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Pulp and Paper Dictionary

This page contains the definition of term, words and/or phrase commonly used in pulp and papermaking, printing, converting and paper trading.

A

Abrasive Papers

Papers covered on one or both sides with abrasive powder, e.g. emery, sandpaper etc.

Absorbent Paper

Papers having the specific characteristic of absorbing liquids such as water and ink. These papers are soft, loosely felted, unsized and bulky.

Acetate Pulp

A highly purified (high alpha cellulose) pulp made especially to be dissolved in acetic acid, acetic anhydride and sulfuric acid to make acetate rayon and acetate fiber.

Acid Free Paper

A type of paper which does not contain any acidic substance that may affect acid sensitive material. Acid free paper is anti rust and is used for metal wrapping.

Acid Proof Paper

A paper that is not affected by acid physically or chemically. This paper is used with substance containing acid.

Acid Sizing

Internal sizing carried out in acidic pH range (0-7). Rosin and alum sizing is acid sizing.

Activated Carbon

A highly absorbent powdered or granular carbon used for purification by adsorption.

Activated Sludge

The biomass produced by rapid oxygenation of effluent.

Additives

Clay, fillers, dyes, sizing and other chemicals added to pulp to give the paper greater smoothness, color, fibered appearance or other desirable attributes.

Adsorbable Organic Halogen (AOX)

A measure of the amount of chlorine that is chemically bound to the soluble organic matter in the effluent.

Aerated Lagoon

A biological waste water treatment method in which air (oxygen) fed into an aeration basin reduces the effluent load.

Against the Grain

Cutting, folding or feeding paper at right angles to the grain or machine direction of the paper.

Aging

Irreversible alteration, generally deterioration, of the properties of paper in course of time. Aging also causes reduction in brightness and yellowing effect.

Agitator

An equipment used to keep content of a tank or chest in motion and well mixed.

Air Brush Coater

A coater which uses the pressurized air to atomize the coating mixture and spray it on the paper.

Air Dry (AD)

Refers to the weight of dry pulp/paper in equilibrium with the atmosphere. Though the amount of moisture in dry pulp/paper will depend on the atmospheric condition of humidity and temperature but as a convention 10% moisture is assumed in air dry pulp/paper.

Air Drying

Using hot air to dry pulp or paper sheets.

Air Filter Paper

A type of paper used for filtration of air to remove suspended particles. (car air filter, vacuum bag etc.)

Air Knife Coater

A device that applies an excess coating to the paper and then removes the surplus by impinging a flat jet of air upon the fluid coating, leaving a smooth, metered film on the paper.

Air Mail Paper

It is lightweight, high opacity, good quality writing/printing type paper used for letters, flyers and other printed matter to be transported by airlines.

Air Pollution

The contamination of air around the plant due to the emission of gases, vapors and particulate material in the atmosphere.

Albumin Paper

A coated paper used in photography; the coating is made of albumen (egg whites) and ammonium chloride.

Algae

Micro organic plant life that forms in paper mill water supplies.

Alkali Resistance

Freedom of paper from a tendency to become stained or discolored or to undergo a color change when brought in contact with alkaline products such as soap and adhesives.

Alkaline Papermaking

Paper manufactured under alkaline conditions, using additives, basic fillers like calcium carbonate and neutral size. The anti-aging properties in alkaline paper make it a logical choice for documents where permanence is essential.

Alkaline Pulping

Pulping by alkaline solutions of sodium hydroxide, with or without sodium sulfide. Without sodium sulfide, soda process with sodium sulfide, Kraft or sulfate processes.

Alpha Pulp

A specially processed, high alpha cellulose content, chemical pulp. It is also called dissolving pulp.

Alum

The paper maker alum is hydrated Aluminum Sulfate {Al2(SO4)3}. It is used to adjust the pH of the mill water or as a sizing chemical in combination with rosin size.

Anthra Quinone (AQ)

A quinoid compound added to white liquor (alkaline cooking liquor) to improve pulp yield and to increase the rate of delignification.

Antique Finish

A term describing the surface, usually on book and cover papers, that has a natural rough finish.

Approach Flow System

The stock flow system from fan pump to headbox slice.

Archival Paper

A paper that is made to last for long time and used for long lasting records.

Ash Content

The residue left after complete combustion of paper at high temperature. It is generally expressed as percent of original test sample and represents filler content in the paper.

Azure

The light blue color used in the nomenclature of "laid" and "wove" papers.

B

Back Liner

The back side layer in a multi-ply paperboard. Normally back liner is made out of inferior grade pulp compared to top liner.

Back Water

See White Water.

Bag Paper

Any paper made to be used in the manufacturing of bags.

Bagasse

Sugarcane residue after extracting the juice.

Bale

A large rectangular shaped compressed package of waste paper, rag, pulp etc. Bale dimensions and weight varies widely depending on the baling material and handling capabilities.

Bamboo

A plant of grass family grown in Asian countries and used for papermaking fibers.

Barker

An equipment used to remove bark from wood.

Base Paper

Refers to paper that will be subsequently be treated, coated or laminated in other ways.

Basis Weight

In English system of units, basis weight is the weight in pounds of a ream (500 sheets) of paper cut to a basic size. (Basic size differs from category to category of the paper. Basic size for Bond and Ledger is 20"x26", book, offset and text paper have basic size of 25"x38"). In metric system of units, basis weight is the weight in grams of a single sheet of area one square meter. Basis weight is also called as substance and grammage in metric system of units.

Beater

An equipment used for beating, refining and mixing pulps.

Beating or Refining

The mechanical treatment of the fibers in water to increase surface area, flexibility and promote bonding when dried.

Biodegradable

Capable of destruction by biological action.

Biochemical Oxygen Demand (BOD)

When effluent containing biodegradable organic matter is released into a receiving water, the biodegradation of the organic matter consumes dissolved oxygen from the water. The BOD of an effluent is an estimate of the amount of oxygen that will be consumed in 5 days following its release into a receiving water; assuming a temperature of 20°C.

Biological Waste Water Treatment

A method of cleaning up waste water using living micro-organisms such as bacteria

Black Liquor

The liquor that exits the digester with the cooked chips at the end of the Kraft cook is called "black" liquor.

Biomass Boiler or Hogged Fuel Boiler

Biomass boilers burn bark, saw mill dust, primary clarifier sediment and other solid waste, and other wood-related scrap not usable in product production. Also called "hogged fuel" boilers, biomass boilers make steam and heat for mill use.

Blade Coater

A device that first applies a surplus coating to paper and then remove extra color after evenly leveling by means of a flexible steel blade.

Bleaching

A chemical process used to whiten and purify the pulp. Bleaching also adds to the sheet's strength and durability.

Blotting Paper

An unsized paper used generally to absorb excess ink from freshly written manuscripts, letters and signatures.

Blow

It is the discharging of the pressure and contents of the digester in to Blow Tank.

Blow Tank

The tank in which pulp is blown from digester.

Board

Thick and stiff paper, often consisting of several plies, widely used for packaging or box making purposes. Its grammage normally is higher than 150 g/m2 or thickness is more than 9 point (thousandth of an inch).

Bond Paper

The name "bond" was originally given to a paper, which was used for printing bonds and stock certificates. It is now used in referring to paper used for letterheads and many printing purposes. Important characteristics are finish, strength, freedom from fuzz, and rigidity.

Bone Dry

Moisture free or zero moisture.

Book Paper

A general term used to define a class or group of papers having in common physical characteristics that, in general, are most suitable for the graphic arts, exclusive of newsprint.

Boxboard

A paperboard used in the manufacture of light non-corrugated container.

Breaking Length

The length beyond which a strip of paper of uniform width would break under its own weight if suspended from one end. Usually expressed in meters.

Brightness

The reflectance or brilliance of the paper when measured under a specially calibrated blue light. Not necessarily related to color or whiteness. Brightness is expressed in %.

Bristol Board

A fine quality cardboard made by pasting several sheets together, the middle sheets usually of inferior grade.

Broke

Paper that is unusable because of damage or non-conformity to the specifications. It is put back in to the pulping system.

Brown Stock

The unbleached chemical pulp.

Bulk

Reverse of density, expressed as cubic centimeter per gram.

Brush Coating

A Coating method in which the freshly applied coating color is regulated and smoothed by means of brushes, some stationary and some oscillating, before drying.

Bursting Strength

The resistance of paper to rapture as measured by the hydrostatic pressure required to burst it when a uniformly distributed and increasing pressure is applied to one of its side.

C

Calender

A stack of highly polished metal cylinders at the end of a paper machines that smoothes and shines the paper surface as sheets pass through.

Caliper

The thickness of paper usually expressed in thousandths of an inch in English system of units and in millimeter in Metric system of units.

Carbon paper

A low basis weight paper (8 to 15 g/m2) with very low air permeability, free of pin holes and with a waxy coating, that is used to produce carbon copies on typewriters or other office equipment.

Carbonless Paper

A paper that uses a chemical reaction between two different contacting coatings to transfer image when pressure is applied.

Cast Coater

A device that applies a wet coating color to a paper web before it contacts a heated drum having a highly polished surface, which cast the coating in to an image of the smooth, mirror-like drum surface.

Causticizing

It is the process in which Green Liquor is converted in to White Liquor. Technically speaking it is the process of converting sodium carbonate in to sodium hydroxide.

Cellulose

It is a high molecular weight, stereoregular, and linear polymer of repeating beta-D-glucopyranose units. Simply speaking it is the chief structural element and major constituents of the cell wall of trees and plants.

Cellulose Fiber

An elongated, tapering, thick walled cellular unit, which is the main structural component of woody plants. Fibers in the plants are cemented together by lignin. In British English Fiber is spelled as Fiber.

Check or Cheque Paper

A strong, durable paper made for the printing of bank checks or cheques.

Chemical Pulp

Pulp obtained from the chemical cooking or digestion of wood or other plant material.

Chemical Recovery

It is the process in which cooking chemicals are recovered.

Chipper

The machine that converts wood logs in to chips.

Clay

A natural substance used as both a filler and coating ingredient to improve a paper's smoothness, brightness, opacity and/ or affinity for ink.

Closed System

Papermaking system wherein white water is mainly recirculated and not discharged as effluent.

Coarse Paper (also Industrial Paper)

Various grades of papers used for industrial application (abrasive, filter etc.) rather than cultural purposes (writing, printing etc.)

Coat Weight

The amount of coating applied to base paper, expressed as pounds of air-dried coating on the surface of a 25X38 in ream or grams per meter square.

Cockle Finish

Produced by air drying paper with controlled tension. This uneven surface is available in bond papers.

Cogeneration

It is the process to generate electricity from high pressure steam and using low and/or medium pressure steam in the mill process. 

Coniferous Trees

Cone bearing and evergreen trees. Also known as soft wood trees. e.g. pine, spruce etc.

Consistency

The percentage of bone dry solids by weight in pulp or stock.

Continuous Pulping

Production of pulp in continuous digester as compared to a batch digester.

Cooking

Reacting fibrous raw material with chemical under pressure and temperature to soften and or remove lignin to separate fibers.

Core

Fibrous tube used to wound paper for shipment.

Corrugated Board

Usually a nine-point board after if has passed through a corrugating machine. When this corrugated board is pasted to another flat sheet of board, it becomes single-faced corrugated board; if pasted on both sides, it becomes double-faced corrugated board or corrugated (shipping) containerboard.

Cotton Fiber

Cotton is a natural fiber and is one of the strongest and most durable fibers known to man. Papers manufactured of cotton fiber will last longer and hold up better under repeated handling and variant environmental conditions than paper made from wood pulp. Generally, given reasonable care, one can expect one year of usable life for every 1% of cotton contained in the sheet. Typically cotton fiber papers are made of either all cotton fiber (100% cotton) or a blend of cotton and wood pulp

Cotton Paper

Paper made with a minimum of 25% cotton fiber. Cotton paper is also called rag paper.

Cross-machine Direction

A direction perpendicular to the direction of web travels through the paper machine.

Curl

Tendency of paper by itself to bend or partly wrap around the axis of one of its directions.

Cut Sheet

Paper cut in sheets (letter, legal, A, B or any other standard size) to be used in printer, photocopier, fax machines etc.

D

Dandy Roll

A hollow wire covered roll that rides on the paper machine wire and compacts the newly formed wet web to improve the formation and if required to impart watermark or laid finish the paper.

Deciduous Trees

Broad leafed or hardwood trees which lose their leaves in fall such as birch, maple etc.

Decker

A drum type filter used for pulp thickening.

Deckle

The width of the wet sheet as it comes off the wire of a paper machine.

Deckle Edge

The untrimmed, feathery edges of paper formed where the pulp flows against the deckle.

Deinking

The process of removing inks, coatings, sizing, adhesives and/ or impurities from waste paper before recycling the fibers into a new sheet.

Delignification

The removal of lignin, the material that binds wood fibers together, during the chemical pulping process.

Digester

The reaction vessel in which wood chips or other plant materials are cooked with chemical to separate fiber by dissolving lignin.

Dimensional Stability

The ability of paper or paperboard to maintain size. It is the resistance of paper to dimensional change with change in moisture content or relative humidity. Dimensional stability is essential for keeping forms in registration during printing and keeping sheets from jamming or wrinkling on press or in laser printers.

Direct Cooking

Batch cooking in which digester contents are heated by blowing steam directly into the digester.

Dissolving Pulp

A high purity special grade pulp made for processing in to cellulose derivatives including rayon and acetate.

Doctor Blade

Thin metal plate or scraper in contact with a roll along its entire length to keep it clean. Blades are also used for creping.

Double Coating

Coating of paper or paperboard twice on one or both sides.

Draw

Difference in speed between two adjacent section of the paper machine.

Dregs

The solids which settle down in the clarifiers in the causticizing process.

Dry End

That part of the paper machine where the paper is dried, surface sized, calendered and reeled.

Durability

The ability of paper to maintain its properties with continued usage and handling.

Dust

Loose flecks of fiber, filler and/or coating on the paper that sometimes sticks to the printing blanket and prevents ink from reaching the paper surface.

E

Electrical Grade Paper

Strong, pin-hole free paper, sometimes impregnated with synthetic resins and  made from unbleached Kraft pulp. Electrical insulating paper must neither contain fillers nor conductive contaminants (metals, coal, etc.) nor salts or acids. Lava stone bars are used on rotor and stator to avoid any metal contamination. Cable papers, that are wound around line wires in a spiral-like fashion, are electrical insulating papers with a particularly high strength in machine direction. Electrical grade papers include cable papers, electrolytic papers and capacitor paper.

Electronic Printing

Photocopiers, ink jet, laser printers and other similar printing methods that create images using electrostatic charges rather than a printing plate.

Electro photography

A printing process that uses principles of electricity and electrically charged particles to create images - e.g., photocopiers and laser printers.

Elemental Chlorine Free (ECF)

ECF papers are made exclusively with pulp that uses chlorine dioxide rather than elemental chlorine gas as a bleaching agent. This virtually eliminates the discharge of detectable dioxins in the effluent of pulp manufacturing facilities.

Envelop Paper

The paper made specifically for die cutting and folding of envelopes on high-speed envelop machine.

Extensible Kraft

Very strong virgin Kraft papers which stretches more and tears less easily than regular Kraft paper.

External Fibrillation

A refining action that results in partial detachment of fibrils from outer layer of a fiber.

F

Felt

A woven cloth used to carry the web of paper between press and dryer rolls on the paper machine.

Felt Side

The side of the paper which does not touch the wire on the paper machine. The "top side" or felt side is preferred for printing because it retains more fillers.

Fiber

A term used to define pulp after the basic preparation in the paper making process.

Fiber Axis Ratio

Ratio of fiber width to fiber thickness.

Fiber Coarseness

Weight per unit length of fiber.

Fibrils

Thread like element in the wall of the fiber.

Filler

Any inorganic substance added to the pulp during manufacturing of paper.

Filtrate

The effluent from the washing or filtering process.

Fines

Small particles fiber defined arbitrarily by classification.

Fine Papers

Uncoated writing and printing grade paper including offset, bond, duplicating and photocopying.

Finish

The surface characteristic of a sheet created by either on-machine or off-machine papermaking processes. Popular text and cover finishes include smooth, vellum, felt, laid, and linen.

Finishing

The trimming, winding, rewinding and packing of paper rolls or trimming, cutting, counting and packing of paper sheets from parent roll.

Flashing

Spontaneous boiling and cooling of a liquid caused by the reduction of pressure below the vapor pressure of the liquid. Flashing occurs in blow tank during blowing.

Flexography

A form of rotary letterpress using flexible rubber or photopolymer
plates

Flotation Deinking

Using flotation method for removing ink from paper during the deinking process.

Fluorescent Dye

A coloring agent added to pulp to increase the brightness of the paper. It may give a slight blue or green cast to the sheet.

Fluorescent Inks

Printing inks that emit and reflect light. Generally, they are brighter and more opaque than traditional inks, but they are not color fast, so they will fade in bright light over time. Their metallic content will also affect dot gain and trapping.

Flute

One of the wave shapes pressed into corrugated medium. These are categorized by the size of the wave.

Formation

The dispersion of fibers in a sheet of paper. The more uniform and tightly bound the fibers, the better the sheet will print and look.

Fourdrinier

Named after its inventor, the Fourdrinier papermaking machine is structured on a continuously moving wire belt on to which a watery slurry of pulp is spread. As the wire moves, the water is drained off and pressed out, and the paper is then dried.

Freeness

A term used to define how quickly water is drained from the pulp. The opposite of freeness is slowness. Freeness or slowness is the function of beating or refining. Freeness and slowness reported in ml CSF and degree SR respectively are also the measurement of degree of refining or beating.

Freesheet

Paper that is free of mechanical wood pulp, which is true of virtually all fine printing papers.

Furnish

A blend of fibers, pigments, dyes, fillers and other materials that are fed to the wet end of the paper machine.

Fuzz

Fibrous projections on the surface of a sheet of paper, caused by excessive suction, insufficient beating or lack of surface sizing. Lint appears in much the same manner but is not attached to the surface.

G

Glassine Paper

A translucent paper made from highly beaten chemical pulp and subsequently supercalendered.

Grade

Papers are differentiated from each other by their grade. Different grades are distinguished from each other on the basis of their content, appearance, manufacturing history, and/or their end use.

Grain

The direction in which most fibers lie in a sheet of paper. As the pulp slurry moves forward on the papermaking machine's formation wires, the fibers tend to align themselves in the direction of movement. Binding books parallel to the grain allows for a smoother fold then working across the grain. Grain direction of sheet fed papers is usually indicated by underlining the number, e.g., 23" X -35". On a web press, the grain direction should run along the length of the paper web.

Grain Long

Grain running lengthwise along a sheet of paper.

Grain Short

Grain running widthwise along a sheet of paper.

Greaseproof Paper

A protective wrapping paper made from chemical wood pulps, which are highly hydrated in order that the resulting paper may be resistant to oil and grease.

Greenfield Mill

Mill or production facility built on undeveloped site.

Green Liquor

The liquor that results when the inorganic smelt from the recovery furnace is dissolved in water is called "green" liquor.

Groundwood Papers

A general term applied to a variety of papers made with substantial proportions of mechanical wood pulp together with bleached or unbleached chemical wood pulps (generally sulfite), or a combination of these, and used mainly for printing and converting purposes.

H

Half Tone

Picture with gradations of tone, formed by dots of varying sizes in one color.

Hard Cook

Undercooked pulp with respect to target conditions.

Hard Sized Paper

Paper treated with high degree of internal sizing.

Hardwood

Wood from trees of angiosperms class, usually with broad leaves. Trees grown in tropical climates are generally hardwood. Hardwood grows faster than softwood but have shorter fibers compared to softwood.

Head Box

The part of the paper machine whose primary function is to deliver a uniform dispersion of fibers in water at the proper speed through the slice opening to the paper machine wire.

Hemicellulose

A constituent of woods that is, like cellulose, a polysaccharide, but less complex and easily hydrolysable.

Hydrophilic

Having strong affinity for water.

Hydrophobic

Lacking affinity for water.

Hygroscopic

Having the property to absorb water vapor from the surrounding atmosphere. Most of the papers (except glassine, greaseproof or wet strength etc.) are hygroscopic in nature.

I

Imbibitions

The absorption of liquid by a fiber without a corresponding increase in volume.

Industrial Papers

A very general term, which is used to indicate papers manufactured for industrial uses as opposed to cultural purposes. Thus, building papers, insulating papers, wrapping papers, packaging papers, etc. would be considered industrial papers.

Ink

Printing inks are made up of pigment, pigment carrier and additives formulated to reduce smudging, picking and other printing problems associated with ink. The choice of ink depends on the type of paper and printing process.

Ink Absorption

A paper's capacity to accept or absorb ink.

Ink Holdout

The way the ink pigment sits on the surface of the paper. Strong ink holdout results in a sharp, bright image.

Internal Fibrillation

Loosening of internal bond within a fiber.

Internal Sizing

Occurs when sizing materials are added to the water suspension of pulp fibers in the papermaking process. Also known as Beater, or Engine sizing.

K

Kappa Number

A term used to define the degree of delignification.

Kenaf

An annual agricultural plant, native of India, which has along fiber in the bark that, is suitable for papermaking.

Knotter

Vibratory screens used for separating knots, uncooked chips and shives from the pulp at the blow tank.

Kraft Paper

A paper of high strength made from sulfate pulp. Kraft papers vary from unbleached Kraft used for wrapping purposes to fully bleached Kraft used for strong Bond and Ledger papers.

L

Laid

A finished produced with a dandy roll having closely spaced wires.

Laminated Paper

A paper built up to a desired thickness or a given desired surface by joining together two or more webs or sheets. The papers thus joined may be alike or different; a totally different material, such as foil, may be laminated with paper.

Ledger Paper

A strong paper usually made for accounting and records. It is similar to Bond paper in its erasure and pen writing characteristics.

Lignin

A complex constituent of the wood that cement the cellulose fibers together.

Like-Sided

Paper that has the same appearance and characteristics on both sides.

Lint

Loosely bonded fibers at the paper surface that attached to the plate or blanket of the printing machine.

Litho

A generic term for any printing process in which the image area and the non-image area exist on the same plate and are separated by a chemical repulsion. Usually oil based offset printing.

Loading

Addition of fillers.

M

M Weight

The weight of one thousand sheets of paper, any size; or double the ream weight.

Machine Direction

The direction of the web through the paper machine.

Manifold Paper

A light weight bond paper used for making carbon or manifold copies or for airmail correspondence.

Manila

A semi-bleached chemical sulfate paper. Not as strong as Kraft, but have better printing qualities.

Market Pulp

Pulp which is made to be used elsewhere for the production of paper. Usually dried to reduce freight costs but may be "wet lap" ( 50% water).

Matte Finish

A dull, clay-coated paper without gloss or luster.

Mechanical Pulp

Pulp produced by mechanically grinding logs or wood chips. It is used mainly for newsprint and as an ingredient of base stock for lower grade printing papers.

MG Machine

A paper machine incorporating a Yankee or a MG drying cylinder in the drying section to produce MG paper.

Multiply Paper Making Process

A paper/board making process in which different layers of fibers are deposited one over the other to form the sheet. The multiply process is used to make the optimum use of various type of fibers available. It is also used to make heavy basis weight papers.

N

Newsprint

A paper manufactured mostly from mechanical pulps specifically for the printing of newspaper.

Non Wood Fibers

Papermaking fibers derived from plants other than trees such as cotton, hemp, bagasse, jute, bamboo or straws.

Nonwoven

Fabric-like material made from long fibers, bonded together by chemical, mechanical, heat or solvent treatment.

O

Off-Machine Coating

Application of coating to the paper off the paper machine, or as a separate operation to the papermaking.

Offset Paper

Also known as book paper. General description of any paper primarily suited for offset printing. Can be coated or uncoated. Characterized by strength, dimensional stability, lack of curl and freedom from foreign surface material. Finish can be vellum or smooth.

Offset Printing

Also know as web offset or lithography. Offers highest degree of precision, clarity, and quality

On-Machine Coating

Application of coating to the paper at the paper machine, or in line as it is being made.

Opacity

That properties of paper which minimizes the "show-through" of printing from the backside or the next sheet.

Oxygen Delignification

A process in which oxygen gas and sodium hydroxide are used to remove lignin from brown stock.

Ozone (O3)

A highly reactive gas with molecules made up of three oxygen atoms.

Ozone Bleaching

A process that uses ozone to whiten cellulose fibers following the Kraft pulping and oxygen delignification processing.

P

Paper

A homogeneous sheet formed by irregularly interviewing cellulose fibers.

Paperboard

A heavy weight, thick, rigid and single or multilayer 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 fibers and dissolve lignin, then washed to remove impurities. Most printing papers are then bleached to lighten the color 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 fibers 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 fiber 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.

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.

Parchment

To simulate the look of ancient parchment, which was made from animal skin, text and cover versions are made with a variegated surface, translucent colors and rigid feel. Parchment is often used for diplomas, certificates and contracts.

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.

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.

Picking

The problem of ink picking off paper fibers 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 colored sheet.

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.

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.

Porosity

The property of paper that allows the permeation of air, an important factor in ink penetration.

Post-Consumer Waste Paper

Waste paper materials recovered after being used by consumers.

Pre-Consumer Waste Paper

Paper recovered after the papermaking process, but before used by a consumer.

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 fibers in water.

R

Rag

The term “rag” is often used interchangeably with “cotton fiber content” and harkens to a period of time when paper was actually made using cotton rags which were cleaned and then broken down into fibers which were then used to manufacture paper. In a sense it could be stated that the fine paper business has been engaged in recycling materials for production since its very beginning. Today paper is no longer made from rags and the term “rag” is falling in disfavor by the industry in lieu of the phrase “cotton fiber content”.

Ream

500 Sheets of paper.

Refiner

An equipment used to give mechanical treatment to the fibers.

Refining

Mechanical treatment of fibers to enhance bonding.

Roe Number

Measure of the amount of chlorine required for bleaching pulp.

S

Salt Cake

Or sodium sulphate added to the black liquor to compensate for the soda loss.

Save-All

Equipment used to reclaim fibers from white water.

Score

To impress or indent a mark with a string or rule in the paper to make folding easier.

Secondary Fibers

Fibers recovered from waste paper and utilized in making paper or paperboard.

Semichemical Pulp

Pulp produced by chemical treatment followed by mechanical treatment.

Show-Through

The undesirable condition in which the printing on the reverse side of a sheet can be seen through the sheet under normal lighting conditions. The more opaque a sheet, the less the show-through.

Shives

Small bundles of fibers that have not been separated completely during pulping.

Sizing

The treatment of paper which gives it resistance to the penetration of liquids (particularly water) or vapors. Sizing improves ink holdout.

Slimes

Fungus or other bacteriological growth. If not controlled in papermaking system, may cause process and quality problems.

Slitter

Rotary knife used to slit or trim a paper web into specified width.

Slowness

Measure of pulp drainage. Has an inverse relationship to freeness.

Smelt

Inorganic chemicals obtained in molten form from the recovery furnace.

Smoothness

The surface uniformity of paper. Sheets that are flat and even provide better ink dot formation and sharper images.

Soft Cook

Over-cooked pulp.

Specific Energy (Refining)

Energy applied per unit weight on oven dry basis (KWH/MT) during refining.

Specific Surface (Fiber)

Fiber surface area per unit weight (OD basis)

Supercalender

A stack of alternating steel and fiber-covered rolls at the end of the paper machine which is used to increase a sheet's gloss and smoothness.

Surface-Sized

Paper that has been treated with starch or other sizing material at the size press of the paper machine. This term is used interchangeably with the term "tub-sized", although tub-size more properly refers to surface sizing applied as a separate operation where the paper is immersed in a tub of sizing (starch or glue), after which it passes between squeeze rolls and is air dried.

Swelling

An increase in volume of fiber due to the absorption of liquid.

T

Tear Strength

A measure of how likely a paper will continue to tear once started. Tear strength will differ with and against the grain.

Tensile Strength

A measure of how likely a paper is to break when pulled at opposite ends. This is very important when running through high-speed web presses.

Text Paper

Text papers are defined as fine, high quality uncoated papers. Typically, they are made in various colors, with numerous textures and a variety of surface finishes. Text papers are made from high-grade bleached wood pulp, cotton fibers, or tree-free pulp such as bamboo. Recycled sheets include high quality recycled waste paper and post-consumer waste pulp, in addition to bleached wood pulp, tree-free pulp or cotton fibers.

Thinning

A practice in which certain trees are removed from a dense stand to allow the remaining trees adequate sunlight, nutrients and moisture to grow at an even rate.

Tissue

A low weights and thin sheet. Normally a paper sheet weighing less than 40 gram per meter square is called tissue.

Totally Chlorine Free (TCF)

Totally chlorine free applies to virgin fiber papers that are unbleached or processed with a sequence that includes no chlorine or chlorine derivatives. (Also see ECF)

Two-Sidedness

The property denoting a difference in appearance and printability between its top (felt) and wire sides.

U

Union Kraft

A packaging material comprising two layers of Kraft paper bonded together by means of a laminant that is resistant to the transmission of water in liquid or vapor form. E.g. bitumen or plastic.

UV Coating

A very glossy, slick coating applied to the printed paper surface and dried on press with ultraviolet (UV) light. UV coating can cause slight variations in match colors, so consult an ink manufacturer or printer for best results.

UV Ink

An ink specially formulated to dry quickly with ultraviolet light while still on press. Fast UV drying eliminates the need to wait for the first side to dry before printing the second side.

V

Vehicle

The liquid part of the ink, giving it the flow properties that enable it to be applied to a surface.

Virgin Fiber

Fiber that has never been used before in the manufacture of paper or other products.

Virgin Kraft

First run or non-recycled Kraft paper.

W

Wall Paper

A paper used for wall covering. Also known as hanging paper.

Washing

A process of separating spent cooking or bleaching chemicals from pulp fibers.

Water-Color Paper

A medium weight, hard sized, coarse surface paper, suitable for painting with water based colors.

Water Finished Paper

A high glazed paper produced by moistening the sheet with water or steam during calendering.

Watermark

The image impressed into the formation of paper by the dandy roll on the wet end of the paper machine; can be seen by holding the watermarked sheet up to the light. Can be either a wire mark or a shaded image.

Web

Term used for the full width of the paper sheet in the process of being formed, pressed, dried, finished and/or converted.

Wet Strength Paper

A chemically treated paper strong enough to withstand tear, rupture or falling apart when saturated with water.

White Liquor

White liquor is the aqueous solution of sodium hydroxide & sodium sulfide used as the cooking liquor in Kraft pulping.

White Water

The filtrate from the wet end of the paper machine.

Wire

The moving "screen" at the wet end of a paper machine where the sheet is formed.

Wire Side

The side of a sheet next to the wire in manufacturing; opposite from the felt or top side; usually not as smooth as the felt or topside.

Wood-Free

Pulp furnish without mechanical pulp.

Wove

The Paper having a uniform surface and no discernible marks. Soft, smooth finish, most widely used writing, printing, book and envelope paper. Relatively low opacity, brightness and bulk.

X

Xerography

The printing process used by photocopying machines. Electric charge creates the image on an eloctro-photographic surface that works as a plate. This surface is cleared after each copy is made, and used over again for the next copy.

Y

Yankee Machine

A type of Fourdrinier paper machine employing a single dryer of large circumference with highly polished surface.

Yellowing

Or brightness reversion is the discoloration of white paper primarily due to aging.

Yield

Ratio of product output and raw material input, expressed in percentage.

Z

Z-Direction Tensile Strength

The tensile strength measured perpendicularly to its surface.