OA of Register
When two-sheet passes on a press are misaligned.
Oblong
A term used to describe printed books, catalogs, etc., that are bound on their shorter side; also referred to as album bound.
Offset
The 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 Gravure
A complex offset process involving multiple transfers between the gravure plate, the plate cylinder, and a solid rubber plate.
Offset Lithography
Indirect 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 Paper
A term for uncoated book paper.
Onionskin
A light bond paper used for typing and used with carbon paper because of its thinness.
Opacity
Quality of papers that defines its opaqueness or ability to prevent two-sided printing from showing through.
Opaque
A quality of paper that allows relatively little light to pass through.
Opaque Ink
Ink that completely covers any ink under itself.
Overhang Cover
A cover of a book that extends over the trimmed signatures it contains.
Overlay
A 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 Proof
A 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.
Overprinting
Any printing that is done on an area that has already been printed.
Overrun
Surplus of copies printed.
