What Are Offset Printers?

Johann Gutenberg is credited with the first printing press using carved wood letters.

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Offset printers are in common use today, with origins in Gutenburg's original printing press. Magazines and newspapers employ a version of the offset press using a web attachment that holds rolls of paper for printing the individual pages, later cut or bound together. Standard offset presses use a single sheet feeding process. Both offset press types can print colors. An offset press gets its name from how it produces the finished image. A metal plate transfers or “offsets” the inked image to a rubber roller that imprints the image on the page.

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A graphic designer or other creative person generates a positive image by hand or by using a computer. The image may only be text or may be image and text together. A special camera takes a picture of this image producing a negative used to make the printing plates. For items that contain multiple colors, several plates are made for each color, up to six, depending upon the capability of the individual printer.

Sheet-Fed Offset Presses

You’ll find these types of presses in shops that produce business cards, brochures and other printed materials based upon customer needs. Each press has a series of rollers through which the blank material feeds to get the image on the page. The image plate attaches to a roller next to the inking station or roller. Once inked, the image transfers to a rubber “blanket” roller, which presses the image on the page. The image offsets from the original plate to the roller before printing. The page fits between the image roller and the impression roller, which helps to press the image up against the roller containing the image.

Multiple Runs

The size of the press will determine how many times the printed page goes through the printer when printing multiple colors. Sometimes the offset press can only handle one color at a time. In these cases, the printer operator must clean the press between colors and use the plate for the specific color when printing.

Large Offset Printers

Larger offset printers house multiple stations for each color so the paper goes through the complex process only one time. For plates with multiple colors, four little registration marks, often a circle with a cross through it, appear on all four corners outside of the area printed, but on the page. These registration marks allow the printer to adjust the printed material to line up the colors appropriately.

ReferencesPSPrint: Introduction to the Offset Printing ProcessLytePrint: Offset PrintingPhoto Credit Comstock/Comstock/Getty ImagesRead Next:

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