Glossary of Printing Terms

Here is a short glossary of words that printers use. Good to know if you ever decide to professionally output your work.

Basis Weight: Weight in pounds of a ream in the basic size from that weight. The basic size for “book” would be 25”x38”.

Bleed: Image is extended beyond final trim size to prevent white edges when cut.

Coverage: Amount of ink printed per sheet expressed as percentage of sheet size.

Commercial Register: Fitting of process colours to within 1/300th of an inch.

Contone (Continuous Tone): An image such as a photograph that is made up of gradient tones (no screen). Cannot be reproduced without screening.

Hairline Register: Fitting of process colour to within 1/600th of an inch.

C.M.Y.K.: Cyan (C), Magenta (M), Yellow (Y) & Black (K). The 4 colours needed to make a full colour print.

Gripper Margin: 3/8” unprintable area on feed edge of paper needed for gripper to pull paper into press.

Halftone: The reproduction of Contone images using a screen to break the image into various size dots to give the illusion of shades of a colour.

Imagesetting: Process of producing film from a computer file with all type and images included.

Moire: “Tartan” pattern created by incorrect screen angles when printing two or more colours.

Mottle: The spotty or “Orange Peel” look to solid print areas.

Offset Press: Type of press where the image is printed from the plate onto an intermediary then onto the paper. There are two main types of offset presses, sheet fed which uses sheets of paper and web which use rolls of paper.

Opacity: The degree to which the paper “shows through” the image from the other side. Important for books and double sided pieces.

P.M.S. (Pantone Matching System): System used by printers to match spot colours, also provides mixing guides for C.M.Y.K. colours. Each colour is given a number, for example: P.M.S. 152 is an orange.

Paper Grain: Direction of fibers corresponding to the direction of paper. Important for paper stretching and folding. For example if paper grain is going across a fold then it will usually crack when folded.

Plate: Sheet on which image is etched so that it will pick up ink to be transferred onto the paper for printing, can be made of “paper”, “metal” or other material.

Process Colour: Printing term for full colour, also known as C.M.Y.K.

Ream: 500 sheets of paper.

Register: Close fitting of 2 or more coloured images.

Spot Colour: Specific ink colour, see also P.M.S.

Substance Weight: Weight in lbs of 500 standard size sheets of paper. The standard size changes depending on the measure of paper being used. Bond, Ledger and writing use 17”x22”. Book, offset and text use 25″x38″. Cover uses 20″x26″. Each measure of paper is available in usually available 3 or more sizes, not just the standard sizes, which can then be cut down to various finished sizes like 8.5×11 (letter), 8.5×14 (legal), and 11×17 (tabloid).

Trapping: Slight overlapping of colours to ensure precise fit and no paper (white) showing through between different colours.