PAPER GLOSSARY

I - R

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)