To assist with understanding the information presented we have included a glossary of papermaking terms. This covers all aspects of papermaking: processes, materials and additives.

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Abaca

The name of the fibre from a species of banana that originated in the Philippines, but is now grown throughout the tropics for its fibre. It is also known as Manila hemp.

Acid free

A lignin free paper produced with pH of 7 or higher, with no acid producing chemicals or residues, that also contains an alkali reserve of at least 2%. This is an unregulated term and caution should be exercised when purchasing or using products labelled as "acid free".

Air dried

Paper made with the sheet drying by contact with air, either normal or heated, as opposed to by drying with heated rollers.

Airmail/Aerogramme paper

A light weight paper, pre-folded and with three gummed sections for sealing, usually between 20 and 40gsm.

Alkaline papermaking

Papermaking at a pH of 7 or higher is referred to as alkaline papermaking. Due to the use of calcium carbonate as a filler, alkaline papermaking usually has a pH of 8-8.4. Both the soda and the sulphate processes are forms of alkaline papermaking.

Alkaline reserve

An alkaline calcium carbonate reserve in the pulp that acts to neutralize acidity and lengthen the life of the paper. The minimum calcium carbonate reserve is 2%.

Alkaline sizing

An alkaline pH internal sizing in paper and alkaline fillers that mean that the sheet is above pH 7 when formed. Common alkaline sizes are Alkyl Ketene Dimer (AKD), and Alkenyl Succinic Anhydride (ASA). Alkaline sizing enables better archival properties in the paper.

Alkenyl succinic anhydride

Alkenyl succinic anhydride (ASA) is a widely used neutral/alkali internal sizing agent. It was first developed in 1974, and its usage became widespread in the 1980’s. It is a waxy emulsion composed of a linear chain of five member anyhydride ring. It is dispersed and retained to the sheet with the aid of a cationic starch or other type of cationic stabilizer. It has become widely used with the spread of alkali calcium carbonate filler which is unstable in acidic papermaking systems.

Alkyl ketene dimer

Alkyl Ketene Dimer (AKD), first developed in 1956, is one of the most widely used internal neutral/alkaline sizing agents. It is a waxy unstructured lactones emulsion with waxy solid sizes of 0.5-2mm that is dispersed into water. AKD is retained, and stabilized into the sheet with a cationic starch or other type of cationic stabilizer. It has become widely used with the spread of alkali calcium carbonate filler which is unstable in acidic papermaking systems.

Alum

In papermaking two chemicals, both called Alum, have been used in conjunction with gelatine or rosin for paper sizing. Alum is also to control the pH, improve retention and bonding of fillers and pigment. Aluminium potassium sulphate was the earliest used alum, and was used as a paper sizing agent from the 16th century. It is thought that alum was first used to slow down the mould growth in gelatine, and only later its sizing properties were noticed. There is a reference to the use of alum in Germany in 1579. Alum could become contaminated by iron compounds, but could be freed of these through repeated recrystallization. Aluminium sulphate started to be used in 1876. This type of alum could not be so easily purified of contaminants, so it often contained iron, silica and sulphurous contamination. In the nineteenth century 1 part rosin to 1.5 parts alum were used to size paper.

Alpha cellulose

The portion of cellulose with the highest molecular weight, which is considered to be the purest cellulose. It is insoluble in a 9.5% solution of sodium hydroxide after being swollen in a 17.5% solution of sodium hydroxide. It is found in pulp and paper made from cotton and chemical pulp.

Antique laid

A laid paper made prior to 1800 in which there is a slight shadowing around the chain lines visible with transmitted light.

Archival paper

A class of especially long lasting acid free paper. For paper to be classed as archival it should have passed testing to the standard of ISO11108. Conservation grade archival paper is acid free chemically treated wood pulp, while archival grade or museum grade are made from a rag based pulp, or have a high rag content.

Bagasse

The fibre produced from sugar cane as the waste product of sugar production.

Bank paper

A high quality writing paper, made with chemical and/or rag pulp, with similar working properties to Bond paper but lighter, less than 50gsm.

Basic Size

The standardized size used for measuring the Basis weight in the USA. Some of the sizes for Basic size are:

Paper	Inches	Metric (cm)
Bond, Ledger, Mimeograph, Onionskin, Rag paper, Manifold, Writing	17" x 22"	43.18 x 55.88cm
Offset, Book, Gummed, Bible, Coated paper	25" x 38"	63.5 x 96.52cm
Cover	20" x 26"	50.8 x 66.04cm
Glassine, Newsprint, Poster, Tag stock, Tissue, Waxing, Wrapping	24" x 36"	60.96 x 91.44cm
Index, Bristol	25 ½" x 30 ½"	64.77 x 77.47cm

Basis weight

A system used in the USA to express the weight of a particular standardized size for a particular type of paper in pounds for a 500 sheet ream. The standardized size for particular paper type is known as the Basic Size. The rest of the world measures a papers weight in grams per square metre; GSM or g/m²

Bast fibres

The fibres from the inner bark or phloem of a plant. Plants whose bast fibres are used include kozo (paper mulberry), gampi, mitsumata, flax, hemp and jute.

Beater

A machine to fibrillate, break apart and disperse the fibres in the pulp. It consists of a revolving roller, and a bedplate. The fibre source and water are either fed through a pump in a premixed form, or the fibre and water are slowly added separately with the proportions monitored so that the machine can still operate smoothly. Dyes, fillers and sizing can be added to the beater to disperse them through the pulp. Hollander beater is another name for a beater. A naginata beater is a Japanese designed beater that uses slightly curved dull blades to beat through the pulp, rather than a dull bladed roller.

Beater Sized

Another name for internally sized. A beater sized paper has had the sizing agent mixed into the pulp

Blotter

An unsized paper used for absorbing liquid. It is made of rag or chemical pulp or a combination of fibre types.

Bond Paper

A high quality writing or printing paper with a weight greater than 50gsm. Originally it had cotton content, however today it may be a machine pulp paper. Important characteristics of this paper are finish, printability, erasability, strength and freedom from fuzz. It is now used for letterhead and stationery and printing. Its name originally came from being the type of paper on which legal documents or government bonds were issued.

Book paper

Book paper is paper produced specifically for usage in books. Book paper is noted as being opaque, not high white, and frequently between 60 and 90gsm. The caliper thickness to gsm ratio is measured as this can calculate the number of printed pages per inch. A range of paper types and pulps can be used to make book paper.

Bleach

A chemical process to decrease colour and increase whiteness of the pulp. From 1804 calcium hypochlorite was used as bleach; in the first half of the twentieth century a multistage bleaching process was developed using hypochlorite bleach and an alkaline extraction. In the 1960s and 1970s oxygen bleaching was developed and started to be used. The environmental damage caused by chlorine bleaching became an issue through the 1970s and 1980s, and led to the adoption of Elemental Chlorine Free (ECF) and Total Chlorine Free (TCF) bleaching throughout the 1990s. ECF often uses chlorine dioxide bleaching, sometimes with a small amount of hydrogen peroxide, and alkali washes. TCF bleaching uses peroxide and ozone for bleaching. Many contemporary bleaching processes, such as oxygen bleaching, include delignification.

The short hand way of describing bleaching process when used in sequence:

• C: Elemental chlorine bleaching with chlorine gas
• E: Extraction with sodium hydroxide
• H: Hypochlorite (either sodium or calcium)
• D: Chlorine Dioxide bleaching
• P: Hydrogen peroxide
• O: Oxygen bleaching
• N: Nitrogen dioxide
• Z: Ozone bleaching

Brightness

Brightness is a measure of the percentage of light reflected by a sheet of paper. There are two standard measures of brightness: TAPPI and ISO.

Bristol board

A paperboard that is uncoated, machine finished on both sides in either plate or vellum finish, and with a weight of between 220 and 250gsm. It can come in a number of different ply with two and three ply the most common, and can be used for a wide range of uses, from drawing, paperback book covers, folders, tickets and tags.

Buffering

Buffering is the inclusion of an alkaline reserve to slow acid hydrolysis of the cellulose.

Calcium Carbonate

Calcium carbonate has been used historically in hand papermaking in the form of chalk, or ground sea shells, to increase the brightness of the sheet. In more recent times it has been used in its purer chemical form as an alkaline filler, usually between 10% and 20%, or coating agent in paper. It is largely replacing kaolin and other fillers as it is generally cheaper, more archival , creates stronger paper, retains brightness for longer, more easily used as a substitute for expensive fibres, and since it cannot be used in a papermaking machine working at below pH 6.5 has increased in usage with the increase in alkaline papermaking. It is used as either Ground Calcium Carbonate, GCC, or Precipitate Calcium Carbonate, PCC. In 1986 a PCC satellite plant was introduced in the USA. Calcium carbonate is not suitable for use in acid paper making or papers with a high lignin content.

Calcium hypochlorite

A chlorine based bleach, Ca(ClO)², invented in 1799 by Charles Tennant in Glasgow, Scotland. It was the dominant form of bleaching until the introduction of gaseous chlorine and dioxide bleaches about 150 years later.

Calender

Calendering is a step in the modern papermaking process where, towards the end of the papermaking machine, the sheet is smoothed by passing it through hard rollers. The rollers can be metal, or of a softer polymer depending on the finish required. They can also be embossed with a texture to achieve a particular surface finish, for example linen finish paper. Paper that has been supercalendered has passed through alternating metal and fibre covered rollers and is known for its highly glazed surface that is used in publishing. Paper can also be 'platen calendered' as a separate processing step; in this case sheets are cut and pressed between metal plates.

Casein

A group of proteins found in milk, usually derived from cow milk. It has been used as a glue, or binder, in coating formulation. A coating formulation made of a combination of casein, or animal glue, and kaolin was introduced in 1807. Since then it has been used as a coating binder.

Cationic starches

A modified positively charged starch used in the wet end of a papermaking machine to increase the interfibre and fibre to filler and size bonding. The use of cationic starches increases sheet strength, sizing, filler and fines retention

Cellulose

Cellulose fibres are the basis of the pulp from which paper is made. Cellulose is a long chained linear polysaccharide that plays an important structural role in the cell wall of plants. It was first discovered in 1838 by Anselme Payen, and the structure was discovered in 1920. The formation of hydrogen bonding between oxygen atoms in different hydroxyl groups holds the chains of cellulose firmly together giving tensile strength to the cell wall, and then later to paper. Cellulose breaks down through hydrolysis into smaller polysaccharides or glucose, this process is sped up in an acidic environment. Cotton is composed of 90% cellulose, making it one of the purest naturally occurring forms.

Chain Lines

In a laid paper the chain lines are the thicker, less frequent, lines in the paper sheet. A traditional handmade paper mould is a series of fine wires through which the water could drain while the wires would catch the pulp. The chain lines are the thicker wires that the many finer parallel running wires were attached to. The finer lines created by the finer wires are referred to as laid lines.

ChemiMechanical Pulp

A pulping process in which the wood chips are pretreated with chemicals to soften the lignin. Unlike chemical process the aim is not to dissolve or break apart the lignin and remove it – ChemiMechanical pulping aims to only loosen and soften it. Common types of ChemiMechanical pulp are hot sulphite, using sodium hydroxide and sodium sulphite; and cold soda, using sodium hydroxide. It is often used on hardwoods, and has a pulp yield of 80-90%. It is often referred to as CMP.

ChemiThermoMechanical Pulp

A process in which the lignin is softened with sodium sulphite or sodium hydroxide, and then mechanically pulped under heat and pressure. It is often used with hardwoods and has 80-90% pulp yield. It is often referred to as CTMP.

China clay

Another name for Kaolin.

Chlorine dioxide bleaching

An oxidizing bleach, referred to as (D) that was usually done in sequence with alkali washing of the pulp. As it reacts selectively to lignin and wood resins without effecting cellulose under ideal conditions it was widely used, especially in the five stage CEDED bleaching process. Chlorine dioxide bleaching was first used in Canada in 1946. Elemental chlorine free bleaching, ECF, still uses chlorine dioxide bleaching, while total chlorine free bleaching, TCF, does not. In 2005 85% of world chemical pulp was bleached with chlorine dioxide.

Chrome yellow

A deep yellow pigment that was first encountered in its natural form of crocoite in 1766 in mines in the Ural Mountains of Russia. It was synthesized in the laboratory by mixing a solution of lead nitrate and potassium chromate, and then filtering off the lead chromate solution. It has the chemical formula of PbCrO4. It was first created by Louis Vauquelin in 1797, and its first recorded use as a colour in English is in 1818. Since it darken with air exposure, and contains toxic heavy metals it is currently rarely used.

Coal tar dye

Aniline synthetic dyes developed between 1834 and 1843 by the chemists Otto Unverdorben, Friedlieb Runge, Carl Fritzsche, Nikolay Zinin and August von Hofmann. In 1856 William Perkins discovered mauveine and started the industrial production of synthetic dyes.

Coated paper

A paper that has had its surface treated with a glue, such as casein; clay, pigment and adhesive mixture is used to improve smoothness and gloss, and reduce ink absorbency. Kaolin and calcium carbonate are frequently used in combination with organic or inorganic binders as coating agents to improve printing quality of papers.

Cold pressed

Cold pressed paper has been air dried and then pressed in an unheated hydraulic press or through cold calendering. They generally have more surface texture than hot pressed papers.

Commodity paper

A low grade bond or offset paper.

Cone refiner

A type of fibre refiner that may or may not be used in conjunction with a standard, Hollander beater. It consists of a conical rotating plug and the matching shell in which it is fitted. Both the plug and shell are covered with knives or bars, and as the pulp is fed through the rotating plug the fibres are pulled apart. It was first invented by Joseph Jordan in 1860. It is also called a Jordan refiner.

Continuous wire

Also known as the continuous web, it was originally a woven metal mesh onto which the pulp is sprayed, although currently it may be a plastic mesh.

Cotton

A plant whose soft fluffy fibres around the seed have been used for papermaking for centuries. This protective soft, fibrous barrier around the seed, known as the boll, is almost pure cellulose. Paper made from cotton is known as rag paper, or cotton fibre content paper, and is generally high quality due to the absence of lignin from cotton.

Cotton linters

Cotton linters are the short fibres that adhere to the cotton seed after the ginning process.

Cotton Fibre Content Paper

Paper made of at least 25% cotton derived cellulose.

Counter mark

The countermark is a watermark that gives the name of the manufacturer, their initials, mill or place of manufacture of the sheet. Often when one side of the sheet would contain an image this was referred to as the ‘watermark’ and the other mark on the opposite side of the sheet giving the name of the manufacturer, initials, place of manufacture etc being called the ‘countermark’. It is formed with raised wires in the mould in the same way as a standard design watermark. Not all sheets will contain both a 'watermark' and a 'countermark'. Countermarks started to be used in the 17th century in England and earlier in France.

Cross grain

A fold or cut running against the grain direction of a sheet.

Cut size

A smaller sheet of business paper that has been cut down from a larger sheet with a guillotine. Sizes are measured in inches and are 8" x 10", 8½" x 11", or 8½" x 14".

Cylinder mould machine

Developed in 1809 by John Dickinson in England, the cylinder mould machine differs from the standard Fourdrinier machine in that the instead of the pulp slurry being poured onto the wire, a wire covered cylinder is dipped into the vat of pulp slurry. Unlike the Fourdrinier machine the cylinder mould produces genuine watermarks that are wires woven into the cylinder mould, and can produce paper with four deckled edges by having thicker wires to mark the sheet size that can be torn through to give a deckled edge. It can also produce rolls of paper. Although they can be slower than other machines they allow a strong sheet, greater dimensional stability through a thicker cellulose fibre web, and true watermarks on the wire side. It is also called a mould made machine.

Dandy Roll

The dandy roll is a hollow wire-covered roll that passes over the still wet paper on the web near the wet end of the papermaking machine. The dandy roll was invented by John Marshall (1826) as part of the papermaking machine. It was created to allow water in the paper to be removed, and to impress a watermark or laid impression into the still damp paper.

Deckle

In traditional handmade papermaking the deckle was the wooden frame that held the papermaking screen.

Deckled Edge

In traditional handmade papermaking the deckle was the wooden frame that was held over the screen on which the pulp was placed and the water drawn through. The deckled edge of a sheet of paper is formed at the deckle and is generally thinner and irregular in shape. Hand made papers will have four deckled edges, and generally machine made papers will have two, although there are techniques by which a machine made paper can also have four deckled edges.

Deinking

A process in which ink, fillers and sizing is removed from used paper that is going to be recycled into paper again. The recycled pulp after deinking can be added to virgin pulp or used alone to create a range of paper types. Justus Claproth developed a deinking process in 1774, and in 1801 Mathias Koop patented a deinking a paper recycling process. In the 1950s froth flotation deinking started to be used.

Delignification

A chemical process in which lignin is removed from paper pulp leaving cellulose and hemicellulose. The sulfate, sulfite and soda processes are all methods to delignify wood to turn it into pulp.

Density

The weight of a paper of a particular size. In the USA it is expressed as the Basis weight, and in the rest of the world as grams per square metre, which is written as g/m² or gsm.

Diatomaceous earth

An amorphous silica that is used as a dulling or flattening agent in coating and a filler in paper. It is also known as diatomaceous silica, diatomite, infusorial earth and kieselguhr.

Disc refiner

A machine that is used to defibrillate pulp. It consists of ribbed or serrated discs that are rotating and static, or rotating counter to the first disc, through which the pulp is forced. The disc refiner has the advantage over previous beaters in that it can be used continuously, rather than by batches of pulp.

Duplex paper

Paper or card stock that is made with two sheets that have been laminated together. Each sheet may have a different texture, colour or finish appropriate to the usage.

Dry end

On a papermaking machine the dry end is the end involved with the drying, calendering, reeling and slitting of the paper.

Elemental chlorine bleaching

Also known as chlorination (C) it is a bleaching process in which the pulp is exposed to gaseous chlorine, Cl2, which reacts with the lignin to make water and alkali soluble orange coloured chlorolignins. It was often the first stage of the five stage, CEDED, bleaching process that was used with Kraft pulp from the 1950s, until chlorination and chlorine derived bleaches were phased out after the 1980’s. It has been mainly phased out due to environmental concerns.

Elemental chlorine free

Is a pulp bleaching technique that may use chlorine dioxide, but not gaseous elemental chlorine.

Esparto

A grass originating in North Africa or Spain that has been used in papermaking in Great Britain from the 1850s. It was first used in Great Britain by Thomas Routledge in 1857. It was often used in book paper. Esparto is rarely seen in American paper due to the cost of transport.

Etching paper

Printmaking paper used for producing etchings. Such papers are able to withstand dampening and soaking, are dimensionally stable in moisture, and are able to withstand the pressure of the printing press. Etching papers are either unsized or lightly sized, and many are rag papers or have a high rag content.

Eucalypt

A wide range of fast growing hardwood trees that primarily grow in Australia, although they are now grown in plantations around the world. They were not able to be used in paper making machines until 1938, following research by Boas and Benjamin in Australia.

False watermark

This is an impression on the paper that appears to be a watermark, however it was not created by the thinning of the pulp in the sheet as formed by a traditional watermark. These false watermarks have been created in a number of ways. One way was by drawing the design with an oily substance that make the paper translucent which makes the design appear lighter. Another way to make a false watermark is to impress the paper and emboss it at the dry end of the machine, as opposed to the wet end.

Fibre

Long strand-like filaments that are usually derived from plant material used to form paper. Fibres are usually held tightly together in wood and need to be broken apart by mechanical or chemical means.

Fibrillation

In wood pulp, fibrillation is the breaking apart of the fibres from each other into a dispersed pulp.

Filler

A chemical that is added to the pulp prior to the sheet forming that adds to the bulk, opacity, brightness and smoothness of the formed sheet. Kaolin and Calcium carbonate are common fillers.

Finish

The appearance or process which improves the surface or appearance of a sheet.

Foolscap

A traditional paper size based on inches, still in use in the USA. Foolscap measures 13½ x 8inches, or 13½ x 16inches for a full sheet. There is some variation in traditional sizing of up to half an inch. The name is derived from paper produced to this size in the UK bearing a watermark of a fool wearing a belled hat.

Fourdrinier machine

The first papermaking machine produced in England was granted a patent in 1801 and made in 1803, financed by the Fourdrinier brothers Robert and Sealy. This machine was based on the design by the Louis-Nicholas Robert of France who had taken out a patent in France in 1799 for a papermaking machine. The Fourdrinier machine formed the basic principles on which all later modern papermaking machines have been based. There is a wet end, which can encompass the headbox and the sheet forming section where the dandy roll passes over the still wet sheet, then the press section in which the paper passes through rollers to remove excess water, then the drying section in which the paper is further dried, and finally the calendering section where the paper is smoothed by rollers.

Foxing

Red-brown spotting marks on paper that appear over time, and through the effects of moisture. Foxing is caused by a combination of metallic impurities and mould.

Fuzz

Fibres coming out from the surface of the formed sheet of paper.

Gampi

A shrub growing in Japan whose bast fibres have been used in papermaking for centuries. Gampi has been used to make Torinoko paper for Kana script calligraphy.

Gelatine

A colourless mix of proteins and peptides derived from the partial hydrolysis of collagen from bones and tissues of animals. It was first used in papermaking in Fabrino, Italy in the mid thirteenth century and was commonly used in paper sizing before the introduction of alum-rosin sizing in 1807, although it was still widely used into the 1840s and 1850s.

Glassine paper

A paper made from heavily beaten chemical pulp that has been supercalendered. This paper is smooth and dense on both sides it is also transparent or semitransparent. As it is resistant to the passage of oils, grease and smells it is often used in wrapping foods, tobacco, chemicals and greasy metal parts.

Grain direction

Paper produced on a machine and some handmade papers will have had the wet pulp shaken in one direction resulting in many of the fibres aligning in that direction. In machine made papers this is the direction of the continuous mesh on which the pulp is sprayed. Paper tends to tear more readily along the grain direction.

Groundwood pulp

A mechanical pulp made by pressing debarked wood through a rotating grinder with water or steam. The pulp is generally short fibred and if not further chemically treated high in lignin. It is also known as Stone Groundwood Pulp (SGW), and if the grinding is done under pressure with heated water it is known as Pressure Groundwood (PGW).

GSM

The weight of a paper measured in grams per square metre. It is more accurately written as g/m²

Gypsum

A soft mineral composed of calcium sulphate dihydrate, with the chemical formula of CaSO₄.2H₂O. A form of it is alabaster which is used in sculpture.

Hardwood

Wood from the angiosperm order of trees. Although generally harder than softwoods, there are examples of hardwoods that are softer than softwoods and vice versa. Hardwoods have more vessel elements and generally shorter fibre length than softwoods. Examples of hardwoods are birch, beech, maple, oak, eucalypt and poplar.

Head box

In a papermaking machine the head box holds the pulp, also called stock, before it is sprayed onto the continuous wire for sheet formation.

Hemicellulose

A group of polysaccharides associated with cellulose in the plant cell wall. They are less crystalline than true cellulose and also shorter and less resistant to hydrolysis.

Hot pressed

Hot pressed papers have been heated, either in a press or by heated rollers, to remove water from the still wet sheet. Hot pressed papers generally have a smoother surface than cold pressed papers.

Hydrogen peroxide

An oxidizing bleach that was first discovered in 1818 by Louis Thenard. Although the chemical itself can be expensive, its ease of use and low plant capital cost outlay have made it a popular pulp bleach. In the shorthand for describing bleaching processes it is represented by the letter 'P'.

Indanthrene blue

A deep, dark blue dye that is also written as Indanthrone blue. It is made by aminoanthroquinone treated with potassium hydroxide and is known to be very lightfast. It was first manufactured in 1901, and became widely available in the 1950s.

Internal sizing

Internal sizing is when the sizing agent is applied to the pulp from which the sheet will be formed. This process is also called engine sizing.

Jordan refiner

This is another name for a cone refiner.

Kappa number

The kappa number is an indication of residual lignin in a pulp. The kappa number is determined by the amount of potassium permanganate that the pulp will absorb and is used as a measure to determine the amount of bleaching required.

Kaolin

A white clay, composed mainly of kaolinite, an aluminium silicate. It can be added to pulp as a filler, to increase opacity or as component of coating. It is also known as China clay.

Kozo

The Japanese name for the paper mulberry. The bast fibres of the paper mulberry have been used in papermaking for centuries. The fibres are very long and strong meaning that the fibres may be added to a wide variety of other fibre types, and the resulting paper used in a wide variety of uses, from writing, painting, calligraphy, folding screens, umbrellas, sliding doors, toys, lanterns etc.

Kraft Process

Another name for the sulphate process of chemical pulp processing.

Laid paper

Laid paper is made with the distinctive laid and chain lines. Traditionally the laid and chain lines where created in the sheet through the wires on the handmade screen, however today they are recreated through an impression into the wet formed sheet by a dandy roll. A paper without laid and chain lines is known as wove paper.

Laid Lines

In laid paper the laid lines are the thinner lines that run counter to the thicker, more widely spaced, chain lines. A traditional handmade paper mould is a series of fine wires through which the water could drain while the wires would catch the pulp. The laid lines are the thinner wires that are attached to the thicker lines known as chain lines.

Lignin

A series of complex chemical compounds found most commonly in wood as a means of supporting and strengthening. Lignin fills the space between the cell walls, especially in the xylem, and helps binds cells and fibres together. Papers with lignin content are known to darken, become acidic and degrade more quickly than lignin free papers. Rag papers have no or very little lignin and generally last longer.

Linen Finish paper

A sheet that has been given the impression of linen cloth through pressing. The linen cloth impression can be given to the paper by pressing it between linen cloth, between linen covered rollers/belts or having a dandy roller with a linen cloth pattern on it.

Machine coated

Paper that has been coated during its processing through the papermaking machine.

Machine direction

The direction in which the paper pulp runs onto the papermaking web in the papermaking machine. It is also the called the grain direction on the paper.

Machine dried

A drying process in which the paper is dried by passing through heated rollers.

Mechanical Pulp Process

This is pulp produced without chemicals. There are two main methods of producing mechanical pulp: groundwood pulp and thermomechanical pulp. Groundwood pulp is created by feeding wood through metal grinders; if it is created through the use of a refiner it is called refined groundwood pulp. If the grinding takes place at high pressure it is called pressure groundwood. Thermomechanical pulp is created by grinding the wood while it is being steamed at pressure, this reduces the energy needed and results in less damage to the fibres. Mechanical pulping usually requires more energy than chemical pulping. The process does not remove lignin from the pulp so papers produced using this method is prone to high acidity, discolouration and embrittlement. Mechanical pulp paper is often used for the production of newspapers. Mechanical pulp has a pulp yield of over 90%.

Manila hemp

A traditional name for fibre from abaca, a species of banana originated in the Philippines, and which is now grown in the tropics for its fibre.

Mitsumata

A shrub growing in Japan that is used for papermaking. The inner bast bark is used in papermaking.

Modern laid

A laid paper in which there is no shadowing around the chain lines visible through transmitted light. Modern laid paper was developed around 1800 with an improvement in handmade paper mould design, and then the introduction of machine making paper and the dandy roll.

Multi-tonal watermark

This type of watermark incorporates light and shade into its design as opposed to the linear watermarks previously used. It is formed by instead of using wires on the dandy rolls surface it has areas of relief forming the image in the dandy rolls wire surface. T H Saunders exhibited examples of multi-tonal watermarks in 1851. They are often used in security papers, such as in cheques and passports. They are also known as chiaroscuro watermarks or light and shade watermarks.

Newsprint

A low cost, non-archival paper that is used for printing newspapers. It is usually composed mainly of mechanical pulp.

Naginata beater

A naginata beater is a Japanese designed beater that uses slightly curved dull blades to beat through the pulp, rather than a dull bladed roller as used in a Hollander or standard beater.

Neutral sulphite pulp

A process in which the lignin is softened, but remains in the pulp during refining. This process involves mild cooking with sodium sulphite combined with sodium carbonate to produce a neutral pH cooking liquor. Since it does not remove the lignin the process is a semi-chemical one and the resulting sheet or board suffers from the same long term acidity and loss of strength as other mechanical processes.

Onion skin paper

A lightweight writing paper. It has been used for writing especially airmail letters, typing and making carbon copies with a typewriter. It generally has a weight of less than 20gsm and will be a chemical and/or rag pulp with a smooth, glazed, semitransparent and cockled finish.

Optical Brightener

Optical brighteners are chemicals added to the pulp to make the formed paper appear whiter. Generally they are fluorescent synthetic dyes that absorb visible and ultraviolet light and then re-emit it at a higher wavelength often in the violet or bluish end of the spectrum, therefore adding brightness to the paper.

Organosolv pulp

A pulping process in which organic chemicals, such as ethanol, methanol, acetone, butanol, ascetic acid and formic acid are used to solubilize lignin. It was first discovered by Theodore Kleinert in 1971. Organosolv pulping offers the advantage of higher pulp yields than sulphate pulping, less water and odour pollution, recoverable usable lignin, recoverable carbohydrates for ethanol production and easy chemical recovery; however it does produce slightly weaker pulp.

Oxygen bleaching

An oxidizing process in which the wood or pulp is exposed to oxygen in an alkali medium to oxidize and degrade the lignin. In the bleaching sequence it is referred to by the letter 'O'. The alkali used is compatible with the Kraft process, and can be recovered in a recovery boiler, thereby reducing the overall amount of chemicals required. Oxygen bleaching was developed by Nikitin and Akim in 1952 in the USSR and was commercialized in the late 1960s, and in the 1970s the first displacement bleaching plant was operated. It is also referred to as oxygen delignification.

Ozone bleaching

An oxidizing bleaching/delignification process introduced in the 1990s. The process involves exposing the pulp or wood to ozone at low pH, 2 to 4, at temperatures of 50°C to 60°C. Ozone is used in both TCF and ECF bleaching and has the advantages of reduced chemicals, fast action and high brightness. As the ozone process is not selective to lignin care should be taken not to damage the cellulose. In the bleaching sequence it is referred to by the letter 'Z'.

Papermakers alum

Aluminium sulphate which was introduced in 1876 as a replacement to Aluminium Potassium Sulphate. It was used for sizing and water purifying.

Paper mulberry

The Japanese name for paper mulberry is Kozo. The bast fibres of the paper mulberry have been used in papermaking in Asia for centuries. The fibres are very long and strong meaning that the fibres may be added to a wide variety of other fibre types, and the resulting paper used in a wide variety of uses, from writing, painting, calligraphy, folding screens, umbrellas, sliding doors, toys, lanterns etc.

Parchment

A thin writing material made of the prepared hide of a calf, goat or sheep. Parchment was used in Europe until the introduction of paper in the Middle Ages. Parchment is made through first soaking, then retting the skin and then stretching and scrapping with a curved blade to remove all of the remaining flesh and hair. It is then stretched and dried, and may have the surface treated with pumice powder, starches, albumen, flour or milk to improve the whiteness and writing properties. As parchment is untanned, unlike leather, it is very susceptible to any changes in moisture.

Parchment bond

A paper made of over beaten rag or chemical pulp. It is known for its durability and velvety surface.

Parchment paper

A paper created by passing an unsized rag, or chemical pulp, paper through a bath of sulfuric acid or zinc chloride, and then washing it thoroughly. The acid hydrolyses the cellulose and leaves the paper heat, grease and moisture resistant as well as being translucent. It is frequently used in baking where its heat resistance and non-stick characteristics are useful.

Platen calendared

Paper that is platen calendered has been cut and pressed between metal in a press.

Ply

A layer of paper.

Prussian blue

Developed in Berlin in 1706 by the paint maker Johan Diesbach, Prussian blue was one of the first synthetic pigments . It is a dark blue colour. The earliest known usage of the pigment in art was in 1710, and by the 1720s it was widely available. Prussian blue is an oxidized iron cyanide salt that has the formula Fe₇(CN)₁₈.

Pulp

The mix of paper fibre and water after the fibres have been defibrillated and dispersed.

Rag

The first papers made in Europe were made from used clothing rags. These clothes were made of cotton, linen, and ramie, and today the term rag means the fibres from cotton, linen and ramie. These fibres are all high in cellulose and low in lignin and make some of the highest quality papers.

Rag content paper

Paper with a content of rag.

Rattle

The noise produced when sheet of paper is shaken. Its presence can be indicative of stiffness or rigidity; however its absence is required for certain usages.

Ream

Depending on the type of paper, a name for a unit of 480 or 500 sheets of paper.

Ream weight

The weight of a ream of paper of particular type and size.

Retention aids

A chemical that helps the pulp retain certain fillers, sizes, brightening agents etc. when it is formed into a sheet, without affecting the water drainage properties. With the use of retention aids, fewer chemical additives are wasted in the process of forming the sheet. Examples of retention aids are polyacrimide, polyethyleneimine or bentonite.

Recycled paper

Paper that has been made from waste paper. The paper used in recycled paper is either mill broke, trimmings or scrap from papermaking, pre-consumer waste, paper which has left the mill but is unused, or post-consumer waste which is paper that has left the mill and been used. The paper for recycling is first broken down, heated, strained, deinked, bleached and then formed into a pulp to be remade into paper again. Justus Claproth first developed deinking in 1774, and then in 1801 Mathias Koop patented a way of deinking and recycling paper. In the 1950s froth flotation started to be used to deink paper. Paper fibres can usually be recycled about five or six times before the fibres all become too short to be recycled again.

Refiner

A device for defibrillating wood into pulp. The two most common types are the disc refiner and the cone refiner.

Rice paper

Fine oriental paper, which is actually not made entirely of rice, but a mix of rice and any number of longer fibres.

Rosin

A derivative of resin extracted from coniferous trees. It has been used with alum in paper sizing since 1807, and by the mid-19th century was in common usage. Rosin has a hydrophobic and hydrophilic end to the molecule, and is precipitated onto the fibres by alum. The hydrophobic portion of the molecule reacts with ink preventing it from being absorbed straight into the paper fibres. Sizing most effectively occurs at pH 4-5.5 which leads to acidic paper that will increase in acidity and weakness over time. Papers sized with alum-rosin tend to become acidic through hydrolysis.

Rosin wax size

An aqueous emulsion of a paraffin or microcrystalline wax and rosin used in sizing. It is often anionic (negatively charged).

Security thread

An anti-counterfeiting measure used in passports and bank notes. It consists of a fine ribbon of plastic or metal that has been woven or enmeshed into the surrounding paper fibres.

SemiChemical pulping

A pulping process in which the wood chips are mildly cooked in a chemical pulping solution, such as in soda, sulphite or sulphate pulping, before being ground in a disc refiner. Neutral sulphite is a common method used in semi chemical pulping, in which sodium sulphite combined with an alkali salt is used. Semichemical pulping uses less chemicals and less cooking time than chemical pulping, while having a higher pulp yield. The pulp yield is 60-80%, however much of the lignin remains in the pulp.

Shadow watermark

This is a watermark that is created through a recessed area in the dandy roll pressing onto the still wet pulp. Since it is recessed it draws more pulp into the void, and through transmitted light this area appears darker. This technique is often used in combination with raised area to produce a multi-tonal watermark that is often seen in security papers.

Sizing

Sizing is the addition of certain chemicals to paper to reduce the absorbency and improve the writing and printing properties of the paper. There are two methods of sizing: internal sizing and surface sizing. Internal sizing is also sometimes known as engine sizing, while external sizing is sometimes known as tub sizing, as traditionally the formed sheet was dipped into a tub of sizing agent. Common chemicals used for sizing include gelatine, alum-rosin, starch, alkyl ketene dimers and alkyl succinic anhydride.

Soda Pulp Process

A chemical process involving cooking wood pulp in sodium hydroxide or a caustic soda solution, to create pulp. The first mill using this method was started in the USA in 1860. This process has the advantage of being able to better handle the silicate found in agricultural waste, such as straw and bagasse. The pulp produced from this method is weaker than other chemical pulping methods, producing paper with low tear strength, and used large amounts of the then expensive sodium hydroxide, leading to the development of the chemically cheaper and stronger sulphate process. After the invention of sulphate pulping in 1879 many soda mills converted to sulphate mills. It has a 40-55% pulp yield depending on the wood used.

Sodium hydroxide

Discovered in 1807 by Humphrey Davy, it has been used as an alkali wash and in the white liquors of Kraft pulping. In the bleaching sequence, an extraction with sodium hydroxide is referred to in shorthand by the letter 'E'. It has the chemical formula of NaOH. It is also known as caustic soda.

Sodium hypochlorite

A chlorine based liquid bleach with the chemical formula NaClO, invented in 1785 by Claude Berthollet in France. It was replaced by the cheaper calcium hypochlorite discovered by Charles Tennant in 1798. It is sometimes referred to as Eau de Javel.

Softwood

Wood from the gymnosperm order of trees. Although generally softer than hardwoods, there are examples of softwoods that are harder than hardwoods and vice versa. Softwoods have fewer vessel elements and generally longer fibre length than hardwoods. Examples of softwoods are pines, cedars, spruce, douglas fir and yew.

Stamper

An early machine for fibrillating rags into pulp, usually water powered. It beat the rags with hammers striking down into mortars. It was replaced with the Hollander beater which was invented in Holland around 1680.

Straw

An agricultural by product, consisting of the dry stalks, of harvested cereal plants. Matthias Koop produced paper from straw in 1800, and after that was used as in pulp, although not as the primary fibre. During WW1 and WW2 it was used as a replacement for esparto in British paper mills.

Sulphate Process

This process is also commonly known as the Kraft process. The name Kraft comes from the German word for strong as the paper produced by this process is stronger due to the cellulose chain being less likely to be broken than with the competing acidic sulphite process. This process involves the treatment of wood pulp with a mixture of sodium hydroxide and sodium sulphide to break the bonds between the lignin and cellulose and produce a cellulose pulp. First invented in 1879, the first mill to use this process was started in 1890 in Sweden. In the early 1930s the Tomlinson recovery boiler was invented allowing the recovery of the inorganic pulping chemicals. As a result of this invention, sulphate processed papers started to exceed sulphite papers in the 1940s and 1950s. Compared to the sulphite process, sulphate pulp is generally stronger, less acidic, can use a wider range of woods, requires extra refining and is harder to bleach. Sulphate pulping has a 45-55% pulp yield.

Sulphite Process

A chemical process in which wood chips are treated to produce cellulose and lignin is extracted. The cellulose is produced through the treatment of wood pulp with sulphurous acid in large high pressure vessels called digesters. This process was invented by American Benjamin Tilghman, and in 1874 the first commercial sulphite mill was built in Sweden. By 1900 it was the dominant papermaking process. Sulphite pulp has an equal pulp yield to sulphate pulping and the pulp is easier to bleach, however due to the acidic treatment some of the cellulose is hydrolyzed making generally weaker and more acidic paper. The sulphite process cannot process barks, resinous softwoods and tannin containing hardwoods. Until the invention of the Tomlinson recovery boiler in the 1930s sulphite pulp was the predominant method of forming chemical pulp. Sulphite mills currently produce only about 6% of chemical pulp globally. Sulphite pulping has a 40-50% pulp yield.

Supercalendered

Paper that has been supercalendered has passed through alternating metal and fibre covered rollers and are known for their highly glazed surface that is used in publishing.

Surface sizing

The application of sizing to the surface of the already formed sheet. Starches and synthetic sizing agents are the most common forms of surface size used. Papers can be surface sized with starch at the sizing press on a papermaking machine to increase its printing and writing properties, even if it has already been internally sized. It is also called tub sizing.

Synthetic ultramarine

A deep blue created by Jean-Baptiste Guimet in 1826, and then commercially sold in 1828, as a replacement for the very expensive traditional ultramarine derived from lapis lazuli.

Thermomechanical pulp

This is mechanical pulp that is produced from woodchips that have been heated with steam and then pulped or refined in a pressurized vessel, usually at between 30 to 150psi. The advantages of thermomechanical pulping are greater freeness of pulp, longer fibres, greater tear and burst strength in the paper and the ability to add chemicals, such as calcium chloride, magnesium chloride or sodium bisulphite to the process. It is abbreviated to TMP.

Titanium dioxide

A white pigment that was first developed in 1821, although it was not able to be effectively mass produced until 1916. It was commercially available as an oil paint until 1921. It is used in paper fillers and coatings to increase brightness and opacity. Its chemical formula is TiO₂.

Tomlinson recovery boiler

First invented by the Canadian G. Tomlinson in the early 1930s, it is a device for recovering processing chemicals from used, lignin containing chemicals in the Kraft process. The used processing chemicals, called black liquors, contain dissolved organic wood residues, such as resins and lignin, and sodium sulphate used in the cooking in the digester. The recovery boiler combusts the organic material, reduces the inorganic sulphur to sodium sulphide which is then further recycled, production of molten sodium sulphide and sodium carbonate for further recycling and recovery of inorganic dust and sulphur fumes.

Tooth

A term used to describe the surface smoothness or roughness. Tooth is important in many drawing papers because it assists in holding graphite, crayon or pastel.

Total chlorine free

A bleaching process that uses no chlorine compounds. Chemicals used in total chlorine free bleaching include oxygen, ozone, and hydrogen peroxide. It is abbreviated to TCF.

Tracing paper

A translucent paper with no fillers or loaders. It is created by either using overbeaten cellulose fibre with all of the interfibre oxygen removed, or by filling the interfibre spacing with a material with the same refractive index as the cellulose, or by dipping the formed sheet in sulphuric acid. Paper produced by the last method is sometimes referred to as parchment paper.

Tree free

Tree free pulp or paper is made from non-wood sources; such as agricultural by product, textile or cordage wastage or specific fibre crops such as bamboo, kenaf, hemp or linen.

Tub Sizing

Tub sizing is when the sizing agent is applied to the already formed sheet, and not to the pulp before it is made into a sheet. It is also known as surface sizing.

Twin wire machine

This is a variation on the Fourdrinier machine in which the newly formed sheet is pressed between two wires and guided vertically through dryers and the forming section, thus increasing the drying rate and giving a uniform two sided page. It was first invented in 1884 by Escher Wyss. It is also called a gap former.

Urea-formaldehyde resin

A synthetic resin used to increase the wet strength of papers.

Vatman's tears

White dots seen on a handmade sheet when viewed against the light. These are caused by drops of water falling onto the still wet sheet, dispersing the fibres and thinning the paper. They are also sometimes called Vatman's drops or Coucher's drops.

Vegetable parchment paper

A paper created by passing an unsized rag, or chemical pulp, paper through a bath of sulfuric acid or zinc chloride, and then washing it thoroughly. The acid hydrolyses the cellulose and leaves the paper heat, grease and moisture resistant as well as being more translucent. Paper produced this way is sometimes referred to as parchment paper or vellum paper.

Vellum

A type of parchment produced from calf skin. It can also mean fine, high quality parchment produced from other animals than calf.

Vellum paper

This term could refer to paper that is a vegetable parchment paper, or a finish of high grade stationery, or a paper produced using one of the methods to make tracing paper.

Waterleaf paper

A paper with no sizing.

Watermark

An image or text formed in a sheet of paper by the thickness or thinness of the paper pulp. They are usually only visible with transmitted light. Wire, shadow and multi-tonal watermarks are all types of watermarks.

Wet end

In a papermaking machine, the part of the machine consisting of the headbox and the sheet forming section. This term can sometimes include the parts of the pulp process such as the beater, refiner and chest head.

White lead

White pigment traditionally produced by exposing metallic lead to acetic acid. Its chemical formula is 2PbCO₃.Pb(OH)₂. It was used prior to the 20th century as a coating pigment in various formulations. When exposed to atmospheric hydrogen sulphide it can darken to a black colour.

Wire

An endless circular mesh onto which the pulp is flowed to form the paper. They are made of stainless steel, bronze or monofilament fibre woven fabric.

Wire Watermark

This type of watermark is formed by a design made with wire on the paper mould, or on the mesh of the dandy roll. The areas of the paper which have the wire are thinner as the wet pulp slips of the surface of the wire, and so these places of the page appear lighter.

Wood free

Pulp or paper not created from mechanical pulp. As this paper is made from chemical pulp it is more archival as the lignin has been removed.

Wove Paper

A paper with uniform surface, made on a fine mesh, without the visible chain and laid lines found in laid paper. The first wove paper was produced by James Whatman in the 1750s. The invention of the papermaking machine in 1807 led to the easier production of wove paper on a smooth continuous metal mesh.

Zinc oxide

An inorganic pigment used in coating papers. It has the chemical formula ZnO.

Zinc sulphide

A pigment, coating or loading agent with the chemical formula ZnS.