OA Of RegisterWhen two sheet passes on a press are misaligned.
OblongA term used to describe printed books, catalogs etc., that are bound on their shorter side; also referred to as album bound.
Off-shore PaperAny papers made outside the US and Canada.
OffsetThe most commonly used printing method, whereby the printed material does not receive the ink directly from the printing plate but from an intermediary cylinder called a blanket which receives the ink from the plate and transfers it to the paper.
Offset GravureA complex offset process involving multiple transfers between the gravure plate, the plate cylinder and a solid rubber plate.
Offset LithographyIndirect printing method in which the inked image on the press-plate is first printed onto a rubber blanket, then in turn offsets the inked impression on to the sheet of paper.
Offset PaperA term for uncoated book paper.
OnionskinA light bond paper used for typing and used with carbon paper because of its thinness.
OpacityQuality of papers that defines its opaqueness or ability to prevent two-sided printing from showing through.
OpaqueA quality of paper that allows relatively little light to pass through.
Opaque InkInk that completely covers any ink under itself.
OrthochromaticAny light sensitive surfaces that are not sensitive to red.
Over RunSurplus of copies printed.
Overhang CoverA cover of a book that extends over the trimmed signatures it contains.
OverlayA transparent sheet placed over artwork, in register with the work it covers; this is used to call out other color components of the work, instructions or corrections.
Overlay ProofA process of proof making whereby the color separations are individually exposed to light sensitive film. This film is then set in registration with a piece of white paper in the background.
OverprintingAny printing that is done on an area that has already been printed.
OversetType that is set in excess of the allotted space.