ISO range of paper sizes

absorbency

The degree to which paper takes up an amount of liquid, measured by a standard test.

acid free

Free from any acid content or other substances likely to have a detrimental affect on the paper or its longevity

air-dried

Dried with hot or cold air; usually applied to loft drying. A term used for high quality papermaking.

alkaline reserve

A paper additive (such as calcium carbonate) that is used to counteract acidic components within a paper or from the environment

alum

A complex salt, most commonly aluminium sulphate, added with rosin to the pulp while it is in the beater as a sizing agent to impart a harder and more water resistant surface to the finished sheet; it also acts as a preservative, and as a mordant for fixing colour.

ANSI

American National Standards Institute.

antique 

A general term applied to the surface which imitates the laid character of an old sheet. Today the term is often used to denote a rough finish

archival paper

A term loosely used to indicate paper with long lasting qualities, acid-free, lignin-free, usually with good colour retention.

B series

ISO range of papers designed for such items as wall charts and posters

bast fibre

The inner bark of plants such as flax, hemp, gampi, mitsumata and kozo, separated from the outer bark and suitable for papermaking

beater

A machine which alters or modifies the properties of fibres.

beating

hand or mechanical maceration of fibres to modify their characteristics and prepare them to become pulp

board

A general term for thick, stiff paper over a certain weight; on average 250 – 300 gsm.

bonding strength

The ability of fibres on the surface of the paper to adhere to one another and to others below the surface.

brightness

Paper’s ability to reflect white light.

brittleness

The tendency of paper to crack or break when bent or embossed.

buffering agent

An alkaline substance usually calcium carbonate occurring naturally in a water supply or added by the papermaker to help counteract acidity in paper.

bulk

The volume or thickness of a paper in relation to its strength.

C series

ISO range of sizes for envelopes

calcium carbonate

A [igment, which can be used as a filler, a white coating substance and a buffering agent

calendering

The process of pressing paper though roller to increase its surface smoothness

caliper

The thickness of a single sheet of paper measured with a micrometer.

cellulose

The basic substance of papermaking; the main part of the cell wall of a plant. Cellulose fibres are not pure enough (except for cotton) to be used directly for papermaking but contain varying amounts of other material, including lignin from which they must be separated before use.

chain lines

Heavier, more widely spaced lines which run at right angles to lines on the surface of a liad mould. The term is derived from the chain-like stitch used to hold the wires in place.

chemical pulp

Wood reduced to pulp by a variety of chemical processes all of which involve the cooking of the fibrous raw material with chemicals in order to extract the cellulose fibre; the most common are the sulphate (kraft), sulphite and soda processes. The resulting pulp is purified of lignins and other undesirable constituents.

china clay

A filler or loading agent used to obtain opacity, or fill or coat the surface off a sheet.

coated paper

Paper coated with china clay or other filler to give a smooth surface making it suitable for the printing of fine detail.

cockling

Wavy edges caused by unequal expansion due to paper being damper or drier than the atmosphere.

Cold Pressed (CP)

A traditional textured finish to the surface of handmade paper

contraries

Unwanted pieces of material which have become embedded in the sheet such a dust or hairs.

cotton

Cotton is the purest of cellulose produced in nature and it requires the least amount of processing before it can be used for papermaking.

couch

The action of transferring a wet sheet of pulp from the mould onto a damp felt; a specialized action performed by a coucher. From the French coucher, to lay down, hence its pronunciation, ‘cooch’.

coucher

Part of the traditional papermaking team of vatman, coucher and layer, whose task was to couch the newly formed sheet prior to pressing.

cover

A generic term usually indicative of a strong coloured paper suitable for the soft cover of a book; usually heavier than the internal sheets.

cross direction

Paper cut across at right angles to the direction of the paper machine. Paper is weaker and expands more along the cross direction than along the machine direction.

curing

The maturing of paper for an amount of time, before packing and selling.

curling tendency

A curl caused by unequal shrinkage which develops when the moisture content of the paper is changed by the atmospheric conditions or when the paper comes into contact with the moisture of a process such as direct lithography.

cylinder dried

Paper dried by being passed over a machine containing heated cylinders; the term is used to distinguish it from loft-dried.

cylinder mould machine

The machine used to produce mould made papers

dandy roll

A large hollow cylindrical roll covered with a wire gauze used on a Fourdrinier machine which rotates over the web of wet paper as it is being formed and applies surface finishes such as special textures or imitation laid lines or watermarks to machinemade papers.

deckle

The removable wooden frame that fits over the mould to contain the pulp; it also helps to keep the hands away from the fragile wet sheet. The inside measurement establishes the size of a handmade sheet. A Western papermaker’s equipment includes two moulds to every deckle so that the process of papermaking can be continuously performed. A deckle strap on a machine controls the width of the web.

deckle edge

The wavy, feathered or ragged edge on four sides of a sheet of handmade paper caused where the pulp seeps under the deckle frame during formation. Also found on mould made papers on the two outside edges of the web.

deflocculant

A substance which disperses fibres and prevents them from entangling the pulp; in Japanese papermaking, neri.

dimensional stability

The percentage of stretch or shrinkage caused by a given change in the relative humidity or moisture content in the air. It is a measure of the paper’s tendency to misregister especially by becoming wavy edged.

discolouration

The yellowing of a white paper due to influence of heat, light, air, presence of impurities – especially lignin, iron, alum etc. Good handmade papers will discolour very gradually if at all.

double-faced mould

A mould with a secondary supporting wire underneath the formation surface.

dyes

Water-soluable colouring agents which usually penetrate and become attached to the fibres.

embossed finish

A relief surface imparted either to flat paper in sheets or reeled paper by passing it between ambossed rollers bearing the required design.

endpaper

Strong paper used for securing the body of the book to its case.

fastness

Resistance of colour to fading

felt

Also called blanket. A rectangular sheet or absorbant woven material usually of wool, cut larger than the paper, onto which newly formed sheets are couched. Various grades exist to give particular surfaces to the wet sheets.

felt finish

A finish to the top surface of paper created by the texture of the felt; often with a special weave.

felt mark

A mark in the paper caused by the impression of a defect in the felt such as a worn patch.

felt side

The top surface of the pulp, as distinct from the wire side.

fibres

Cellulose-based material derived from plant matter which forms, with water, the basis of a sheet of paper. Papermaking fibres are hollow tube-like structures with walls made up of thread-like ‘fibrils’.

fibrillation

The process of raising the fibrils from the surface of the fibre so that bonds will form between them as paper is being made. This occurs during the beating process.

filler

A substance such as china clay or calcium carbonate usually added to the beater which will fill in the pores of a fibre and change the opacity, weight and surface of the finished sheet.

finish

A general term for the various surface textures of papers and boards. Rough, NOT, Cold Pressed and Hot Pressed are traditionally given to handmade and mould-made papers.

finishing

The practices of drying, sizing and looking over sheets of paper when the making is complete.

formation

The fibre distribution throughout a sheet, observed by holding it up to light. A uniform distribution marks a good sheet formation.

fourdrinier

The standard type pf machine on which paper is made at high speed in a continuous web. Sheets produced in this way are called ‘machinemade’.

foxing

An accumulation of iron, copper or biological organisms in paper (iron is a common impurity in older papers) which forms rusty brown spots under damp conditions.

free sheet

US term for ‘woodfree’ paper. A paper made with chemical pulp that is processed and bleached to remove liginin and other extraneous compounds.

furnish

The substance from which the paper is made; the ingredients of the beater which gives a specific type of paper.

gelatine

A type of sizing agent obtained from animal tissues, which is applied to the surface of paper to make it impervious to water and to aid resistance to bleeding during printing.; it also imparts surface strength to watercolour, writing and drawing papers. Gelatine sizing can affect the colour to some degree.

glazing

A process used to create a smooth surface finish on paper; tpically achieved by running dried sheets through steel rollers or between polished zinc plates, or by pressing or friction.

good

A perfect sheet

grade

When used on its own, another name for a sheet of paper.

grain direction

The alignment of fibres in a sheet of paper caused by the flow of the web of wet paper in a cylinder-mould or Fourdrinier machine; long grain is when the fibres run in the machine direction, short grain in the cross direction.

grammage (gsm)

The weight of the paper and board expressed in metric terms as grammes per square metre.

groundwood pulp

US term for mechanical pulp

hardwood pulp

Pulp made from deciduous trees such as oak, beech, birch and eucalyptus.

hot pressed HP

One of the traditional surfaces of handmade paper. Today this term denotes the smoothest surface achieved by passing sheets between heavy metal boards or rollers (occasionally heated).

hydration

A process occuring during beating in which the bruised fibres begin to accept water more readily.

imperial 

A large-sized sheet of 762 x 559 mm (30 x 22 in).

india paper

Very thin, high quality, opaque rag paper often used for printing bibles.

insides

The perfect internal sheets in a ream of paper.

ISO sizes

Range of paper and envelope sizes established by the International Standards Organisation including the A, B and C series.

laid mould

A mould in which the cover is composed of closely spaced parallel wires (20 – 40 per inch/25.4 mm) held in place by more widely spaced wires worked in the perpendicular direction (chain lines) which produced laid paper. Alternative to a wove mould.

laid paper

Paper that is made on a laid mould. Ribbed lines are seen if held up to light.

layer

Paper of the traditional papermaking triumvirate. The layer works in the vat house removing wet sheets from the felts after a post has been made and restacks them into packs for further processing. The person who sorts the paper and eliminates defective sheets.

lignin

The substance found mainly in woody plants which rejects water and resists bonding and therefore must be removed from the fibres before the papermaking process begins. If it not removed the resulting paper deteriorates quickly.

linen finish

see embossed finish

linters

see cotton, rag.

linting

The process by which clumps of fibres are released from the paper surface during printing due to the tackiness of the ink, especially in lithography.

loft-dried

The traditional manner of drying handmade sheets in a specially ventilated loft by natural evaporation. Sheets are hung singly or in groups (spurs) on drying lines or laid on flat canvas trays.

machine direction

The direction in which fibres lie on the wire of the papermaking machine.

machine dried

Paper dried by being passed over a machine containing heated cylinders; the term to distinguish it from loft-dried.

mature

To allow handmade papers to settle for a considerable period before use (weeks or months), a process which greatly improves them.

mechanical pulp

Wood pulp produced mechanically by grinding.

mediaeval laid

A term applied to an antique finish if the laid lines are very pronounced or irregular.

metric weight

Weight expressed as grammes per square metre

moisture content

Amount of moisture in paper expressed as a percentage of weight

mordant

A substance used to fix dye to a fibre.

mould/mold

The basic tool of a hand papermaker, consisting of a flat frame to which a mesh of brass wires  or a woven cloth is fixed.

mould made

Paper made on a cylinder-mould machine

NOT

Short for ‘Not Hot Pressed’. One of the traditional surface finishes of handmade paper (between Hot Pressed and Cold Pressed), produced by passing between felts. Sometimes called Cold Pressed in the US.

opacity

The quality of opaqueness in a paper, produced by adding ingredients such as china clay, calcium carbonate or titanium dioxide (opacifiers). Governs the degree of show-through of printing on the reverse side of a sheet or on sheets underneath.

outsides

Very badly damaged sheets also termed ‘broke’. These are seriously defective handmade sheets traditionally used as packing at the top and bottom of a ream to protect the good sheets (insides) and sold at a much reduced price.

paper mulberry

This is a broad term for a number of trees from whose inner bark paper is made; Broussonetia papyifera is probably the most widely used; in Thailand it is called saa, in Hawaii wauke and in Japan kozo.

pH

The pH value describes the acidity or alkalinity of a paper; it is a measure of the availability of free hydrogen ions.  7 pH represents a balance between acid and alkaline components and is neutral.

picking

The phenomenon whereby individual fibres are lifted from the surface of a sheet during printing when ink tackiness is stronger than the paper surface.

ply

Single layer of paper or board; can be joined to another for strength, producing 2-ply, 5-ply etc.

post

A pile of wet sheets alternated with felts ready for pressing

pulp

A general term used to describe treated fibres suspended in water from which paper is made.

quire

A twentieth part of a ream; today a quantity of 25 sheets of paper. This is a peculiarly English measure, possibly relating to a time when counting was done in dozens (an old quire = 24 sheets); the two quires used to wrap a ream comprised 20 sheets each.

rag

Formerly the principle raw material used in the papermaking process. The term ‘rag’ or ‘all rag’ properly describes a sheet made entirely from used textiles (usually cotton) as the basis for the pulp; today however more commonly it is a misnomer and indicated that the paper has been produced from cotton linters. The term ‘rag content’ describes the amount of cotton fibre relative to the total amount of material used in the pulp.

rattle

The sound produced by shaking a piece of paper, indicating the hardness of the sheet.

ream

The old word for quantity of paper. Traditionally it comprised 472 sheets (18 quires of 24 sheets plus 2 ‘outsides’ quires of 20 sheets), although the number varied depending on the use that the paper was to be put to (e.g. a printer’s ream was 516 sheets). Today taken to refer to 500 sheets of good paper.

recycled fibres

A general term for fibres recovered from waste paper.

relative humidity (RH)

The amount of water vapour present in the atmosphere expressed as a percentage of saturation, measured with a hydrometer.

restraint-dried

Sheets dried under some form of restraint, i.e in a machine (cylinder or machine dried) or on a drying board.

retree

From the french retire, ‘withdrawn’. Handmade sheets with minor faults, sold at a reduced price. A ream or retree can be identified by the marking of a double cross, XX, or the letter R on the wrapping paper.

retting

The traditional manner of rotting down fibres in preparation for the beater. Rage were heaped in piles to ferment, which involved letting them heat up and begin to rot.

rosin

A commonly used internal sizing agent; occasionally also used for surface sizing. Introduced around the early 1800s, it is acidic in nature and detrimental to the permanence of paper. It requires the addition of alum for precipitation onto the fibres.

Rough

One of the traditional surface finishes of handmade paper; a rough surface properly obtained by loft-drying in natural air.

screen

The covering of the mould

seconds

The term used today to denote imperfect sheets. See also retree.

sheet

A piece of manufactured paper

shives

Specks of impurities in the raw fibre discernible in the finished sheet.

short-grain

see grain

sieve

An area of mesh supported by a frame; in the papermaking process liquids pass through the mesh but solids are kept back.

size

Chemical or chemicals used in papermaking to control the absorbency of the paper. Also means the dimensions of a sheet of paper.

sizing

A solution or the process of applying such a solution intended to make paper moisture-resistant to varying degrees. Size can be added at two stages of the papermaking process. In internal sizing (also called beater or engine sizing) size is added to the beater. In surface sizing (also called external or tub sizing) dried papers are passed through a solution of gelatine (or glue, casein or starch) traditionally contained in a bath or tub; surface size can also be applied by brushing or rubbing. The term animal tub sizing denotes surface sizing with gelatine.

smalt

Deep blue pieces of glass pulverized and used as a colouring agent.

smoothness

Essentially the surface flatness of the paper. It is not the same as gloss and is not related to porosity.

softwood pulp

Pulp made from softwood such as fir, pine, spruce.

special making

Also called custom making. A paper made specially for a client; not part of a maker’s standard range.

spur

A group of sheets dried naturally together.

stampers

a set of large water-powered wooden hammers falling into stone troughs containing raw fibres such as rags. Superseded by the Hollander beater.

standard range

A series of paper regularly produced by a manufacturer.

stock

Also called furnish. The dilute prepared papermaking mixture in the vat; this includes the water, treated fibres, formation aids, sizing agents etc.

stock paper

Standard paper regularly available for sale. Different from ‘paper stock’ which means the chosen paper to be printed.

stuff

The beaten fibres in water before being finally mixed for papermaking.

substance

The weight or grammage of a sheet of paper expressed in gsm of lbs per ream.

sulphate pulp

See chemical pulp.

surface finish

The surface character of a sheet of paper, described in terms of its texture e.g. Rough, Cold Pressed, Not or Hot Pressed, burnished, hammered.

surface sizing

See sizing

texture

The surface detail or finish of a paper, which can be a natural result of the quality of the pulp, processing or drying or a contrived result.

tooth

Describes the surface texture that grips a drawing pigment.

tub sizing

See sizing

vat

A tub or vessel that holds the wet paper pulp

vatman

Part of the traditional papermaking team with the coucher and layer; the vatman is the papermaker scooping the pulp from the vat to form the sheet of paper.

vellum

The prepared inner side of a calfskin or kid skin. Also a paper surface which imitates true vellum, notably any matt wove type, often used to describe mould made (in French, velin) and Japanese papers.

virgin fibre

Fibre used for the first time to make paper (i.e. not recycled)

waterleaf

Used to describe a paper that contains no sizing and is therefore generally very absorbent. These papers are often used in printmaking where oil based inks are used.

watermark

A translucent design in a sheet of paper that can be viewed as a paler area when held up to light. Typically watermarks are linear, formed in wire.

web

Continuous length of paper (a roll or reel).

weight

A quality of a sheet of paper expressed in a number of ways. Imperially in lbs weight per 500 sheets (ream), metrically in gsm, microns and ply refers to boards.

wet strength 

The strength of a finished sheet of paper when it is saturated with water.

wire side

The underside of paper in contact with the mesh during making, as distinct from the felt side.

wove mould

A mould in which the the covering screen is made from a woven mesh. Alternative to the laid mould.

wove paper

Paper made on a wove mould, invented by J Whatman.