Absorption
In paper, the property that causes it to take up liquids or vapors in contact with it. In optics, the partial suppression of light through a transparent or translucent material.

Abrasion resistance
The level at which paper can withstand continuous scuffing or rubbing.

Abrasiveness
The level of wear, resulting from friction, that paper, ink and coatings cause on dies, cutting blades, plates, etc.

Accordion fold
A term for two or more parallel folds that result in the sheet opening like a fan. Accordion folds are used on products such as brochures and maps.

Acetate
A clear, plastic sheet used on mechanicals to prepare an overlay for art or type that, for example, will print in an additional color. Acetate is also used for overhead transparency printing.

Acetate proof
A transparent, acetate printing proof used to reproduce anticipated print colors on a transparent acetate sheet. Also called color overleaf proof.

Achromatic
Having no color or hue. Material that is white, gray and black.

Acid-free paper
Paper manufactured in a neutral or slightly alkaline pH environment, usually buffered with calcium carbonate, to prevent the internal chemical deterioration of paper over time. Because of the absence of acid or acid-producing chemicals, the paper is more environmentally sound and is more stable over long periods of time.

Acidity
The amount of acid contained in paper. The acidity is measured by a pH factor from 0 to 14. The neutral point being 7, 0 to 7 is acid and 7 to 14 is alkaline.

Actual weight
The true weight of any volume of paper, which is used to determine both a paper's purchase price and shipping costs.

Additives
Fillers, dyes, sizing, enhancements and other materials added to pulp to give paper strength, brightness, color, fibered appearance or other desirable attributes.

Adhesives (envelopes)
Back Gum: Adhesive that cannot be remoistened. Used as a permanent seal for envelope seams.
Latex: Made from rubber-based material for self-seal envelopes. Latex is applied to the seal flap and the back of the envelope and sticks only to itself.
Pressure Sensitive: Applied to the seal flap and covered by release paper; self- sealing.
Remoistenable: Adhesive activated by water or solvent. Applied to seal flap of envelopes.
Resealable: Latex adhesive designed to form a lighter bond, for multiple sealing and resealing.
Strip-and-seal: See Adhesive, pressure sensitive.

A4
ISO paper size - 210mm x 297mm (8 1/4" x 11 11/16), most commonly used for letterheads. The International Organization for Standardization (ISO) has established standards for paper sizes based on the metric system (millimeters). The standards have been grouped into three different series of requirements. The "A-series" is for general printing.

Against the grain (also, across the grain)
Folding or feeding paper at right angles (i.e., perpendicular) to the direction of the grain in the paper.

Air-dried paper
Paper that is dried by circulating hot air around it with little or no tension or restraint on the paper. This gives the paper a hard cockle finish typical of bond papers.

Air mail paper
Lightweight, thin and mainly wood-free writing papers for air mail.

Alcohol / alcohol substitutes
Liquids added to the fountain solution of a printing press to reduce the surface tension of water.

Alkaline papermaking
Paper manufactured under alkaline conditions, using additives, caustic fillers like calcium carbonate and neutral size. The anti-aging properties in alkaline paper make it a logical choice for documents where permanence is essential.

Alum
A papermaking chemical that imparts water-resistant properties to paper and keeps sheets from sticking to the presses.

Aluminum plate
A metal press plate used for moderate to long runs in offset lithography to carry the image.

Aqueous coating
A water-based coating applied after printing either in-line or off-press, to help prevent ink from rubbing off. Unlike UV coating or a varnish, aqueous coating will also accept ink jet printing.

Announcement cards
Cards of paper with matching envelopes generally used for social stationery, announcements, weddings, greetings, etc.

Antique finish
A paper finish, usually used in book and cover papers, which has a tactile surface. Usually used in natural white or cream-white colors.

Apron
Extra space at the binding edge of a fold-out, usually on a French fold, which allows folding and tipping without interfering with the copy.

Archival paper
Acid-free or neutral paper that will not deteriorate over time. National standards for permanence dictate that archival papers must be acid free and alkaline with a pH of 7.5 to 8.5, include minimum 2% calcium carbonate as an alkaline reserve (to increase the longevity of the paper), and not contain groundwood or unbleached wood fiber.

Archival quality
Neutral pH for permanence.

Art paper
High-quality and rather heavy two-sided coated printing paper with smooth surface. The reproduction of fine screen single or multicolor pictures ("art on paper") requires a paper that has an even, well-closed surface and allows for uniform ink absorption.

Artwork
A general term used to describe materials prepared and readied for print.

Ascenders
The tops of lower case letters such as: b, d, h and t.