PULP AND PAPER DICTIONARY
This page contains definitions of the terms, words and phrase commonly used in pulp and papermaking, printing, converting and paper trading.
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
PACKAGING PAPER A paper or paperboard used for wrapping or packing good.
PALLET A platform with a slatted bottom, used to hold and ship cartons of paper stacked on top of each other.
A standard amount of paper that fits on a wooden pallet. In cut-size sheets, a pallet equals 40 cartons.
PAPER A homogeneous sheet formed by irregularly intervening cellulose fibres.
PAPERBOARD A heavy weight, thick, rigid and single or multi-layer sheet. What differentiates paperboard from paper is the weight of the sheet. If paperboard is very heavy it is called Board. Paper heavier than 150 gram per meter square are normally called Paperboard and paperboard heavier than 500 gram per meter square are called board.
PAPERMAKING Invented in China by T'sai Lun some 2,000 years ago, papermaking still follows the same basic procedures. Today wood chips are cooked with chemicals to release cellulose fibres and dissolve lignin, then washed to remove impurities. Most printing papers are then bleached to lighten the colour of the pulp. Pulp is mechanically and chemically treated to impart certain desired characteristics such as strength, smoothness and sizing. Large quantity of water is added to uniformly distribution of fibres and additives. The resulting slurry, which is 99 to 99.5% water, is cascaded onto the continuously moving forming fabric of the Fourdrinier paper machine. Side-to-side shaking distributes the slurry, forming a tangled web of fibre as the water drains off. A wire mesh roll called a dandy roll, moves over the surface to modulate the turbulence and smooth the topside of the paper. A felt blanket absorbs more water from the paper and sends the sheet on through a channel of hot metal drums that dry and press the paper at the same time to give it a more even-sided finish. At this point the paper is fully dry and ready for off-machine processes such as coating, embossed finishes and supercalendering.
PAPER CUT The excruciating, often unforeseeable, and usually invisible-to-the-naked-eye cut received when skin slides along the edge of a piece of paper at just the wrong angle.
PAPER-INK AFFINITY The tendency for paper and ink to attract and stay attracted to each other. This keeps the ink on the paper and off the reader's hands or the next sheet. An incompatibility between ink and paper can cause printing problems.
PAPER SURFACE EFFICIENCY (PRINTING) Measure of the printability of a sheet of paper which is dependent upon the amount of ink the paper absorbs, the smoothness of its surface, and the evenness of its calliper.
PAPETERIE A paper used for greeting cards, stationery, etc…which is distinctive from regular stock in that special watermarks and embossing may be used.
PAPYRUS The Egyptians used this aquatic plant to create a writing sheet by peeling apart the plant's tissue-thin layers and stacking them in overlapping, crosshatched pieces to form a sheet. Despite giving us the word "paper," papyrus is not a true paper. To view a picture of papyrus plant click here.
PARCHMENT Animal skins or linings stretched and prepared as writing/painting surfaces. Produces a smooth, buttery surface.
PARCHMENTIZATION Method of treating a paper sheet with sulphuric acid to make it greaseproof.
PARTICULATE Airborne solid impurities such as those present in gaseous emissions (sodium sulphate, lime, calcium carbonate, soot).
PEEL STRENGTH The amount of normal force required to delaminate a multiply paper. Strength measured by TAPPI useful method UM808 or other similar methods.
PERMEABILITY Degree to which a fluid (gas or liquid) permeates or penetrate a porous substance such as paper or fabric.
PERFECTING PRESS A printing press that simultaneously prints both sides of a sheet of paper as it passes through the press. On other presses, printing both sides means running the sheet through the press to print one side, allowing the ink to dry, turning the paper over, and then running the sheet through the press again to print the other side.
PERMANENT PAPER A paper that can resist large chemical and physical changes over and extended time (several hundred years). This paper is generally acid-free with alkaline reserve and a reasonably high initial strength.
PERMANENCE The degree to which paper resists deterioration over time. There is an international norm which applies to woodfree papers. The ISO 9706 international norm defines the conditions for producing "permanent" papers. A paper which fulfils these criteria can be stocked for many years under archival conditions (temperate medium and protected from light).
Furthermore there is also the German DIN 6738 norm which can be applied to all papers.
Under the DIN 6738 norm, longevity is classified under the following categories :
CL 24-85 : these papers can be described as ageing-resistant,
CL 12-80 : the lifespan of these papers is of several centuries,
CL 6-70 : the lifespan of these papers is of at least 100 years,
CL 640- : the lifespan of these papers is of at least 50 years.
However in the German introduction to the ISO 9706 norm, there is a clear restriction concerning the DIN 6738 norm : "The task of archives, libraries, museums and other collections is to conserve documents on a long lasting basis". That is why printers and editors should take care to respect the requirements of the ISO 9706 norm. DIN 6738 is valid for books which will predictably be destroyed after use.
PERMANGANATE NUMBER (K NUMBER) Chemical test performed on pulp to determine the degree of delignification.
PERMEABILITY Degree to which a fluid (gas or liquid) permeates or penetrate a porous substance such as paper or fabric.
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
PEROXIDE BLEACHING OR HYDROGEN PEROXIDE BLEACHING Method of bleaching pulp with hydrogen peroxide (H2O2) to remove lignin; reduces or avoids the need for chlorine dioxide in final bleaching.
PH (HYDROGEN ION CONCENTRATION) A measure of the acidity (or alkalinity) of a solution. Range from 0-14 with 7 being neutral, less than 7 being acid; higher than 7 being alkaline.
PHOTODEGRADABLE A material which undergoes destruction of its chemical structure when exposed to light. Typically, the materials become brittle with time and fragment into small pieces or powder.
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.
PICK OUT A problem on press caused by unevenly sealed paper, or paper with low bonding strength. The ink "picks" off weak areas of the paper, lifting coating from a coated stock or lifting fibres from an uncoated stock, and transferring them to the printing blanket.
These fibres will eventually be transferred back onto the sheets being printed, causing inking and surface inconsistencies.
PICK RESISTANCE The ability of paper fibres to hold together during the printing process.
PICK UP ROLL Roll, which lifts the wet paper or paperboard off the wire to transfer to press.
PICKING (PAPERMAKING) To transfer the wet sheet from wire part to press part. If the sheet moves unsupported is called "poor man pick up". If a solid/suction roll is used to lick/pick the sheet, it is referred as closed transfer.
PICKING (PRINTING) The problem of ink picking off paper fibres during printing. This may be an indication of a paper with low bonding strength or the use of an ink with too much tack for the paper it is printed on.
PIGMENT An ingredient added to pulp to increase the brightness and opacity of white paper or dye the pulp to create a collared sheet. Pigments have very high light fastness and bleedfastness.
PIGMENTIZING Coating of paper with a chemical agent (pigment) to reduce surface porosity and increase opacity.
PIN HOLES Imperfections in paper which appear as minute holes upon looking through the sheet. They originate from foreign particles, which are pressed through the sheet.
PIPING Defect in reels, consisting of ridges running around the circumference, due to moisture take-up by the surface layers or uneven binding or hard and soft spots.
PITCH Resinous material present in wood (mainly softwood) that carry over into the pulping and papermaking system to form insoluble deposits.
POLYMER Organic chemical compounds consisting of repeating structural units. Cellulose is a polymer.
PLY The separate webs, which make up the sheet formed on a multi-cylinder machine. Each cylinder adds one web or ply, which is pressed to the other, the plies adhering firmly upon drying.
POINT A unit of paper or paperboard thickness measuring one-thousandth of an inch.
POLYMER A chemical term for several classes of organic or carbon containing chemicals where a monomer or single chemical molecule is connected to itself in repeating units to form a chemical "chain." An example of a polymer is cellulose, a repeating chain of glucose (sugar). Other examples are polyesters, nylons, viscose, lyocell, polyolefins and polystyrenes.
POROSITY The property of paper that allows the permeation of air, an important factor in ink penetration.
POSTCARD BOARD Postcard board is either slightly mechanical or woodfree and calendared.
POST-CONSUMER WASTE PAPER Waste paper materials recovered after being used by consumers.
POSTER PAPER Poster paper is a highly mechanical, highly filled, mostly coloured paper that has been made weather resistant by sizing.
PRECISION SHEETING Converting rolls of paper into finished sheet sizes in a single operation.
PRE-CONSUMER WASTE PAPER Paper recovered after the papermaking process, but before used by a consumer.
PRESS A combination of two or more rolls used to press out water from wet paper web. Following are some of the types of the press.
1. Plain Press or Solid Press This is the simplest and the oldest type of press which is now a days rarely used except on very slow speed machine. The solid press consist of two solid rolls covered with rubber and or granite. The top roll is somewhat offset for the squeezed out water to flow by gravity.
2. Suction Press In this type of press, one roll is drilled and shell of the drilled roll rotates over a suction box. The squeezed water is sucked out through the felt.
3. Grooved Press In this type of press, one roll is grooved. The squeezed water is hold in the groves and removed by doctoring or sucking out on the return run of the roll.
4. Smoothing Press A plain roll press just before the dryer section start, used to smoothen the paper surface.
PRESS PART OR PRESS SECTION The section of the paper machine which contains press (es). It is usually located between wire part and dryer part.
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 characterized 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.
PRESSURIZED GROUNDWOOD PULP (PGW) Mechanical pulp produced by treating logs with steam before defibration against a grindstone under externally applied pressure.
PRINTABILITY The overall performance of the paper on press.
PRINTING The transfer of ink onto paper or other materials to reproduce words and images.
PULP A suspension of cellulose fibres in water.
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 collared.
PULPER Unit for defibrating (slushing) pulps and paper machine broke, usually at the wet end of the paper machine.
PULPING Pulping is the process by which plant material (wood, grass, straw etc.) is reduced to a fibrous mass. It is achieved by rupturing bonds within plant structure. It can be accomplished mechanically, thermally, chemically or some combinations of these treatments. Following table provides pulp yield and relative strength achieved using various pulping methods.
Classification Process Yield of Pulp Relative Strength (SW) Relative Strength (HW)
Mechanical Stone Groundwood (SGW) Pulping 90-95% 5 3
Refiner Mechanical Pulping (RMP) 90-95% 5 - 6 3
Thermo Mechanical Pulping (TMP) 90% 6 - 7 **
Chemi-mechanical Chemi-groundwood Pulping 85-90% * 5-6
Cold Soda Pulping 85-90% * 5 - 6
Semi-chemical Neutral Sulphite Semi Chemical (NSSC) Pulping 65-80% * 5 - 6
High Yield Sulphite Pulping 55-75% 7 6
High Yield Kraft Pulping 50-70% 7 6
Chemical Kraft Pulping 40-50% 10 7-8
Sulphite Pulping 45-55% 9 7
Soda Pulping 45-55% * 7-8
* Process not used for Softwood (SW). ** Process not used for Hardwood (HW).
PUNCTURE RESISTANCE The puncture resistance of combined board indicates the ability of the finished container to withstand external and internal point pressure forces and to protect the product during rough handling.