Editing Offset printing (section)

== Process variations ==
Several variations of the printing process exist:
; Blanket-to-blanket : A printing method in which both sides of a sheet of paper are printed simultaneously, with two blanket cylinders per colour; a sheet of paper is passed between them, with each cylinder printing on one side of it.<ref>Commercial Color Offset Printing – A Compendium of Commercial Printing Terminology</ref>
Blanket-to-blanket presses are also called perfecting or duplex presses because they print on both sides of the sheet at the same time.<ref>{{Cite book |last=Michael Bruno, Frank Romano, Michael Riordan |url=https://www.amazon.com/Pocket-Pal-Production-Handbook-Nineteenth/dp/B000TXI4QA |title=Pocket Pal - A Graphic Arts Production Handbook |publisher=INTERNATIONAL PAPER CO |year=2003 |pages=137}}</ref> There is no impression cylinder because the opposite blanket cylinders act as impression cylinders to each other during print production. This method is most used on offset presses designed for envelope printing. There are also two plate cylinders per colour on the press. Web and sheet-fed offset presses are similar in that many of them can also print on both sides of the paper in one pass, making it easier and faster to print duplex.
; Blanket-to-steel : A printing method similar to a sheet offset press; except that the plate and cylinder pressures are quite precise. Actual squeeze between plate and blanket cylinder is optimal at 0.005″; as is the squeeze or pressure between the blanket cylinder and the substrate.<ref name="romana139" /> Blanket-to-steel presses are considered one-color presses. In order to print the reverse side, the web is turned over between printing units by means of turning bars.<ref name="romana139" /> The method can be used to print business forms, computer letters and direct mail advertising.
; Variable-size printing : A printing process that uses removable printing units, inserts, or cassettes for one-sided and blanket-to-blanket two-sided printing.<ref name="romana139" />
; Keyless offset : A printing process that is based on the concept of using fresh ink for each revolution by removing residual inks on the inking drum after each revolution.<ref name="romana139" /> It is suitable for printing newspapers.
; Dry offset printing : A printing process which uses a metal backed [[photopolymer]] relief plate, similar to a [[letterpress]] plate, but, unlike [[letterpress]] printing where the ink is transferred directly from the plate to the [[Substrate (printing)|substrate]], in dry offset printing the ink is transferred to a rubber blanket before being transferred to the [[Substrate (printing)|substrate]]. This method is used for printing on injection moulded rigid plastic [[buckets]], tubs, cups and [[flowerpot]]s.