PAPER GLOSSARY

A

Absorbency
The ability of paper to absorb fluids such as water or printing ink
Acidification
Decrease in the pH of soil and water due to precipitation containing dissolved ammonium compounds, sulphur and nitrogen oxides; an indirect cause of forest damage
Activated sludge treatment
A biological method of cleaning up waste waters in three stages. Stage I involves (anaerobic) equilibration. In stage II activated sludge containing micro-organisms is led into an aeration basin to speed up oxidation of organic matter and ammonia. In stage III the sludge is allowed to settle and the treated waste water is run off. Some sludge is removed and a portion is returned to the aeration basin
Aerated lagoon
A biological waste water treatment method in which air (oxygen) fed into an aeration basin reduces the effluent load
Air drying
Method of drying the paper web on the paper machine by blowing air along the direction of the web
Air mail paper
Light weight, thin and mainly woodfree writing papers for air mail. Anaerobic treatment Process employing micro-organisms to reduce organic matter in waste water in the absence of oxygen
AOX
Absorbable organic halogens. AOX is a sum parameter measuring total concentration of chlorine bound to organic compounds in waste water. AOX measures all chlorine compounds both harmful and harmless (a sum parameter)
Art paper
High quality and rather heavy two-side coated printing paper with smooth surface. The reproduction of fine screen single- and multicolour pictures ("art on paper") requires a paper that has an even, well closed surface and a uniform ink absorption
Artificial parchment
Woodfree 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 fibre structure closes homogeneously. It is used e.g. for wrapping meat and sausages or as corrugating medium for biscuit packaging
Auxiliary chemical
A chemical added to a stage of paper-making aimed at improving the efficiency of a part of the process.

B

Back-pressure power
Generation of both heat and electricity from fuel; gives greater efficiency than condensing power
Bale
Solid, compressed stack of pulp or paper sheets
Banknote paper
Highly resistant, age-resistant, suitable for 4-colour printing, with watermark and other falsification safeguards such as embedded metal strip. Often containing cotton fibres (See "Rag paper")
Basis weight
See Grammage
Bast
Fibres located in the inner bark layer of trees and in outer portions of other fibrous, woody plants.
Beatability
The ease with which pulp can be beaten to achieve the desired properties
Beating
Mechanical treatment of fibres to improve fibre bonding
Bible paper
Woodfree, sometimes rag-containing speciality printing paper with a low grammage, mostly with a high filler content
Biodegradation
Breakdown of organic matter by micro-organisms into carbon dioxide and water or into less harmful compounds
Biological waste water treatment
A method of cleaning up waste water using living micro-organisms such as bacteria. See: Activated sludge treatment, Aerated lagoon, Anaerobic process
Biosludge
Sludge formed (in the aeration basin) during biological waste water treatment or other biological treatment process
Black liquor
Mixture of cooking chemicals and dissolved wood material remaining after sulphate cooking; recovered during pulp washing, concentrated by evaporation and burned in the recovery boiler to regenerate the cooking chemicals and generate energy
Bleach plant
Department of a pulp mill where pulp is bleached
Bleached lined folding boxboard
Bleached lined folding boxboard is a multi-layer paperboard that has a bleached woodfree liner on one or both sides. Between two liners there are intermediate layers and middle layers of mechanical or waste paper pulp
Bleached pulp
Pulp whose natural brightness has been improved using chemicals
Bleaching
Removal or modification of coloured components in pulp to improve brightness. Bleaching is normally carried out in several consecutive stages
Blotting paper
Bulky, highly absorbent, filler-free paper which is mostly produced from pure cotton in the form of bleached linters and from chemical pulp
Board
Generic term for stiff paper usually made in several layers with a substance normally varying from 160 to 500/g/m², for certain grades even higher; widely used for packaging (e.g. folding cartons) and graphic applications
Book paper
Woodfree or mechanical paper used for printing book
Brightening
Addition of optical brighteners to the stock to make the pulp/paper appear whiter
Brightness
A measure of the whiteness of pulp and paper
Broke
Papermakers own waste paper created during papermaking process it is usually repulped
Brush glazing
Glazing of coated paper with the aid of brushes
Bulk product
A mass-produced product sold in large volumes without individual specifications, usually in compliance with a standard. For example, newsprint

C

Cable paper
See "Electrical insulating paper"
Calcium carbonate
Used in papermaking as a filler or coating pigment
Calender
Machine in which paper is given a glazed finish by passing it between two or more rolls, either on or off the paper machine
Calendered paper
Paper that has been smoothed and compacted between the rolls of a calender and is thus more or less glossy (sharp or matt calendered). The effect produced in the calender unit is the result of friction combined with temperature and pressure
Caliper
Thickness of paper, usually measured in nanometers
Capacitor paper
See "Electrical insulating paper"
Capacity utilisation rate
Indicates the efficiency (%) at which a mill or machine is operating
Carbon dioxide (CO₂)
Produced by burning coal and other carbon containing products. Burning fossil fuels or wood based products raises atmospheric carbon dioxide levels
Carbon paper
Carbon paper is a thin paper with a waxy coating, that is used to produce carbon copies on typewriters or other office equipment. Carbon base paper is made from chemical pulp
Carbonless copy paper
Paper that permits making multiple copies without intervening layers of carbon paper. The paper translates pressure into a dye reaction which transfers the image to the copy. Carbonless copy papers are mainly used for continuous form sets, for cov-ered pay slips, for vouchers to be dispatched by post and for payment forms. In the US and some other countries, carbonless copy paper is also called NCR paper (= Non Carbon Required)
Cast-coated paper
Cast-coated papers are coated papers that have obtained their high gloss by moulding on a highly polished, chromium plated drying cylinder
Causticizing
Process by which green liquor from sulphate pulping is converted to white liquor, thus allowing the cooking chemicals to be reused
Cellulose
Structural material giving strength to wood cells
Chemical oxygen demand (COD)
The amount of oxygen consumed in complete chemical oxidation of matter present in waste water; indicates the content of slowly degradable organic matter present.
Chemical pulp
Pulp in which wood fibres have been separated by chemical, rather than mechanical, means
Chemicals recovery
In chemical pulping, the recovery, treatment and regeneration of cooking chemicals
Chemi-thermomechanical pulp (CTMP)
Chemi-mechanical pulp produced by treating wood chips with chemicals (usually sodium sulphite) and steam before mechanical defibration
China clay
Mineral (kaolin) used in papermaking as both filler and coating pigment
Chipboard/Grey board
Paperboard made from waste paper pulp, rough or machine glazed, also lined on one or two sides or unlined
Cigarette paper
This light weight, unsized paper (grammage 18 to 24g), converted to improve glowing. It normally has a filler content of approx. 30%
Clarification
Separation of a solid component from a solution
Clarifier
Basin where sludge is removed from treated effluent by settling; see Activated sludge treatment
Coated paper
The uniform application of a coating yields a more even and more closed surface of printing papers, which is suitable for the reproduction of fine screen artwork. The coating is applied in separate coaters or in the paper machine
Coating
Process by which paper or board is coated with an agent to improve its brightness and/or printing properties
Coating colour
Mixture used to coat paper and board: contains pigment, binder, special additives and water. Also coating slip
Coating colour kitchen
Department where coating colour is prepared and mixed
COD
See Chemical oxygen demand
Combined deinking
Deinking process combining flotation and washing; cf. flotation deinking, washing deinking
Condensing power
Power generation in which fuel is burned for electricity production only
Consistency
Dry solids content (%) of pulp present in a pulp slurry
Continuous cooking
A method used in chemical pulping in which raw material is fed continuously into the digester, while at the same time pulp and black liquor are removed (cf. batch cooking)
Converting
The operation of treating, modifying, or otherwise manipulating the finished paper and paperboard so that it can be made into end-user products
Cooking
A process for producing chemical pulp by treating wood with a cooking liquor at a certain temperature and pressure
Cooking liquor
Liquor made up of selected chemicals and used for cooking pulp
Copying paper
Copying paper is an uncoated paper in woodfree or mechanical grades, white or col-oured in A4 and A3.
Core
The tube, usually made of paperboard, on which a paper roll is wound
Corrugated board
Corrugated board is produced by guiding a paper web, the corrugating medium or fluting, through a slit between two corrugated rolls and pressing it into a waveform through a combination of pressure and heat. In the same machine, an even paper web (facing or liner) is then glued on to this corrugated paper on one or both sides. See "Kraftliner".
Corrugating medium
Papers used as fluting for the production of corrugated board.
Critical load
Highest pollutant load that, in the long term, does not damage essential characteristics in an ecosystem
CTMP
See chemi-thermomechanical pulp

D

Dandy roll
A cylinder on a paper machine used to improve formation; also wire roll
Decor paper
Woodfree, white or single-colour paper, often printed with various patterns, e.g. wood grains. The final product consists of laminated boards or directly coated particle boards used for furniture production.
Defibration
Separation of wood fibres by mechanical and/or chemical means
Deinkability
Suitability of recovered paper for deinking; depends on paper grade, printing process used, age of paper, and other factors
Deinked pulp (DIP)
Paper pulp produced by deinking of recovered paper
Deinking
Removal of printing ink and impurities from recovered paper; to produce recycled fibre pulp with maximum whiteness and purity
Deinking loss
Unwanted loss of solid material from pulp during deinking (usually 10-40%)
Delignification
The removal of lignin, the material that binds wood fibres together, during the chemical pulping process
Deposit
Mass of airborne pollutants deposited on a unit area of land or water in a given time, e.g. grams per square metre per year (g/m²/a)
Deresination
Reducing the resin (pitch) content of wood prior to cooking either by storage or using bleaching chemicals to reduce the resin content in pulp
Digester house
That part of a chemical pulp mill where cooking takes place
Direct cooking
Cooking in which heating is achieved by blowing steam into the cooking liquor
Dispersion
The separation of a substance into the smallest possible particles using another substance (the medium). Used in papermaking to homogenize pulp properties and remove impurities
Dissolving pulp
A chemical pulp grade used, for example, in the production of acetate and viscose fibres and cellulose films
Document paper
Document paper is paper with a high ageing resistance. It is woodfree but may also contain rags or be fully made from rags and is used for documents that have to be preserved for a longer period
Double coating
Coating of paper or board twice on one or both sides
Drainage
Formation of a paper or board web on the wire by removing water at the paper machine wet end
Drawing paper
The range of drawing papers includes woodfree and mechanical grades with proper-ties that are tailored for specific drawing techniques. They have a low opacity and are erasure proof and often also wash-fast
Dry coating
Coating method in which a binder is applied to the paper surface followed by dry coating pigment
Dry creping
Creping of a dry paper web
Dry end
Final part of the paper machine from the drying section onwards
Dry solids
Mass of dried sample as a percentage of mass of original sample
Dry strength
Mechanical strength of a dry paper sheet (includes tensile strength, tearing resistance and folding endurance)
Duplex board
Duplex board consists of two layers, mostly made from waste paper pulp. It is used for packaging purposes

E

Elastic strength
The ability of paper or board to resist stress acting in the plane of the sample
Electrical insulating paper
Strong, pore-free paper, sometimes impregnated with synthetic resins, made from chemical pulp. Electrical insulating paper must neither contain fillers nor conductive contaminants (metals, coal, etc.) nor salts or acids. Cable papers, that are wound around line wires in a spiral-like fashion, are electrical insulating papers with a par-ticularly high strength in machine direction. Electrical insulating papers also include electrolytic papers and capacitor paper
Electrostatic precipitator
Used to clean up flue and process gases. Removes 99.5-99.8% of dust particles emitted from recovery boilers, lime kilns and bark-fired boilers
Emulsion coating
Coating of paper with an emulsion containing plastic or resin
Envelope paper
Envelope paper can be woodfree or wood-containing, machine glazed or calendered, white or in colour and is used for envelopes. It must be opaque, writable, and printable and must have a high folding strength
Enzyme bleaching
Bleaching technique in which cooked and oxygen-delignified chemical pulp is treated with enzymes prior to final bleaching. Allows pulp to be bleached without chlorine chemicals
Evaporation plant
Unit used at pulp mills to concentrate spent liquor to make it suitable for burning and chemicals recovery
Extended cooking
Method of cooking pulp to low lignin content, thereby reducing the need for bleaching chemicals

F

Fibre loss
Loss of fibre material in pulp and paper processing
Fibreboard
Board made from defibrated wood chips, used as a building board
Fibrillation
A structural change occurring in the walls of chemical pulp fibres during beating
Filler
Pigment, added to papermaking stock to improve properties such as opacity and smoothness, and often to reduce cost
Filler content
Percentage of filler in a paper
Filter paper
Unsized paper made from chemical pulp, in some cases also with an admixture of rags, sometimes with a wet strength finish. Filtration rate and selectivity, which are both dependent on the number and the size of the pores, can be controlled by specific grinding of the pulps and creping
Fine paper
High-quality printing, writing or copy paper produced from chemical pulp and usually containing less than 10% mechanical pulp
Fine paper
Quality term for a large number of woodfree printing papers, based on chemical pulp with usually less than 10 % mechanical pulp. Sometimes fine paper also is made with an admixture of rags or wholly from rag pulp
Flame resistant paper
Flame resistant paper may ignite but must extinguish immediately so that it chars. This property is imparted to the paper by impregnation with certain chemicals
Flong paper
A pulp-like, coated-type paper
Flotation deinking
Deinking process in which air is blown into a dilute fibre suspension. Ink particles adhere to the air bubbles and rise to the surface, where they are removed
Flue gas scrubber
Equipment for removing impurities from flue gases by dissolving them in aqueous solution
Fodder pulp
Protein produced from pulp mill spent liquors and sometimes mixed with animal feeds
Folding boxboard
Single or multilayer paperboard made from primary and/or secondary fibres, sometimes with a coated front, used to make consumer packaging (cartons)
Fourdrinier wire
Horizontally moving metal or plastic mesh belt (wire) on which the paper web is formed
Fraction
A component of a mixture that can be separated on the basis of some property or properties
Fully bleached pulp
Pulp that has been bleached to the highest brightness attainable (> 90 ISO)

G

Glassine paper
Paper made from finely ground chemical pulp that is largely greaseproof but does not have wet strength. Its high transparency is achieved by very intense calendering (smoothing between rolls). Used as chocolate wrapping, in photo albums, wrapping for fish preservatives, protective covers for leaflets, envelope windows etc.
Glazing
First calendering, in which paper is passed through a roll nip to give it a smoother surface
Grammage
Weight in grams of one square metre of paper or board; also basis weight
Gravure paper
Mostly mechanical, highly calendered (smoothed) paper with a high ash content, which is produced as coated or uncoated grade (See "Coated paper"). It must ensure uniform ink trapping at high printing speeds. In order to accept the ink from the deep etched or engraved ink cells of the gravure cylinders, gravure paper must have a certain degree of softness and suppleness. Applications: magazines and reviews, mail-order and travel catalogues, brochures and inserts with high print runs
Greaseproof paper
Greaseproofness is either achieved by grinding of the pulp and pore-free web formation or by special additives
Grinder
A machine in which logs are defibrated against a revolving grindstone
Groundwood mill
An installation for producing mechanical pulp by grinding
Groundwood pulp
A fibrous slurry produced by mechanically abrading the fibres from barked logs through forced contact with the surface of a revolving grindstone. It is used extensively in the manufacture of newsprint and publication papers
Gumming
Paper with a coating of an adhesive which becomes sticky when wet

H

Hard pulp
A commonly used term to describe chemical pulp with a high lignin content
Hardwood chemical pulp
Chemical pulp made from hardwood
Headbox
Chamber at the beginning of a paper machine that dispenses pulp stock evenly onto a moving wire
Hood
A hood covering the paper machine drying section and designed for moist air removal
Hot screening
Pulp cleaning at elevated temperature using pressure screens
Hot-ground wood pulp
Mechanical pulp produced by grinding logs that have been pre-treated with steam
Humus
Dead organic material derived from decomposition of plant and microbial wastes

I

Immission
The level of a particular pollutant in the environment. Widely used for air emissions and noise
Impregnation
The absorption of an impregnating agent into paper; in pulping, wood chips are impregnated with cooking liquor; timber is impregnated with preservative
Impressed watermark
Semi-genuine watermark made in the paper machine press section using engraved rolls while the web is still wet
Index board
Woodfree and mechanical board for office and administration purposes
Integrated Mill
Mill where timber is pulped and then made into paper
ISO brightness
The brightness of paper and board measured at a wavelength of 457 nanometres under standard conditions

J

Jumbo roll
Large roll of paper coming off the paper machine before cutting; a large customer roll

K

Kappa number
Measure of the amount of lignin remaining in pulp after cooking
Kitchen wipes
Kitchen wipes consist of creped paper made from chemical or waste paper pulp. They are used in private households or in trade and industry
Knotter pulp
Pulp made from the rejects from chemical pulp screening
Kraft paper
High-strength paper made almost entirely of unbleached kraft pulp. Kraft paper is suitable for the production of paper sacks and paper bags
Kraft pulp
Chemical wood pulp produced by digesting wood by the sulphate process (q.v.).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
Kraftliner
Paperboard of grammages of 120g and more, generally made from bleached or unbleached sulphate pulp and used as an outer ply in corrugated board

L

Label papers
Mostly one-side coated papers which must be printable in 4-colour offset and gravure printing. These papers are usually suitable for varnishing, bronzing and punching and sometimes also feature wet strength and alkali resistance (See "Wet strength and alkali resistant paper") in order to en-sure the removal of the labels e.g. in the bottle rinsing machines of breweries
Lacquering
Application of lacquer to give paper greater gloss and stiffness (brochures and some magazine covers)
Laminate
Material used to bond together two or more layers of paper, board, etc.; also a laminated product
Lamination
Laminating paper or board with foil, plastics etc
Lightweight coating
Coating applied at 7-10 g/m² on one or both sides of the paper
Light-weight printing paper
Light-weight paper has a low grammage and is made from rags and bleached kraft pulp and is used e. g. for advertising material (catalogues, leaflets, mailings etc.), commercial and/or jobbing work (magazines, brochures, instruction leaflets, forms etc.)
Lignin
Natural "adhesive" which binds wood fibres together in the tree and imparts rigidity. Pulp brightness depends on the amount of lignin remaining in the pulp. Paper containing high content will "yellow" in sunlight
Lime kiln
Used to reburn lime sludge (CaCO₃) to form calcium oxide (CaO), which can be reused
Lime sludge
Sludge of calcium carbonate (CaCO₃) formed during preparation of white liquor in the chemical pulping process
Linen finish
Imitation linen texture impressed onto the paper surface
LWC
Lightweight coated. See Lightweight Coated Printing paper
LWC paper
Light weight, two-side coated mechanical reel printing paper with a grammage of less than 72g. It is used for magazines, mail-order catalogues etc. that are mostly produced in gravure or web offset printing (See "Coated paper")

M

Machine creping
Creping of paper on the paper machine using a large drying cylinder known as a Yankee
Machine roll
See Jumbo roll
Machine stack
Used for first calendering (glazing) of paper on the paper machine
Machine width
Width of the paper web in the paper machine
Magazine paper
The selection of the magazine printing paper is mainly dependent on the print run and the demands on the print quality (image reproduction, outer appearance, advertising appeal). High runs are mostly produced in rotogravure, rotary offset printing or rotary letterpress printing on uncoated or coated reel printing papers (mainly SC and LWC. See "SC" and "LWC"). Magazines with medium or smaller circulation are generally produced in sheet-fed offset or sheet-fed letterpress printing
Marbling
Addition of strongly stained fibres to the stock to give the paper a marbled appearance
Market pulp
Pulp produced for sale on the market or for the producer's units abroad rather than for own use
Matt finish
A dull finish given to the surface of paper and board
Mechanical paper
This paper contains mechanical pulp, thermomechanical pulp (TMP) or chemithermo-mechanical pulp (CTMP) and also chemical pulp. The shares of chemical and mechanical pulp vary depending on the application. Highly mechanical papers such as newsprint tend to yellow more rapidly if exposed to light and oxygen than woodfree papers so that they are mainly used for short-lived products. In printing papers the mechanical pulp improves opacity
Mechanical pulp
Pulp consisting of fibres separated entirely by mechanical rather than chemical means
MF
Machine finished. Smooth paper calendered on the paper machine
MG
Machine glazed. Paper with a glossy finish on one side produced on the paper machine by a Yankee cylinder
Micro-creping
A way of improving the extensibility of paper by pressing a wet mesh against the paper web
Mineral fillers
Materials such as chalk and china clay that are added to paper in order to change its density or improve its surface and optical properties
Multi-layer web forming
Usually applied to a board machine on which several webs are combined into one
Multi-stage cooking
Chemical pulping process in which the alkalinity of the cooking liquor is varied by charging the alkali in several stages

N

NCR paper
See "Carbonless copy paper"
Newsprint
Newsprint is a highly mechanical, machine-finished or calendered rotary printing paper (40 - 56g) mainly made from mechanical and increasingly waste paper pulps. In line with its intended use as a short-lived information medium, the demands on newsprint in terms of optical properties or printability are lower than those on other, e.g. coated printing papers. Newsprint must have a very good runnability: today's state-of-the-art printing techniques require a paper with a good tear strength so that the uninterrupted production on high-speed rotary presses is ensured. Newsprint is used for dailies, weeklies and free journals produced in letterpress or offset printing
Nitrogen emission
Emission of nitrogen compounds which, as nutrients, cause eutrophication and acidification in water systems
Non-Wood Pulp
Pulp made from materials other than wood, for example straw, grasses, bagasse etc
Nutrients
Generally refers to nitrogen and phosphorus compounds, which act as fertilisers in water systems

0

Off-machine coating
Coating of paper on a separate coating machine
Off-machine creping
A method whereby paper is creped in a separate operation rather than by the paper machine's Yankee cylinder
Offset paper
Collective term for printing papers with special properties for offset printing. For in-stance, the paper must not emit dust during processing and must be pick resistant. Offset paper may be woodfree or mechanical, coated (matt, glossy, embossed) or uncoated and is processed in sheets as well as in reels
On-machine coating
Coating of paper on the paper machine
Optical characteristics
Characteristics of the appearance of paper or board. Most important are colour, brightness, opacity and gloss
Oxygen bleaching
A process in which pulp is initially treated with oxygen followed by 4-5 bleaching stages
Ozone bleaching
Pulp can be treated with ozone at the start of the bleaching sequence to lower its lignin content. Ozone allows bleaching to high brightness without chlorine chemicals

P

Packaging paper
Collective term for papers of different pulp composition and properties, sharing only the application. Selection and mixture of the pulps depend on the demands made on the paper. Important are tear strength, bursting strength, creaseproofness, abrasion resistance as well as elasticity and stiffness. Often also good printability is demanded (packaging as advertising medium). For special purposes packaging paper can be imparted wet strength or water repellent properties or made impermeable for aromas or water vapour. For these purposes either special additives are admixed to the pulp or the paper is coated, impregnated or combined with plastic and/or metal film
Paperboard
Monolayer paperboard is basically thicker paper, frequently used in multilayers
Parchment paper
See "Vegetable parchment"
Particulates
Airborne solid impurities such as those present in gaseous emissions (sodium sulphate, lime, calcium carbonate, soot)
Peroxide bleaching
Method of bleaching pulp with hydrogen peroxide (H₂O₂) to remove lignin; reduces or avoids the need for chlorine dioxide in final bleaching
PGW
See Pressurised groundwood pulp
Photographic paper
The base paper used for the production of photographic papers is a dimensionally stable, chemically neutral chemical pulp paper with wet strength properties, that must be free from contaminants. Today papers are coated on both sides with a thin polyethylene film. The cooking prevents chemicals and water entering the paper during development. This also permits shorter rinsing and drying cycles
Picking
Removal of particles from the paper surface during printing when ink tack is greater than surface strength
Picking resistance
Ability of a paper surface to resist picking by tacky printing inks
Pick-up
Roll which lifts the wet paper or board web off the wire before the drying section
Pigmentizing
Coating of paper with a chemical agent (pigment) to reduce surface porosity and increase opacity
Plasticizer
Agent mixed into coating colour to give a more flexible coating
Porosity
A structural property of paper reflected by the size distribution of pores
Postcard board
Postcard board is either slightly mechanical or woodfree and calendered
Poster paper
Poster paper is a highly mechanical, highly filled, mostly coloured paper that has been made weather resistant by sizing.
Press nip
On a paper machine, a pair of rotating rolls between which the paper web passes
Pressurised groundwood pulp (PGW)
Mechanical pulp produced by treating logs with steam before defibration against a grindstone under externally applied pressure
Primary fibre
See Virgin fibre
Printability
Describes how smoothly paper runs in a printing press and the quality of the printed image
Printing paper
Printing paper is a collective term for all printable mechanical or woodfree papers that may serve as the medium for printed information. In addition to uniform and fast ink trapping and drying (printability) as well as dimensional stability, sufficient opacity (no show through of the back print) and smoothness, such papers require a certain degree of strength and stiffness, so that the paper may run through the printing machine fast and without any problems (runnability). Many printing papers are coated to improve printability (See "Coated paper")
Process flowchart
Layout showing process equipment and material flows
Pulper
Unit for defibrating (slushing) pulps and paper machine broke, usually at the wet end of the paper machine
Puncture resistance
Force acting perpendicular to a paper or board surface needed to puncture the sheet

Q

R

Rag paper
Today rag paper is mostly made from vegetable fibres consisting of cellulose, such as cotton, linen, hemp and ramie. Rags are the most precious raw material for the papermaker. Rag papers and rag-containing papers with admixtures of chemical pulp are used for banknotes, deeds, documents, books of account, maps and copperplate engravings and as elegant writing papers. They are also used for special technical applications
Rag pulp
Papermaking pulp made from textile waste, cotton, hemp or flax
Ream
Unit consisting of 500 identical sheets of paper
Recovered paper
Paper recovered for recycling into new paper products. Recovered paper can be collected from industrial sources (scraps, transport packaging, unsold newspapers...) or from household collections (old newspapers and magazines, household packagings)
Recovered Paper Base
Solid, compressed stack of recovered paper, sorted by grades, intended to be recycled by some papermills, to produce paper and board
Recovered Paper Grades
Recovered paper sorted by types in order to be recycled by paper mills. Specific grades are used by paper mills, in order to produce different types of paper and boards
Recovery boiler
Boiler used to burn black liquor from chemical pulping for recovery of inorganic chemicals as well as for energy production
Recovery rate
Volume of paper recovered as a percentage of volume of paper consumed
Recycled fibre
Fibre obtained from recovered paper; also secondary fibre (cf. virgin fibre)
Recycled fibre pulp
Pulp produced from recovered paper to be used in papermaking
Recycling
Use of recovered waste paper and board by paper mills to produce paper and boards
Refiner
A machine containing rotating disks between which wood chips are broken down into fibres for pulp making
Refiner mechanical pulp (RMP)
Mechanical pulp produced by passing wood chips between the plates of a refiner
Refiner sawdust pulp
Mechanical pulp produced from sawmill dust
Reflectivity
Ability of paper or board to reflect light; a measure of gloss
Reinforcement
Method for strengthening paper with an insert or surface layer of glass or other synthetic fibre or metal
Reinforcement pulp
Softwood chemical pulp added to give paper greater strength and to improve runnability on the paper machine or printing press
Reject
Material removed and discarded during the cleaning of pulp/stock
Relative density
Mass of a unit volume of a particular substance
Release paper
Release paper is used to prevent the sticking of glue, paste or other adhesive substances. Coating paper with silicone yields papers with a surface that prevents adhesion of most substances. Application: cover material for self-adhesive papers or films, e.g. in label production.
Retention
Proportion of fibre and filler retained on the paper machine wire
Roofing paper
Board that is impregnated with tar, bitumen and/or natural asphalt.
Runnability
How smoothly paper runs through a paper machine or printing press (also how well cartons run on an automatic packaging line)

S

Sack paper
See "Kraft paper"
Safety paper
Papers with a special protection against abusive imitation. The safeguards used during the production of the paper - some of them chemical - are secret
Sanitary papers
The group of sanitary papers includes cellulose wadding, tissue and crepe paper, made from waste paper and/or chemical pulp - also with admixtures of mechanical pulp. As a consequence of the importance of tissue today, this name is now used internationally as a collective term for sanitary papers. These grades are used to make toilet paper and numerous other sanitary products such as handkerchiefs, kitchen wipes, towels and cosmetic tissues
Sanitary tissue paper
Tissue is a sanitary paper made from chemical or waste paper pulp, sometimes with the admixture of mechanical pulp. It has a closed structure and is only slightly creped. It is so thin that it is hardly used in a single layer. Depending on the requirements the number of layers is multiplied. Creping is made at a dryness content of more than 90 %. The dry creping (unlike with sanitary crepe papers) and the low grammage of a single tissue layer result in a high softness of the tissue products. For consumer products it is normally combined in two or more layers. The flexible and highly absorbent product [is mainly produced from chemical pulp and/or DIP - sometimes also with admixture of groundwood pulp] can also be provided with wet strength. Applications: facial tissues, paper handkerchiefs, napkins, kitchen rolls, paper towels, toilet paper
SC
See Supercalendered
SC paper
SC stands for supercalendered. This is a calendered, uncoated mechanical paper with fillers
Secondary fibre
See Recycled fibre
Security paper
Woodfree, sometimes rag-containing but always high quality paper with a genuine multistage watermark to avoid falsification
Semi-alkaline pulp (SAP)
Sulphite pulp cooked at slightly alkaline pH (normal sulphite pulp is cooked at acid pH). SAP is superior in strength to normal sulphite pulp. Used mainly in printing papers
Semi-bleached
Pulp bleached to a brightness somewhere between that of unbleached and fully bleached pulp
Semi-chemical pulp
High yield pulp in which the fibres have been separated mechanically after a preliminary chemical treatment; e.g. NSSC pulp
Settleable solids
Suspended solids that will settle out of an effluent during mechanical treatment
Sheeter
Machine for cutting the paper web into sheets
Short fibre
Applies to paper or pulp containing a high proportion of short wood fibres
Sized paper
Sizing reduces the water absorbency of the paper and thus creates the condition for the writability with ink. Sized paper is also used for many other purposes (printing, coating, gluing, etc.), and the sizing agents must fulfil a wide range of tasks. For instance, they control the water absorbency and increase the ability to retain water and ink (pick resistance)
Sizing
Treatment of either stock or paper surface with size to improve strength and reduce absorbency of water
Sludge handling
Compaction and dewatering of sludge separated from treated effluent
Softboard
Softboards are soft, bulky boards with a felt-like character. They are used for protective covers, roofing papers, beer mat boards, packaging boards and flongs
Solid fibre board
Collective term for all solid board grades
Special pulps
Chemical pulps used for purposes other than ordinary papermaking (e.g. in textile production)
Speciality paper
The group of speciality papers comprises numerous paper grades, each characterised by particular properties. These properties often require special raw materials
Spent liquor
Waste liquids from pulping and washing (cf. black liquor)
Steam calendering
See steam finishing
Steam finishing
A way of treating paper before calendering to improve its density and surface smoothness
Steaming
Wood chips are often treated with steam prior to pulping; used in thermomechanical pulping
Stock
Suspension in water (slurry) of fibres and other components for papermaking during the period between defibration and web formation
Strength
Ability of paper or board to withstand mechanical stress
Suitcase board
Sized, high-density and strong board which generally is water repellent on both sides as a result of surface finishing. It may be pressed, folded, moulded, bent, riveted and sowed. Thickness 1 - 3 mm
Sulphate pulp
Chemical pulp produced by cooking wood in a liquor containing sodium hydroxide and sodium sulphide
Sulphite pulp
Chemical pulp produced by cooking wood in a liquor containing sodium, magnesium, ammonium or calcium bisulphite
Supercalendered (SC)
Paper treated in a supercalender, usually separate from the paper machine; uncoated magazine paper
Supercalendering
Treatment of paper on an off-machine supercalender to improve smoothness and gloss
Surface treatment
Treating the surface of paper or board with size or coating colour
Surface-sized paper
Paper that has been sized on the surface, generally using a size press inside the paper machine
Suspended solids
Bark, fibre and other wood-based material released into water during debarking and pulping; filler and coating colour residues from paper mills; solid impurities formed during waste water treatment. Solids can be removed from waste water by settling or filtration
Synthetic fibre paper
Papers made from synthetic fibres such as polyamide and polyester, from viscose staple fibre or sometimes also with fillers. The fibres are mainly held together by binders. The durable synthetic fibre papers are used for maps and highly important documents such as driving licences or vehicle registration books

T

Talc
Mineral used in papermaking as a filler and coating pigment
Tearing resistance
Force needed to tear a sheet of paper under specified conditions
Testliner
Mainly produced from waste paper used as even facing for corrugated board or as liner of solid board. They are often produced as duplex (two-layer) paper. The grammage is higher than 125 gsm
Thermal papers
One-side coated thermoreactive papers used for printing text and illustrations on telefax machines, thermoplotters (e.g. for technical drawings) and thermoprinters (e.g. for labels, tickets, sales slips and other vouchers)
Three-layer paperboard
Paperboard consisting of three layers: front liner made from chemical pulp and/or waste paper pulp, middle made from waste paper pulp and back made from mechanical and/or chemical and/or waste paper pulp
Tissue paper
Collective term for papers of a grammage of less than 30 gsm that differ in applica-tion and composition but have the common feature of being thin. They are mainly used to wrap delicate items, as tissue for bottle wrapping, as fruit tissue wrappers for oranges or as wet strength flower tissue. They are also used as base paper for the carbon paper production, as lining tissue for envelopes and as lining paper (e.g. as a composite with aluminium foil in cigarette packaging). The extremely thin Japanese tissue papers are sometimes produced in grammages as small as 6 to 8g
Toilet papers
See "Sanitary tissue papers" and "Sanitary crepe papers"
Totally chlorine-free (TCF)
Pulp bleached entirely without chlorine chemicals
Totally Chlorine-free paper (TCF)
Abbreviated used for papers made from pulps that were not bleached with chlorine compounds. The paper itself is not bleached
Transparent paper
Extended and particularly careful grinding of high quality fibres (hard chemical pulps, rags) yields a raw material permitting the production of transparent paper
Trimmings
Paper or board left over from web or sheet cutting operations
Twin-wire machine
Paper or board machine in which the web is formed and partially dewatered between two wires
Typewriter paper
Typewriterpaper (bank paper) is often woodfree, usually sized, erasure resistant and in rare cases coloured. It can be both with and without watermark and can also be embossed. Typewriterpaper (bank paper) is often woodfree, usually sized, erasure resistant and in rare cases coloured. It can be both with and without watermark and can also be embossed

U

Unglazed (UG)
Uncalendered paper

V

Vegetable parchment
Vegetable parchment, often also called parchment paper, is a highly pure packaging material that is impermeable for grease and has a particularly high dry and wet strength. It is made from an absorbing, pure, bleached chemical pulp in a special process using concentrated sulphuric acid
Veining
Uneven colouring of pulp
Virgin fibre
Wood fibre never before used to make pulp, paper or board. Also primary fibre (cf. secondary fibre)
Viscose pulp
Dissolving pulp intended for the manufacture of viscose

W

Wall base paper
Collective term for papers that are suitable for wallpaper production. These papers may be monolayer or multilayer (simplex/duplex), woodfree or mechanical, uncoated or coated, and can also be laminated, pre-pasted or peelable
Washer room
Pulp mill department where pulp is washed free of cooking chemicals
Washing deinking
Deinking in which solid particles are separated on the basis of their size by washing
Waste paper
Paper after it has been used. Most can be recycled into new paper products. Known also as recovered paper and secondary fibre
Watercolour paper
Woodfree (See "Woodfree paper") drawing paper with a rough or structured surface, sometimes also rag-containing or pure rag paper. Sizing is adapted to ensure that the water colours are well accepted by the paper but do not strike through. The paper must be erasure resistant. If they are hand-made, water colour papers have the additional advantage that they expand evenly in all directions when they are moistened
Watermark
A localised modification of the formation and opacity of the sheet, so that a pattern or design can be seen
Waxed paper
Nearly woodfree papers that are impregnated with paraffin, wax or wax/paraffin/plastic mixtures. With the appropriate saturation agent and process the product may be tailored for specific applications, e.g. packaging of bread or sweets or wrapping razor blades
Waxing
Coating or impregnating of paper or board with paraffin or wax
Web
Continuous sheet of paper formed on the paper machine wire
Web glazing
Imparting a gloss to the paper web; calendering
Wet end
First part of the paper machine up to the drying section
Wet strength
Mechanical strength of paper when wet, measured under specific conditions
Wet strength and alkali resistant paper
Adding alkali resistant wet strength agents to the fibre suspension yields papers that have a remarkable strength even when wet
Wet tensile strength
Ability of wet paper to resist tension in the plane of its surface
White water system
Flow circuit for paper machine white water (includes pipes, storage tanks, cleaning equipment, water from forming section and return feed)
Winder
Machine for cutting the paper web longitudinally into narrower webs, which are then wound to reels; also slitter-winder
Winding
Operation whereby a web of paper or board is wound into one or more reels
Wire
Flat belt of metal or plastic mesh on which the paper or board web is dewatered
Wood containing
Paper containing a certain proportion of mechanical pulp
Wood pulp
Mechanical or chemical pulp made from wood (cf. Non-wood pulp)
Woodfree
Paper made using the chemical rather than the mechanical pulping process
Woodfree paper
Paper consisting of chemical pulp fibres. It does not contain any mechanical pulp beyond a permissible content of 5 % by mass
Writing paper
Uncoated paper that is suitable for writing with ink on both sides. The writing must neither bleed nor strike through. Writing paper is always fully sized (See "Sized paper") and also suitable for printing. It can be woodfree or mechanical, depending on the intended purpose. The admixture of fillers makes it less translucent

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