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Paper & Pulp Dictionary Glossary "A"

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 Definitions for commonly used terms, words and phrases used in the pulp and paper trade



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A4 (size)
A common ISO A-size of about 8 ¼ by 11 ¾ inches or 210 x 297mm. For all sizes see International Paper and Board Sizes.
A fiber also known as manila hemp or manila fiber, prepared from the outer sheath of the stems of manila.
ABCD Scheme
An initiative in the UK designed to classify the type and amount of Recycled Fiber in a paper product. The scheme grades four types of waste used in paper manufacturing, as follows:
A -
Woodfree, approved own mill waste (waste that has not left the mill. i.e. mill broke).
B - Woodfree unprinted waste (waste that has left the mill but not reached the consumer, typically from the printer or converter).
C - Woodfree printed waste (
post consumer waste, collected from homes, offices etc).
D - Printed mechanical waste (post consumer waste, typically newspapers).
To be classified as recycled, the grade has to contain no less than 50% of the total fiber from any combination of the above sources, with the percentages given for each..
A material that resists adhesion. Abhesive coatings are applied to surfaces to prevent sticking, etc.
Abrasion Resistance
The extent to which paper can withstand continuous scuffing or rubbing.
Abrasive Papers
Papers covered on one or both sides with abrasive powder, e.g. emery, sandpaper etc.
Absolute Humidity
The actual weight of water vapor contained in a unit weight of air, expressed in grams per cubic meter in metric system and pounds per cubic feet in English system.
Absolute Viscosity
A characteristic of one-component liquids which have a constant ratio of shear stress over shear rate (constant viscosity)
Absolute White
In theory a material that perfectly reflects all light energy at every visible wavelength; in practice a solid white with known spectral data that is used as the "reference white" for all measurements of absolute reflectance. (When calibrating a spectrophotometer, often a white ceramic plaque is measured and used as the absolute white reference).
The extent to which a paper will take up and hold a liquid.
Absorbent Core
The principal fluid-holding component of disposable hygiene products. Absorbent cores usually contain a combination of absorbent cellulose fibers (fluff pulps) and super-absorbent polymers composed of polyacrylates. Advanced cores  can contain very specialized absorbent cellulose fibers, synthetic fibers and super-absorbent polymers as well as fluff pulps.
Absorbent Paper
Papers having the specific characteristic of absorbing liquids such as water and ink. These papers are soft, loosely felted, unsized and bulky e.g. blotting paper.
Accepted portion of pulp after cleaning and or screening operation.
Acetate Pulp
A highly purified (high alpha cellulose) pulp made especially to be dissolved in acetic acid, acetic anhydride and sulfuric acid to make acetate rayon and acetate fiber.
Accelerated Aging
Exposing paper at elevated temperature usually at 110C in an oven or on a hot plate. The purpose of accelerated aging is to simulate the effect of aging in the laboratory.
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.

Material that is white, gray and black and have no color or hue.
Acid Detergent Fiber (ADF)
Organic matter that is not solubilized after 1 hour of refluxing in an acid detergent of cetyltrimethylammonium bromide in 1N (Normal) sulfuric acid. ADF includes cellulose and lignin. 
Acid Free Paper
A type of paper, which does not contain any acidic substance that may affect acid sensitive material. Acid free paper is anti rust and is used for metal wrapping.
Acid Hydrolysis
The treatment of cellulosic, starch, or hemicellulosic materials using acid solutions (usually mineral acids) to break down the polysaccharides to simple sugars..
Acid Migration
The transfer of acid from an acidic material to a less acidic or neutral-pH material. Occurs when neutral materials are exposed to atmospheric pollutants or when two paper materials come in contact. Acid can also migrate from adhesives, boards, endpapers, protective tissues, paper covers, acidic art supplies, and memorabilia.
Acid Proof Paper
A paper that is not affected by acid physically or chemically. This paper is used with substance containing acid.
Acid Sizing
Internal sizing carried out in acidic pH range (0-7). Rosin and alum sizing is acid sizing.
Activated Carbon
A highly absorbent powdered or granular carbon used for purification by adsorption.
Activated Sludge
The biomass produced by rapid oxygenation of effluent.
Active Alkali (AA)
Caustic (NaOH) and Sodium sulfide (Na2S) expressed as Na2O in alkaline pulping liquor.
Clay, fillers, dyes, sizing and other chemicals added to pulp to give the paper greater smoothness, color, fibered appearance or other desirable attributes.
Absorbable Organic Halogen (AOX)
A measure of the amount of chlorine that is chemically bound to the soluble organic matter in the effluent.
Aerated Lagoon
A biological wastewater treatment method in which air (oxygen) fed into an aeration basin reduces the effluent load.
Against the Grain
Cutting, folding or feeding paper at right angles to the grain or machine direction of the paper.
Irreversible alteration, generally deterioration, of the properties of paper in course of time. Aging also causes reduction in brightness and yellowing effect.
Equipment used to keep content of a tank or chest in motion and well mixed.
Air Brush Coater
A coater, which uses the pressurized air to atomize the coating mixture and spray it on the paper.
Air Dry (AD)
Refers to the weight of dry pulp/paper in equilibrium with the atmosphere. Though the amount of moisture in dry pulp/paper will depend on the atmospheric condition of humidity and temperature but as a convention 10% moisture is assumed in air dry pulp/paper.
Air Drying
Using hot air to dry pulp or paper sheets.
Air Filter Paper
A type of paper used for filtration of air to remove suspended particles. (car air filter, vacuum bag etc.)
Air Knife Coater
A device that applies an excess coating to the paper and then removes the surplus by impinging a flat jet of air upon the fluid coating, leaving a smooth, metered film on the paper.
Air Mail Paper
It is lightweight, high opacity, good quality writing/printing type paper used for letters, flyers and other printed matter to be transported by airlines.
Air Permeability
Commonly referred to as "porosity." The ease with which pressurized air can flow through a paper's thickness. Typically measure by the Gurley or the Sheffield porosity tests, which measure the volumetric flow of air through the paper thickness.
Air Pollution
The contamination of air around the plant due to the emission of gases, vapors and particulate material in the atmosphere.
Albumin Paper
A coated paper used in photography; the coating is made of albumen (egg whites) and ammonium chloride.
Micro organic plant life that forms in paper mill water supplies.
Alkali Lignin
Lignin obtained by acidification of an alkaline extract of wood.
Alkali Resistance
Freedom of paper from a tendency to become stained or discolored or to undergo a color change when brought in contact with alkaline products such as soap and adhesives.
Alkaline Extraction
Alkaline extraction, i.e. E stage, is used in lignin removal before or between bleaching stages; the stage is often enhanced with an oxidizing agent, oxygen (Eo stage), hydrogen peroxide (Ep stage) or both (Eop stage).
Alkaline Papermaking
Paper manufactured under alkaline conditions, using additives, basic 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.
Alkaline Pulping
Pulping by alkaline solutions of sodium hydroxide, with or without sodium sulfide. Without sodium sulfide it is called soda process and with sodium sulfide it is known as Kraft or sulfate process.
Alkenyl Succinic Anhydride (ASA)
ASA is a sizing agent designed to increase resistance to water penetration in the case of paper formed under neutral or alkaline conditions. ASA is especially used in cases where full cure is desired before the size press and where it is important to maintain a high frictional coefficient in the paper product. ASA can improve paper machine runnability and preserve paper's dimensional stability by limiting penetration of size-press solution into the sheet.
Alpha Cellulose
The portion of the pulp or other cellulosic material that will not dissolve in 17.5% NaOH (Sodium Hydroxide) solution at 20oC.
Alpha Pulp
A specially processed, high alpha cellulose content, chemical pulp. It is also called dissolving pulp.
Alternative Fibers
Common name for non-wood or tree free fibers.
The paper maker alum is hydrated Aluminum Sulfate {Al2(SO4)3}. It is used to adjust the pH of the mill water or as a sizing chemical in combination with rosin size.
Aluminium Foil Lamination
The combination of thin Aluminum foil with a paper backing used as a positive moisture barrier. Normal combination is kraft backing with Aluminum foil laminated to the kraft by means of asphalt, adhesive, or polyethylene. The Aluminum foil can also be coated with polyethylene.
Annual Vegetable Fiber or Agricultural Residue Fiber
A source of fiber for pulp and papermaking, including, for example, wheat or rice straw or other fibrous by-products of agriculture.
Anaerobic Reactor System 
An effluent treatment system that uses microbes in the absence of oxygen to break down effluent constituents into methane, carbon dioxide and hydrogen sulfide.
Anthra Quinone (AQ)
A quinoid compound added to white liquor (alkaline cooking liquor) to improve pulp yield and to increase the rate of delignification.
Anti-foam or Defoamer
Chemical additives used at wet end to reduce or eliminate tendencies of the machine white water to foam.
Anti Rust Paper
Paper containing added substances which give it the property of protecting the surfaces of ferrous metals against rusting.
Antique Finish
A term describing the surface, usually on book and cover papers, that have a natural rough finish.
Means of applying the aqueous coating, sizing or coloring to the paper web.
Apparent Density 
Weight (mass) per unit volume of a sheet of paper obtained by dividing the basis weight by the Caliper (thickness).
Apparent Viscosity
A characteristic of multi-component liquids that have a variable ratio of shear stress over shear rate (variable viscosity depending on conditions).
Approach Flow System
The stock flow system from Fan pump to headbox slice.
Aqueous Coating
A water-based coating applied after printing, either while the paper is still on press ("in line"), or after it's off press. An aqueous coating usually gives a gloss, dull, or matte finish and helps prevent the underlying ink from rubbing off. Unlike a UV coating or a varnish, an aqueous coating will accept ink-jet printing, making it a natural choice for jobs that require printing addresses for mass mailings.
Archival Paper
A paper that is made to last for long time and used for long lasting records.
Art Paper
High quality and rather heavy two-side coated printing paper with smooth surface. The reproduction of fine screen single- and multicolor pictures ("art on paper") requires a paper that has an even, well closed surface and a uniform ink absorption.
Artificial Parchment
Wood free paper that is produced by fine and extended grinding of certain chemical pulps and/or the admixture of special additives. As a result of the "smeary" grinding, the fiber structure closes homogeneously. It is used e.g. for wrapping meat and sausages or as corrugating medium for biscuit packaging
Ash Content
The residue left after complete combustion of paper at high temperature. It is generally expressed as percent of original test sample and represents filler content in the paper.
Aseptic Packaging
Extends the shelf life of non-refrigerated beverages and foods. Laminates and extruded coatings applied by the customer ensure an appropriate liquid barrier. Aseptic grade board is clay-coated on one side and is suitable for gravure, offset, and flexographic printing.
Asphalt Laminated Paper
Two sheets of natural kraft paper laminated in a single ply by means of asphalt. This is used as a moisture barrier; also to resist action of weak acids and alkalis.
Automatic Packaging System
Term applicable to any one of several available systems for open mouth and valve bag packaging where bags are automatically applied to filler spout, filled, weighed, closed (if open mouth), palletized, and shrink wrapped.
The light blue color used in the nomenclature of "laid" and "wove" papers.
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