Glossary of carton and cartonboard terms

Pro Carton

Glossary

A guide to the terminology

used in the Cartonboardand Carton

manufacturing industries

Association of European Cartonboard and Carton Manufacturers

Index

Outline description of Cartonboard Page 3

Outline description of pulp and recovered fibre Page 3

Types of Cartonboard Pages 4-5

Cartonboard properties Pages 6-9

Printing methods Pages 9-10

Printing terminology Pages 11-12

Finishing terminology Pages 13-15

Outline description of Cartonboard

Cartonboard, or cardboard as it is sometimes called, is the essential raw material forcarton production. In Europe about 7 million tonnes of this material is manufacturedeach year and whilst there are a large number of variants, most of the cartonboard usedfalls into one of four distinct types. All cartonboard is manufactured from renewableresources.

All the grades manufactured are made using a multi ply construction and the differencesin what is used to make each layer creates the differences between the four basicgrades. Some use 100% pulp as a raw material, some use 100% recovered fibre andsome use a combination of both. On the following pages are illustrations of the fourbasic types of cartonboard along with a brief indication of what they are called, how theyare made and what they are generally used for.

Virtually all the cartonboard manufactured in Europe has a coating on the top or printingsurface. This is designed to enhance gloss and print quality. It is however possible to getuncoated cartonboard for specialised uses such as blister cards. Cartonboard comes inmany different weights or grammages. It is generally accepted that cartonboard beginsat a grammage of around 160 gm2 and it can go up to weights of over 600 gm2.

In addition to the basic grades there are many different variants that are adapted forspecial uses. For example, special additives can be included in the cartonboard to makeit resistant to water and moisture for use in the chilled and frozen food sector. Plasticcoatings can be applied, usually by extrusion coating, directly onto the cartonboard toprovide a waterproof and grease proof barrier for use, for example, in pet foodpackaging. Cartonboard can also be laminated with either foil or metallised polyestergiving a metallic finish to the material. These types of specialised boards are becomingmore widespread and there are also others such a specific material for microwaves,security board and a great many others.

Outline description of pulp and recovered fibre

Cartonboard is made from different types of pulp or from a combination of different typesof pulp. The most commonly used types of pulp are as follows:

Chemical Pulp – In the production of chemical pulp, cellulose fibres are extracted fromwood by cooking the wood chips in chemical solutions

Mechanical Pulp – In the production of mechanical pulp, cellulose fibres are extractedfrom wood by a grinding and refining process.

Recycled fibre pulp – Recycled fibre pulp is produced by using previouslymanufactured material based on cellulose fibres. For cartonboard, suitable sources ofrecycled fibre are waste from paper and board production and collected paper andpackaging.

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Basic types of cartonboard

SOLID BLEACHED BOARDSBB / SBS / GZ

This grade is typically made from purebleached chemical pulp with two or threelayers of coating on the top surface and onelayer on the reverse. It is used in such marketsas cosmetics, graphics, pharmaceuticals,tobacco and luxury packaging. It can also becombined with other materials to make liquidpackaging board.

SOLID UNBLEACHED BOARDSUB / SUS

This grade is typically made from pureunbleached chemical pulp with two or threelayers of coating on the top surface. In somecases a white reverse surface is applied. It isprimarily used in the packaging of beveragessuch as bottles and cans as it is very strongand can be made resistant to water which isessential during the packing process. It is alsoused in a wide variety of general packagingareas where strength is important.

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FOLDING BOXBOARD —FBB/GC/UC

This grade is typically made from layers ofmechanical pulp sandwiched between twolayers of chemical pulp with up to three layersof coating on the top or printing surface andone layer of coating on the reverse. It is used insuch markets as drinks, pharmaceuticals,frozen, chilled and other foods, confectioneryand a wide range of other markets.

WHITE LINED CHIPBOARD -WLC/GD/GT/UD

This grade is typically made usingpredominantly recovered fibres. It ismanufactured in a number of layers each ofwhich use selected grades of raw materials. Ittypically has two or three layers of coating onthe top or printing surface and one layer on thereverse. It is used in a range of applicationssuch a frozen and chilled foods, breakfastcereals, shoes, tissues, toys and many more. Itcan have either a white or grey colouredreverse side.

Basic types of cartonboard - continued

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Glossary

GRAMMAGEThe weight of the cartonboard in grams persquare metre (g/m2). Paper with a grammageof more than 160 g/m2 is normally calledcartonboard, since it is first at that level that afibre-based material can be sufficiently stiff andsturdy to function as packaging. Mostcartonboard packaging has a grammage in therange of about 160 to 600 g/m2.

THICKNESSThe distance between the two surfaces of thecartonboard sheet measured in thousandths ofa millimetre (µm). The material used in mostcartonboard packaging has a thickness of 300to 800 µm.

DENSITYDescribes how compact the cartonboard is,measured in kilograms per cubic metre (kg/m3).

grammage (g/m3) x 100Density (kg/m3) = (kg/m3)

thickness (µm)

BULKDescribes how bulky (voluminous) thecartonboard is, measured in cubic metres perkilogram (m3/kg).

1Bulk (m3/kg) = =

density

thickness (µm)= (m3/kg)

grammage (g/m3) x 1000

Cartonboard which is bulky (voluminous) inrelation to its weight is said to have high bulk.Compact cartonboard has low bulk.Cartonboard with high bulk generally feelsstiffer and thicker than cartonboard with thesame grammage but with low bulk.

CARTONBOARD PROPERTIES

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MACHINE DIRECTIONWhen cartonboard is manufactured the pulpfibres are aligned parallel to the direction inwhich the cartonboard web is moving. Thismeans that cartonboard is always stiffer andstronger in that direction.

The machine direction is therefore at rightangles to the width of the web. In terms ofcreaseability, a crease across the machinedirection is better than a crease parallel to themachine direction (See “CREASING”).

STIFFNESSStiffness is one of the most importantproperties of cartonboard. The demand forstiffness occurs throughout the entire chainfrom shipping via the store shelf to theconsumer. Cartonboard is the only materialwhich has this ability to offer high stiffness perunit of weight. Without stiffness, cartonboardcould not fulfil its primary function, which is toprotect the contents of the packaging.

COMPRESSION STRENGTHWhen cartons are stacked on top of each otherthe bottom layer naturally bears the greatestload. To avoid the cartons collapsing, the mostimportant property of cartonboard as amaterial is good compression strength.

TEAR STRENGTHThe force required to tear a cartonboard sheetalong an existing incision. This is important, forexample, so that a tear strip will work whenpackaging is being opened.

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SURFACE STRENGTHCartonboard’s ability to tolerate forces on itssurface, for instance from the tackiness of theink during printing, is important. Thecartonboard surface must not be torn away bythe printing ink during the printing process.

SURFACE SMOOTHNESSA measurement of how smooth thecartonboard surface is. A smooth cartonboardsurface is important for achieving satisfactoryprinting and varnishing results.

DIMENSIONAL STABILITYResistance to dimensional changes in acartonboard sheet due to changes in suchproperties as moisture content. Dimensionalstability is important during printing andconversion to avoid such errors as misregister(see also “REGISTER”).

FLATNESSThe cartonboard’s ability to remain flat (retainits shape) during printing and converting.

WHITENESSThe Cartonboard’s visual impression ofwhiteness. Whiteness is expressed by meansof a single value.

BRIGHTNESSBrightness is a concept used in two differentcontexts:1) When referring to image reproduction,brightness describes the intensity of thecolours. This is also called luminance, i.e. howlight or dark an image is.2) When referring to cartonboard, brightness isexpressed as the precentage of light which isreflected from a cartonboard surface at awavelength of 457nm (nm = nanometre).

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GLOSSThe more light which is reflected by thecartonboard surface, the higher the gloss.Gloss can be achieved with various varnishingmethods.

OPACITYOpacity is a measurement of the capacity ofcartonboard to obscure what lies behind it, andis expressed as a percentage. A highpercentage corresponds to a cartonboardsheet with low transparency (high opacity). Acartonboard sheet with 100% opacity iscompletely opaque. The degree of opacitydepends on how well the light is scattered andabsorbed by the cartonboard. High opacity isimportant when printing on both sides of thecartonboard sheet.

LETTERPRESSIn this printing method the ink is applied intothe raised types of the printing cylinder andthen transferred to the cartonboard surface.

PRINTING METHODS

GRAVUREGravure is a direct printing method in which theimage areas to be printed are made up ofmany small recesses which are engraved on acopper printing cylinder and are filled with ink.Gravure printing presses are reel-fed presseswhich print at very high speeds.

Gravure is best suited to long print runsdue to the high initial cost and low unit cost.The method gives good image reproduction.

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FLEXOGRAPHYIn this direct printing method the image areasto be printed are raised above the non-imageones. The printing plate is made of rubber orphotopolymer.

The advantage of flexography is that it canbe used to print on most materials. Water-based printing inks can be used. Thedisadvantage is that flexography often hasdifficulty reproducing all colour hues.

DIGITAL PRINTINGA printing press which prints informationdirectly from a computer in a similar way to acomputer printer. There is therefore no need toproduce film or a printing plate. Theadvantages are speed and low costs for smallfour-colour print runs.

OFFSETOffset is the most common printing method forcartonboard. The most frequently used methodis sheet-fed offset, in which the printing pressis fed with cartonboard sheets. This contraststo web offset, which is reel fed.

Offset is an indirect printing method. Theink is not transferred to the cartonboard sheetdirectly from the printing plate. The printingcylinder sets off (hence “offset”) the printing inkonto a rubber-covered blanket cylinder, whichtransfers the ink/printing image to thecartonboard sheet. “Offset” usually refers tooffset lithography, a printing method in whichthe image areas to be printed are distinguishedfrom the non-image areas by the use ofchemical properties rather than differences inlevel.

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PRINTING PLATEThe printing image used in offset printing.

RUBBER BLANKETA rubber sheet which transfers the printingimage from the printing cylinder to thecartonboard sheet in offset printing.

PRINTING INKColoured pigment which is transferred from theprinting plate with the aid of a vehicle (acarrier) and is then bound to the cartonboardsurface with a binding agent such as resin.

VARNISHThere are different kinds of varnish, all of whichhave their own advantages and properties. Acartonboard surface is varnished to protect itagainst scratches or to stop it getting dirty.Varnish can also be used to emphasise thegloss of a design in whole or in part. Thevarnish is either applied to the cartonboarddirectly on the printing press or afterwards in aseparate operation.

Printing varnish - an oil-based varnish whichis spread on in a printing press. Protectsagainst scratches.

Emulsion varnish - is spread on in theprinting press at a varnishing station. Protectsagainst scratches.

UV varnish - is spread on either directly inthe printing press or in a separate varnishingmachines. Gives a glossy surface.

PRINTING TERMS

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DAMPENING SOLUTIONUsed in web offset printing. The dampeningsolution has three fuctions in offset printing:• to ensure that the ink does not adhere to the

non-image areas• to clean away cartonboard fragments• to cool down the pressSince dampening solution is required in offsetprinting, the dimensional stability and flatnessof the cartonboard are important (See“DIMENSIONAL STABILITY” and “FLATNESS”).

REGISTERWhen all printing inks are in exact alignmentrelative to each other, e.g. the separate colourimages in four-colour printing, or duringsubsequent die-cutting, cutting, embossingetc. Misregister occurs when the separatecolour images are not printing exactly on top ofeach other. Misregister creates unclearimages, discoloured edges etc. To avoidmisregister it is important that the cartonboardsheet is dimensionally stable(see“DIMENSIONAL STABILITY”).

HALF-TONE PRINTINGPrinting in which the colour images are in theform of small dots (known as half-tone dotsand forming a half-tone screen).The size of thedots determines the colour intensity. Thecombination of different colours creates amultitude of hues.

SCREEN RULINGScreen ruling (also called screen frequency orhalf-tone resolution) is the number of screenlines per unit of length. It is measured in linesper inch (lpi). The higher the lpi, the greater theamount of details in an image. The kind ofcartonboard and the choice of printing methodgovern the screen ruling that can be usedduring printing.

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LAMINATIONThe printed sheet is coated with a protectivelayer of plastic or metal foil - the laminate.There are gloss and matt laminates. They areapplied by a special lamination machine. Thelaminate provides excellent protection againstdirt, moisture and wear. Lamination can alsobe done for aesthetic reasons.

FINISHING

PASTINGTo join two or more cartonboard sheets withadhesive or wax to create a single unit.

SCORINGA fine line is scored in the cartonboard tocreate a flexible hinge. A scored line is lessdurable than a crease line (See “CREASING”).

DIE CUTTINGDie cutting occurs when the cartonboard sheetis cut into a shape, e.g. to create a blank whichcan be folded and erected to form a carton.After printing, die-cutting and creasing aredone simultaneously in die-cutting machines.Die-cutting and creasing can be combined withembossing (See “EMBOSSING”).

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NICKSNicks are non-die-cut sections which hold theblanks together to facilitate handling during thesubsequent conversion process.

PERFORATIONA row of punched holes which make it easier totear off e.g. a coupon or reply card.

CREASINGTo facilitate folding, a well-defined folding lineor crease is made. A perfect crease can becompared with a hinge and its aim is toproduce the desired shape and function in acarton or in printed material.

EMBOSSINGEmbossing means that the cartonboard isshaped into well-defined, permanent reliefpatterns. Before the cartonboard sheet isembossed it is often printed or foiled. If therelief is raised it is described as positive. If it isimpressed, it is negative. Embossing which isdone without prior printing with ink is calledblind embossing.

Embossing can also create a pattern whichcovers the entire surface.

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HOT FOIL STAMPINGA text or pattern in metallic foil is applied to thecartonboard with the aid of heat, often incombination with embossing.

FOLDING WITHOUT PRIOR CREASINGWhen a cartonboard sheet is folded without apre-existing crease or scoring (see“CREASING” and “SCORING”). This is usuallydone in a folding machine.

FOLDING/ERECTINGA die-cut and creased cartonboard blank ismade into a carton (see “DIE CUTTING” and“CREASING”).

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