Vintage poster market > What is an offset print

Lithographic printing is well suited for printing both text and illustrations in short to medium length runs of up to 1,000,000 impressions. Typical products printed with offset printing processes include:

• General commercial printing Quick printing
• Newspapers Books
• Business Forms Financial and Legal Documents

Lithography is an "offset" printing technique. Ink is not applied directly from the printing plate (or cylinder) to the substrate as it is in gravure, flexography and letterpress. Ink is applied to the printing plate to form the "image" (such as text or artwork to be printed) and then transferred or "offset to a rubber "blanket". The image on the blanket is then transferred to the substrate (typically paper or paperboard) to produce the printed product.

On sheet-fed presses, the substrate is fed into the press one sheet at a time at a very high speed. Web fed presses print on a continuous roll of substrate, or web, which is later cut to size. There is a total of 3 types of offset printing: non-heatset sheetfed, heatset, and non-heatset web offset. The difference between heatset and non-heatset is primarily dependent on the type of ink and how it is dried

As the plate cylinder rotates, the plate comes in contact with the dampening rollers first. The dampening rollers wet the plate so the non-printing areas repel ink. Then the inking rollers transfer ink to the dampened plate, where ink only adheres to the image areas. The inked image is transferred to the rubber blanket, and the substrate is printed as it passes between the blanket and impression cylinder.

More information and Source:www.pneac.org