The plate is brushed with rollers coated in water, and then with rollers covered in ink. The ink is attracted to the parts of the plate which were exposed earlier, while the water keeps the unexposed portions clear so that they do not smear or transfer ink. Then, the plate transfers the ink to a rubber roller known as a “blanket,” and the blanket rolls across the paper; typically the paper is fed between the blanket and another roller to ensure that the image stays crisp.

An offset press can run continuously, which makes it extremely fast. Depending on the job, the press may be sheet fed, which means that individual pieces are pulled from a stack by the press and run through, or web-fed, in which case the paper is on huge rollers. In both cases, the paper is typically run through an oven after printing so that it dries quickly, preventing smears, and then it can be cut, bound, folded, and prepared for distribution.

The first press for offset lithography was developed in 1903, and the concept quickly caught on in the printing community. Offset presses vary in size from the massive presses used at commercial publishers, which can be bigger than a house, to smaller models around the size of dump trucks used at smaller printing companies.

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Discuss this Article

nana1hd2012
Post 8

I believe that I have an offset lithograph of Mater Dolorosa, Madonna with wreath of thorns produced in 1965, artist, John the Baptist Salvi (Salvi Giovanni Battista) called II Sassoferrato. I am trying to find out if it is worth anything.

anon147588
Post 6

i have a double sided lithograph one side abraham lincoln by William A Smith, other side on sharon mountain by Harold McIntosh. Is this worth anything?

anon70701
Post 5

dawnsparta, you should go to the official website of Leroy Neiman. Incidentally, the prints were categorized as posters. As far as the price you paid for the two prints, you did mention that you got them at a charity auction - "charity" being the clue that you basically paid more for the prints' real value.

cocolove
Post 3

I'm trying to sell a offset lithograph of maurice utrillo. my grandmother got it in paris around 60 years ago i'm trying to find the value of an utrillo lithograph in today's market.

anon61035
Post 2

to dawnsparta: Maybe both, maybe neither. Try getting a second opinion. Just remember that the market is rather poor right now.

dawnsparta
Post 1

A few years ago I bought 2 Leroy Neiman Offset Lithographs at a charity auction sponsored by a reputable gallery. Today I took it to an art gallery in NY and the director said they were worth about $40.00 each, that they were posters. They are signed by the artist and I paid over $600 for them 7 years ago. Is an offset lithograph nothing more than a poster or was this guy a scheister?

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