Look around you—on store shelves, in your home—and you’re certain to see material that’s been printed by flexography. Though often taken for granted, packaging is everywhere, and so, too, is flexography; it prints candy wrappers, shopping bags, corrugated boxes, milk cartons, gift wrap, wallpaper, and many other goods and packages. on packaging is essential to businesses around the world. In fact, graphics on packages provide some of the most important advertising for the products themselves. ’s soft compressible plates, fast-drying inks, and its simple, efficient inking system make it possible for manufacturers to reproduce high-quality graphics on a wide variety of surfaces.

Over the last decade, the use of the flexographic printing process has been growing approximately eight percent a year, a rate unparalleled by any other printing technology. Although some of this growth can be attributed to a greater need for packaging, flexography is increasingly used in markets traditionally served by gravure and offset . Since advances in technology have significantly improved flexography’s ability to print accurate type, color, and halftone images, manufacturers and print buyers are recognizing flexography as a high-quality, economical alternative to gravure and lithographic printing.

This booklet describes the flexographic printing process from start to finish, including design, color, and considerations. Understanding the requirements of flexography helps ensure that designs will look their best, and will aid in the communication between print buyers, in-house prepress departments, service bureaus, and printers. 18 16 15 14 13 12 11 10 22 21 20 19 2 9 8 6 4 Glossary &IndexGlossary Prepress Checklist&ThePress Check Proofing Prepress Output Step-and-Repeat &Die-Cutting Halftones &Screening Dot Gain Type Trapping Color Capabilities Substrates Plate Elongation &Distortion Flexographic Plates Flexographic Technology Traditional Printing Processes Flexographic Markets also befoundintheglossary. throughout thisguidecan The termsprintedinred

1 Contents 2 Flexographic Markets ten yearslater, its caliperandweight.Approximately tension systemswererefinedtohandle phane’s non-absorbentsurface,andpress drying systemswereimprovedforcello- ing material.Whiteinksweredeveloped, duction ofcellophaneasaclearpackag- printers respondedquicklytotheintro- In theearly-to-mid1920’s,flexographic Clear Packaging are tosuccess. crucial low-cost,run, andhigh-quality printing markets, where short ing inpopularitytoday’s The useofflexography isgrow- and a waytoprintkraftpapergrocerybags when letterpressprintersneededtofind can betracedbacktothelate1880s, The firstuseofsoftcompressibleplates known today. ery, hasledtoflexographyasitis equipment, ratherthanasinglediscov- of improvementsinmaterialsand ing industry.Anevolutionaryprocess in responsetotheneedsofpackag- has beenwillingandcapableofchange a printingtechnologyandculturethat the developmentofflexographyreveals ble packaging. commonly usedmaterialforclear, flexi- duced, andwentontobecomethe most for flexography. decision thatbegananewgrowthperiod gated boxasashippingcontainer, merce Commissionapprovedthecorru- industry. In1914,theInterstateCom- also grewsteadilyinthebagprinting method forprintingcorrugated,and lead. Thisquicklybecamethedominant from rubber,ratherthanwoodor problem, printersbegancreatingplates of hardletterpressplates.Tosolvethe respond welltotheinktransferpressure were roughintexture,anddidnot corrugated polyethylene boxes. Thematerials A lookat was intro- Market Categories ground color. seam, areusedtoprintacontinuousback- Design rolls products suchaswallpaperandgiftwrap. applied byflexography. on theinsideofmanyenvelopesisoften overnight delivery.Thesecurityprinting mail, sweepstakes,generalmailing, and of envelopes,includingthosefordirect Flexography isusedtoprintmanykinds Envelopes neckties. are usedforbakeryproducts,shoes,and Rigid paperboxes,orpre-formedboxes Rigid PaperBoxes its marketshareduetoimprovedquality. cesses, flexographyhasrecentlyincreased by boththe detergent, andcosmeticboxes,areprinted Although foldingcartons,includingcereal, Folding Cartons A Gift WrapandWallpaper textile wrap. food bags,candywrappers,pouches,and polymer film,includingbreadbags,snack Most flexiblepackagingusesnon-absorbent Flexible Packaging printing corrugatedboxesinlargequantities. pressure makeflexographywellsuitedfor conforming plate,andlightimpression Fast dryingwater-basedinks,thesoft, corrugated isprintedonsheet-fedpresses. By farthelargestmarketforflexography, Corrugated including thosethathavetraditionallyusedgravureandlithographicmethods. The useoftheflexographicprocesshascontinuedtogrowinallpackagingmarkets, continuous repeat , whichdonothaveaplate lithographic allows theprintingof and gravure pro- Origins of the Name Originally, flexography was known as aniline printing, a name taken from Paper Grocery Bags the aniline dyes used as colorants for The paper bag is the original flexographic product. In the late 1800’s flexography the ink. Aniline dyes, however, were evolved from the need to apply graphics considered toxic and eventually banned to plain brown grocery sacks. The evolution continues today. for use on food packaging. New inks were developed as replacements, but the name remained until 1951, when Franklin Moss, a leader in package Plastic Carrier Bags printing, started a campaign to change Flexography can add advertising and it. He asked aniline printers and suppliers graphics to plastic bags that are carried for suggestions, receiving over two by customers in stores. hundred. Of those, three finalists were selected: permatone process, rotopake process, and flexography. After a vote, the process came to be known as flexog- raphy in 1952. Milk Cartons Approximately 90% of all milk cartons In the United States, the Clean Air Act are printed using flexography. of 1980 began a development in flexog- raphy toward environmentally friendly printing using low-solvent and no-solvent inks. Today, flexography is often chosen because of the ability to print with clean water based or solventless ultraviolet inks. Newspapers In the United States alone there are Today the process continues to adapt. between 35 and 40 newspapers using the flexographic printing process for the As the technology is refined, quality entire paper. Many newspapers use flex- continues to increase, making flexogra- ography to print the Sunday comics. phy the leader in packaging graphics applications.

Tags and Labels The fast drying fluid inks used by flexogra- phers allow inline die cutting immediately after printing. The quality of many flexo- graphic labels is equal to or better than that offered by lithography or gravure.

Pre-printed Linerboard Pre-printing linerboard allows high-quality graphics to be placed on corrugated containers.

3 4 Traditional Printing Processes plate design ofthe for eachmethoddifferprimarilyin solution The Gravure lithographic pasteink,whilea plate arechemicallytreatedtoattractthe most offsetpresses,imageareasonthe areas ononeflatsurfaceorplane.On holds boththeimageandnon-image process, meaningthattheprintingplate try, Widely usedinthepublicationindus- Offset Lithography system totheprintingplate. and flexography. are offsetlithography, gravure, printing processes inusetoday The three mostwidelyused material, knownasthe offset), andthentothepaperorother isa Offset lithography such ascartons,labels,andbags. can alsoprintpaper-basedpackaging, and artreproduction.Offsetlithography pers, aswellannualreports,advertising, magazines, catalogs,anddailynewspa- presses areused to printlabelsorlogos In addition,offsetversionsofgravure advertising insertsfoundinnewspapers. such aspackaging,magazinesand the used toprinthigh-volumeproducts third intheUnitedStates.Gravure is in EuropeandtheFarEast, It isthesecondmostoftenusedprocess ing, woodgraindesktops,andpaneling. ety ofsubstrates,includingvinylfloor- as roto-gravure,isusedonawidevari- of heat. certain periodoftimeoranapplication dry, mostlithographicinksrequirea transferred toa inking. Fromtheplate,imageisfirst protectsnon-imageareasfrom treatment o gravure , theink,andinkdelivery ffset lithography or inkrepellentchemical image carrier method, sometimesknown blanket Printing presses planographic substrate (hence theterm presses print or fountain printing . To Flexography Gravure Offset Lithography Traditional Printing Processes on medicine capsules and the “M” on M&M® candy. Offset Gravure Flexography Lithography Gravure is an process, in which the image area is recessed below the level of the non-image areas. The image Typical Magazines, Magazines & Newspapers, Uses newspapers, catalogs, Sunday phone directories, is etched or engraved in a cell format advertising pieces, supplements, candy corrugated onto a copper plate or copper-plated annual reports, cereal wrappers, cereal containers, bread boxes, bags, tags & boxes, snack food bags, cereal boxes, cylinder. By varying the size and depth labels bags, vinyl flooring milk cartons, gift of each cell, a printer using a gravure wrap press can vary tones. Often, after the Substrates Coated & uncoated Coated & uncoated Coated & uncoated copper is etched or engraved, the plate papers, newsprint, papers, newsprint, papers, newsprint, some polymer paperboard, foil, paperboard, or cylinder is plated with chrome to add packaging films metallized paper, corrugated board, durability and increase its run-length. polyethylene vinyl, foil, metallized paper, A fast drying ink fills the recessed cells, polypropylene, polyethylene vinyl, cellophane, polypropylene, a thin metal strip called a doctor blade polystyrene cellophane, clears the non-image area of ink, and polystyrene the image is transferred directly to the Impression Moderate to heavy Heavy Light substrate under heavy pressure from a Pressure rubber covered impression cylinder. Plate Run- 300,000 to 400,000 6 to 7 million 1 to 2 million Length maximum impressions average; impressions average Flexography impressions longer with rechromed cylinder Because its soft compressible plate con- forms to uneven surfaces, flexography Press Width Sheet-fed: to 60" 2" to 144" Narrow web: 6" to 24" Web: 11" to 60" Wide web: 24" to 90" is often used for printing on packaging 120" for corrugated materials, such as corrugated and paper- presses board. The fast-drying fluid inks used Repeat Standard format with Infinitely variable Variable repeat length in flexography are ideal for such materi- Length limited repeat length repeat length als as polyethylene films, used for plastic Press Speed Product dependent: Product dependent: Product dependent: grocery bags. Flexographic presses are (feet per Magazines: 2,500 fpm Magazines: 3,000 fpm Toilet tissue: 3,000 fpm minute) Sheet fed: 12,000 Bread bags: 500-900 Bread bags: 500-900 fpm often part of a manufacturing process, impressions per hour fpm Pressure sensitive in which packaging is printed, folded, Vinyl flooring: 50 fpm labels: 100-300 fpm shaped, and die-cut.

Ink Paste ink Fast drying fluid ink Fast drying fluid ink Flexography is characterized as a relief Oil & soy based Solvent & water-based Solvent & water-based Heat set & non-heat set Dry trapping UV curable process. The image areas on the com- Wet trapping Dry trapping pressible plate are raised above the sur- rounding non-image areas. An ink Screen 65-300 lpi 120-300 lpi 45-150 lpi metering cylinder called an anilox roll Ruling Most common: Most common: Most common: 133-150 lpi 150 lpi 100-133 lpi applies ink to the raised areas. The plate is then moved into light contact with Minimum 3-5% 3% 8-12% the substrate to transfer the image. The Printed Highlight Dot minimal pressure during image transfer allows printing on material, such as cor- Dot Gain Midtones: 20% Midtones: 23-26% Midtones: 20-25% rugated board, that may be adversely affected by impression pressure.

5 Flexographic printing units in Flexographic Ink Delivery System use today consist of three basic Two Roll with Doctor Blade types: the two roll unit, the two roll unit with a doctor blade, and the dual doctor ink chamber system.

Two roll units are usually found on older flexographic presses, and on narrow web presses. Narrow web presses equipped for process colors often use the two roll unit with a doctor blade, and more modern wide web presses use the dual doctor ink chamber system. Flexographic Technology Flexographic

On a two-roll flexographic printing unit, Each type of flexographic press uses an the rubber covered fountain roll rotates anilox roll. The surface of every anilox in a fluid ink bath, dragging ink from the pan to cells of the anilox roll. The soft roll is engraved with a pattern of tiny rubber fountain roll is held in tight con- cells, so small they can only be seen tact with the anilox roll. As the anilox under magnification. The size and rotates past the nip point, the fountain Dual Doctor Ink Chamber System roll wipes excess ink from non-cell number of these cells determine how areas. Once past the nip point, each cell much ink will be delivered to the image is filled with ink, and a measured, repeat- able amount of ink is available to the areas of the plate, and ultimately to the printing plate. The metered anilox roll substrate. An anilox roll is either copper is moved into light kiss contact with the image areas of the plate, and the plate engraved and then chrome-plated, or cylinder is moved into kiss contact with ceramic coated steel with a laser engraved the substrate to transfer the image. The steel impression cylinder supports the cell surface. substrate. When a thin metal or poly- ethylene doctor blade is used with a Anilox rolls are carefully selected for two-roll unit, the nip point between the fountain and the anilox roll is opened to specific types of printing, substrates, allow ink to flood the anilox and fill the and customer requirements. Often the cells. The doctor blade comes into con- tact with the anilox to clear excess ink flexographic printer will perform test from non-cell areas. With a dual doctor runs to determine the ideal anilox for ink chamber, the fountain roll and inking pan can be eliminated; ink is delivered producing the desired ink distribution directly to the anilox through an enclosed for halftones, spot color, and solids. chamber.

The design of the flexographic printing Characteristics of Anilox Rolls

unit enables press manufacturers to Cell Per Inch Range: 140 to 1200 CPI. As cell count increases, ink delivered to plate build presses in any one of three config- (CPI) decreases. As line screen resolution increases, CPI should also increase. urations: the stack press, the inline Cell Volume Range: 1.8 to 17 BCM (Billion Cubic Microns per square inch of cells). As CPI press (including corrugated presses), increases, cell volume decreases. and the common impression cylinder Cell Angle Typical anilox cell angles are 30°, 45°, and 60°. A 60° angle allows for more complete ink transfer, and is the preferred cell angle. The screen angle of the press. Each configuration can be printing plate and the cell angle can combine to cause a moiré pattern, even equipped with any of the basic printing with one color halftones. Moiré is avoided by angling separation screens. units, depending upon the needs of the Application Substrate Cells Per Inch Cell Volume flexographic printer. line art corrugated board 200-280 7-8.5 BCM halftones at 65 lpi corrugated board 360-400 4.0-5.5 BCM 4/c halftones at 133 lpi polyethylene bags 600-900 1.8-2.0 BCM

6 Press Configurations

Common Impression Cylinder (CIC) Press Stack Press • 4-8 color units • 1-8 color units • Limited to one-sided printing • Some presses can print on both sides • Ideal press for hairline register at high speeds on stretchable • Traps should be no less than 1/64" for thin films films • Often used inline with other converting operations such • Longer make-ready times required because printing units are as lamination, rotary and flatbed die cutting, and sideseal more difficult to access bag converting.

Inline Press Corrugated Press • Up to 12 color units • Same configuration as the inline press • Can print two sides with the aid of a turn-bar • Sheet-fed; widths up to 120" • Used for printing thick substrates such as paperboard • Usually no more than 4 colors • Not recommended for printing thin packaging film • Limited to one-sided printing • Often used inline with other converting operations such as • Less accurate registration capabilities lamination, rotary and flatbed die cutting, and sideseal bag converting.

Repeat Length

Plate cylinders with different diameters can be mounted on many flexographic presses, allowing for variable repeat lengths. Printing a roll of packaging, such as gift wrap, uses a continuous repeat, where the same set of images is repeated many times on a continuous stream of substrate. To avoid the plate seam, images may require nesting, an arrangement that creates a staggered effect. Staggering im- ages gives the appearance that the design is continuous, no matter where the sub- strate is cut. 7 8 Flexographic Plates laser imaging,called rate colorregistration.Direct-to-plate vide higherresolutionandmoreaccu- introduced inthe1970’s,generallypro- since the1930’s,photopolymerplates, molded rubberplateshavebeenused resolution, registration,andcost. the customer’srequirements,suchas press, theplatecylinderinventory,and particular typeofplatedependsonthe able forbothmaterials.Selectionofa to-plate for theappearance ofcontinuousrepeat. must benestedto hidetheplateseam background color.Laserablated plates continuous repeatwitha laser. Designrollscanprovidea true polymer andmoldedorimaged bya a cylindercoveredwithrubberor photo- to theplate,aprocessknownas fer imagesdirectlyfromthecomputer Some platemakingmachinescantrans- Laser AblatedPlates image areaisremovedbyprocessing. traviolet light.Afterexposure,thenon- of honey,solidifies , abouttheconsistency exposed throughafilmnegative.Liquid state. Theimageareaoftheplateis in eithersolidsheetsorathickliquid Light-sensitive photopolymerissupplied Photopolymer the rubberplateusingamoldingpress. a mold,andthenplacingtheimageon and etchingamagnesiumplate,making multistep processthatinvolvesexposing Molded rubberplatesarecreatedina Molded Rubber flexographic presses Printing platesusedonmodern exposing andprocessing in threedifferentways:moldingrubber, mer ventionally processed.A directly imagedbylasersandthencon- film. Somephotopolymerplatescanbe , andimagingwithlasers.While that avoidstheproductionof when exposedtoul- ablating photopoly- design roll are produced , isavail- direct- is Laser AblatedPlatesandDesignRolls Photopolymer Plates Molded Rubber Plate Types Laserablatingisavailableforboth • Platesordesignrollsimageddirectly • Designrollscanprovideatruecontinu- • Filmisnotrequired. • Linescreeningislimitedto100lpifor • • Direct-to-platelaserimagingisavailable. • Positioningandregisterdeviceson • Nestingisrequiredfortheappearance • Linescreeningisatleast150lpiandcan Itisdifficulttomoldaccuraterubber • Nestingisrequiredfortheappearance • Registrationcanbemoredifficultthan • Linescreeningislimitedto120lpi. • Moldedrubberplatesshrinkwhenthey • rubber andphotopolymer. sation forplateelongation. on thecylinderdonotrequirecompen- ground color. ous repeatwithacontinuousback- lpi fortints. tone reproduction,butcanbe200-300 plates. designed forone-piecephotopolymer most modernflexographicpressesare of continuousrepeat. be ashigh200lpi. plates foreachcolor. designs mustbeplacedonmultiple plates largerthan24"X36".Larger of continuousrepeat. with photopolymerplates. platemakers. nicated betweenproductionartistsand shrinkage amountsshouldbecommu- grain, and.5%-1%acrossit.Exact 1.5%-2.0% inthedirectionofrubber pensate forshrinkage,whichistypically Plate filmsshouldbeadjustedtocom- are removedfromthemoldingpress. Plate Elongation When designing images for flexographic printing, it is As the soft plate wraps around the cylinder, it can important to understand the elongate, stretching images, halftones, and text across the curve dimension. Without compensation for plate effects of plate elongation. Because elongation, images will not print as designed. In the flexographic plates are made with soft example, if no compensation is applied, the sun image is printed as an oval and the vertical lines on each side material, they tend to stretch when are lengthened. mounted on the plate cylinder, some- times distorting images and text. A cir- cle, for example, may be stretched to Before plate mounting Expected result look more like an oval. Plate Plate centerline Fortunately, special flexographic soft- ware can compensate for plate elonga- tion by slightly distorting images. Plate elongation occurs around Distortion is usually performed within the cylinder

the flexographic software application & Distortion Elongation Plate or at the RIP stage before the film is imaged. The amount of distortion

After plate mounting depends on the thickness of the plate and the mounting tape used to fasten Spreading Stretching it, and on the circumference of the cylinder (the repeat length). In general, thicker plates and shorter repeat lengths increase the elongation. Printed piece with- out compensation for elongation To be sure that images will be printed with the correct size and shape, the Distortion design should be output to film after Special flexographic software can compensate for plate elongation by adding distortion, plate thickness has been determined using a basic formula, as shown in the following example. and the proper distortion factor has x 2(T) = 3.1416 been applied. Improperly calculated RL RL = 18.8"; repeat length of plate cylinder T = 1.27"; plate thickness with mounting tape distortion may also cause misregistration.

3.1416 x 2(1.27") For every linear inch of plate used around the = 0.0424" cylinder or curve direction, the images will 18.8" Direct-to-plate imaging, which is becom- increase at the rate of 0.0424". ing more widely available, avoids the Design measures 12" in the curve direction. need for distortion if the imaging is Calculate plate elongation: 12" x 0.0424" = 5.09" 12" applied directly on a design roll, or on a plate already mounted on the cylin- der. Because the image is applied to a The image is distorted to compensate for plate elongation. Film is output to 11.491" (12" – 5.09") curved surface, no stretching occurs. or 95.7% in the curve direction, and 100% in the 11.491" non-curve direction.

12"

Final design prints correctly since plate elongation has been compensated for. 12"

9 Flexography is ideal for printing Substrate Characteristics packaging materials because the soft plates can transfer ink to many Paper/ Polymer Multilayered/ Paperboard Films Laminations different kinds of substrates—anything from corrugated board to candy wrap- Substrates pers. The quality of a printed product

is determined not only by the type of kraft linerboard: polyethylene (PE): metallized papers: plate, but also by the substrate itself. corrugated, for boxes dry cleaner bags, bakery, gift wraps Different substrates allow varying degrees coated kraft: textile bags metallized film: corrugated, for boxes polypropylene (PP): snack food bags of ink absorption, gloss, brightness, and solid bleached sulfate (SBS): snack packages, candy polyethylene coated solid color definition. The chart on this page folding cartons wrappers, cookie bleached sulfate: packaging labels lists the characteristics of some common recycled paperboard: milk cartons folding cartons polyvinyl chloride: substrates. vinyl films, labels, wall coated paper: coverings labels, gift wrap uncoated freesheet paper: paperback books

Color Dependent upon substrate material; substrate White, brown kraft, a variety Clear, white or colored. Determined by the top-most color will significantly influence ink. of colored papers. layer.

Whiteness/Brightness The strength of white or color of a substrate. Increases with bleached & Determined by the opacity Determined by the top most coated papers. Decreases of white film. Clear films layer. Foil & metallized sur- with greater amounts of re- require the use of a white faces require the use of a cycled fiber. Optical bright- plate. white plate. eners can be added.

Opacity Amount of light transmitted through the Thin, lightweight papers Low for thin, lightweight Higher with multiple layers substrate. A lower opacity allows more light have lower opacity & are papers, which are more of material. to pass through. more likely to have ink show likely to let ink show through through. on reverse side.

Smoothness Smoother substrates allow higher lpi; rough, Newsprint, corrugated liner- Smooth printing surfaces; Determined by the top-most irregular surfaces require much lower lpi. board & paperboard are rela- ink adhesion is sometimes layer. tively rough; calendered & a problem. coated papers smoothest.

Absorption Determines how ink dries and spreads. Low Newsprint, corrugated liner- Non-absorbent, with no dot Usually low, but determined absorption produces drying at the surface, board & paperboard are very gain. by the substrate used as a increasing color saturation and decreasing absorbent, calendered; coat- printing surface. dot gain. Higher absorption increases dot gain. ed papers are less absorbent & exhibit high ink hold-out.

Gloss Reflective quality of the substrate. Gloss Calendered & coated papers High for most films, but Determined by the top-most can be increased with varnish or lamination are high gloss; corrugated films can be produced with layer. and can be decreased with matte or low-gloss linerboard, newsprint & a matte finish. finishes. paperboard are low gloss.

Caliper Thickness of a substrate, as measured by a Range: .002" to .010"; Ranges from .00065" to Increases as layers are micrometer. paperboard .010". Thin .006". Thin films may stretch; added. Thin layers may be papers more consistent in inconsistency in caliper can laminated together to ob- caliper; paperboard more cause misregistration and tain the required thickness. inconsistent. wrinkling.

10 White Plate Reverse-Side Printing Multicolor Options In background forcolors. white inkisprintedfirsttoprovidea any sequence.Fortransparentsubstrates, parent pigmentsandcanbeappliedin Process colorinksaremadefromtrans- printed intheorderoflightesttodarkest. fl exography, opaquespotcolorsare a solidwhiteinkisprinted In ordertoplacecolorsonatransparent substrate, background. colored inksarethenprintedontop ofthewhite background thatimprovesthecolor intensity.The also donethisway. Some snackfoodpackagingis ing areverse-sideprinted are oftendecoratedbylaminat- printing. ing, sometimescalled job callsforreverse-sideprint- when aspotcolororlineart est todarkestprintingoccurs An exceptiontotheruleoflight- fi rst tocreateare ” Styrofoamproducts “ fl back ective fi lm. a substrates, suchaspolypropylene,require applied inanysequence.Transparent from transparentpigmentsandcanbe to darkest.Processcolorinksaremade colors areusuallyprintedfromlightest ensure properinkcoverage,thespot opaque orsemi-opaquepigments.To Most flexographicinksconsistof seven processcolors. ing thecolorgamutbyprintingsixor printing, whichisamethodofincreas- color, flexographic presses is significantlyenhancedby Because theappealofpackaging including multiplespotcolorsand a numberofdifferentcombinations, applications. Designerscanchoosefrom even asmanytwelveforlimited monly offersixandeightcolors, to transparentsubstratesis Another techniqueusedforapplyingink and translucent. ors; otherwise,colorswouldappearflat “choke” plate,asabackgroundforcol- labels toachieve highqualitygraphics. avoiding thecostlypracticeofapplying or claycoatedcorrugatedlinerboard, cases, printingisdonedirectlyon awhite four-color processcapabilities.In some taking advantageofmultiplespot and paper linerboard,butmoredesignersare been onlyonecoloronbrownkraft Corrugated containershavehistorically printed filmlayertotheplate. decorated bylaminatingareverse-side tion. Paperorstyrofoamplatesareoften used forreverse-sideprintinglamina- ish. Insomecases,awater-basedinkis surface totheinklayer,andaglossyfin- substrate. Thisprovidesascratchproof displayed fromthenon-inksideof darkest tolightest;thepackagingisthen and colorsareprintedinsteadfrom printing white backupplate . Theimageislaterallyreversed, provided bya reverse-side com- HiFi

11 Color Capabilities Trapping is a technique of over- Choking and Spreading lapping colors to avoid unsightly gaps created by misregistration. Small variations in the placement of

Trapping color, called misregistration, can be caused by substrate handling and ten- sion problems on the press, irregular plate elongation from one color to the next, inaccuracies in plate mounting, plate bounce, and limited register capa- bilities, especially with molded rubber

plates. A test run, called a fingerprint- Spread lighter color Choke lighter color ing analysis, can determine the registra- tion tolerances. Traps are created by spreading or choking graphic elements, depending on adjacent colors. When a lighter element appears against a darker background, the lighter color is spread into the darker color, slightly increasing the size of the graphic element. When a When designing packaging for flexo- darker element appears against a lighter background, the knockout is choked by slightly filling it with the lighter color. Both methods create a small overlap of ink colors, called graphic printing, it is best to avoid the the trap width. This width depends on the thickness and size of type, the adjacent colors, requirement for tight registration, to and the registration capabilities of the press. Script, serif fonts, or small type can be spread or choked only small amounts before the shapes are compromised. In general, design images with dominant colors light and dark colors allow for greater trap widths than colors that are similar. printed on top of lighter ones, and to avoid trapping on gradations. Typically, a designer will build traps into the file Overprints and Traps if the design is simple, using options in publication or illustration software; more complicated designs require the help of service bureaus and special trapping software programs, such as TrapwiseTM from Luminous Corporation or DK&A Island TrapperTM.

Trap affecting colors Trap widths on narrow web presses should be set at a minimum of 0.005"; some presses require as much as 1/32" (0.031"), which is large compared to average traps of 0.002" - 0.005" for off- set lithography. A typical trap width for polyethylene printed on a wide web press is 1/72" (0.014"), though if an objectionable dark trap line is created, the width may need to be cut in half. Nailheads Trapping for linerboard or corrugated Printing inks on top of each other is called overprinting. In flexography, one ink can cardboard may require a trap width of be printed on another only after the first has been completely dried or cured. For this 1/64" to 1/8". reason, flexographic presses use dry trapping, where the printer must allow for drying. For substrates like clay-coated liner, or non-absorbent packaging such as polymer film, drying time can be a problem. Overprinting a second color when the first is not dry cre- ates an unattractive blotchy effect (often called nailheads), especially on large solids. Excessive trapping can cause such problems and can slow down the printing process.

12 Type Weight In flexography, printing consis- tently well-defined type is

In flexography, the Over-impression Substrate Deforming plate complicated by the soft plate, Type soft plate compresses in the printing nip, irregular substrate surface, and causing the fluid ink the fluid ink. Ink tends to spread out- to flow slightly out- Ink spreading ward from the image ward, sometimes obscuring the defini- area. Thus the weight tion of small point sizes or the fine of type may appear to Ink detail of certain letter shapes. Reverse increase, and reverse type may fill-in. type, which uses the substrate or a back- ground color to define the letter, tends

Pressure to get filled in.

Typographic Guidelines To help compensate for the typographic weight gain, it is possible to use the

4 point minimum positive san serif type for narrow web presses trapping techniques of spreading on 6 point minimum positive san serif type for wide web presses positive type and choking on reverse type. Software programs, such as TM 6 point minimum reverse type for narrow web presses MacroMedia FreeHand and Adobe TM 9 point minimum reverse type for wide web presses Illustrator , let the designer adjust the thickness of type. Some compensation can be done by choosing either a lighter 8 point minimum positive serif type for wide web presses or bolder face. For example, if medium positive type is desired, use a lighter Kerning may cause squeezing across cylinder, avoid tight linespacing weight face; if a medium reverse type is Kerning may cause squeezing across cylinder, avoid tight linespacing desired, specify a bold face. When possi- ble, sans-serif fonts should be used. In Letterspacing and/or linespacing may general, larger point sizes produce more EDIENTS: FILTER EDIENTS: FILTER increase slightly from plate elongation. AR, CORN SYRUP AR, CORN SYRUP consistent type. A AND LOWFAT A AND LOWFAT CESSED WITH AL CESSED WITH AL IN, NATURAL VA IN, NATURAL VA Letterspacing must also be considered. Letters squeezed together for a denser All positive text should be printed in a single color if possible PMS 407 appearance with offset lithography may All positive text should be printed in a single color if possible 6m 8.5y 27.5k merge together unacceptably in flexog-

Avoid placing fine type on the same color plate raphy. Ideal letterspacing keeps letters with line work and solid printing areas. close enough together so that they lend Made in the U.S.A. support to each other while under the pressure of the printing nip, but sepa- 47c 47c Avoid reversing type out of two or more colors rated enough to avoid merging. unless a dominant color outline is used. 94m 94m 15y 15y 5k 5k

Specify type accurately to the service bureau or prepress department.

13 The wide variety of substrates, Test Targets lack of standard ink hues, and unique dot gain characteristics High total ink amount Saturated colors with Saturated colors with to check density no black 20% black all contribute to the difficulty of com- municating and reproducing color by

Color Manage- 123 45 123 4 A B C D E F the flexographic process. A ment Systems (CMS), such as Agfa’s B C ColorTune 3.0 are software systems D used to ensure color consistency among E 23456 1 different input and output devices so Color Management that printed results match originals. The use of these systems aid in the color communication process by corre- lating colors on computer monitors and proofing devices with the actual or expected color results from the print- IT8.7/3 ing press. A G B H C I D J Because a color monitor can produce a E K much wider gamut of colors than the F L 1 234 5678 910111213 M inks on a , the designer N 123 4 5 6 7 8 9 10 11 12 13 needs to know the range of printable colors available on the computer. To find this range, a color specialist can run Shadows CMYK density wedges Neutral greys printed with CMY to check dot gain (and K in some cases) to check a CMS test on the flexographic printing grey balance Solid CMY press under controlled conditions, using patches the same ink, plates, mounting tape, and anilox rolls required for the actual pro- Color Management Systems build profiles by analyzing standard color data from test duction run. Since each substrate affects targets. The IT8 series of test targets can be used to calibrate prepress input devices (such as scanners), and output devices (such as proofing devices), monitors, and the color in a different way, a new test needs press itself. The IT8 7/1, IT8 7/2, and the IT8 7/3 (shown above) test targets all contain to be run for each new type of material. the same standard color information, but each uses a different format.

IT8 7/1 is a reflective color test target input to calibrate scanners for reflective art in a The results of the test are entered into color management system.

the CMS software, which sets up cali- IT8 7/2 is a transparency of the same format as IT8 7/1, but used to calibrate scanners bration tables and builds press profiles. for reading transparencies, rather than reflective art.

Digital cameras, scanners, monitors, and IT8 7/3 is a digital file of the same format used to calibrate imagesetters. To build a press proofing devices are all adjusted by the profile, the imagesetter is calibrated and the IT8 7/3 file is output to film. Plates are made CMS, based on the colors printed by the and mounted, and the IT8 7/3 is then printed under the actual production conditions. individual press. Input devices such as Printed samples are measured for density, dot gain, and colorimetric values, and the cameras and scanners, and prepress out- resulting data is entered into the color management system. CMS software then recali- brates monitors, digital proofing devices, and imagesetters to correlate the output at put devices including monitors and each of these devices with the expected output from the actual press run. proofing systems are adjusted according There are several color measurement tools used by flexographers to measure printed to the predicted outcome on press. samples. Used primarily in the press room, the reflection densitometer can only truly measure reflectance. It is used by the flexographer to measure density for pro- cess . The colorimeter, important because it assigns numerical values to all colors in the gamut, measures hues printed as either spot colors or screen tint combi- nations of CYMK. The spectrophotometer is most useful for ”fingerprinting“ specific hues of CYMK and base colors used for ink mixing.

14 Substrates Inks Plate Durometer Impression Pressure Dot GaininFlexography soft plate;ontherightitmeasuresaharderplate. image ontheleftshowsscalemeasuringa plate hardness,whichiscalled An instrumentcalledaShoreAscalemeasures absorbing thefluid inkandcausingittospreadbeyond thedotshapeandpattern. uncoated paper,newsprint,andcorrugated linerboard,thepaperfibersactasawick, preserving thedotshape.Withmore absorbentandirregularprintingsurfaces,suchas applied tosmoothnon-absorbentfilms andcoatedpapersittendstospreadverylittle, The printingsurfaceorfinishofasubstrate alsoinfluencesdotgain.Wheninkis durometer . The pressure. ible tapeorablanketthatabsorbs mounting theplatewithcompress- Dot gaincanalsobereducedby than thesupportingplatematerial. surface withahigherdurometer a thin(0.002"-0.005")cappinglayer Dot gaincanbeminimizedbyusing completely. however, transfersolidimagesmore produce lessdotgain.Softerplates, press asmuchsofterplates,they Because harderplatesdonotcom- or lower viscosity.Thespreading, spread asquicklyonewith A higherviscosityinkwillnot excessive flow-out. consistency, andisnotproneto graphic inkisathicker,paste dot gain.Bycomparison,litho- before itdries,contributingto transferred tothesubstrateand flexographic inkoccursasitis flow-out increasing dotgain. causes inktospread, image transfer.This compresses during deforms slightlyand soft flexographicplate in theprintingnip, relatively lightpressure transferred under Even thoughinkis , of alowviscosity rence known asdotgain. ject totheunavoidable occur- All printingprocesses are sub- tor, canalsomakeadjustments. processors (RIPs),suchasAgfaCalibra- bration packagesbuiltintorasterimage color separationfilms.Inaddition,cali- conditions, dotscanbeadjustedinthe printing suchatargetundercontrolled get usedforapressfingerprint.By page 14showsanexampleofatesttar- or desktopdesigner.TheIT8charton gain informationtothecolorseparator printing analysis,whichprovidesdot Typically, theprinterperformsafinger- measurements suppliedbytheprinter. tion softwarecanadjustdotsbasedon and predictable.Imageorcolorsepara- Dot gain,however,isoftenconsistent rugated linerboard. as uncoatedpapers,newsprintandcor- absorbent andirregularsurfaces,such papers willhavelessdotgainthan Smooth non-absorbentfilmsandcoated to thetypeofpressandsubstrate. increase dotgain,butitvariesaccording plates usedinflexographytendto Thefluidinkandcompressible dot. flexographic pressasa65%orgreater a on theplate,andeventuallyprint began as50%onfilmcangrowto51% spreads duringabsorption.Adotthat increase insizeonceagainastheink from theplatetosubstrate,itcan sure. Whenaninkdotistransferred tend togrowinsizeduringlightexpo- are transferredfromfilmtoplate,they As dots

15 Dot Gain Throughout its history, flexog- Halftone Dot Shape raphy has been printing quality line art and spot colors on a Square dots at 50% Stochastic dots at 20% wide variety of substrates. How- ever, it is the recently improved capabili- ty of high-quality, economical four-color process printing that has given flexogra- phy an edge over other processes for packaging applications. Symetrical round dots at 65% The Halftone Dot To minimize density jumps in halftones, round dots are preferred. Round dots do In flexography, the shape of the halftone

Halftones & Screening Halftones not touch until coverage is nearly 65% dot used to reproduce a continuous tone for the symmetrical round dots and 75% for asymmetrical dots. Dot gain is less image can significantly affect the density at these higher coverages, and is more of the image. Halftone dots can be gen- easily controlled or compensated for. erated in a number of shapes, including Asymetrical round Asymetrical round square, elliptical, octagonal, and both dots at 75% dots reversed at 80% symmetrical and asymmetrical dots. At 50% coverage, for example, square dots produce a pattern resembling a checker- board, with individual dots just begin- ning to join at their corners. When plates are created from film, dot gain increases the joining of the dots, which causes sudden jumps in density in the Screen Tints and Gradations

printed image, rather than a smooth, Highlights continuous transition. Most photopolymer plates are capable of holding a 2% highlight dot. If plates aren’t properly exposed, however, screen tints and To minimize the density jumps, printers highlight dots less than 3% tend to drop out. can use other kinds of dots that remain Because the small dots of highlight areas are subject to relatively large dot gain, it is impor- discreet and retain their shape, even at tant that any highlight limitations are dis- coverages of sixty and seventy percent. cussed with the printer before separations are made. Although printers in offset lithogra- A round dot, or octagonal dot are often phy can print acceptable highlights using 5% used. Though most design software film dots, flexographic printers may have to reduce a similarly bright highlight to 2%, tak- can specify round dots, selection of dot ing into account the additions of dot gain. shape should occur early in the process to avoid choosing a shape not available Offset Gradations and Vignettes lithography Flexographic dot gain on highlights makes in the RIP, imagesetter, or platesetter. it difficult to print a fade-to-white gradation without a harsh break at the highlight edge. Conventional Screen Ruling When designing images for flexography, it is best to fade off the end of the design (rather Selection of proper screen ruling, which than to white), or place a border at the high- is critical to four-color process flexogra- light end of a vignette. phy, is often dictated by the type of sub- Flexography strate. Anilox cell count and screen ruling for separations should be correlated for best results. The cells of the anilox, which ink a halftone plate, should be large enough to produce appropriate

16 Line Screens and Cells Per Inch color strength, but not so large that the halftone dots will dip into them like Screen Ruling Cells Per Inch Application an inkwell. For conventional halftones, (lpi) (cpi) resolution is expressed as the number The corrugated of lines of halftone dots per inch, also industry prints called screen ruling or lpi. Higher halftones screened at 45, 55, 65, or screen rulings produce higher resolution 85 lpi. images because there are more dots per square inch used to reproduce detail. 65 lpi 280-360 cpi Corrugated Compare the images in a newspaper

Flexographic (low screen ruling) to a picture in a newspaper printers monthly magazine (high screen ruling). print halftones screened between 65 and 100 lpi. Stochastic Screening Stochastic, or frequency modulated 85 lpi 360-400 cpi Newspaper (FM) screening, can offer advantages over conventional halftone screening. Flexible packaging on film substrates Stochastic screening eliminates the possi- is commonly done bility of moiré, and also allows the at 120 to 150 lpi. flexographic printer to use HiFi color, which involves the application of six or 133 lpi 500-600 cpi Flexible packaging seven process colors.

High quality label printers have the Dot size used for stochastic screening, capability of print- however, is extremely small, comparable ing 200 lpi images. in size to the highlight dot of conven- tional screening. Since flexography is 150 lpi 800 cpi Labels subject to significant dot gain, stochas- tic screening should only be used after the printer and color separator have Anilox Cell Angles and Halftone Screen Angles performed press fingerprints to deter- mine the ideal dot size and accurate Cells are engraved on an anilox roll at compensation for dot gain. one of three angles: ° 45° 60 30° 30°, 45°, or 60°.

Offset halftone screen angle 7.5° from cell angle

Anilox cell angle

To avoid anilox moiré, film or plate The number of lines per inch on the screen angles should be at least 7.5° plate should be no more than 25% of away from the anilox cell angle. Cyan, the cells per inch on the anilox. Ideally, magenta, yellow, and black screen the anilox should contain a minimum angles should also be set at least 15° of 4 cells for every halftone dot. apart from each other.

17 18 Step-and-Repeat & Die-Cutting often use correct positions.Packagingengineers must haveallgraphicalelementsinthe label orfoldingcarton,forexample, the designerandprinter.Adie-cut ments mustbeexactlyspeci design. CAD layouttouseastemplate for boxes; designersmayalsoimport the corrugated containers,orrigidpaper (CAD) industry usesaprintingtechniquecalled perly constructed, inline. Inorderforpackagingtobepro- folded, scored,sealed,orglued,often After printing,mostsubstratesarecut, anilox roll. inking ifthemovementistoward from theimpression,orareasofexcess skip ormisprintifthebounceisaway der. Bouncingcancauseprintareasto with ananiloxrollorimpressioncylin- when comingintojarringcontact of theplate,andcanproduceabounce graphy, imagesareontheraisedareas problem called area, staggeringimagescanalsoavoida In additiontomaximizingsubstrate gift wrap. images arepartofasingleroll,suchas repeat, andisusedforjobswhereallthe can givetheappearanceofacontinuous accommodate thearrangement.Nesting plate seam.Theendsarecutto mizes therepeatlengthandavoids staggered inanarrangementthatmaxi- be required.Imagesarestrategically step-and-repeat mize productivity, To save materialcostsandmaxi- Often, atechniquecalled width ofthesubstratewhenprinting. to such aslabels,arearrangedontheplate fi ll itsrepeatlengthandusetheentire systems todesignfoldingcartons, Computer AidedDesign plate bounce . Differentimages, die-cutting the packaging nesting fi ed forboth . In require- fl will exo- Plate Bounce Die-Cutting Step-and-Repeat tain contact. non-image areastomain- printing necessary toplacenon- bounce. Sometimesitis cylinders, minimizingplate continuous contactbetween the platecanhelpkeep Staggering imageson Cut Areas press. precise amountofbleeddependsonthe extend beyondfoldandcutlines,butthe cut, folded,andjoined.Ingeneral,bleeds must knowwherethepackagingwillbe Bleeds should makesurethatregistrationisprecise. ly foldatscorelines,wherethedesigner Score Lines especially thosesealedbyheat. areas shouldbefreeofinkandvarnish, Glue &SealAreas should notbeplacedtooclosetocutareas. with theprintedcol cutting, thediemustbeheldinregister connected toinline To specifybleeds,thedesigner bearer bars When Die-cut foldingcartonsusual- fl exographic printersare To ensuresealing,glue ors. Graphicelements on fl atbed orrotarydie- two dimensionallayoutofthejob. programs, providingthedesignerwitha exported fromCADsystemstoillustration Die-Cut Templates must allowfordotgain. parallel tothedirectionofweb,and cise forlasers,theyshouldbeprinted Bar Coding before includingtheminthedesign. machines. Alwayscheckwiththeprinter but maynotbeavailableonalldie-cutting tons orlabelsshouldbeclearlyindicated, Windows varnish. dates variable information,suchasfreshness Varnish-Free Areas and productcoding,mustbefreeof Die-cut windowsforfoldingcar- To helpkeepbarcodespre- widths. repeat lengthsandweb repeat optionsforspeci software offerstep-and- ing. Layoutandimposition for step-and-repeatprint- and avoidtheplateseam maximize theplatearea Nesting imagescan Templates canbe Areas thatcontain fi c The Prepress Process After a design has been trapped, distorted to compensate for plate elonga- Following design, production, and ripping, a job may take different paths through the pre- press output and platemaking stages. For conventional photopolymer or rubber plates, jobs tion, and electronically imposed (consid- are first processed through an imagesetter, creating film output, which is used for plate ering step-and-repeat requirements), the exposure and processing. Plates are then placed on a mounting machine where, in some cases, a plate proof is made. A platesetter device essentially follows the same flow with the file is processed by the raster image exception that the film processing step is eliminated. With direct-to-plate (or cylinder), de- processor (RIP) and output to film or vices, shown below as laser ablation, both platemaking and processing steps are eliminated. plate. The RIP converts PostScriptTM data into a series of bitmapped images. The

laser output device records this visual Output Prepress information received from the RIP onto film or plate material. Larger, more complex files will take longer to process through the RIP than simple text files.

Flexographic Imagesetting Requirements

Accuracy To optimize registra- tion, output devices should meet a minimum standard of 1 mil over multiple separations. Geo- metric and absolute accuracy capabilities are also important imagesetters considerations.

Size The imagesetter format size should be large enough to make the most effective and economic use of film, given the particular application.

Film All film for soft photopoly- mer plates should be output to matte emulsion film (minimum thickness: 0.004"; 0.007" is pre- ferred). This helps avoid trap- ping air between the film and plate during exposure.

Calibration Film dot percentages below 10% should not vary by more than 1%; areas over 10% should not vary by more than 3%.

Uniformity Screen tints should be a uniform dot percentage, with no variation in size be- tween individual dots.

Dot Shape The imagesetter should be capable of outputting a “hard” round dot.

Resolution Resolution should be between 1200 and 3600 dpi. For line art, solids and type, 1200 dpi is adequate; halftones require a minimum of 2400 dpi.

Density Film density is an important factor; imagesetter exposure levels and film pro- cessing chemistry should provide DMax areas of 3.5-4.0. 19 In flexography, proofing for Proofing for Flexography ng halftone accuracy and color

fi Soft Proof matching can be difficult and inexact. A digital or film-based proof- During preliminary design, proofing starts with a monitor, some- times called a soft proof. A monitor can provide an overall view Proo ing method used in offset lithography of the design, but RGB colors on a monitor will probably not may not be suitable for different kinds match CMYK or spot colors printed on the substrate. Higher color fidelity is possible by calibrating the monitor and by using a color of substrates, for matching spot colors, management system. or for reproducing flexographic dot gain. Accurate proofing may require using two or more methods. Digital Print Proof

Substrates Flexographic printers often provide mock-up pack- ages, using proofs from digital laser printers. Most proofing methods are limited to Many high-end digital proofing methods meet a small number of substrates. Because industry color standards for prepress proofing systems. Inexpensive desktop color printers can ink colors are affected by the absorption also give an approximation of specified colors. and color of the substrate, proofing to When used with a color management system, digital printers can provide contract proofs. Most another material cannot provide accurate digital systems are based on CMYK toner applica- color matching. tions, so spot colors may not be accurate.

Spot Colors Film Proofs Since most film-based and digital proof- Most film-based proofing systems are designed to ing methods apply toner in CMYK compensate for dot gain occurring in offset lithogra- colors, spot colors often cannot be accu- phy. To use these systems for flexography, two sets of film must be printed. The first set, which is used rately produced. If matching spot colors for platemaking, reduces dots to compensate for the is critical to a job, some printers can actual flexographic dot gain during printing. The sec- ond set, used for proofing, increases the dots to simu- provide a catalog of colors that they can late dot gain in the film proof. consistently print on a variety of sub- strates. Catalogs may contain specially formulated colors, or use systems similar TM Plate Proof to Pantone® or FocolTone . Sometimes it is possible to request samples. To For many years, flexographic printers have used a plate proof created on a mounter- ensure accurate matching, spot colors proofer during plate mounting to verify plate should also be evaluated by a color mea- register, quality, and content. Though expen- sive and not intended for customer approval, surement instrument. the plate proof today is mostly used on wide web presses. Plate proofs can be created for Dot Gain color matching, but they more commonly use ink hues that are not intended to match press Adjustments for flexographic dot gain colors. Color matching from a plate proof is are often not available in proofing sys- very difficult due to the differences between proofing and press equipment. tems designed to mimic the dot gain found in offset lithography. For this reason, halftone images and smaller Press Proof

type may not be accurately reproduced Printed on the press, a press in the proof. However, once a character- proof is the most accurate method, but because it is also ized profile is established for a given the most expensive, it is not press using a color management system, common. dot gain can be simulated by a digital proofing system.

20 What to Look For During a Press Check Before a flexographic job is printed, a number of factors Type Is the type sharp? Has the weight of the type changed? With need to be checked to ensure a loupe, look for outline halos. accuracy. Makeready on a flexographic press includes installation of the required plate cylinders and inks, setting levels Registration for impression and ink pressure, register Are the colors in register? Make sure colors line up and check adjustment, and any setup for inline areas where inconsistent elongation may have caused mis- registration. For a four-color process with traditional screen- finishing, such as cutting, folding, or ing, color-to-color register should not vary by more than a gluing. Pressure levels are particularly single row of halftone dots. critical for accurate printing. Finally, Density/Color Intensity Is the density of the color appropriate, especially in situations after press adjustments are complete, the where screens and solids are printing from the same cylin- press operator checks colors for the job, der? Is the color strength consistent from side to side? running a sample at (or near) produc- tion speeds. Designers should also make Color Match sure to perform a press check for the first Do spot colors match? Each color should be verified under actual print run. 5000° Kelvin lighting conditions. When appropriate, use color measurement instruments to verify acceptable match.

These are some of the elements that Prepress Checklist & The Press Check Checklist & The Press Prepress Ink Laydown should be verified prior to printing. Is the ink laydown consistent, without mottle? Are there pinholes or voids? Under a loupe, halftone dots should Type appear sharp, not slurred. Is the point size and font correct? Is the typography what was expected? Has plate elongation affected leading, letterspacing, Substrate or word spacing? Is the width, caliper, and type of substrate as specified? If the substrate is an opaque film, is the opacity appropriate? Line Art Have all of the images elongated and reproduced accurately? External Register Does the print line-up with the specified finishing operation, Register such as diecuts, sideseals, slots, scores, and glue areas? Internal (color to color) and external Request a mock-up container to check accuracy of external (images to die-cut, sealing areas, perfora- register. tions, etc.) If all colors have been accu- rately distorted, and the plates accurately mounted, the job should be in register. Ink and Impression Levels Look at the edges of solids for an outline halo, which is the result of excess ink or impression pressure. The press Traps operator may be able to relieve some pressure; some plates Have plate mounting and plate elongation may have spot color inaccuracies that require a plate remake maintained accurate trap areas? or remount. Bar Coding Dot Gain Have the bar codes been positioned to Dot gain levels should be comparable to those achieved allow proper open area surrounding the during fingerprint trial. code for scanning? Has the bar code been positioned with the bars parallel or per- pendicular to the web direction? When UPC and Bar Coding mounted perpendicular to the web direc- Over-impression can change the width of bars and spaces, tion, bar codes will be affected by plate potentially making the bar code unreadable. elongation.

Wind Direction Has the job been set-up to print in the Wind Direction right direction on press? Will the print Has the job been installed in the right direction on press? If the press is running roll-to-roll, is the print rewind in the direction match the packaging or labeling proper direction? operation?

21 ablating: 8 colorimeter: 14 design roll: 2, 8 To remove by cutting, erosion, evaporation, Any of various instruments used to determine A rubber covered cylinder often used as an or vaporization. In flexography, laser ablating or specify colors. A colorimeter measures the image carrier by flexographic printers. Relief is used to image design rolls and plates. spectral reflectance of a color, and computes patterns and images are created by ablating numeric values for the hue, intensity, and the surrounding non-image area with laser anilox: 5, 6, 17 purity. light energy. An engraved metal or ceramic roll used to meter ink in the flexographic inking system. color management system (CMS): 14 die-cutting: 18 A software system used to ensure color con- The process of using sharp steel rules to cut bearer bars: 18 sistency among different input and output shapes for labels, boxes and containers, from Continuous strips of plate material usually devices so that printed results match originals. printed sheets. Die-cutting can be done on placed on the outside of printing areas to either flat-bed or rotary presses. Rotary die- Glossary & Index minimize plate bounce and over-impression common impression cylinder press (CIC): cutting is usually done inline with printing. by taking up excess impression pressure dur- 6, 7 ing printing operations. A printing press configuration that positions direct-to-plate: 8 all color decks around a central impression The process of using digital information to blanket: 4 cylinder. The CIC press configuration offers laser image a printing plate or design roll, by- In , a rubber-surfaced fabric web support throughout the printing opera- passing the film stage of production. which is clamped around a cylinder, to which tions, and optimum registration capabilities. the image is transferred from the plate, and distortion: 9 from which it is transferred to the paper. computer aided design (CAD): 18 Intentional compensation for flexographic Electronic equipment used by package design plate elongation. bleeds: 18 engineers to layout and design in three An image or color that extends to, and slightly dimensions the structure of a package. distortion factor: 9 beyond, the trimmed edge of a printed piece. A percentage number calculated by a plate continuous repeat: 7 elongation formula and applied to images calendered paper: 10 The ability to print patterns or images on a prior to output of flexographic films. Paper that has been passed through a group of web of substrate, void of any gaps in the rolls to reduce thickness, increase density, and printing. dot gain: 15, 16 improve its surface smoothness and gloss. An unavoidable increase in the size of half- contract proof: 20 tone dots as they pass through the stages of caliper: 10 A proof supplied to a printer to document platemaking and printing. Dot gain varies Thickness of a substrate, usually measured in the color results expected on the press. according to the characteristics of the press, thousandths of an inch. ink, and substrate used. If dot gain is not ac- converting operations: 7 counted for during the creating of color sepa- cell angle: 6, 17 In packaging, any process performed to man- rations and proofs, unexpected color shifts or On an anilox roll, the measure of a line ufacture a completed package from a raw loss of detail will occur on press. drawn through the center of a row of cells material or an unfinished material. and a line drawn parallel to the shaft of the doctor blade: 4, 6 anilox. The angle at which cells are arranged corrugated: 6, 7, 10 A thin blade of metal or polyethylene mount- on an anilox roll. The combination of linerboard and corrugat- ed parallel to and in contact with an anilox ing medium as a fluted material. roll to meter excess ink from the non-cell areas. cells per inch (CPI): 4, 17 On an anilox roll, the number of cells in a corrugated press: 2, 7 dry trapping: 12 linear inch. An inline sheet-fed press (usually a flexo- The technique of printing multiple colors by graphic press) designed for printing sheets drying each color immediately after it is ap- cell volume: 6 of corrugated. plied and before the next ink is applied on or A measure of the capacity to carry ink of a over it. Flexography and gravure print by dry square inch of anilox roll. Cell volume may cut areas: 18 trapping. See wet trapping be calculated as theoretical volume, or mea- In die-cutting, a region of a package that will sured by a technique of liquid volume mea- be cut-out as a window or as part of the dual doctor ink chamber: 4, 6 surement, or scientifically measured by a package construction, or as a slot for a clo- On a flexographic press, a cartridge designed technique known as infratometry. sure tab. to supply ink to the anilox roll in an enclosed area. Ink is pumped into and circulated choke: 12 cylinder: 5 through the cartridge which is positioned on A trapping technique of slightly reducing the In flexography, the term cylinder usually the anilox roll. Two thin strips of metal or size of a line, an image element, or a dot to refers to the rollers on which plates are polyethylene (doctor blades) are in direct create a trap. mounted (plate cylinders), and the impres- contact with the anilox roll. One of the sion roller (impression cylinder). blades contains the ink within the cartridge, clay coated: 10 the other blade contains and meters the ink A high-quality paperboard having a surface from the non-cell areas of the anilox. When of pigment or pigment like solids and using a dual doctor ink chamber, the foun- appropriate binders. tain roll can be eliminated. 22 ing, folding,andsealing. including lamination,die-cutting,perforat- tinuous processwithaprintingoperation, Any convertingoperationdoneasa con- inline ing imagetransferfromplatetosubstrate. The cylinderthatprovideswebsupportdur- impression cylinder of asubstrate. distribution systemtotheappropriateareas responsible fortransferringinkfromthe The physicalcomponentofaprintingpress image carrier times seven,processcolors. printing gamutbysix,andsome- A methodofincreasingtheprocesscolor HiFi, high speciality products,andpublications. Gravure isusedforprintingpackaging, engraved plateasamasterimagecarrier. An intaglioprintingprocessthatusesan gravure A smoothtransitionbetweenshades. gradation Paper freeofmechanicalwoodpulp. freesheet paper areas fromacceptingink. to dampentheplateandkeepnon-printing or syntheticgum,andotherchemicalsused In lithography,asolutionofwater,natural fountain solution is todeliverandmeterinktheaniloxroll. tion ofthefountainrollinatwosystem two roll In fountain roll strength tocorrugatedboard. boards. Flutingmaterialaddsstructural and sandwichedbetweentwopaperliner- A papersubstrateformedintoroundedpleats fl ing pressbyuseofatestplate. A methodoftestingcharacteristicsaprint- fi a measuring instrumentmostwidelyusedis A measureofthehardnessrubber.The durometer uted material ngerprint “ Shore A fl exography, arubbercoveredrollinthe fi nishing fl : exographic inkingsystem.Thefunc- 2, 4 : ” fi : : durometergauge. 14 delity 12, 14,15 15 : : 6 4 : : 7 10 : : 11, 17 4 : 4, 6 paper or molecules collectonthecoolweb,giving over thepointofvaporization.Vaporized web ofpaperaroundachilledrollerand ing aluminuminavacuumwhilepassing available inavariety oftypesandthicknesses. plates toplatecylinders. Mountingtapesare and usedforaf strate withadhesiveappliedtoboth sides, A compressible,oranon-compressible sub- mounting tape having adifferingpitchorangle. overlapping symmetricalgridsofdots orlines A repetitiveinterferencepatterncausedby moir or microscopic Paper or metallized frequency ofthehorizontalandverticallines. exposing ittoproducedots.Lpirefersthe placing anetchedglassplateoverimageand 55-300. Originally,halftonesweremadeby of ahalftonescreen,usuallyrangingfrom (lines perinch)Ameasureofthefrequency lpi tive andthenonprintingareainkrepellent. which theimagetobeprintedisink-recep- (such asasmoothstoneormetalplate)on A methodofprintingfromaplanesurface lithography image areawithlaserlightenergy. created byablatingthesurroundingnon- topolymer designrollsorplates.Imagesare A processofimagingontorubberorpho- laser ablation fer toasubstrate. pressure necessaryforcompleteimagetrans- In kiss and bottomlayersinasheetofcorrugated. pulped wood A typeofpapermadefromchemically kraft linerboard and steeldieengraving. below thenon-imagearea,usedingravure A processinwhichtheimageisrecessed intaglio done simultaneously. nation ofprintingandconvertingoperation with oneanother.Alsoreferstoanycombi- are assembledonacommonplane,orinline A multicolorpresswheretheprintingunits inline press : fi fl 5,16, 17 lm isproducedbymeltingandvaporiz- exographic printing,thelightestcontact : é 6 : 6, 17 : fi fi 4 lm ametallic lm thathasbeen fi : fi : lm, metallizedpaper fi 6, 7 lm ofmetal.Ametallizedpaper 2, 4 fi : bers, andusedasthetop xing 8 : : 9 10 fl exographic printing fi nish. “ coated ” : witha 10 bounce. waste, and/ortominimize layout. Nestingisdonetominimizesubstrate wide webfromnarrowweb. the exactcut-offwidththatdifferentiates dustry. Thereispresentlynoagreementon wide as32"byvarioussourceswithinthein- been speci images ona A techniqueofplacingimagesbetweenother nesting The limitofnarrowweb narrow web area thatresemblestheheadofanail. the successiveinklayers,andanpick-off situation, resultinginincompletedryingto printed ontopofoneanotherinatrapping lem usuallycausedbytwoormorecolors In nailhead during theplatemounting step. the cylinderorcurvedirection,that occurs between theplateandimpressionroll. ing ofthe In plate elongation common planeasinlithography. both imageandnon-imagearecarried ona A processforprintingfromaplanesurface, planographic light. chemical changewhenexposedtoultraviolet Any ofavarietymaterialsthatundergo photopolymer sidered tobepaperboard. thickness of10points(0.010")arealsocon- board, however,somethinnerpaperswitha points (0.012")thickisconsideredpaper- rigid thanpaper.Mostpaperthatisover12 is thicker,heavierinbasisweight,andmore between paperandpaperboard.Paperboard There issomequestionastothedistinction paperboard In a over-impression the lithographicplatetosubstrate. blanket cylindertotransferanimagefrom Planographic printusinganintermediate offset lithography ered roller. metal drivenrollerandundrivenrubbercov- Contact pointbetweentworollers,usuallya nip fl fl : exographic printing,aninkdryingprob- exographic printing,aphysicallengthen- fl 6 exographic pressset-up,excesspressure : : 7, 18 fi fl 12 ed tobeasnarrow18"or exographic imagecarrieraround fl : : exographic step-and-repeat 10 : 6 : 4 8 : : 13, 15 9 : 4 fl exography has fl exographic plate

23 Glossary & Index plate bounce: 18 resolution: 16, 17 trap, trapping: 12 An erratic rotation of a printing press cylin- The measure of fineness and detail in an In prepress, a technique which allows for der, such as a plate cylinder, that results in image. The scale of resolution depends on variation in registration during the press run. defective impressions. This is caused by the the device being measured. Scans are mea- On the desktop, this is done primarily by al- lead edge of image areas on a flexographic sured in samples per inch (spi) or pixels per lowing an overlap between abutting colors. plate cylinder coming in contact with the inch (ppi). Monitors are measured in ppi. anilox or impression roll. Halftone screens can be measured in lines per variable repeat length: 7 inch (lpi). In all cases, the higher the resolu- In printing, the capability of a printing press plate proofs: 20 tion, the more detailed the image. to print from various size plate cylinders or A print made from the “live” production printing plates. plates prior to going to press. Plate proofs are reverse side printing: 11 usually not appropriate for evaluating color Printing the underside of a clear substrate. vignettes: 16 Glossary & Index results, but may be used as an in-house quali- Sometimes called back printing. An image in which the background fades ty control proof before going to press. gradually away until it blends into the run-length: 5 unprinted substrate. plate thickness: 9 The size of a printing job, usually indicated A measure of the height of a flexographic by the number of impressions or footage re- wet-out: 10 plate from the back to the top of the image quired to complete the job. Also, the number The tendency of an ink to level-out as would area, usually expressed in thousandths of an of impressions that may be expected from a a true liquid. On a substrate, an ink film inch. printing plate or a set of printing plates. should flow and level itself rather than beading.

polyethylene films: 2, 5, 10 solid bleached sulfate: 10 wet trapping: 12 Thin clear substrates used as packaging Paperboard made with sulfate pulp contain- The technique of printing multiple colors materials, commonly known as plastic as in ing 100% bleached fibers. whereby each succeeding ink film remains plastic bags. open (not dry) as the next color is applied spectrophotometer: 14 on or over it. polymer films: 10 An instrument used to determine the distri- Any one of a number of different non- bution of light energy reflected by a color or white back-up plate: 11 absorbent, thin, clear, or colored substrates a printed ink. A printing plate made for applying a solid used as packaging materials, and commonly white ink as a reflective base under all colored referred to as plastics. spot color: 11 images on a clear substrate. Color printed with a custom ink, rather than printing plate: 4 with a process color combination. wide web: 6 In flexography, a rubber or photopolymer The lower limit of wide web flexo has been material used as the image carrier to transfer spread: 12 specified to be as narrow as 18" or as wide as ink from anilox to substrate. A prepress function that compensates for 32" by various sources within the flexograph- printing press misregistration. A spread is the ic industry. There is presently no agreement proof, proofing: 20 slight size increase of the inserted image. on the exact cut-off width that differentiates A prototype of a job to be printed that is wide web from narrow web. made from plates, film or electronic data. stack press: 7 Used for in-house quality control and/or for A multicolor printing press where all color windows: 18 customer inspection and approval. units are built vertically or stacked. In packaging, an area of a package that will be cut out (or left clear on clear substrates) to raster image processor (RIP): 19 step-and-repeat: 18 expose the product held within the package. The computerized process that results in an In photomechanics, imagesetting, or plate ex- electronic bitmap which indicates every spot posure, the procedure of multiple exposures position on a page in preparation for actual using the same image information by step- printout. ping it in position according to a predeter- mined layout. reflection densitometer: 14 An apparatus for measuring the optical densi- stochastic screening: 17 ty, or light absorbing qualities, of an ink. Also called frequency modulated or FM screening. An alternative to conventional relief: 5 screening that separates an image into very In printing, a process that prints from raised fine, randomly placed microdots, rather than image areas. a grid of geometrically aligned halftone cells.

repeat length: 7 substrate: 4, 10 Printing length of a plate cylinder determined A material on which print or coating is by one revolution of the plate cylinder gear. applied, such as paper, polyethylene, or foil.

24 Other Educational and Reference Materials from Agfa

An Introduction to A Guide to Color Separation Working With Prepress Digital Color Prepress—1997 Edition Digital Color Prepress - Volume Two and Printing Suppliers A fundamental reference for anyone interest- This booklet provides a more advanced Digital Color Prepress - Volume Three ed in PostScript color. Basic concepts are ex- look at the topic of PostScript color. A special This booklet explains key elements in the plained in a clear, objective and highly visual emphasis is placed on reproducing color pages relationship between document creators and way. A useful and award-winning volume, in print, including the use of HiFi color and their service providers. Contains time-saving with over 400,000 copies in print in eight stochastic screening. tips to ensure successful transition of jobs languages. from design to film output to final print.

An Introduction to Digital Scanning An Introduction to An Introduction to Digital Color Prepress - Volume Four Digital Photo Imaging Digital Color Printing This booklet focuses specifically on many This booklet looks at how computer technol- A first-ever publication that provides an objec- key aspects of scanning. Contains 40 pages ogy is blending with and changing traditional tive look at technology, applications, and of both basic and advanced information, photography, and the impact it has on photog- processes. Learn how to save time and money presented objectively and graphically. An raphers and imaging professionals. Explains and use to your best advantage. essential reference for scanner users with how to evaluate digital cameras, scanners, Includes a bound-in digitally printed insert any level of expertise. input and output devices, and how to get for comparison with offset printing. started in this emerging field.

A Guide to Digital PostScript Process The Agfa Guide to Photography Color Guide—1996 Edition Digital Color Prepress Theory and Basics This 52-page oversized reference contains Macintosh CD-ROM Edition This all-new guide is a must read for any- over 17,000 electronically created CMY and The ultimate companion to the award- one working with or interested in digital CMY+K process color combinations (on winning Digital Color Prepress series. photography. Offers clear, visual explana- coated and uncoated stock), intended to help This CD-ROM contains over 630 Mb of tions on traditional photography basics as predict how colors on the screen will look interactive content, including 350 screens well as key concepts from the emerging in print. Also includes production tips, of detailed information, numerous anima- digital realm. instructions for use, and special color viewing tions, videos, voiceovers, glossary, timeline, templates. Available in U.S. (SWOP) and a build-a-page game, and more. multilingual European standard version. For more information or to order, see contact listings on back cover. Credits Production Notes

Writing and Technical Direction: This booklet was produced using a variety Barry Lee of Macintosh computers. The illustrations Rochester Institute of Technology, were created using Adobe Illustrator and Rochester, NY Adobe Photoshop. All images and text were imported into QuarkXPress for page layout. Creative Direction and Design: Pages were individually output to the Agfa Lynne Stiles and Maria Giudice SelectSet 5000 imagesetter using Agfa YO, San Francisco, CA Balanced Screening. Printing was done in four-color process plus one spot color, PMS Copyediting: 407, on Centura Dull Coated 80# book stock. Robert Shuster Seattle, WA Film Preparation: Digital Pre-Press International Illustrations: San Francisco, CA Steve McGuire McGuire Design, Martinez, CA Printing Supervision: Jack Gaido Special Thanks: Hemlock Printers, Burlingame, CA Don Haaga, Ben Seibel Printing: This publication copyright ©1997 Hemlock Printers by Bayer Corp. All rights reserved. Vancouver, Canada

No portion of this publication may be Ordering Information: reproduced in any form without expressed This booklet is part of a series of educational written permission from the publisher. and reference materials published by Agfa. If you’d like to be on our mailing list, or obtain information about other publications in the Digital Color Prepress series, contact us via the numbers or addresses below. Quantity discounts and foreign language versions available.

AGFA, the Agfa rhombus, ColorTune, and Digital Color Prepress are trademarks of Agfa-Gevaert AG. Macintosh is a registered trademark of Apple Computer Inc. PostScript, Photoshop and Illustrator are trademarks of Adobe Systems Inc. and may be registered in certain jurisdictions. QuarkXPress is a registered trademark of Quark Inc. Pantone and PMS are registered trademarks of Pantone, Inc., for color reproduction and color reproduction materials. FreeHand is a trademark of Macromedia, Inc. Windows is a trademark of Microsoft Corporation. FocolTone is a trademark of FocolTone USA Inc. Trapwise is a trademark of Luminous Corporation. DK&A Island Trapper is a trademark of DK&A Inc. All trademarks have been used in an editorial context with no intention of infringement.

Agfa Educational Publishing Agfa Educational Publishing P.O. Box 787 P.O. Box 200 Randolph, MA 02368-0787 USA Stephenson Road – Groundwell Phone: 1-800-395-7007 Swindon, Wilts SN2 5AN UK Fax: 1-617-341-6261 Phone: 0793-707099 http://www.agfahome.com Fax: 0793-705745

NEEJ1 First Printing May 1997 Printed in Belgium by The Color Revolution