Substrate guide for HP Indigo digital pressesUS edition

OverviewThis guide has been written to help HP Indigo digital press owners have agreater understanding about media, their properties and characteristics, i.e.,how they behave in various conditions and how to optimize their effectiveness.Some non-paper substrates are also discussed in relation to generalrequirements or notable special considerations.

While written for HP Indigo commercial press users, this guide also containssome information about other forms of HP Indigo digital printing, especially toillustrate the different stresses they put on paper. We hope this will help you tounderstand why media and digital press compatibility are important to youand your customers.

The advice and suggestions for paper storage and handling demonstrate howoptimum conditions will ensure runnability and print quality, as well as achievethe best results from finishing processes. This guide will provide guidanceregarding media selection and use, enhance your understanding of thechoices, and contribute to your knowledge of digital printing.

Table of contents

Chapter 1 How paper is made . . . . . . . . . . . . . . . . . . . . 5Chapter 2 Paper sizes and finishes . . . . . . . . . . . . . . . . . 9Chapter 3 The HP Indigo digital printing process . . . . . . . 13Chapter 4 Using the right paper. . . . . . . . . . . . . . . . . . . 17Chapter 5 Printing applications . . . . . . . . . . . . . . . . . . . 21Chapter 6 Paper problems . . . . . . . . . . . . . . . . . . . . . 27Chapter 7 FAQs about substrates . . . . . . . . . . . . . . . . . . 31Chapter 8 Finishing—a brief guide . . . . . . . . . . . . . . . . 35

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Variables in the papermaking process and thematerials it involves have a major bearing onprintability and the performance of the printedproduct. An understanding of the basics ofpapermaking helps to clarify the suitability of certainpaper grades for particular end-uses.

Take a treePrinting paper is made from 70-75% wood—a mixtureof hardwood and softwood varieties which arecarefully combined to give specific characteristics tothe paper sheet. Pulp made from recycled fiber is alsowidely used in papermaking.

Hardwoods produce short fibers, which help producea smooth, opaque sheet with good runnability, whilesoftwoods yield long fibers that are essential forstrength. Hard and softwood pulps tend to be used incombination to achieve the desired sheetcharacteristics. Within the broad categories of hardand softwood, the species of tree largely determinesthe type of pulp produced, and affects suchcharacteristics as tensile strength, tear strength,brightness, bulk, stiffness and opacity.

Other factors such as climate, soil conditions and theage of a tree can also have a significant effect on fiberquality. The nature of recycled fiber depends largelyon the source of the fiber—office wastepaper orhousehold wastepaper collections—and the processinvolved in its recycling.

Recycled fiber is widely used—particularly innewsprint, super-calendered and lightweight-coatedpaper as a substitute for mechanical pulp, oftenreinforced with specific grades of softwood virgin pulp.Papermakers cannot control the quality of fibers inrecycled pulp to the degree possible with virgin pulp.However, sophisticated sorting and processing systemsdesigned for handling waste paper are able to removeink, dirt, glue and unsuitable fibers to a degree whichallows the use of up to 100% recycled pulp in thegrades mentioned above.

Pulp fact—chemical and mechanicalWood is prepared for papermaking either byshredding it mechanically into fibers to makemechanical pulp or by cooking it in chemicals todissolve the fiber-binding lignin to make woodfreepulp. The wood pulp made by these processes isbleached and produces mechanical and woodfreegrades of paper, although many grades contain amixture of pulps from both processes. The brightestpapers are those that are woodfree becausechemically-pulped fiber is easier to bleach and thepulping process removes more impurities.

Chapter 1How paper is made

Chemical pulp is also stronger than mechanical pulpand more resistant to aging. It is the absence ofmechanical pulp, known in North America asgroundwood pulp, which gives woodfree papers theirname. Most paper compatible for digital printing iscoated or uncoated woodfree paper. Woodfree paper,coated and uncoated, is often referred to as art paper.

PapermakingPut simply, papermaking is a continuous process ofwater removal. The paper machine comprises threebasic parts: the wire section, press section and dryersection. In the wire section, a highly diluted mixture ofpulp, fillers and chemicals is uniformly distributed froma headbox across a moving wire mesh up to 10 meterswide. In this part of the process, water is removedthrough gravity, vacuum and centrifugal force.

Then the web is drawn through a series of presses—thepress section. These presses consist of pairs of steelcylinders which squeeze water out of the paper weblike a mangle. As the paper leaves the final press, itbears some resemblance to a sheet, although it stillcontains some 60% water. In the dryer section, theweb is carried over numerous steam-heated cylinders,which evaporate most of the remaining water. Thesheet is finally wound on a roll ready for furtherprocessing into sheets or printer-sized rolls. Thedemands of quality, consistency and efficiency meanthat printing grades of paper are made at highspeed—up to 6,00 feet/minute—and the processinvolves absolute precision and high-level automation.

Coated or uncoated?Digital printing uses both coated and uncoated papersCoated papers offer superior smoothness, opacity,color, contrast and print definition. Uncoated papersoffer a range of textures, shades and pleasing tactilecontrast. Coated paper also offers benefits for theprinting press—it produces less dust and otherpotential contaminants. Its use prolongs the life of theblanket, increases runnability and reduces downtime.

Single or double layers of coating may be applied onone or both sides of the paper. Single-coated papertends to have greater bulk than double-coated paper,while double-coated paper can achieve higherbrightness and opacity.

Coating produces a matte surface, which can bemade glossy through calendering. The higher the coat-weight, the greater the gloss potential. There isconsiderable cross-over in the end uses of papercoated on just one side (C1S) and paper coated ontwo sides (C2S).

Application examples unique to C1S papers includeproducts where one side of the sheet carries glossyimages and the other side, text, such as advertisingflyers, postcards, calendars, labels and packaging.Book and document covers also suit this type of paper.Where the same surface is required on both sides ofthe sheet, as in most publication and commercialprinting applications, C2S papers are used.

Calendering and coatingPaper may be coated on-line using a unit added afterthe paper machine's dryer section or in a stand-alone,off-line process once papermaking is complete.Coatings are prepared in an automated, computerizedcoating kitchen to a formulation that reflects the enduse. The coatings applied in the paper mill consist ofvarious combinations of clay, pigments, binding agentsand small doses of special additives.

Coating is usually applied using an applicator roll oradjustable blade which controls the amount of coatingapplied to the paper. Other coating methods includeroll coating, air knife coating and brush coating. Thecoating is dried by non-contact methods such asinfrared, hot air or a combination of the two. Whenpaper is double-coated, the formulation of the first andsecond coats is different, with the formulation optimizedto achieve the desired opacity and gloss level.

Coated surfaces which are matte provide goodreadability. Where a gloss surface is required,however, the paper is subsequently calendered. Acalender works like an iron. A nip formed by a pair ofhorizontal cylinders smoothes and levels out the paperand improves its gloss. Most printing papers arecalendered to some extent, using systems which varyfrom a single pair of metal cylinders after the dryersection on the paper machine, to an on- or off-linesupercalender with multiple cylinder-pairs designed toimpart extra gloss, using paper- or cotton-covered rollsarranged alternately with metal rolls. Thesupercalender gives its name to SC grades of paper.

Another calender variety is the soft calender, whichuses a roll with a soft, pliable cover, against which thepaper is pressed by a hard-surfaced roll to enhancegloss and printability. Film-coated offset is a typicalgrade for which soft calendering is used and softcalendering has often been specified because it canrun faster than a supercalender and therefore be usedon-line. Variants of the supercalender theme haveemerged which can cope with on-line operation on afast paper machine.

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The highest gloss is achieved by cast coating, whichmeans the freshly coated paper (always coated off-line) is brought into contact with a highly polishedchromium plated heated metal surface. The heatedmetal solidifies the coating, which results in a mirror-like surface.

Opacity—shut out the lightTo test a paper sheet's opacity, hold it up to the light—paper's opacity is a measure of its ability to preventlight from passing through. A major benefit of opacityis that it prevents show-through of dark print from thereverse side of the sheet or of print in contact with thereverse side. In other words, you do not want the textor images from pages 4 and 5 to show through if youare reading page 3.

So it is particularly important for duplex printing,where visibility of images and readability of text canbe adversely affected by low opacity. Opacity isachieved through the use of fillers and pigments suchas titanium dioxide and calcium carbonate. The varietyof pulp used also affects opacity. For example, pulpproduced from the eucalyptus tree produces goodlevels of opacity.

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Paper finished to reels and sheets(image courtesy of International Paper)

Fast, modern paper machines, like the one at Metso Paper/Yueyang Pulp & Paper Group Company Ltd., occupy mills that can be the size of a smalltown, like International Paper's Inverurie Mills in Scotland (opposite). Machine image: Metso Paper/ Yueyang Pulp & Paper Group Company Ltd.

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Paper suppliers and manufacturers promote theirindividual brands but common classification, gradingand grade-naming practices simplify the paper buyingprocess.

Matte or glossy?The terms matte and glossy describe the way in whichlight is reflected off a sheet of paper. Coated paper canhave a matte or glossy finish. Gloss is achieved throughcalendering but only on a coated surface. Glossincreases with coat weight and the degree ofcalendering. Matte paper absorbs and diffuses light,making a non-reflective, easy-to-read surface. Glossypaper reflects light to give a shiny, lustrous appearance,which can enhance printed images.

A glossy surface provides a smoothness that produceseven printing and minimizes mottling. The almost mirror-like finish of cast coated papers is achieved when thefreshly coated paper surface is brought into contact witha highly polished chromium-plated heated metalsurface. The coating mix solidifies while in contact withthe metal surface, thus locking in a high-gloss finish.

Uncoated paperThere are many grades of uncoated paper; they can betextured or smooth, considered premium or commodity.Calendering allows uncoated paper to have a smooth,silky surface. Other processing during papermaking canresult in the surface to take on embossed finishes like feltor linen. The use of uncoated papers and applicationsare increasing in digital printing. Coated media exhibitsmore tactile appearance.

Recent developments in the paper industry have resultedin a healthy variety of premium and opaque uncoatedoptimized media for use on HP Indigo digital presses.

With digital printing becoming a mainstream productionprocess, the gamut of paper for HP Indigo digital pressescontinues to expand rapidly as the market grows. Themajority of HP Indigo media approved solutions havelittle or no changes made to them for compatibility. Theyare precision cut to size, sold and supported by virtuallyevery paper manufacturer one could name. Surfaceoptimization and treatment is an option, but finishes andwell-known name brands have been developed andapproved and backed by third party suppliers.

Chapter 2Paper sizes and finishes

Wide range of finishesThe surface characteristics of paper depend on thegrade and can differ considerably. The finish affectsgeneral printability, ink adhesion and smoothness. Italso helps create the impact of the finished product.

The variety of finishes available is virtually limitless butthere are broad categories which are self-explanatoryand widely applied. Uncoated paper finishes includevellum, felt, smooth, laid, embossed and linen. Coatedpaper grades usually come in a choice of gloss, dull,matte, silk, velvet and embossed.

Grain direction and stiffness—whythey matterThe direction in which the wood fibers lie (i.e., the grain)in a sheet of paper is significant. It affects the paper'sstiffness and is determined by how the supplier cuts itinto sheets. A sheet is stiffest in the direction of the grainand stiffness needs to be optimized for printing quality,runnability and finishing requirements such as folding.A typical 8.5” x 11” sheet is cut from the roll such thatthe grain runs in the direction of the long dimensionfrom top to bottom (the long grain).

The grain direction of a sheet is determined by how apaper is cut from the master roll. There is no singleinternational standard for indicating whether a paper islong or short grain, and a number of local conventionsexist, among them: indicating the grain direction by thenumbers in the sheet measurement, i.e., grain directionis indicated by the second dimension and is sometimesunderlined. For example, 12” x 18” indicates grainlong. 18” x 12” indicates grain short. For moreinformation, consult your paper merchant.

For effective transport, long grain should be used whenprinting paper weights of 65 lb. cover and below, andshort grain above 65 lb. cover weights. There are anumber of simple tests that can be carried out if graindirection needs to be determined.

The tear test:Tear a sheet of the paper both along its length andacross its width. One result will be relatively straight, andthe other more jagged. The straighter tear is in the graindirection.

The bend test:Bend a square test sheet in both directions. The bend ofleast resistance is along the direction of the grain.

The fold test:Fold a test sheet both lengthwise and across. Thesmoother fold is in the direction of the grain.

The nail test:Using the nail on your thumb and middle finger, scorethe test sheet across and down its length. The scorealong the grain is relatively straight, while the scoreacross the grain is wavier.

The moisture test:Sprinkle a few drops of water on the test sheet. After amoment, the wet area will pucker. The direction of thelength of the pucker is the grain direction.

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To understand the principles of HP Indigo printing is toappreciate why the process is so convenient and theprinted image of such high quality.

The HP printing engine performs its operations in thefollowing order:

1. Electrostatic charging of the electrophotographicPhoto Imaging Plate (PIP) which is mounted on theimaging cylinder

2. Exposure of the PIP by a scanned array of laseriodes. These lasers are controlled by the raster imageprocessor, which converts instructions from a digitalfile into 'on/off' instructions for the lasers

3. Image development performed by the Binary InkDeveloper (BID) units

4. Transfer of the inked image to the blanket cylinder

5. Removal of any residual ink and electrical chargefrom the PIP

6. Heating of the inked image carried by the blanket

7. Transfer of the heated inked image to the substrateheld by the impression cylinder

The above operations are repeated for every colorseparation in the image.

Additional details about the process are as follows:

1. PIP charging. A clean, bare PIP segment rotatesunder a corona wire called the Scorotron unit. TheScorotron unit generates electrical charges whichflow towards the PIP surface and cover it with auniform static charge.

2. PIP exposure. As the PIP cylinder continues to rotate,it passes the imaging unit, where up to 12 laserbeams expose the image area, dissipating(neutralizing) the charge in those areas. When theexposed PIP rotates toward the next station, it carriesa latent image in the form of an invisibleelectrostatic charge pattern, which replicates theimage to be printed.

Chapter 3The HP Indigo printing process

Laser Imager

PIP

Blanket

Impression

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3. Image development. There is one BID for eachcolor. During printing, the appropriate BID engageswith the using an inking roller. HP ElectroInk is alsocharged. The opposing electrical fields between thePIP and the BID attract the ink particles to the imagearea and repel them from the non-image areas.

4. First transfer. The PIP rotates to come in contact withthe electrically charged blanket on the transfercylinder and the ink layer is transferred electricallyto the blanket.

5. Cleaning station. Finally, the PIP rotates past acleaning station, which removes any residual ink. Atthis point, this part of the plate surface has made acomplete rotation and is ready to be recharged forthe next image.

6. Second transfer. In the meantime, the HP ElectroInkis heated on the rotating and heated blanket. Thiscauses the particles to melt partially and blend,forming a hot adhesive liquid plastic. As the inkcomes into contact with the substrate, which issignificantly below the melting temperature of theparticles, the ink solidifies, sticks to the substrateand peels off the blanket completely, ensuring totaltransfer from blanket to substrate. This leaves theblanket clean to accept the next impression as itrotates past the PIP cylinder.

HP Indigo digital presses print multiple colors fromthe same offset blanket. The cycle repeats itself foreach color separation, and the only differencebetween the cycles is in the ink application and theimage data, which correspond to the printed colorseparation.

One shot, multi-shot, sheet and rollHP Indigo's web-fed digital presses use a one-shotcolor process, as it is not possible to wrap the materialaround the impression cylinder for multiple passes.In the one-shot process, the PIP cylinder rotates severaltimes, transferring a succession of separations andbuilding the colors up on the blanket, before they aretransferred to the substrate, all in the same impressionpass.

This process applies to HP Indigo's industrial pressesfor printing on synthetics, films, and “stiff” substrates,such as cartons and plastics. In the multi-shot process,suitable for sheet fed applications, one colorseparation is created at a time on the Photo ImagingPlate (PIP), then transferred to the blanket and on to thesubstrate. The substrate stays on the impressioncylinder for several rotations as it receives eachseparation, printed separately, one after the other. Asthe final separation is printed, the substrate is deliveredfor duplexing or to the output tray.

HP ElectroInkHP ElectroInk, as used on all digital HP Indigo digitalpresses, is a liquid ink containing electrically chargedink particles, available in a wide range of colors. HPElectroInk enables digital printing by controlling thelocation of print particles electrically, as with otherdigital printing technologies, such as dry tonerxerography. Only one formulation of HP ElectroInk isneeded to print on any substrate the press can handle.This allows rapid switching between substrates withouthaving to worry about changing ink.

Advantage over dry tonerUnlike dry toner xerography, HP ElectroInk usesparticle sizes as small as one to two microns. Theparticle size used in dry toner xerography is limited, asparticles that are too small can become airborne anduncontrollable. The higher the printing speed, thelarger the particles need to be. The advantage ofsmall particle size in a liquid carrier is that it enableshigher resolution, uniform gloss, sharp image edgesand very thin image layers. The thin image layerclosely follows the surface of the paper, resulting in ahighly uniform finish, complementing that of the paper.

So, HP ElectroInk produces results to match thosepossible with conventional offset printing. Dry tonerdepends heavily on the electrostatic properties ofpaper and small changes in relative humidity in theenvironment can cause noticeable variables in printquality. The high fusing temperature required forxerography limits the choice of coated paper or plasticfilm that can be printed.

HP Indigo press 5500

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FeedingHP ElectroInk comes in a concentrated paste which isloaded in the press in tubular cartridges in a “clean-hands” operation. In the press, the paste is fed into inksupply tanks and diluted with oil to form a fluid ofcarrier and colorant particles ready for printing.

HP ElectroInk transferThe HP thermal offset process uses a heated blanket,which melts the pigment-carrying particles and blendsthem into a smooth film. When this film makes contactwith the cooler substrate, the ink solidifies immediatelyand then transfers and adheres strongly to thesubstrate.

Fiber orientation and formationThe use of sheets with the correct fiber orientation isessential for meeting the stiffness and runnabilityrequirements placed on paper.

To achieve optimum runnability when using papers65 lb. cover and above on HP Indigo digital presses,we recommend the use of short grain sheets, where thefibers usually lie parallel to the short dimension of thesheet. This enables the sheet to transport properly and beflexible enough to rotate around the cylinders to acceptthe ink evenly. When using sheets below 65 lb. cover,long grain sheets are recommended for the print run.

Formation describes how the distribution andorientation of fibers is controlled at the “wet end” ofthe paper machine. Good sheet formation reduces therisk of curl, bent edges or waviness and ensures theuniformity of print quality over the printable surface.

Duplex printingAutomatic duplex printing requires the press or printerto print on both sides of the page without the use ofturning or an intermediate drying stage. HP ElectroInkenables duplex printing, as the sheet is sufficiently dryas soon as it leaves the first pass of the press setting itup properly for the duplexing action. Printing on bothsides of the sheet demands high standards in paperproduction. Cutting must be absolutely square forrunnability and register. Also, opacity must beadequate to prevent show-through of text from thereverse side of the sheet.

Duplex printing is particularly sensitive to curl, bentedges and waviness, which emphasizes the need forgood sheet formation in the paper making process.

The HP ElectroInk cartridges

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HP recommends the use of approved papers whichhave the appropriate components that contribute tothe right surface chemistry and are thereforecompatible with HP ElectroInk. Using non-approvedmedia could encounter risks, such as paper jams,reduced blanket life on the press and diminishedscratch resistance. They can also affect your warrantyor service contract. An inappropriate choice of papercan render the quality of commercial workunacceptable.

Paper surface chemistry is important for HP ElectroInkbecause the paper and the ink need to be attracted toeach other. Incompatible paper chemistry will result inreduced HP ElectroInk transfer, poor ink adhesion,reduced productivity and quality of the output, andincreased use of consumables. The compatibility of theink with the paper is heavily reliant on the chemistry ofthe binder and the pigment. Styrene butadiene ispreferable to acrylics as a binder, while calciumcarbonate is the pigment of choice, rather than chinaclay.

HP has taken the guesswork out of media selectionand provides an approved list of substrates, suitablefor every application.

ECO friendly and recycled papers There is an evolutionary change happening in theworld of paper. Fiber conservation, forestrystewardship, energy reduction and clean streamemissions are of high priority to the manufacturers andusers of papers. No longer maintaining the status quo,the paper industry is now leading the charge in bigbusiness energy conservation, ethical use of fibers andforestry and clean water emissions.

Today's printer has an amazing choice of ecologicalfriendly papers to provide to the customer. Vast arraysof these papers are readily available for HP Indigoprinters. No longer relegated to recycled papers,multiple classifications of paper and substrates areavailable that can give you piece of mind that theproducts you produce are sound for the environmentand for your press.

The following guide is intended to help throw light onthe certifications and classifications that can beassociated with “eco” friendly papers. We hope thatyou will continue to seek and support these papers foruse in your HP Indigo digital press.

Chain of Custody. The unbroken path which productstake from the forest to the consumer, including allstages of manufacturing, transformation anddistribution. Chain of Custody certification is requiredwhenever a company carries out any physicalalteration to the timber/product, when they takephysical or legal ownership of the timber/product, andwhenever a company wishes to make independent useof the FSC trademark.

Chapter 4Using the right paper

FSC. Forest Stewardship Council—established and wellknown in the graphic arts industry, this certificationhas been granted to numerous paper mills, distributorsand printers. It is widely promoted by conservationadvocacy groups (e.g., Forest Ethics, Greenpeace andSierra Club) and often drives initial demand for Chainof Custody systems.

SFI. Sustainable Forestry Initiative—this standard is arelatively recent addition to the Chain of Custodymarket. Supported by some conservation groups, SFIalso has the participation of many of the region'slargest wood–product manufacturers—particularly inthe paper sector.

PEFC. Program for the Endorsement of ForestCertification—this international organization facilitatesthe mutual recognition and co-endorsement of nationalforest certification systems. SFI is a memberorganization of PEFC in the US.

Carbon neutral. The use of electricity and fossil fuels(such as natural gas and petrol) results in the release ofcarbon dioxide—the main greenhouse gas—into theatmosphere (CO2 emissions). Greenhouse gases trapheat from the sun, causing global temperature to rise,which in turn alters the world's climate patterns. Tohelp counter these changes some manufacturers ofpaper have become 'carbon neutral' by reducing netcarbon emissions to zero, or by purchasing carboncredits from renewable energy sources.

Recycled papers. While there are varying degrees ofrecycled fiber in the different brands of recycled paper,most mills follow the EPA guidelines that requireminimums of 30% post-consumer content for mostuncoated printing and writing papers, and 10% formost coated papers. Many mills list up to 100%

recycled content, composed of PCW (post-consumerwaste) and pre-consumer waste.

Choosing the right paperTesting and certificationOnly paper that meets certain criteria can be expectedto provide trouble-free performance in the digitalprinting press and produce high quality results.Rigorous testing is essential to ensure that a paperproduct is suitable for digital printing.

A comprehensive testing and certification systemmeans suppliers can establish a paper's compatibilityquickly and easily.

Certification programExtensive facilities are available to test substratecompatibility for use on HP Indigo digital presses atthe Rochester Institute of Technology (RIT) in NorthAmerica, a highly respected independent teachingand research institution. These resources allowsubstrate manufacturers and suppliers to checksubstrate suitability for HP Indigo digital presses.RIT is at the forefront of HP Indigo's drive to enhancesubstrate availability.

The certification program continues to expand thenumber of media that provides excellent results on HPIndigo digital presses. With more than 1,200 approvedmedia available worldwide, the HP Indigo family ofpresses prints on the industry's widest range of substratesfor high-end digital color printing—from standardpapers, to transparencies, labels and plastic stocks.Substrates for specialty printing include PVC, polyesterand polycarbonate. This extensive selection enables HPcustomers to broaden their digital printing applications,differentiate themselves and add value to their services.

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Qualification/testing procedureThe qualification procedure for substrates comprisestwo parts. The first is a screening test to checkfundamental compatibility. During the second test, thesubstrate is subjected to a more comprehensiveevaluation and many parameters of the press-mediainteraction are checked.

The tests ensure the substrate can be used in duplexand collation modes. Upon completion of the varioustest procedures, a full, detailed report and printedsamples for each substrate tested are provided to thesupplier. If the substrate is successful, the media isapproved and posted on RIT's website, as well as onthe Media Locator section on the 'My HP Indigo' portal(www.hp.com/go/myhpindigoweb), which is anexclusive portal for HP Indigo customers, offering acomprehensive resource for the digital printingbusiness.

The substrate qualification process involves a series oftests:

Runnability. How smoothly the substrate runs throughthe press.

Ink transferability. The quality of ink transfer from theblanket to the substrate, demonstrated by highlight dots,thin lines, heavy images and image edge integrity.

Blanket-substrate compatibility. The meeting ofsubstrate and blanket can leave a blanket memoryeffect, causing gloss differences between solids andbackground areas of the previously printed image.

Blanket-temperature operation window. The range ofblanket temperatures across which the substrateperforms. The wider the range, the greater thesubstrate's compatibility.

Ink-substrate interaction, reflected in:

• The degree of ink fixing to the substrate

• Ink layer abrasion resistance (depends onapplication)

• Ink layer flaking, the degree of which determines theprinted substrate's ability to withstand a variety ofpost press operations

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The HP Indigo digital family of presses prints on abroad range of substrates so they are suitable for anunusually wide range of applications.

If your HP Indigo digital press has just been installedand you are familiarizing yourself with its operation,it is strongly recommended that you use approvedsubstrates, whose performance is backed andsupported by the suppliers and manufacturers.Usually you will buy the substrates from a local papermerchant, who will offer a range of approved and/oroptimized substrates.

It is important to build a close working relationshipwith the supplier or merchant of approved andoptimized substrates, in order to secure supplies.

When your HP Indigo digital press was installed, youwere given a user ID number and password to accessthe 'My HP Indigo' portal, where you will findcomprehensive information about the types ofsubstrates available and relevant suppliers. The site isupdated regularly so check it frequently.

Digital printing requires different disciplines from thoseassociated with conventional presses, and changesrequired to integrate digital technology will affect yourentire organization. Remember the three “M”s—Man,Machines and Materials—and you cannot go farwrong.

“Man”—refers to human resources and training. Manynew skills will need to be acquired to achieveoptimum performance and quality output.

“Machines”—when digital printing is integrated intothe workflow, changes don't end with the press:environmental condition requirements and theinformed use of ancillary equipment will be requiredin the process to meet the needs of digital technology.

“Materials”—it is likely that you will need to developrelationships with new suppliers or place differentdemands on your existing ones.

Chapter 5Print applications

Recommended and approved media can be foundvia the Media Locator located on the customer portalwww.hp.com/go/myhpindigoweb. In the documentlibrary, access “print media,” under which you will findthe Media Locator. This will list approved substrates forthe end uses you have in mind. But when choosing asuitable paper substrate for a printing job, it is also agood idea to ask yourself a few basic questions toavoid the unnecessary cost of over-specification or thepoor result that comes from under-specification.

Essentially, a substrate must be fit for purpose in termsof reliability, quality and performance, while meetingcost, availability and variety criteria. Here are some ofthe questions you might consider. It is not anexhaustive checklist, but it offers examples of typicalissues which, if not addressed, can give rise toinappropriate choice of substrate.

Will the finished item be laminated?If so, there is no need to specify either a glossy orparticularly heavy weight paper.

How stiff does the finished item need to be?Just make sure the stiffness is appropriate for theend-use. A tent card is no good if it is flimsy. A wallcalendar need not be self-supporting. So for a tentcard the basis weight is a practical considerationwhich determines whether the product “works” or not.For a wall calendar the weight of the paper is anaesthetic and tactile, rather than a practical,consideration.

How much handling must the product withstand?A menu card in a restaurant that does not change itsmenu frequently needs to be tough enough to copewith extensive handling. But a take-away “flyer” left onthe table in the same restaurant to promote a special

deal will only need limited endurance. Choose theweight accordingly.

How resistant should the product be to tearing?Lamination greatly reduces the risk of tearing butsynthetic paper is another option. Synthetic paper isplastic made to resemble paper. It will not deterioratewhen exposed to moisture. These substrates willbehave like synthetics and should be understood andutilized accordingly.

How resistant should the product be to scratching?If scratch resistance is important, lamination or otherprotective coatings such as varnishes are advisable.

Is readability important?If a brochure is full of text, think carefully about opacityand gloss. You will need to use a grade of paper thatlimits show-through of image and text on the oppositeside of the sheet to ensure readability. An uncoatedpaper or a matte-coated paper with low surface glossalso improves readability.

Will the printed item be sent by mail?Consider the basis weight used. A small difference inthe weight of the piece can make a big difference tothe cost of a promotional mailing.

If the printed piece or surface is going to come indirect contact with mailing or sorting devicessubjecting it to duress, protective coatings are needed,i.e. laminate or varnish. Protective coatings arecommonly used in printing—this is not unique to HPIndigo. HP provides 'how-to' information and guideson protective coating recommendations, and sells andsupports an off-line UV coating device to further aidcustomers with this type of application requirement.

Main applicationsThe following are the main applications for HP Indigo digital presses:

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A3 posters

Agendas and badges

Books

Brochures

Business cards

Calendars

Car manuals

Conference materials

Corporate Identity

Manuals

Coupons

Direct marketing and mail materials

Educational manuals

Exhibition handouts

Greetings cards

Invitations

Labels

Leaflets

Menus

Newsletters

Personalized catalogs

Photobooks

Point of sale materials

Product datasheets

Sales materials (presenters, etc.)

Stationery

Tent cards

Tickets

Transactional printing

Is image definition a top priority?For the best contrast and quality appearance, choosea high-whiteness paper. A more neutral whiteness willbetter suit warm colors and skin tones.

Is whiteness of the paper a top priority?If yes, choose an uncoated paper. With pure fibers ahigher whiteness can be achieved than with a coatinglayer containing calcium carbonate or china clay.

Will you be duplex-printing?You will need to pay particular attention to the sheet'strim accuracy. This is another reason for usingapproved media solutions and suppliers products,which follow strict industry tolerance guidelines forcutting and squareness. Opacity will also be animportant feature of the paper you specify.

Does the product need to be folded?Heavily coated and higher weight papers are morelikely to crack when folded. So when specifyingheavily coated and heavier basis weight papers for anapplication that needs to be folded, bear in mind theneed for pre-scoring when assessing the job.

Shelf life?If the printed item is going to be a source of referencefor years to come, pay close attention to the paper'sspecification and longevity of any coatings andtreatments.

Some common problemsMost problems encountered in the use of digitalpresses can be avoided as long as you followrecommended procedures. Here are some practicalways to avoid trouble:

• Optimized or approved media saves time andreduces waste. Do your own surface treatment onlywhen you are sufficiently experienced.

• Make sure your material choices are compatible,otherwise acceptable quality will not be possible.

• Operate and maintain the press and the press'environment pursuant to the instructions in your usermanual and those received during the requiredtraining courses.

• Color adjust on the press as necessary, but alwaystry to ensure that files from prepress are accurateand production-ready.

• Specify colors accurately.

• When laminating or varnishing, adhere to strictprocedures to avoid melting the HP ElectroInk.Remember that digital press printed sheets aregenerally half the size of conventionally printedsheets, so you will need new lamination cassettes.

• Make sure printed matter is protected from abrasionthat can occur in converting operations.

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Printing on special substratesFrom coated and uncoated papers to transparencies,labels and synthetic substrates, the HP Indigo family ofdigital presses prints on a wide variety of substratescompared to other digital printing processes.The extensive substrate range allows HP customers tobroaden their digital printing applications capability andtime to market, adding value to the services they offer.

Only one formulation of HP ElectroInk is needed to print onany substrate that is compatible with the press. This allowsrapid switching between substrates. Some surfaces need asimple treatment to ensure the image binds to the surfaceproperly and can withstand handling and conversion.

FilmsSubstrates such as polyester, polythene, polypropylene(PP, OPP and BOPP), vinyl (PVC), polystyrene,polycarbonate and heat transfer film can be printed withHP Indigo technology. Finishes include metallic, coated,clear, white opaque, matte and textured. Note that notall synthetic products are sufficiently stable for the HPIndigo multi-shot process. Use of non-approved syntheticsubstrates might lead to color-to-color registrationcomplications or problems in substrate transport and mayvoid your warranty or service contract.

The one-shot process is ideally suited to printingsynthetics. Applications are virtually limitless but the mainones are flexible packaging, membrane touch switches,control panels, automotive and appliance graphics,point-of-sale displays, nameplates, labels, windowsigns/decorations, manuals, chip and smart cards,membership and ID cards, backlit signs, tags, shelfdanglers, calendars and mouse pads. Cost-effectiveprinting of films is a great advantage for the packagingindustry, as it allows realistic mock-ups of products to bemade pre-launch.

Flexible packaging and films represent a specific marketopportunity for on-demand printing. HP Indigo digitalpresses can even print on shrink-wrap film, which is notpossible using digital xerography, because the heatrequired to fix the toner would shrink the substrate.

Self-adhesive labelsHP Indigo technology can print on any self-adhesivelabel stock, as long as the surface is compatible with theHP ElectroInk. A good understanding should be gainedin such areas as step-and-repeat, the use of white ink andother spot colors, HP IndiChrome on-press, as well as theimplications of finishing for prepress. Film converted intopressure sensitive label stock may be used for outdoor orindustrial label applications, bumper stickers, specialtydecals, warning/safety labels and product/barcodelabels.

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Self-adhesive labels

25

Paper is a finely engineered material but its principalingredients are wood fiber and water, which causeexpansion and contraction according to relativehumidity. This means that to get the optimal use out ofpaper and to minimize printing problems, handlingand storage need to be carefully managed.

Storage and handlingPaper reams should be kept in their moisture resistantpackaging until required, as this minimizes theexchange of moisture between the paper and itsstorage environment. Ideally paper should be stored inhumidity- and temperature-controlled conditions.

Direct sunlight and extremes of temperature should beavoided, so keep paper away from radiators and airconditioning units. Always store according to the first-in, first-out principle, and store boxes and reams on apallet rather than directly on the floor, in order to avoiddamage. Do not place anything on top of reams orboxes.

Paper producers will specify ideal storage conditionsbut 50% relative humidity between 66° and 73°F istypically recommended. Where there is no automaticclimate control, winter will be the time of year whenthe risk of problems is greatest. Ideally, an airconditioning unit should be used to maintain the rightlevel of humidity all year round.

Paper sheets should be allowed to settle at the print roomtemperature in their wrappers before use. The time thistakes depends on the amount of paper in the reel or reamand the temperature difference between the paper and theprint room. Allow up to 24 hours. Partly used reams andreels should be returned to their moisture-proof wrapping.

Paper used by xerographic printers is usually very dryand therefore ready to absorb moisture from thesurrounding environment. Most papers that have beenapproved for use on HP Indigo digital presses have thesame moisture content as offset papers, so are lesssusceptible to moisture absorption. Careful monitoringof storage conditions remains crucial for best results.

Fiber dimensions and storageHumidity is significant because the fibers in the papercan swell and shrink with changes in humidity.

Fibers are generally orientated along the length of thepaper (long grain), and dimension changes mainlyaffect the width of the fiber. As a result, expansion andcontraction tend to occur across the paper's width,leading to curl, wavy edges or tight edges.Dimensional changes will continue until the papermoisture reaches equilibrium with the surrounding air.

CurlAll paper will tend to curl in the direction it was woundon the reel at the end of the paper machine. A ream ofpaper will have a defined curl direction and the papershould be loaded curl down in the press. The price ofleaving sheeted paper unwrapped and exposed to dryor moist air can be excessive curl—this can causepaper jams. Excessive curl can also result from anuneven built-in tension in the sheet, which is apapermaking issue, or from a significant rise intemperature, whitch takes place in the fusing station ofxerographic digital presses and printers.

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Chapter 6Paper problems

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StaticPress and finishing equipment jams are common whenpaper sheets or synthetics, which are especially proneto electrostatic attraction. Static interferes withstacking, collation and feeding, causing jams.

Static can also give minor electric shocks and affectvarnishing and lamination. It can even interfere withthe electronic circuitry of finishing equipment, causingbreakdown.

Causes of static include excessive moisture, whichincreases paper's electrical conductivity and allowscharge to leak away. This can result in mottle and low-density prints. Reduction in moisture can becounter-productive as it increases the chances of staticbuild-up. Be prepared for static problems on drywinter days when central heating can lower relativehumidity and cause static build-up on long runs.

Humidifiers in the printing room can be used to controlthe humidity within the defined specification.

Scratch resistanceSince HP ElectroInk can be prone to severe scratching,protective coatings are recommended for applicationssubject to abrasion, rough handling and duress—suchas mailing systems and sorting processes. Otherprinting processes use protective coatings andvarnishes to protect the printed surface fromscratching. They also enhance the printed image.

When paper problems occurThe problems described above, which can affectpaper, relate to storage and handling conditions.If paper-related problems continue to occur despitecompliance with the supplier's storage and handlinginstructions, contact the paper supplier.

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1. Why does HP recommend approved media?Paper that meets our compatibility criteria providesoptimum performance in the digital printing pressand produces high quality results. Non-approvedpapers can adversely affect productivity, causingincreased paper jams, reduced blanket life, andmay lead to quality problems, such as reduced inkadhesion and service risks. It may even void yourwarranty or service contract.

2. How do I find out which media are approved?The Media Locator is part of the 'My HP Indigo'portal (www.hp.com/go/myhpindigoweb). It is asearchable database and is the main source ofinformation on approved substrates for HP Indigocustomers.

The Media Locator provides a selection of mediawith basis weight, grade (coated gloss, matte, silk,etc.) and supplier names, in addition to links tosuppliers' home pages for local contact details.The majority of media is supplied and supported byindependent manufacturers. HP does not guaranteethe continued availability of any of the media listedor that the manufacturer will not alter productcomposition or a production process which maychange the media printing characteristics.

The Media Locator can be found on the HP customerportal at www.hp.com/go/myhpindigoweb.

Here is how to use it:

Access the website and log in

1. Select “print media”

2. Select the Media Locator

3. Specify your media requirements according to:

a. The HP Indigo digital press you use

b. The type of media on which you intend to print

c. Basis weight

d. Your location

Additional information about approved media, testingand certification of HP Indigo media can be found onRIT's (Rochester Institute of Technology) website:www.printlab.rit.edu

3. How is a substrate tested for compatibility?The qualification procedure for substrates comprisestwo parts—the initial phase evaluates basiccompatibility, ink adhesion and transportability,while the second phase evaluates all the parametersfor optimum performance and press productivity.The tests check substrates for:• Runnability of the substrate, i.e. how smoothly it

runs through the press• Ink transferability and adhesion-quality of the ink

transfer from the blanket to the substrate, asreflected in highlight dots, thin lines, heavy linesand image edge integrity

• Blanket-substrate compatibility-interaction betweenthe substrate and the blanket might cause a“blanket memory” effect, reflected in glossdifferences between solids and background areasof the previously printed image

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Chapter 7FAQs about substrates

• Blanket temperature operating window—the abilityof the substrate to perform through a wide range ofblanket temperatures; the wider the blankettemperature range, the greater the substrate'scompatibility

• Ink-substrate interaction as reflected in:- The degree of ink fixing to the substrate-theadhesion of the image to the substrate

- The resistance of the ink layer to abrasion(application dependent)

- The degree of flaking of the ink layer thatreflects the printed substrate's ability towithstand various post-press operations

These parameters are then examined through awindow of blanket temperatures to obtain acomprehensive compatibility evaluation.

4. What are the media specifications for every press?In general, for all our sheet-fed machines, long grainis recommended for optimal performance up to65 lb. cover. See product data sheets for individualpress media specifications via:www.hp.com/go/graphicarts, select HP Indigodigital presses.

5. Can papers out of the weight specification of thepress be printed?The recommended paperweight specification isbased on lab testing and field experience of typicalpapers running under typical circumstances. Papersoutside of this may perform in certain aspectsadequately, however, they may require morehandling, interrupt workflow, impact on productivitydue to jams or ultimately affect the integrity of theprinted output. For this reason in order to achievethe highest degree of productivity, runnability andquality, the press specifications and use of approvedand recommended media is the proper way toensure press performance.

6. Which protection varnishes and primers can beused on HP Indigo digital prints?Protective coatings and varnishes are used inprinting to protect output intended for direct mailand extensive handling. A comprehensive list ofcompatible varnishes and primers suppliers and'how-to' guidelines can be found under the 'Media,Priming and Finishing' guide located in thecustomer portal. In addition, HP will soon releaseand sell an off-line UV coating device which canapply matte or gloss UV varnishes for addedprotection and graphical enhancement of HP Indigoprints.

7. Can HP Indigo digital presses print on offset media?Many coated and uncoated offset grades are usedand approved for use on the HP Indigo commercialpresses. The majority of the current approvedsolutions are supplier supported, off the shelfproducts, no special handling required. The HPIndigo press 5500 has taken one step further andintroduced a feature called “SPP” which involvesautomation of the press' substrate parameters. Theseadjustments to the press enable the use of certainwell known, highly used, uncoated commodity offsetpapers, widening the market for publishing,educational and transactional printing applications.

8. Can recycled papers be printed on HP Indigodigital presses?Not just recycled, but “Eco” friendly papers. Thereare evolutionary changes happening in the worldof paper today. There are multiple classificationsand organizations dedicated to advancing andrecognizing environmentally responsible processesand organizations. Many suppliers are seeking andachieving recognition for; fiber conservation,forestry stewardship, energy use reduction andclean stream emissions.

All these concerns are high priority to themanufacturers and end users alike, environmentalresponsibility has extreme importance and value inthe Graphic Arts Community. HP Indigo supports avast array of eco-friendly solutions and suppliers.For more information see our Eco Guide, under thePrint Media section of our website mentionedabove.

9. Can synthetic products be printed on HP Indigodigital presses? Who are the suppliers?Several suppliers have developed a range ofoptimized product for HP Indigo digital presses,which you can find on the approved list in theMedia Locator. Since synthetic products aresensitive to heat, certain products might not bestable enough for a digital printing process, leadingto mis-registration. Therefore, only approvedsubstrates should be used.

10. Can self-adhesive or pressure sensitive labelmaterial be printed on HP Indigo digital presses?Who are the suppliers?Labels are a very effective solution/application forthe HP Indigo digital presses, which offers highvalue return and superior output. Several suppliershave developed a range of optimized self-adhesivelabels for HP Indigo digital presses, which you canfind on the approved list in the Media Locator.Only approved substrates should be used.

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11. Which other specialty products can be printed onHP Indigo digital presses?On the approved list you will find specialty productslike: coated one side for postcards and covers,t-shirt transfer paper, etc. Check the Media Locatoron the customer portal for details.

12. Can HP Indigo digital printed materials be used foroutdoor applications?Check the HP ElectroInk FAQ document on theportal for details on light fastness. Depending onthe substrate used, protection (varnish, lamination)might be required.

13. What are the influences of climate conditions onpaper transport?All paper contains moisture and can take on or losewater content depending upon the surroundingenvironment. The potential changes to the papercan affect its performance. The HP Indigo SitePreparation Guide sets out climate requirements foroptimum performance of paper and press. Papershould be acclimated to the press room environmentfor a minimum of 24 hours prior to printing, so thatit reaches equilibrium with the environment andpress.

14. What are the basic paper properties that lead togood ink adhesion?The most important paper property is the surfacechemistry of the paper. For coated paper both thebinder and pigment are important in obtainingoptimum adhesion. Another important property isthe wetting and absorption rate of the imaging oilinto the paper. For uncoated papers, the chemistryof the paper surface (sizing agents, pulp, pigments,etc.) and surface topology are important. Thepaper and HP ElectroInk need to be attracted and

bond to each other to obtain good ink adhesion.This is why the use of certified, approved media isrequired for press/media performance assurance.

15. What are the guidelines for handling printingpaper?Once the paper or specialty media product hasbeen selected, it has to be stored, handled, andloaded properly in order to maximize performanceand machine productivity.

General: Do not store paper directly on the floor, sincethat increases the possibility of moisture absorption.Paper should be stored on pallets, shelves, or incabinets in an area protected from extremes oftemperature and humidity.

Do not open sealed reams of paper until you areready to load them into the printer. Leave paper in theoriginal ream wrapper and leave the reams in theshipping carton.

Stacking: If cartons or individual reams are to bestacked, they should be placed carefully on top of oneanother, in order to avoid crushing the edges orcausing any other damage.

Temperature: The temperature of the room wherepaper is stored can have a significant effect on howthat paper performs in the machine. Optimum paperstorage and printer operating temperature is 68° F to77° F.

Humidity: Optimum storage conditions include areaswith a relative humidity of 50% to 70% (40% for HPIndigo digital press 1000/1050). Before you load thesubstrate on the feed tray, make sure that the sheetsare trimmed correctly and are not stuck together.If necessary, trim the stack on two axes (top and leftedges), and then fan the sheets before using them.

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Effective finishing adds value to any job and greatlyenhances quality printing. Equally, perfect paper andperfect printing can be rendered worthless by poorfinishing. If lamination is inadequate, cracking mayappear at folds and the overall finish can be prone toscratches, abrasion, rub-off and other damage. Thesedefects will be seen by the customer, whatever thestandard of printing. Most finishing for digital pressestakes place off-line.

The requirement to be efficient puts time pressure onmost print jobs but this needs to be balanced againstquality. To achieve a quality look and feel against theclock means set up times must be quick and downtimeminimized. So choose approved media, which run wellin the finishing equipment. Clearing paper paths afterjams is a major timewaster. Also, keep to a minimumthe number of sheets required to set up the machine.This is particularly important with smaller print runs,where a 200-sheet set up is simply uneconomical.

In-house or trade finisher?The choice of whether to finish the printed work in-house or use an external trade finisher depends onindividual circumstances and the local marketconditions. In-house finishing can be more flexible andthe printer retains greater control. But idle capacity is awaste of resources and some technologies are only

worth the investment for large volumes. Usually thebest solution is to do the basic finishing work in-houseand leave the more complicated finishing to specialistfirms. Equipment a printer might expect to have on thepremises includes cutters or guillotines, plus facilitiesfor scoring and folding, lamination and encapsulation,taped adhesive bindings, wire stitching and Wire-O orspiral binding.

FoldingFolding transforms the flat sheet into a variety offormats, each of which suits particular end-uses.Common formats include single-fold, letter, and doubleparallel, gate, foldout, cross and zigzag.

Folding is affected by a number of variants, includingsize, weight, bulk, grain direction and surface coating.Factors such as humidity, curl, toner/ink coverage,static and the time elapsed since printing will all affectfolding. The most basic fold, which is the halving ofone sheet to make four pages, is a simple one-foldoperation. But as soon as another fold is involved tomake eight pages, a closed edge will need to be slitand trimmed and the sheets glued or stitched to keepthem together.

For a very small run, folding can be undertaken byhand but high-speed folding machines arerecommended for quantities of 100 or more. The twomain types of folder are the knife and buckle folder.

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Chapter 8Finishing—a brief guide

Knife folderThe knife folder is used by in-line finishers andcomprises a knife blade which is controlled by a camwhich times the folding action and drives the paperbetween the two counter-rotating fold rollers. Thefolded product is carried to the next station betweenstraps and the process repeated as necessary.

Buckle folderThe buckle folder is a stand-alone machine for offlineapplications. It consists of two rollers which push thesheet between the fold plate (two metal plates) until ithits a pre-set stop. The rollers continue to push thesheet so it buckles downwards until it is caughtbetween two counter rotating rollers which pull it downand create the fold.

Cracking—why it happens and howbest to prevent itCracking is usually a problem associated with drytoner rather than HP ElectroInk, which is flexible.Cracking is mainly the result of paper fibers that breakduring folding, but certain factors increase itslikelihood. Dry paper, folding against the grain,heavier coatings and higher paper weights all makecracking more likely. Any specified time betweenprinting and finishing should be observed. HP'scontinuous improvements in ink and paper technologyare regularly extending the performance of processesand materials.

The correct choice of folding machine and variousproduction techniques can help reduce the risk ofcracking. Solutions include wet scoring andlamination. Reduced machine speed can help, too.Scoring before folding is recommended for papersabove 100 lb. The scoring line should be 1 to 1.5

times the thickness of the paper and run parallel to themachine direction of the paper to avoid folding acrossthe fiber direction.

Lamination/encapsulationFortunately, protection and enhancement of the printjob go hand-in-hand. The better a product is protected,the better its appearance tends to be.

Lamination/encapsulation consists of a sheet of clearfilm applied to the printed matter, which preserves theprint and gives it an attractive finish.

Encapsulation refers to lamination that is performed onboth sides of a sheet, though lamination is often usedto describe this, too. If the product needs to beprotected and readability is a priority, then mattelamination is the answer. Gloss lamination provides avery attractive appearance but can make a printed jobhard to read.

There is a wide choice of laminates available so mostrequirements can be met. Cellulose acetate provides avery high gloss, for example, while orientatedpolypropylene (OPP) is formulated to allow foldingwithout cracking.

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BindingThe main binding methods are:

• Saddle stitching. Saddle stitching is one of thesimplest binding techniques. It is also the most widelyused. Folded signatures are placed over a "saddle"and then stapled along the spine. This style ofbinding is excellent for booklets, brochures,newsletters, pamphlets, direct mailers and catalogs.Page numbers have to be in multiples of 4 to makethe folded booklet. As few as 8 pages with covercan be used, or up to 64 with self-cover.

• Perfect binding. Perfect binding is a method ofbookbinding where a flexible adhesive attaches apaper cover to the spine of the assembled signatures.Paperback novels are an example of perfect binding.

• Spiral, Wire-O and plastic comb. These are all atype of mechanical binding which uses a series ofdouble wire loops formed from a single continuouswire run through punched holes on the bindingedge. These techniques allow the document to beopened completely flat so are suitable to bindprinted matter which requires constant reference,such as instruction manuals. These techniques arerelatively cheap and fast so they suit short runs.

• Drilling. Produces holes in those documents that areintended for presentation in loose-leaf binders, ringbinders, etc. Drilling allows thicker document piles tobe processed in a single operation than punching.

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A note about unapproved substratesHP Indigo digital presses use unique technology to print on anexceptionally wide variety of substrates. To ensure the highestquality of reproduction, and smooth, reliable running of yourpress, the use of unapproved substrates and media is notrecommended. Doing so may ultimately pose a risk and couldvoid your warranty or service agreement.

In some circumstances, new (unqualified) substrates may betested on behalf of a specific customer either via RIT or at HPIndigo facilities worldwide. In North America, the Suppliesand Shared Maintenance agreement states: “Operate theEquipment using only paper and substrates described inSeller's paper and substrate information,” which can be foundin the list of certified substrates, in the Media Locator on the'My HP Indigo' portal, www.hp.com/go/myhpindigoweb

www.hp.com/go/graphic-artswww.hp.com/go/myhpindigoweb

© 2008 Hewlett-Packard Development Company, L.P. The information contained herein is provided forinformational purposes only and is subject to change without notice. The only warranties for HP products andservices are set forth in the express warranty statements accompanying such products and services. Nothingherein should be construed as constituting an additional warranty. HP shall not be liable for technical oreditorial errors or omissions contained herein.

4AA18224ENUS, 02/2008, Ver.01This is an HP Indigo print.

North America

Hewlett-Packard Company1001 Summit BoulevardMailstop 401Atlanta, GA 30319USATel: +1 800 289 5986Fax: +1 404 648 2054

Europe, Middle East and Africa

Hewlett-Packard CompanyRenier Nafzgerstraat 1006221 KL MaastrichtThe NetherlandsTel: +31 43 356 5656Fax: +31 43 356 5600

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Hewlett-Packard Company138 Depot RoadSingapore 109683Tel: +65 6727 0777Fax: +65 6276 3160

Latin America

Hewlett-Packard Company5200 Blue Lagoon DriveSuite 950Miami, FL 33126USATel: +305 267 4220Fax: +305 265 5550informahpindigo@hp.com

Israel

Hewlett-Packard CompanyKiryat WeizmannP.O. Box 150Rehovot 76101IsraelTel: +972 8 938 1818Fax: +972 8 938 1338