Glossary of Paper Terms

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z #

Select the first letter of the word from the list above to jump to appropriate section of the glossary. If the term you are looking for starts with a digit or symbol, choose the '#' link.

- A -

ABSORBENCY The extent to which a paper will take up and hold a liquid. 

ACID-FREE PAPER In principle, paper which does not contain any free acid. Special precautions are taken during manufacture to eliminate any active acid that might be present in the furnish.

ADDITIVE A mineral, chemical or dye added to pulp and coatings to give it special qualities such as opacity.

AIR DRIED PAPER Paper dried by exposure to air, generally warm.

AIR-DRY PULP Technically, pulp of which the moisture content is in equilibrium with the ambient atmosphere. Commercially, pulp at a theoretical moisture content agreed between the buyer and the seller (e.g. 10 per cent is common).

AIR-KNIFE COATED PAPER Paper coated by a process where the freshly applied wet coating is smoothed and the excess removed by means of a jet of air discharged from a slit orifice placed at an angle to the web.

AIRMAIL PAPER Paper made in the lightest substance consistent with strength and a good surface, for reasons of postage costs. Generally produced in white, off white or a pale blue for stationery purposes, usually below 40g/m2. Manifolds and lightweight bonds are also often known as airmail papers.

ALUM A term commonly, but incorrectly, applied in the paper industry to various qualities of aluminium sulphate.

ANTIQUE A characteristic low degree of surface finish which typifies certain commercial descriptions of paper such as Antique Wove, Antique Laid etc.

ANTI-RUST PAPER Paper containing added substances which give it the property of protecting the surfaces of ferrous metals against rusting.

ANTI SET-OFF SPRAY A device used on the delivery end of the printing machine to prevent set-off by projecting a fine spray, of liquid or powder, at the sheet.

AOX Adsorbable Organic Halogens. AOX expresses the amount of organic chlorine compounds in effluent produced as the chlorine chemicals react with the residual lignin (q.v.) in the bleaching of pulp. A safe AOX limit is easier to achieve using chlorine dioxide than with chlorine.

APPARENT DENSITY The quotient of the grammage of a paper and its thickness in micrometres.

ART PAPER This is a generic term given to woodfree coated papers, which has traditionally referred to papers in the upper quality bracket and which have a high polished surface. Today the term is less used because of the introduction of more categories in the sector. However, ‘Real Art’ is still used for those woodfree coated papers, gloss or matt, which are considered to be of the very highest quality.

ASH CONTENT The amount of residue when a sample of paper is burned under controlled conditions so that all ignitable matter is removed. The ash derives from the mineral loading in the paper.

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- B -

To print on the reverse side of a printed sheet.

BACKWATER The liquid which passes through the forming surface when stock is deposited upon it. It is essentially water, but generally contains dissolved matter or suspended matter such as fines, filler, etc. Backwater is normally recirculated within the paper making process, or sent to treatment plant for the recovery of materials in suspension.

BAGASSE PULP Pulp obtained by chemical means from bagasse, the residue after extracting the juice from sugar cane.

BAMBOO PULP Pulp obtained by chemical means from the stems of bamboo, a type of grass common to Asiatic countries.

BANKS AND BONDS A range of printing and writing papers, the better qualities of which were at one time made largely from rags. The heavier substance papers, above a substance of about 60g/m2, are often used for correspondence and letterheads, and are known as bonds, while the lighter weights called banks used largely for file copy papers have less use today with the introduction of the automated office.

BARK WASTE A major source of energy for pulp mills. The raw timber is debarked before chipping, the bark being recovered and burnt at a steam power plant.

BASE PAPER Paper intended to be converted, e.g. by a coating process or by impregnation. Term sometimes used also for paper to which a layer of other material (aluminium, plastics, etc.) is bonded. Also called Body Paper or Rawstock.

BEATING OR REFINING The mechanical treatment of fibrous materials in a beater or refiner to modify certain of their characteristics in order to give them the properties necessary for the manufacture of a desired quality of paper.

BIBLE PAPER Very thin printing papers. Originally made specifically for bibles and prayer books, this grade of paper is also used for other commercial purposes, such as dictionaries, where many pages are required with an overall low volume. Bible paper is also known as India paper.

BINDER The adhesive used to stick the layers of coating together and to the paper or board surface. The most frequently used binder is starch, but synthetic binders are also used to give improved performance.

BIODEGRADABLE A substance which will decompose as the result of action by bacteria and other living organisms.

BIOLOGICAL OXYGEN DEMAND (BOD) This expresses the amount of dissolved oxygen consumed by micro-organisms as they decompose organic material in polluted or natural water. The higher the amount of decomposable material, the higher the BOD value.

BIOLOGICAL WASTE WATER TREATMENT A variety of methods are used by pulp and paper mills for purifying their waste water (such as the activated sludge method) in which natural micro-organisms decompose the organic substances. The organisms constitute a nutrient cycle consisting of bacteria, protozoa and higher organisms. The method reduces the biological oxygen demand by over 95% and removes about 50% of the organic compounds from effluent, organic chlorine compounds included.

BLACKENING Defect associated with calendered paper occurring as unintended local areas of apparently darker or greyer colour due, for example, to the paper being too damp when passed through the calender.

BLADE COATED PAPER Paper coated by a process in which the freshly applied wet coating is smoothed and the excess removed by a thin, flexible metal blade which bears on the coated surface.

BLANKET CYLINDER The cylinder on a printing machine covered with a rubber (or similar) blanket, which conveys the image from the plate to the sheet.

BLANKET-TO-BLANKET MACHINE A printing machine in which the blanket cylinders act as opposing impression cylinders, so allowing both sides of the web or sheet to be printed simultaneously.

BLEED The part of a printed image beyond the area to which the finished print will be cut.

BLISTER PACK This term describes a packaging system which is a combination of board and plastics. The product is sealed to the board by a transparent plastics film. This system is often used for small products of difficult shapes and sizes.

BLOTTINGS Highly absorbent papers which can be watermarked, white or in colours. With the advent of the ball-point pen, the original use where hand writing ink is absorbed has greatly reduced demand.

BOARD Heavy weight paper. The line of demarcation between paper and board is indeterminate. For many purposes it is taken as 220 or 225g/m2 but many products below these levels are described, commercially, as board.

BOD7 The biological oxygen demand (q.v) of a waste water sample, measured over seven days’ exposure (c.f. BOD5,BOD10).

BOND See Banks and Bonds

BREAKING LENGTH The calculated limiting length of a strip of paper of any uniform width, beyond which, if such a strip were suspended by one end, it would break by its own mass.

BROKE Paper and pieces of paper arising at any point in the mill which are suitable only for repulping, e.g. wet paper removed from the paper machine or dry paper arising as trimmings etc., faulty paper etc.

BRUSH COATING A method of coating a web of paper in which the applied coating slip is distributed and smoothed by means of brushes, some stationary and some oscillating across the web.

BULK PACKED ON PALLETS BPOP A method of packing paper in which the sheets are not wrapped in parcels but stacked on the pallet, tabbed at the required intervals to indicate quantity and over-wrapped.

BULKY MECHANICAL A mechanical paper made to a specific caliper as opposed to a fixed grammage. Typical calipers are 102 and 127 microns. This type of paper, used mainly for mass market paperback books, also has several uses when converted, such as cash register rolls.

BULKY PAPER Paper which appears to be thick in relation to its grammage.

BURST FACTOR The quotient of the bursting strength of a paper and its oven-dry grammage as defined in the standard method of test.

BURST INDEX The quotient of the bursting strength of a paper and its grammage in the conditioned state as defined in the standard method of test.

BURSTING STRENGTH The pressure necessary to rupture a sample of paper fixed horizontally between two ring clamps.

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- C -

CALENDERED Paper which has been smoothed and polished between sets of rollers called a calender; this process is usually done at the dry end of a paper making machine.

CALIPER See thickness.

CARBON PAPER A thin tissue paper coated on one side with colouring agent or carbon black which is transferred to a sheet of paper underneath when pressure in applied.

CARBONLESS COPY PAPER This consists of two sheets of paper; the underside of the top sheet is coated with colourless dye in minute gelatine capsules; the underneath sheet is coated with a reactive chemical which turns blue or black when mixed with the colourless dye; pressure from a pen or typewriter on the top sheet causes the gelatine capsules to break, the dye and chemical mix and the blue or black copy appears on the bottom sheet.

CARTON A container usually made of relatively thin carton or folding board, but sometimes partially or totally of plastic; it is delivered by the carton manufacturer to the user in either flat or collapsed form.

CARTRIDGE PAPER Slightly rough coated or uncoated printing surfaced paper used for a variety of graphic purposes such as envelopes. The name comes from the original use for the paper which was for forming the tube section of a shotgun shell.

CASES, CORRUGATED Large boxes made of board which are used as containers for packages; cases are mainly used for transit and storage purposes.

CAST COATED A method of drying coated paper by contact of the freshly coated surface with a highly polished chromium plated heated metal surface.

CELLULOSE WADDING A cręped web or sheet of open formation made of cellulose fibres and comprising one or more plies of light-weight paper.

CHAIN LINES Spaced lines at right angles to laid lines occurring as a watermark in paper.

CHAIN WELTS (CHAIN MARKS, ROPEMARKS) Defect in reels due to variations in thickness across the width, resulting in the slack areas assuming a chain-like pattern around the periphery.

CHALKING The ready removal, in the form of a powder, of an insufficiently bound layer of pigment on the paper surface resulting from the absorption into the paper of too high a proportion of the vehicle of an ink.

CHEMICAL OXYGEN DEMAND (COD) This measures the oxygen demand caused by all impurities in the water when oxidising a sample with a strong oxidant. (c.f. BOD).


CHINA CLAY Natural mineral, consisting essentially of hydrated silicate of alumina, used as a filler or as a component in a coating slip.

CHIP BOARD A cheap board grade usually manufactured from the lower grades of wastepaper.

CHROMO A term used to describe both papers and boards used for subsequent brush coating. The various qualities are determined both by the actual grade of base material used and the quality of the coating, which may be gummed. Coating may be applied to one or both sides, depending on end use.

COATED PAPER OR BOARD Material coated on one or both sides with a mixture of china clay, latex and other loadings to fill up surface pits and improve the printing surface. The process can be accomplished either on-line on the paper making machine or away from the paper making machine as a separate operation. There are a variety of coating methods, these include: roll coating, blade coating, air-knife coating and brush coating, or combinations of these types. A very high quality form of off-machine coating is cast coating.

COATING (MINERAL) A layer of minerals applied to one or both sides of paper or board to improve brightness, gloss and printability; the mineral most often used is china clay, hydrated aluminium silicate, but calcium carbonate and titanium dioxide are also used; the coating is held together and stuck to the paper by a binder.

COCKLE Local deformation of a sheet of paper due to unequal shrinkage giving it a slightly crumpled appearance.

COD See Chemical Oxygen Demand

COLLOTYPE A planographic printing process capable of producing high fidelity continuous tone colour reproductions, i.e. no screen is used in producing the negatives from which the plates are prepared.

CONDITIONED PAPER Paper which has been treated in the mill by exposure to hot, moist air to increase the moisture content of the paper to what is considered to be an optimum level for flatness and stability.

CONTAINER BOARDS These boards are made to provide a variety of product containers and are made from waste materials. They may, however, be lined with bleached or unbleached kraft, or other papers, depending on end use. Some of these boards may also be treated with plastics to provide special characteristics.

CONTINUOUS STATIONERY A grade widely used on modern high-speed accounting and similar machines. The paper is supplied in reel form and along with the printing process many finishing techniques can also be used, such as perforation and special folds. A particular use is for invoices, statements and similar documents, when it is normally fan-folded.

CONTINUOUS TONE An image in which tonal gradation is produced by changes in density.

CONTRARIES Unsuitable material found in wastepaper which must be removed from the pulp before making it into paper, e.g. paperclips, string, plastics.

CONVERTER A firm that specialises in converting reels and sheets of paper and board into packaging or finished goods for sale to the public.

COOKING Treatment of fibrous raw material by heat in the presence of water, usually with added chemicals.

COPIER PAPER Lightweight grade of good quality, used for copying correspondence and documents. May be glazed or unglazed. Most copier papers are laser compatible and special grades are made for colour copying.

CORRUGATED FIBREBOARD Board consisting of one or more sheets of fluted paper stuck to a flat sheet of paper or between several sheets. The following are the main classifications:

(a) Single face corrugated fibreboard. Board consisting of one sheet of fluted paper stuck to one sheet of facing.

(b) Single wall corrugated fibreboard (also known as double faced). Board consisting of one sheet of fluted paper interposed between and stuck to two facings.

(c) Double wall corrugated fibreboard (also known as double-double faced). Board consisting of two sheets of fluted paper interposed between and stuck to three facings.

(d) Triple wall corrugated fibreboard. Board consisting of three sheets of fluted paper interposed between and stuck to four facings.


COUCH That section of the wet end of the paper or board machine at which the wet web leaves the vat machine cylinder or Fourdrinier wire part or other forming surface.

CRĘPING Operation of crinkling paper from a roll or cylinder in order to increase its stretch and softness. This process may be carried out on or off the paper making machine. Two types are recognised:

Dry cręping An on-machine operation carried out on a dried web.

Wet cręping On or off-machine operation carried out on a wet or partially dried web.

CROSS DIRECTION The direction in the plane of the sheet, at right angles to the machine direction (q.v), in a sheet or web of paper; the set expansion coefficient of paper is about three times as much in the cross section as in the machine direction.

CTMP See Thermo Mechanical Pulp.

CUTTING AHEAD Operation of slitting and cutting watermarked paper without regard to where the design falls in each sheet. The design(s) may fall in different places in successive sheets and some may be cut.

CUTTING TO REGISTER Operation of slitting and cutting watermarked paper so that the design falls approximately in a given position in each sheet.

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- D -

DAMPING The process of applying water to the lithographic plate on a litho printing machine. Also the application of moisture to paper in preparation for a subsequent process, e.g. supercalendering.

DAMPING ROLLER The roller on a printing machine which applies the moisture directly to the printing plate.

DANDY ROLL The roll on the wet end of a paper making machine which is covered with a woven wire and carries a design to form a watermark in wet pulp.

DECKLE See Machine Deckle

DECKLE FILL See Machine Fill

DE-INKING The removal of printing ink and mechanical impurities by flotation and/or washing pulped wastepaper before it is recycled.

DIMENSIONAL STABILITY Ability of a paper to retain its dimensions and its shape (a) despite changes in its moisture content under the influence of, for example, variations of the surrounding atmosphere, or (b) despite variations of the physical and mechanical stresses during printing and converting operations or use.

DISSOLVING PULP Highly purified chemical pulp intended primarily for conversion into chemical derivatives of cellulose.

DOCTOR A blade-like device which rests on the uprunning surface of a roll in order to keep it clean by removing any foreign matter adhering to the roll.

DOUBLING The appearance on the printed sheet, locally, of two non-coincidental images obtained at one impression.

DRIERS Substances, generally metallic compounds, added to an ink to increase the rate of drying by catalytic action.

DRY END The part of a paper making machine where the paper passes through steam-heated drying cylinders.

DRY OFFSET A method of printing, as in the offset lithographic method, but from a relief plate, and without the use of fountain solution.

DUCT The trough on a printing machine, usually including an adjustable blade, which contains the supply of ink and by means of which the ink is presented to the duct roller.

DUCT ROLLER The cylinder in the duct of a printing machine which, in conjunction with the adjustable knife blade, regulates the amount of ink applied to the feed roller.

DUMMY An unprinted representation of the text pages of a book made by suitably folding and collating sheets of the intended quality and grammage of paper so that an idea may be formed of the general appearance and thickness of the ultimate book.

DUPLEX CUTTING The operation of converting a web of paper into sheets on a cutting machine equipped with two cross-cut knives so that two different lengths of sheet can be cut simultaneously.

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- E -

ECF (ELEMENTAL CHLORINE FREE) A common definition for pulp bleached without using elemental chlorine. Originally any of the bleaching techniques for chemical pulp, when no molecular (elemental) chlorine is used.

EDGE CUTTERS Device comprising two jets of water which are adjustable across the making machine and which divide the wet web on the wire lengthwise so that the edges may be removed, generally at the couch. In this way they control the width of the web going forward from the wire part and give it comparatively clean edges.

EMBOSSED PAPER Paper on which a raised and/or depressed design has been produced by pressure, generally from an engraved or otherwise patterned roll or plate.

EMULSIFICATION Dispersion of water into the ink during printing. An excess of this may cause printing difficulties.

EMULSION COATED PAPER Paper coated by any suitable coating process with plastics or resins applied in the form of an emulsion.

ENGINE SIZING Sometimes known as internal sizing. The addition to the paper making stock of chemicals which ultimately confer on the paper the property of resisting penetration by aqueous liquids, e.g. writing ink.

EQUILIBRIUM MOISTURE CONTENT The moisture content of a paper that has reached a balance with the atmosphere surrounding it, i.e. in a condition in which it will neither give up nor absorb moisture.

ESPARTO GRASS A grass naturally occurring in North Africa which, when pulped, produces a bulky fibre for making good quality paper; it was once a popular paper making fibre.

EXTRUSION COATING A method of coating a web of paper with resins, plastics or similar hot-melt compounds. The coating is applied through an extruder die positioned immediately above the nip between a supporting roll and a chill roll.

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- F -

FEED BOARD The surface on a printing machine over which the stock is conveyed to the lays.

FELT MARK Imprint left on the paper by one or more of the felts used in making the paper. The mark may be wanted or unwanted and special effects can be introduced in this way.

FIBRILLATION Freeing of the fibrils by partial rupture of the fibres when submitted to an appropriate treatment, e.g. beating or refining.

FILLER A material such as china clay or calcium carbonate which is added to make paper smoother and increase opacity.

FILLING IN The addition of components of the furnish of a paper to pulping or slushing equipment in a paper mill. The spreading of the printed image on a sheet to the point where the small unprinted spaces are obliterated.

FINES Small fragments of fibres produced, for example, in the course of beating or refining.

FINISH The surface characteristics imparted to paper by mechanical means.

FLAME-RESISTANT PAPER Paper which has been given a treatment designed to give it a certain degree of non-flammability and/or of incombustibility.

FLOW BOX A container for stock situated immediately before the forming part of a paper or board making machine, capable of supplying stock in the required volume and with the required distribution characteristics to the forming surface. Also known as the breast box or head box.


FLUORESCENT DYE A dyestuff which is capable of converting u/v light into the visible spectrum and improving the brightness of the paper in which it is incorporated. Sometimes known as optical bleaching agent (OBA).

FOILS Static bar-like devices situated below the forming wire of a paper making machine to assist drainage of water from the stock.

FOLDING BOXBOARD Although boxboards can vary in quality from grey board (q.v) to high-class board made from virgin fibre, the term is usually taken to mean white lined boards. They are made on multi-layer machines, and the outer layers may be of a different furnish to the centre layer.

FORMATION The manner in which the fibres are disposed in the sheet as determined by the look-through.

FOUNTAIN ROLLER The roller on a printing machine which initiates the supply of moisture to the damping system.

FOUNTAIN SOLUTION Water, with additives, for application to the lithographic plate on a printing machine.

FOURDRINIER MACHINE A paper making machine that forms the paper in a continuous sheet; it was named after the Fourdrinier brothers who financed the first operational machine at the Frogmore Mill, Hertfordshire, in 1803.

FREE STOCK Stock that, when drained under gravity, parts easily with the water of suspension.

FREENESS VALUE A measure of the drainability of an aqueous suspension of stock, determined and expressed as specified in a standard method of test.

FURNISH The ingredients or constituents of which the paper is made. Fibrous furnish concerns only the types and proportions of the fibres present. Total furnish includes loading etc.

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- G -


(a) An image which appears as a lighter area on a subsequent print, due to local blanket depressions from previous image areas.

(b) Marring of a print by an image on it of work on the reverse side which has interfered with its drying, so that differences in the trapping of some colours or gloss variations are apparent.

GLOSS Gloss can refer to the reflectivity of paper itself or of the printed result on it. Gloss of paper is measured by using a Gardner gloss meter, which measures reflected light at an angle of 75°, and is expressed in Gardner gloss units - the higher the number, the glossier the paper surface.

GRAIN DIRECTION A term applied to the machine direction of papers or boards, as opposed to the cross direction.

GRAMMAGE The term used to denote the weight of paper or board; the measurement used is the weight of a single sheet of one square metre, expressed as grammes per square metre (g/m2).

GREASEPROOF PAPER Paper which resists grease, or prevents the fats found in some goods from soaking into it; the paper is produced by prolonged beating in the pulp stage.

GREEN PAPER Immature paper which has not been conditioned or had the opportunity to mature naturally.

GRIPPER A device on a printing machine for holding the sheet during the printing or similar cycle.

GRIPPER ALLOWANCE The margin of paper along the gripper edge of the sheet held by the grippers and which therefore cannot be printed.

GRIPPER EDGE The edge of the sheet presented to the gripper. The edge of the plate which is fitted to the leading clamp of the cylinder.

GROUNDWOOD PULP Mechanical pulp made by grinding wood against an abrasive surface, e.g. a stone.

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HALF-TONE The representation of tonal gradation by an image composed of dots of varied sizes, the centres of which are equidistant.

HALF-TONE SCREEN A grid in which the lines and spaces are of equal thickness and equidistant used in photographing an original for plate or block making.

HARDWOOD PULP Pulp obtained from the wood of hardwood trees by various processes. The fibres are generally shorter than those of softwood pulp.

HEAD BOX See FLOW BOX An elevated tank or container equipped with an overflow device which, when supplied with excess of a liquid or fluid, can deliver same at a constant hydraulic head to a lower point.

HEAT-SET INK A printing ink produced to dry by the application of heat after printing.

HOT MELT COATING A method of coating with a 100 per cent solids compound of wax, resin of polymer, or mixtures thereof, heated to a fluid state and applied to the substrate by, for example, a roll, gravure or extrusion process with a subsequent chilling device.

HYDROGEN PEROXIDE BLEACHING A method in which pulp is bleached in an alkaline environment with hydrogen peroxide, sometimes using oxygen reinforcement. The method considerably reduces the need for chlorine-containing chemicals in the final bleaching of chemical pulps.

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IMPRESSION CYLINDER That cylinder of a printing machine which supports one surface of the sheet or web while the other surface receives its printed image from a co-operating blanket cylinder.

INK RUB A defect, often associated with matt coated papers, in which parts of a dried ink film are removed by pressure or friction from another surface.

INTEGRATED MILL A mill which starts with logs or wood chips and first produces wood pulp which it then processes to make paper or board; there are only five integrated mills in Britain.

INTERMITTENT BOARD MACHINE A machine for producing sheets of thick board by winding the web formed on a Fourdrinier wire or cylinder mould(s) around a making roll to form a sheet consisting of several layers. When the thickness is sufficient the layers are cut, so forming a sheet which is removed from the machine for drying and any further processing.

INTERNAL SIZING The addition of materials to the stock, generally in order to increase the resistance of the finished paper to the penetration and spreading of aqueous liquids, e.g. writing ink. Frequently described as engine sizing.

IVORY BOARD High-quality board made in white or colours with a bright, clear appearance, particularly used for visiting cards and similar high-class printed work. Original Ivory Board was and still is made in Holland, although the grade is made in many countries.

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- K -

KRAFT PAPER Paper made from a type of chemical wood pulp; it may be bleached or unbleached and produces a strong paper which is used for wrapping and packaging; the term comes from the German word for strong.

KRAFT PULP Chemical wood pulp produced by digesting the wood by the sulphate process. Originally a strong, unbleached coniferous pulp for packaging papers. Kraft pulp has now spread into the realms of bleached pulps from both coniferous and deciduous woods for printing papers.

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LABEL PAPERS A large variety of plain or coloured body papers which are made to be gummed, or for application of a self-adhesive material, and subsequently cut into a vast number of shapes and sizes depending on end use and surface application.

LAID LINES A continuous watermark consisting of very close parallel lines, generally associated with spaced lines (chain lines) at right angles to these.

LAMINATE Overlay of sheets of paper or board either with other paper or board or with other materials such as plastic or metal foil to form a product with special qualities.

LICK COATING A light form of mineral coating, achieved by supplying the surface sizing press of the paper making machine with coating material instead of normal surface sizing solution.

LIGNIN A substance in wood which binds its fibres together and reinforces its structure. Lignin is removed in the manufacture of chemical pulp.

LITHOGRAPHIC PRINTING A planographic printing process in which the non-image areas of the printing plate are made hydrophillic and the image areas are made hydrophobic.

LOADING White, inert mineral matter such as China Clay, Calcium Carbonate, Titanium Dioxide etc. added to the papermaking stock to confer opacity on the finished paper. Loading may also beneficially affect flatness and dimensional stability.

LONG GRAIN See Short Grain

LOOK-THROUGH The appearance of the paper when held up to transmitted light. It discloses whether the formation is even and uniform or lumpy and ‘wild’. For book publishing papers, a regular, even look through is desirable, indicating a well made, uniform sheet.

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MACHINE CLOTHING Fabrics of various types employed on the paper machine to carry the web and perform other functions. It includes the machine wire and wet and dry felts which may be composed of natural or synthetic materials.


MACHINE DECKLE The overall width of the wet web as it leaves the forming zone of the paper making machine. Note: Often used incorrectly to indicate the width of the web at the dry end of the machine.

MACHINE DIRECTION The direction the wire mesh on a paper making machine is travelling; over 50% of the fibres position themselves with their lengths parallel to this direction.

MACHINE FILL OR DECKLE FILL The width of the paper making machine taken up by a making of paper. For reasons of economy it should approach so far as possible the maximum trimmed width of the machine.

MACHINE FINISHED PAPER (MF) Paper which has been made reasonably smooth by means of calender stacks at the end of the paper making machine.

MACHINE-GLAZED PAPER (MG) Paper which has had one side made smooth and glossy by drying in contact with a large, heated, polished metal cylinder which forms part of the drying section of the machine. The other side of the paper remains relatively rough.

MACHINE WIRE The fabric used for converting the dilute stock into a formed sheet by permitting drainage of water and retention of the other elements of the stock. It may consist of a woven wire cloth or a plastics or similar fabric which contains a suitable pattern of perforations.

MANIFOLD See Airmail Paper

MAXIMUM TRIMMED WIDTH The greatest width of usable paper it is possible to make on a given paper making machine, i.e. the full width less the necessary trim to give clean edges. It is not possible to specify sizes which, in aggregate, exceed this width.

MECHANICAL PAPER Paper, the furnish of which contains a substantial proportion of mechanical wood pulp.

MECHANICAL PRINTINGS Printing papers made chiefly from pulp produced by the groundwood method. By this method of pulp production the wood is mechanically ground with water to separate the fibres and produce pulp. This grade may be coated on or off the machine, machine or supercalendered.

MECHANICAL WOODPULP (GROUNDWOOD) Pulp produced from wood solely by mechanical means such as grinding or refining.

MICRO-CRĘPING A process for compacting the paper web in the machine direction and imparting a high degree of stretchability by passing the web between a roll and, for example, an endless rubber blanket. The blanket is extended immediately before the point of contact with the web and allowed to return to its normal state during the passage of the web through the space between the roll and the rubber blanket. A typical example of micro-cręping is the Clupak process.

MICR PAPER (Magnetic Ink Character Recognition Paper) Usually a high-quality bond paper with good surface characteristics and dimensional stability for printing with magnetic inks for computer sorting.

MIDDLE (OF BOARD) Furnish layer of a board situated between the two external furnish layers, or between the underliners, or between an underliner and an external furnish layer.

MILLBOARD A thick, dense, homogeneous board, for book production, made generally from wastepaper, on a special board making machine one sheet at a time. Used in binding case bound books, ledgers etc. as binders’ boards.

MIS-REGISTER The appearance of a printed image out of its correct position.

MOULD MADE Originally, paper made by hand by the traditional method of paper moulds, usually from rag pulp. Today, mould made papers are high quality grades made on a cylinder mould machine, as opposed to a Fourdrinier or other type of machine, and may be made with or without deckle edges.

MULTIPLY BOARD MACHINE A machine in which a number of plies of paper can be combined together in the wet state to produce thick cardboard.

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NBHK Northern Bleached Hardwood Kraft. An important variety of market pulp, produced chiefly from birch trees, it is brighter than NBSK but not as strong.

NBSK Northern Bleached Softwood Kraft. One of the chief varieties of market pulp, produced mainly from spruce trees from Scandinavia, Canada and north-eastern USA. It consists of longer (hence stronger) fibres than NBHK.

NCR No Carbon Required. This expression, which was introduced by the National Cash Register company (which formerly owned the patents), has now been superseded by the term Carbonless (q.v.).

NEWSPRINT The relatively low grade paper intended for the printing of newspapers; it is mainly produced from mechanical softwood pulp and recycled fibres.

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OCR PAPER (Optical Character Recognition Paper) Similar to MICR Paper (q.v.), a high-quality bond paper of good surface and dimensional stability for printing with characters for computer recognition.

OFF-MACHINE COATED PAPER Base paper to which a mineral coating has been applied on a coating machine separate from the paper making machine.

OFFSET BLANKET A covering for a cylinder on a printing machine for accepting the ink image and then transferring it to the surface to be printed.


OFFSET PRINTING A method of printing in which the image on the plate is transferred to the final substrate via an intermediate surface.

OFFSIDE LAY The sidelay opposite to the operating side of a printing machine.

ON-MACHINE COATED PAPER Paper which has been coated with mineral matter by coating equipment installed as an integral part of the paper making machine.

ON-MACHINE COATING The process of covering the surface(s) of a paper with one or more layers of coating slip or other materials in fluid form, without recourse to a separate operation, the necessary equipment being an integral part of the making machine.

OPACITY The extent to which a paper is capable of obscuring matter printed on the verso or on an underlying page or other surface.


OUT TURN SHEET A sheet of paper, taken during manufacture, serving as a reference for the mill or client.

OXYGEN BLEACHING A method of reducing the lignin content of pulp by introducing oxygen in an alkaline environment, thereby reducing the need for other chemicals in final bleaching.

OZONE BLEACHING A method in which the lignin content of pulp is reduced by means of ozone, a triatomic form of the element oxygen. Used in combination with oxygen and hydrogen peroxide, it can with present-day technology produce almost white pulp without any chlorine chemicals. A toxic gas, it has to be removed from the exhaust gases.

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PACKAGING The paper and board used for wrapping or packing goods.

PAPYRUS An ancient writing material made from the stem of the papyrus plant, an African reed. Although the word ‘paper’ is derived from papyrus, papyrus is not paper.

PARCHMENT A sheet of writing material made from animal skin, nowadays usually used to denote Vegetable Parchment (q.v), or parchmentised papers. These have a high resistance to the penetration of grease and atmospheric humidity. Used largely for wrapping purposes, there are also grades of imitation parchments which are less impervious. Similar to greaseproof paper (q.v.). See also Vellum Paper.

PASTEBOARD This grade of board consists of one or more layers, usually of pulp board, pasted together. It may be lined both sides with paper of one type or another, depending on end use.

PERFECTING Printing both sides of the substrate at the same pass through a printing machine.

PERMANENT PAPER Paper free from mechanical woodpulp or unbleached fibre, generally neutral/alkaline sized and containing calcium carbonate filler, made to controlled pH value and alkali reserve, intended for the printing of books and similar works for posterity.

PERNICIOUS CONTRARIES Any material present in waste paper that is difficult to see or detect and which might be detrimental to the paper being manufactured from the wastepaper or which might either damage paper making equipment or render repulping difficult.

PHLOROGLUCINOL SOLUTION An acidic spot test reagent for paper that produces a red coloration in contact with lignified fibre.

PHOTOSETTING The process of composing text matter directly onto a photographic or other light sensitive material.

pH VALUE A number on a logarithmic scale extending from 0.3 to 14.5 which indicates the active acidity or alkalinity of an aqueous liquid. Neutrality is represented by pH 7.07, figures descending below this reading indicating increasing amounts of acidity, and those above, alkalinity.

PICKING The rupture of the surface of a paper during manufacture or during printing, which occurs when an external tensile force applied to the surface is greater than the cohesion of the paper.

PIPING Defect in reels, consisting of ridges running around the circumference, due to moisture take-up by the surface layers.

PLASTERBOARD A type of board with a centre layer of gypsum and outer layers of board, used in the building industry.

PLATE CYLINDER The cylinder in a printing unit to which printing plates are fixed.

POSTER PAPER An MG grade with a quick drying surface used for outdoor poster work. The rough underside lends itself to rapid pasting.

PRESSPAHN This is a German word used to describe a grade of board used for a variety of purposes, often industrial. It is of a light weight, extra hard, rolled and friction glazed.

PRESSURE SENSITIVE COATED PAPER Paper coated with a self-adhesive material which in dry form (solvent free) is permanently tacky at room temperature. A bond with the receiving surface may be formed by the application of pressure (e.g. by the finger or hand). A permanent adhesive is characterised by relatively high ultimate adhesion and a removable adhesive by low ultimate adhesion. Until the time of application, the adhesive surface should be covered by a suitable release coated paper.

PROOF A pre-production print, made for the purpose of checking the accuracy of lay-out, type matter, tone and colour reproduction.

PULP Chemical pulp is made from a cellulose raw material (usually wood) by treating it (cooking) with chemicals to separate the cellulose fibres and dissolve the lignin, etc., which binds them together; it can be bleached or unbleached. Mechanical pulp is made from wood by purely mechanical means, i.e. grinding or refining of chips; lignin and other impurities are not removed, and further processing (bleaching) is required if a white sheet is required. Fibre obtained from wood by either of the above methods is called primary, or virgin, fibre. Some pulping processes involve both methods and also include heat treatment.

PULP BOARD Also known as Printers’ Board, this grade is made from a single web of pulp on a paper making machine, and is produced in various substances. Used for index cards and other general products, these boards may be white or coloured.

PULPER Any apparatus intended for slushing pulp or paper.

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RAG PAPER Paper made from stock containing a substantial percentage of rag pulp. The minimum proportion of such pulp required for a paper to be so designated cannot be specified as it varies from country to country.

REAM A unit of measurement for sheets of paper; normally 500.

REEL UP The final process in making paper; after passing through the drying cylinders and, if appropriate, the calender rollers, the newly-made paper is wound onto a jumbo reel: this is the reel up stage.

REFINER A machine, usually equipped with discs or with a cone and plug, intended for the treatment of fibrous materials in an aqueous medium to give them some of the properties needed for the manufacture of pulp or paper with the necessary characteristics.

REGISTER MARKS A set of fine line crosses or other suitable devices added to the original artwork to provide reference points for the subsequent registration of the colours of a set of printed images.

REINFORCED PAPER Any paper that has been strengthened mechanically by the incorporation of other materials such as plastics, threads, cloth or strips of metal.

RELATIVE HUMIDITY Quotient of the amount of moisture in air and the amount that would saturate it at the same temperature and pressure, expressed as a percentage.

RETREE PAPER Paper which has become available as a result of overmaking or side-runs or because it is in some way less than perfect; perhaps non-standard or slightly sub-standard. Although sold without a guarantee the substance and size tolerances would be expected to conform to industry standards. Often referred to as clearance paper.

RICE PAPER Sometimes a material which has the same appearance and purposes as paper is called ‘paper’. Rice paper is an example, since it is not paper, but the sliced and flattened pith of a plant which grows in Taiwan; it is used by Chinese artists as a surface for painting.

ROLL COATING Any method of coating a web of paper in which the coating is applied directly to the paper by transfer from an applicator roll which carries the coating slip upon its surface. The applicator roll may rotate in the same direction as the paper web or in the reverse direction (reverse roll coating).

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SCUM Traces of printing ink which temporarily adhere, during litho printing, to the non-image area of the plate due to its inability to repel ink.

SECURITY PAPER Paper which includes identification features such as metallic strips and watermarks to assist in detecting fraud and to prevent counterfeiting.

SELF-ADHESIVE PAPER Used essentially for labelling purposes, this grade has a self-adhesive coating on one side and a surface suitable for printing on the other. The adhesive is protected by a laminate which enables the sheet to be fed through printers or printing machines, the laminate subsequently being stripped when the label is applied.

SEMI-CHEMICAL PULP Pulp obtained by partial removal from the raw material of those non-cellulosic components that can be removed by a direct chemical treatment, e.g. cooking: to resolve the fibres, some subsequent mechanical treatment is necessary.

SET-OFF The unwanted transfer of printing ink from a print to a facing surface.

SHIVES Coarse fragments of fibrous materials present in pulp or paper, resulting from incomplete resolution during pulping.

SHORT GRAIN The fibres in a web of paper naturally take up an alignment roughly parallel to the direction of travel of the web on the paper making machine; this becomes the grain direction. When cut, the paper’s grain direction may be parallel either to the long edge of the finished sheet (when it is called long grain) or the short edge (short grain). Papers are normally stocked in long grain form, short grain being supplied to special order. The grain direction affects the stiffness in a particular dimension and must be taken into account when planning a job which needs to be folded, as paper usually folds easier with the grain.

SHOW THROUGH The degree to which a printed film is visible through paper due to the low opacity of the paper.

SIDELAY A datum point on a printing machine for positioning correctly the side of the sheet in relation to the printed image.

Mechanism for moving the sheet to this datum point.


(a) A narrow reel removed from a web during processing, the width of which is less than the size ordered, but is large enough to permit its use for purposes other than re-pulping.

(b) An additional part of an order placed in order to better utilise the maximum trimmed machine width of the making machine.

SIZING This process can either be applied on the surface of the sheet or in the sheet: in the first case starch is applied to the surface to increase its strength and to resist the penetration of oil-based inks (this process is carried out at the size press, which is about two-thirds of the way down the dry end); in the second case chemicals are added to the stock at the pulping stage before the sheet is formed: this is called internal or engine sizing and its purpose is to stop penetration of water-based inks into the sheet.

SLITTING Dividing a web of paper in the lengthwise direction into two or more narrower webs.

SMOOTHNESS The surface smoothness of paper is measured by the Bendtsen smoothness test. The test measures the amount of air escaping between an annular ring and the material surface, and results are measured in ml/min. Papers having a value higher than 50 are usually referred to as Matt, below 50 as Silk (sometimes called Satin or Velvet).

SOFT CALENDERING A relatively new method of smoothing paper. Soft calenders are more compact than other calenders and adopt a system whereby the web is passed between steel and hard rubber rolls. The method permits a wide variety of finishes between gloss and matt and the retention of bulk.

SOFTWOOD PULP Pulp obtained from the wood of coniferous trees by various processes.

SOLID BOARD A board comprising a single furnish layer.

SOLID FIBREBOARD A board, which may be pasted or unpasted, and often incorporating a lining of Kraft or other strong furnish, intended and suitable for the manufacture of fibreboard packing cases and drums.

SOLVENT-COATED PAPER Paper coated by any suitable coating process with resins or plastics dissolved in volatile solvents which are subsequently evaporated.

SPLICE Joint in a web of paper in or approximately in the cross direction, made either by an adhesive or an adhesive strip,

(a) to obtain a reel of the desired length or

(b) to permit, for example in a converting machine, a continuous operation between the end of one reel and the beginning of the next.

SPREAD COATING A method of coating a web of paper by means of a vertical plate restraining a pond of viscous coating material, for example resins, plastics or adhesives, which is drawn through an adjustable gap between the plate and the paper by the forward movement of the web over a horizontal support.

STACK A type of calender, generally situated at the end of the making machine, of which the rolls are of metal only.

STOCK The wet pulp before it is fed onto a paper making machine, or during the paper making processes before it becomes a sheet of paper; contains around 99% water and 1% fibre.

STOCK PREPARATION Collective term for all treatment necessary for the preparation of the stock before it reaches the making machine.

STRAW PULP Paper making pulp obtained from cereal straws by various processes.

STRIKE THROUGH The effect seen on the verso of the sheet due to excess penetration of printing ink or vehicle into or through the paper.

SUBSTANCE The weight of paper or board, shown by scales, taken from a sample. The weight is nowadays almost entirely defined by grammage per square metre of a single sheet (g/m2).

SULPHATE PULP Pulp obtained by cooking the raw material with a mixture consisting of caustic soda, sodium sulphide and possible other compounds, such as black liquor.

SULPHITE PULP Pulp obtained by cooking the raw material with a bisulphite liquor.

SUPERCALENDERED FINISH (SC) A surface finish on paper which may vary from relatively dull but smooth to highly glazed, produced by passing dampened paper through a supercalender stack. This is broadly similar to a machine calender stack except that it is separate from the paper making machine and some of the rolls are of compressed fibre.

SWORD HYGROSCOPE Portable testing instrument designed for insertion into a stack of paper to assess whether the moisture content of the paper is in equilibrium with that of the surrounding atmosphere.

SYNTHETIC PAPER Paper produced by conventional means from furnishes comprising substantially or wholly synthetic fibres.

Sheet material, resembling paper, made from synthetic filaments by other means, e.g. spin bonding. Plastics material in sheet form, surface treated to render it suitable for commercial graphic printing.

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TACK That property, governed by viscosity and adhesion, which renders a film of printing ink sticky to the touch.

TCF (Totally Chlorine Free) Pulp bleached without any chlorine chemicals whatsoever.

TENSILE STRENGTH The maximum tensile force that a test piece of the paper will stand before it breaks under the conditions defined in the standard method of test.

THERMO MECHANICAL PULP Mechanical pulp in which the wood chips are heat treated before refining (commonly referred to as TMP). In some modern plants a degree of chemical treatment is employed as well (chemi-thermo mechanical pulp or CTMP).

THICKNESS The distance between one surface of a paper and the other. Also known as caliper. It is measured in micrometres.

TICKET BOARD Another name for pasteboard, although coated board can be included in this grade, which is used for tickets, showcards or similar purposes. May be white or tinted.

TISSUE PAPER Soft, lightweight paper, often creped, generally between 17 and 30g/m2 in weight which is used for hygienic, household and several other purposes.

TUB-SIZING The operation of surface sizing paper by passing it through a bath of a suitable solution such as gelatine.

TWIN-WIRE Paper or board made on a paper making machine with a duplicated wire part. In this way two sheets are formed and combined wireside to wireside so that the finished sheet has two identical printing surfaces.

TWO-SIDEDNESS An unintended difference of varying degree in surface texture or shade between the two faces of a paper or board, which is inherent in the method of manufacture.

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UNION PAPER Paper produced by combining together two webs or sheets of paper with bitumen, tar, or similar moisture/moisture vapour resistant materials.

URBAN FOREST A description of towns and cities which are the source of wastepaper as one of the raw materials used for paper making.

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VAT MACHINE A paper or board making machine comprising one open ended cylinder, or more than one open ended cylinder in series, covered with fine mesh wire, which revolves in a vat of stock. Water draining through the wire leaves a mat of fibres on its surface and the ultimate thickness of the product may be determined by the number of cylinders used. The resultant web is removed from the last cylinder and then passed through conventional pressing and drying sections.

VEGETABLE PARCHMENT Waterleaf paper that has been modified by the action of sulphuric acid. This treatment gives it a continuous texture, increased surface hardness and a high degree of resistance to penetration by organic liquids, generally and particularly fats, oils and greases. The structure also confers on the paper resistance to disintegration by water, even at boiling point.

VELLUM PAPER Vellum paper - strong, tough and of high class appearance - is made to imitate the fine smooth finish of a parchment made from animal skin. Vellum paper is often used for certificates.

VIRGIN FIBRE Paper or board pulp fibre being used for the first time (as opposed to recycled fibre). See also Pulp.

VOLUME BASIS An expression used principally in the context of papers for book printing to denote the theoretical thickness in mm of 100 sheets (200pp) of the given paper in 100g/m2. It thus gives an indication of the bulk of the paper.

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WATERMARK A deliberate design or pattern in paper made by a dandy roll as the stock passes through the wet end processes; a watermark can be seen by holding the paper up to the light.

WET END The first stages of a paper making machine before the drying process; at the wet end, stock is fed in and much of the high percentage of water is eliminated by drainage, suction and press rollers, leaving a web of paper which then passes to the drying cylinders.

WET-ON-WET The superimposing of successive colours while the printed colour is still wet, in one pass through the printing machine.

WET STRENGTHENED PAPER Paper so treated as to decrease its loss in strength upon wetting.

WET STRENGTH RETENTION The ratio, expressed as a percentage, of the value of a given strength property of a paper in the wet state to that of the same paper in the dry state, measured according to the standard method of test.

WIRE SIDE The face of a web or sheet of paper which was in contact with the forming wire during manufacture.

WOOD FREE Paper made wholly from chemical pulp and free from wood-based impurities, such as lignin, which are present in mechanical pulp.

WORK AND TUMBLE Printing one side of the sheet, then turning the sheet over, retaining the same sidelay edges but reversing the front and back edges, and using the same printing plate.

WORK AND TURN Printing on one side of the sheet, then turning the sheet over, retaining the same front and sidelay edges of the sheet and the same printing plate.

WOVE PAPER Paper first made as early as 1754 by forming it on a mould with a cover made from woven wire cloth, hence ‘wove paper’; the paper has no watermark and an even opacity; it is a type of paper in common use today.

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