With a traditional contact print technol-ogy, such as screen printing, the availableink options are pretty well understood byprint providers, with solvent and UV cur-ing inks dominating. Yes, new versions ofscreen inks appear regularly on the marketas chemistry and manufacturing techniquesimprove but the applications for these inksare fairly well defined. With a relativelynew and developing technology such asinkjet printing, however, the opposite is of-ten true. It seems like everyday a new inkjetprinter is launched along with a new typeof ink. As with any rapidly growing busi-ness, the marketers go into overdrive, andinvent products and brand names that areat best overkill and, at the worst, mislead-ing. This has left many a print maker whois transitioning to digital in a state of con-fusion.

To look at the various inkjet ink op-tions available to graphics producers and tounderstand their uses, we must first under-stand a little about inkjet technology.

Basic Inkjet TheoryIn all inkjet printers, the component

that applies the ink to the media is knownas the print head. In graphics inkjet print-ing, the print head technologies that aremost commonly used are piezo and thermal

inkjet (often referred to as ‘bubble jet’ or‘TIJ’). Both of these print-head types havearrays of very small holes (known as jets)from which droplets of ink are ejected. Thesize of these jets varies from manufacturerto manufacturer but most are smaller in di-ameter than a human hair, and the numberof jets can be in the hundreds.

With piezo print heads, ink droplets areejected by pulsing piezo crystals behind theprint-head jets.

With thermal inkjet heads, small heat-ing elements are used to create gas bubblesin the ink that expand to eject drops fromthe jets.

Both technologies are very fast witheach jet capable of producing tens of thou-sands of droplets per second. The printheads are usually mounted on a head car-riage and passed backward and forward

across the media to produce an image. Thenumber of print heads depends on howmany individual colors are being used in theink setup. Print heads are also often gangedtogether to increase the number of jets —the more jets, the faster the print speed.

In graphics printing, and particularlythe outdoor grand format market, piezohas come to dominate due to the fact thatit can work with many different ink types.Thermal inkjet is normally limited to run-ning water-based inks.

One of the commonly held myths aboutinkjet is that the inks are pumped throughthe jets. The opposite is actually true as allprint heads require aslightly negative pres-sure on the inks tooperate efficiently.The action of firing a

Navigating the Digital Ink Jungle

By Tony Martin, President, Lyson Inc.

It seems like everyday a new inkjetprinter is launched along with a new type of

ink, leaving many a print maker who is transitioning

to digital in a state of confusion.

P R O D U C T I O N

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drop from the jet simply pulls more inkinto the print head from the ink supply.Many inkjet printers do have pumps inthem but these are used to either transportinks from the main ink tanks to a headreservoir, or for head cleaning purposes.

Most of the inks used in graphics inkjetprinting dry by evaporation, with the ex-ception of UV curing ink. In easy-to-under-stand terms, an inkjet ink formulation thatdries by evaporation consists mainly of afluid that is simply there to keep the ink ina liquid state and act as a ‘carrier’ for thecolorant (Figure 1). This carrier fluid evap-orates as the ink dries and leaves the col-orant in or on the surface of the media.When an ink is referred to as something“based” as in “water-based” or “solvent-based” then the carrier fluid is what is nor-mally being described. The colorant is ei-ther dye or pigment, or a combination ofboth. Often, a second carrier fluid (or co-

solvent) is used mainly to control the dry-ing time of the ink. The presence of a sec-ond carrier fluid also controls the viscosityof the ink during manufacture. Smallamounts of several other additives are pres-ent in most inks. These control or help withthings such as adhesion of the ink to themedia, dot gain, drop formation, corro-sion of the print head, pH level, fade resist-ance and color brilliance. In simple terms,however, we can think of an ink as being acarrier fluid and a colorant.

The difference between a dye and a pig-ment can be explained pretty easily also. Adye is a colorant that is dissolved fully intothe carrier fluid and the resultant ink is atrue solution (Figure 2a). Once dissolved

into the carrier fluid, a dye should neverseparate or settle out, unless you havepoorly made ink, of course! An analogy fora dye ink is when you dilute a concentratedjuice drink with water and, once stirred, itnever separates again no matter how longyou leave it. A pigment on the other handis a very fine powder of solid colorant par-ticles that are suspended or dispersedthrough out the carrier fluid (Figure 2b). Acrude analogy for a pigment ink is a sandy-colored river or sea water: if you lookclosely, you can see sand particles dispersedthroughout the water. The secret in makinga good pigment ink is to keep the pigmentsuspended in the carrier fluid for a long pe-riod of time, particularly at the low viscosi-ties required for inkjet printers. Pigmentshave a natural tendency to settle out muchas sandy water, where the sand will fall tothe bed once the water has stopped beingagitated. In a well-made pigment ink, little

or no settling out of the pigment should oc-cur. Unless directed so by the manufacturer,it is not a good idea to shake an ink bottleor cartridge before use. Shaking can intro-duce air bubbles into the ink or re-disperselarge lumps of settled out pigment, whichin turn can lead to blocked jets.

The main difference between an inkjetink and a screen printing ink is the viscos-ity. Inkjet inks have to be very thin to oper-ate successfully in most print heads and aresometimes only three or four times thickerthan water. Screen inks, on the other hand,are more like a paste. The real challenge fac-ing ink chemists is to develop inkjet inksthat have the same performance as screeninks but at a much lower viscosity.

The Golden Rule of InkjetThe golden rule of inkjet is:When any inkjet ink dries by evaporation

then the dried ink must be able to be re-dis-solved by the liquid form of the same ink.

Sounds pretty simple, however, this ruleis vitally important if an inkjet printer is tofunction reliably.

Most photo quality inkjet devices useprint heads that have hundreds of jets, andliquid ink is always present at the orifice ofthese jets. It doesn’t take a genius to real-ize if you use an ink that dries by evapora-tion, there is a very good chance the ink willdry up and clog these jets. The challengethat always faces the printer designer andthe ink and media developer is to make amachine that has fast-drying output yetdoesn’t clog.

The easiest way to remove a clog of driedink from the single jet on a print head (Figure3) is to use liquid ink to re-dissolve the dried

ink. A separate washing sys-tem that bathes the head inan “ink-dissolving” solutionadds considerably to thecomplexity of the printer. Itis simpler to stick to thegolden rule and depend onthe ink to unclog itself.

One commonly held mis-conception is that when a jetor jets clog (evidenced bylines or banding in the print)then the cause is an impurityor lump in the ink. In 99.9percent of the cases, aclogged jet is caused by driedink or by an air bubble in the

ink. Air in the channel behind the jet on aprint head is a sure way of stopping the jetfrom firing correctly. Air in the channel actslike a shock absorber to the firing action.

Another common untruth is that pig-ment inks clog jets worse than dye-basedinks. The perception is that, because pig-ment inks contain solid particles, these lit-tle particles can somehow gang up to forma blockage of the jet. When you considerthat an average pigment particle size is un-der 0.1 micron and the common jet sizes to-day are between 20 –25 microns, it wouldtake several hundred of the little devils tojoin together and block the jet! Only apigment ink that is poorly made or formu-lated could block the jet.

When any inkjet ink dries by evaporation then the dried ink must be able to be

re-dissolved by the liquid form of the same ink.

Colorant - Dye or Pigment

Carrier Fluid mixed with co-solvent

Additives

Figure 1: Dye

A B

Pigment

Figure 2:

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Water-Based InksThe first wide-format graphics inkjet

printers from companies such as Encad(now Kodak) and Hewlett Packard were allbased on thermal inkjet technology andused water-based inks. Early inks all useddyes as a colorant but water-based pigmentinks were quite quickly developed to ad-dress the signage market.

Today, there are literally dozens of wa-ter-based wide-format printer models fromseveral manufacturers using both piezo andthermal print heads. Water-based inkjetprinters are the most commonly used ma-chine types in graphics printing. Waterbased printers are, however, generally lim-ited to producing prints for indoor display.Yes, outdoor graphics can be produced us-ing special media or by applying a protec-tive laminate, but these methods tend toadd considerably to the finished cost of theprint. The reasons for this are pretty obvi-ous if we consider the golden rule. It ispretty difficult to make a water-based inkthat can be re-dissolved by itself and yetmake the finished print water proof.

Hence, water-based inks are usuallyprinted onto coated media for outdoor use.The coating encapsulates the inks to pro-tect the colorant from water. Even so, thesemedia are usually only for short-term out-door use and so lamination is required forlong-term protection. In the inkjet industry,a great deal of development work is goingon at the moment to try to make water-based inks water proof and capable of be-ing printed onto uncoated media and curedby some method after printing. These ideasare in their infancy. For now, it is best to saythat water-based inks are best used oncoated media.

A major debate over the years has beenthe dye vs. pigment argument with water-based inks. The recent increase in the use ofpigment inks in photo quality inkjet print-ers — and the marketing frenzy that hascontinued since their introduction by someprinter manufacturers — has left the aver-age inkjet user somewhat confused and, inmany cases, frankly disappointed. Thereare two commonly held misconceptionsabout the dye vs. pigment argument. First,pigment inks are always more light stablethan dye-based inks. Second, pigments nowmatch dyes in terms of color quality.

It is true to say generally pigments aremore fade resistant than dyes, particularlyfor outdoor exposure where the intensityand type of light is very different from ar-tificial illumination. For indoor display,however, the gap is closer than you mightimagine. All reputable ink makers conduct

extensive internal fade testing of their prod-ucts and there are several third party test-ing institutes that can be hired to predict animage’s useful display life. One of the mostwell known and respected test centers,Wilhelm Imaging Research, conducts accel-erated indoor display life testing on manydifferent inkjet ink/media combinations.They have published results that showsome dye-based products last as long as anestimated 120 years while the leading pig-ment-based ink set on certain media lastsonly 34 years. These facts are always con-veniently ignored by the marketing giantsof our industry.

It is also worth noting that a lot of thetop-end fine art reproduction houses useIris inkjet printers to produce gicleé printsrenowned for their longevity. All Iris print-ers use dye-based inks.

The reason why dye-based inks tend toproduce more brilliant color than pigmentinks can be explained in Figure 4. The waywe see colors of a printed image is by thelight reflected off the surface of the print.The particles in a dried pigment ink have avery rough surface, so the light reflected offthe print tends to scatter in all directions(Figure 4a). A dried dye ink has a smoothersurface, so it reflects the light back moreuniformly (Figure 4b).

The latest pigment preparation technol-ogy has improved color quality by grindingthe particles to the smallest possible sizeand by using resins to coat the particles,which smoothes out their rough surface.One major printer manufacturer producesmarketing material that implies their pig-ment inks contain particles that are perfectround little spheres. I can assure you thatthese particles still look like a load of littleuneven meteorites when viewed under apowerful microscope!

It is a simple fact, however, that dyeinks do produce visually brighter anddeeper colors than pigment inks, and thatsome very long lasting dye inks are avail-able. In the photographicworld, this presents an in-teresting dilemma.Photographers who are usedto the color quality deliveredby traditional silver halidephoto papers are often notable to achieve the same re-sults using inkjet. This is be-cause traditional colorphoto chemistry always usesdyes and they are comparingthis to pigment inkjet prints.This fact is now being recog-nized with many of the lat-

Ink Flow FromCartridge

Liquid Ink inchannel mustbe able tore-dissolvedried ink at jet

Figure 3:

Today, there are literallydozens of water-based

wide-format printer

models from several

manufacturers usingboth piezo and thermal

print heads.

LIGHT

PAPER DyeBA

Pigment

Figure 4:

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est water-based photo printer offeringsfrom Canon and Hewlett Packard usingdye-based ink technology.

Oil-Based InksThe next major step in graphics inkjet

development was the introduction of ma-chines running oil-based pigment inks.These inks use a very slow drying carrierfluid (such as Isopar) that is usually de-rived from a mineral oil source, hence theterm “oil-based.” The benefit of this ap-proach is that the printer is very easy to useand maintain as the print head jets are veryunlikely to clog with dried ink. The down-side is that special coated media is requiredthat quickly absorbs the oil-based carrierfluid onto the media base leaving the col-orant on the surface. These types of mediaare obviously more expensive to manufac-ture than uncoated products and so printproduction costs tend to be higher withoil-based printers. There are many oil-based inkjet printers being used in the mar-ket although there are few machine manu-facturers introducing new models. Thegraphics industry has now moved on tothe more economical and versatile solventand UV curing ink-based printers.

Solvent-Based InksIn the late 1990s, inkjet printers began

appearing on the market that really ad-dressed the needs of sign and screen print-ers — the ability to print onto uncoated,non-absorbent materials with aggressiveinks that had a long outdoor life withoutlamination. The early pioneers of this tech-nology such as Idanit (now Scitex Vision),VUTEk and Rastergraphics (now Océ)paved the way to the point today wherethere are dozens of printer manufacturersaround the globe offering solvent-basedmodels from 36" to over 15' feet in widthand with print speeds in excess of severalhundred square feet per hour. Solvent inkjethas become the dominant method for pro-ducing digital prints in the industrial graph-ics market. Media manufacturers have em-braced the solvent technology andproduced a wide range of low cost sub-strates for solvent inkjet including self ad-hesive vinyls, scrim banners and even tex-tiles.

The make up of solvent-based inks isvery easy to understand. A solvent or mix-ture of solvents is used as the carrier fluidand pigment as the colorant. A resin isadded to the ink, as well as a “glossing”agent. Basically, when a solvent-based inkdries and the carrier fluid evaporates, weare left with pigment particles “glued” to

the surface of the media by the resin. Theglossing agent is present to maintain a glosssurface and help with abrasion resistance.The performance of solvent-based inks andmedia has reached a point where printscan be made that have as much as a fiveyear outdoor life without lamination.Media is a key element to the life of a print.Even the best ink will not last on a mediathat breaks down in a relatively short timeoutdoors — a pretty obvious concept, how-ever, one that is often overlooked by printproviders. Although solvent inks adherevery well to vinyl, they must be over coatedwhen used in high abrasion and chemicalexposure applications such as vehiclegraphics.

The term “solvent” is open to interpre-tation and, unfortunately, is misused bymany in the inkjet industry. If you look upthe word “solvent” in an encyclopedia youwill find something along the lines of “asubstance, normally a liquid, in whichother materials dissolve to form a solu-tion.” This describes pretty well any liquidincluding water. In the inkjet industry, “sol-vent” is used generically to describe any inkthat is not water-based!

On top of this, we have terminologyused to describe ink products such as“soft,” “mild,” “safe” and “green” on onehand; and “hard,” “real,” “true” and“strong” on the other. How can a liquid bedescribed as soft or hard? No wonder peo-ple are confused. One of the more intrigu-ing terms used is “eco” solvent ink. Tomost people, “eco” infers ecological. Theseinks generally contain glycol esters or gly-col ether esters, which are both derivedfrom mineral oil — hardly a renewable re-source or an ecologically sound process!

Perhaps, the terms “mild” and “aggres-sive” might be best suited to describe thetwo groups into which solvent inks fall. Amild solvent ink (i.e., “soft” or “eco”) gen-erally uses very slow drying liquids as thecarrier fluid. Printers that use these inkshave several heaters fitted to aid with dry-ing. The faster the machine prints, the moreheat is required. One of the main benefitsfor using these slow-drying carrier fluids isthat they make it easier to design and man-ufacture a reliable printer. As mentionedearlier, there is a constant trade off forprinter developers between producing amachine with fast drying output and pro-ducing one that doesn’t suffer from driedout inkjet heads. Using mild solvents sim-plifies the design process.

Aggressive solvent inks (i.e., “hard” or“true”), on the other hand, are generallyfaster drying and need fewer heaters on

It is a simple fact,

however, that dye inks do

produce visually brighterand deeper colors than

pigment inks, and that

some very long lastingdye inks are available.

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the system. Because of this lower heat re-quirement, media that are prone to“cockle” under heat, such as some types ofself adhesive vinyl, can be used more suc-cessfully than on a mild solvent ink system.Aggressive solvents also have the addedbenefit of softening up the media surface,which helps the bonding of the pigments.Hence, aggressive solvents tend to be morescratch and weather resistant, and work ona wider range of materials. The types ofresins and additives that can be used withaggressive solvents also make it easier toproduce an ink that is glossy when dry socolors appear to have more “pop.”

In summary, both mild and aggressiveinkjet systems work well and can produceexcellent prints that are suitable for long-term outdoor display. Aggressive solventinks have the added benefits of being lessmedia-dependent, better adhering, moreweather resistant and brighter in colors.While running costs with both ink types areremarkably similar when purchased in car-tridge form, aggressive solvent machinestend to use around 10 percent more ink be-cause increased head maintenance cyclesare required. However, most now comewith bulk ink delivery systems as standardor as an option. This reduces running costsconsiderably versus cartridge-fed mild sol-vent machines. It remains to be seen if themild solvent machine vendors introducebulk ink at a cost to compete. A factorsometimes overlooked when selecting anink is its resistance to other solvents.Finished prints often come into contactwith pretty severe chemicals, particularly incleaning agents. Standard Windex or spe-cialty vinyl cleaning products can quicklyremove some mild and less expensive ag-gressive solvent-based inks. Check withyour ink supplier if this is a concern.

Solvents have come in for a lot of badpress in recent years. For some people, thevery mention of the word conjures up im-ages of spotty-faced, spaced-out youthshanging around on street corners sniffingglue! The fact is there are no golden rulesto solvents, and that there are equally asmany safe aggressive solvents as there aretoxic mild solvents. There are also manycommonly held myths around solvents,such as “if it doesn’t smell, then it’s safe”or “the more aggressive a solvent, the morepoisonous it is.” For instance, dipropyleneglycol mono-methyl ether is a commonlyused material in many low-odor mild sol-vent-based inks and has an exposure limitset by the US Occupational Safety andHealth Agency (OSHA) at a relatively low100 parts per million in the work place,

where as some of the lactates used by sev-eral aggressive ink manufacturers are actu-ally food additives, are easily metabolizedand have no exposure limits set.

The thing to do before using any ink isto request a material safety data sheet(MSDS) from the supplier. By law, theyhave to provide this. A well-written MSDSprovides specific information about expo-sure limits and ventilation/extraction re-quirements. It should also list the compo-nents in the ink, along with the ChemicalAbstracts Service (CAS) registry numberfor each item. A quick search on the webusing the CAS number will provide youwith a wealth of health and safety informa-tion. Good resources are also the OSHAand the US Environmental ProtectionAgency (EPA) Web sites at www.osha.govand www.epa.org.

Unfortunately, a loop hole in the regu-lations exists that allows a manufacturer tostate something along the lines of “propri-etary organic solvent” on an MSDS if theink is supplied in a sealed cartridge format.Even so, the MSDS should still contain ex-posure information. If not, request a writ-ten statement on the safe use of the inkfrom the manufacturer. Failing this, contactyour local OSHA or EPA office for advice.In any case, once you are aware of the safeexposure limits for the ink you are using,then don’t ignore this. If the recommenda-tion is to use in a well-ventilated area or ex-tract the vapors, then do it. The effects onhealth to exposure to the more noxioussolvents such as ketones are not alwaysimmediately apparent, whereas long-termexposure can result in damage to health orthe body becoming sensitized where symp-toms such as nausea, headaches and skinrashes occur. The fact is there are manysafe, solvent-based inks available and, aslong as health and safety guidelines are fol-lowed, they can be used happily with nopersonal risk.

The VOC DebateThere has been much talk recently about

Volatile Organic Compounds (VOCs) andthe government’s commitment to reducingVOC emissions. Solvents that are derivedfrom living things (carbon containing ma-terials) can all emit VOCs, and this includes99 percent of the solvents used in both mildand aggressive solvent-based inks! Don’tbe fooled by claims that solvent-based inksare VOC free or don’t emit VOCs. True,some slow evaporating solvents only emitVOCs slowly at room temperature butwhen force dried by a system’s heater unit,as many VOCs are put into the atmosphere

The types of resins

and additives that can be

used with aggressive

solvents also

make it easier to

produce an ink that is

glossy when dry so

colors appear to have

more “pop.”

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as with a fast drying aggressive solvent.Don’t panic, however. It would take an aw-ful lot of solvent-based printers in an organ-ization to reach a VOC emission level thatrequired regulatory reporting or interven-tion. The term VOC is very generic. If youare concerned about the effect your print-ing is having on the environment, then thereare many solvent-based inks available con-taining solvents whose fumes are biodegrad-able. Many of the lactate family of solventsare recognized by the EPA as environmen-tally preferable chemistry and are madefrom renewable resource materials. TheWorld Wide Web is a good resource for in-formation on this.

UV Curing InksThe latest ink technology is ultraviolet

(UV) curing. The make up of a UV curingink is very similar to a solvent-based ink,and pigments, additives and resins are usedin much the same way, with one distinct dif-ference. The carrier fluid is a substancethat is liquid in its normal state but crosslinks or “cures” when exposed to high lev-els of UV light. Some versions of UV cur-ing ink contain small amounts of solvent,but we can think of a UV curing ink as con-taining 100 percent solids when cured.

There are many benefits to using UVcuring inks. Primarily, they can print onmany materials that are difficult or impos-sible to print on with water- or solvent-based inks. If you take a material such asstyrene or foam core and try to print on itwith a solvent-based ink, for instance, thenyou will probably find that the ink wouldeither absorb into the substrate or bleed allover the place and the print quality wouldbe unacceptable. With a UV curing printer,a UV light source is usually attached to theprint head carriage so that the inks arecured instantly after printing, before thisabsorption or bleeding can take place.Most of the UV printers that have recentlyappeared on the market are of the flat bedtype and are designed for printing ontorigid materials although many models aredual purpose and can accept flexible rollmedia as well. The introduction of UV cur-ing inks has really opened up the range ofmaterials that can be used and increased thenumber of applications for inkjet. UV cur-ing is not the be all and end all, however,and has some limitations and problems

that need to be understood when selectingan ink type.

UV cured inks tend to be more brittlethan dried solvent-based inks particularlywhen made to the low viscosities that arerequired for inkjet. They can crack or breakaway when used in applications where thesubstrate needs to be very flexible orstretched, such as with vehicle wraps. NewUV chemistry has improved this recently,but it can still be a problem. The colorquality of UV curing inks tends to not beas good as with solvent-based inks. This isdue mainly to the inks being cured beforethey “wet” out on the surface of the mediaand so they are rougher and have a morematte appearance. Over coating with a lac-quer is often needed to get the same “pop”as with a good solvent-based ink. UV cur-ing inks tend to have a shorter shelf life intheir liquid state as the curing process canstart to occur in the bottle after a certainlength of time. Avoid storage at high tem-peratures, as this can induce the curingprocess. Currently, most UV curing inkshave a shelf life of around nine months toa year after manufacture compared to sol-vent-based inks at around double this fig-ure. Most UV curing inks are thicker thancan be used through an inkjet head at roomtemperature, so the machine manufactur-ers use heaters in the print head to lower theviscosity of the ink just prior to printing.Bearing in mind that heat can initiate thecuring process, care has to be taken not toleave head heaters on when not printing.Once a print head has been cured, it can’tbe cleaned and has to be replaced.

In terms of health and safety issues, thereare very different concerns with UV curinginks than with solvent-based inks. Little orno VOCs are given off from UV curinginks. The main concern here is the emissionof ozone that many UV light sources create.Ozone is a very corrosive gas that must bevented. Shield the UV light source well andavoid looking at it directly (eye damage canoccur). Avoid physical contact with uncuredinks as many contain initiators that are ir-ritants and bad skin rashes can result. Aswith solvents, it is important to understandthe health and safety precautions when us-ing UV curing ink. As long as guidelines arefollowed, they can be used safely and withgood results.

UV curing is not the be all and end all, however, and has some limitations and problems

that need to be understood when selecting an ink type.

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Look out for

water-based inks that

can print onto non-coated

media and

improvements in UVcuring ink performance

along with safer

solvent-based products.

Best Inks for ApplicationsThere is no doubt that the range of ink options available today for use in inkjet print-

ers has increased the number of applications that can be covered by digital printing. Thereis also, however, no doubt that certain ink types and equipment are better for certain ap-plications than others. Here’s a list of the main applications along with the best ink typesto use for each.

Photographic prints for indoor display Water-based dye, water-based pigment

Fine art prints for long-term indoor display Water-based pigment, water-based dye

General exhibition graphics for indoor use All ink types (water-based with lamination)

General point-of-sale graphics for indoor use All ink types (water-based with lamination)

Indoor signage All ink types (water-based with lamination)

Indoor back light displays Water-based dye, water-based pigment, Solvent-based pigment.

General outdoor signage Solvent-based pigment, UV curing, water-based pigment (with lamination), oil based.

Outdoor banners Solvent based pigment, UV curing, water based pigment (with lamination), oil based.

Outdoor back light displays Solvent based pigment, water based pigment (with lamination), UV curing, oil based.

Vehicle wraps and graphics Solvent based pigment, UV curing, water based pigment, oil based (all need over coating for protection).

Uncoated rigid materials UV curing, solvent based pigment (substrate dependent).

Obviously, there are many crossovers on the list and some inks can be used for manyapplications. When I have mentioned more than one ink type, the best is listed first, whilethe other inks will still provide acceptable results. Some may argue that there are someomissions from this list. A solvent based ink, for instance, can be used to produce a prettygood photographic print for indoor display but it will not have the quality or detail of awater based ink print on coated media.

The FutureThe development of inkjet inks is moving on at a furious pace to meet the demands

of the graphics printing industry. Improvements in chemistry will expand the perform-ance of all ink types and enable many new applications to be encompassed by inkjet. Whiteinks are now becoming a reality that will allow printing onto non-white or clear substrates.Look out for water-based inks that can print onto non-coated media and improvementsin UV curing ink performance along with safer solvent-based products.

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