Dye vs. Pigment

It’s worth noting that many fine art reproduction houses use Iris inkjet printers to produce “Giclee” prints, which are renowned for their longevity. All Iris printers use dyebased inks.

The increase in the use of pigment ink in photo quality inkjet printers - and the marketing frenzy that has followed - has left the average inkjet user confused, and in many cases, disappointed. There are two misconceptions about dye versus pigment. First, pigment inks are always more light stable than dye-based inks; and second, pigments now match dyes in terms of color quality.
It’s true that pigments generally are more fade-resistant, particularly for outdoor exposure where the intensity and type of light is very different than artificial illumination. However, for indoor display, the gap is closer than you might imagine. All reputable ink makers conduct extensive internal fade tests, and several third-party testing institutes can be hired to predict an image’s useful display life. The test standards vary dramatically from organization to organization, but more on this later. The most respected test center - Wilhelm Imaging Research - conducts accelerated indoor display life tests on many different inkjet ink/media combinations. Their published results show that some dyebased products last as long as an estimated 120 years, while the leading pigment-based ink set on certain media lasts only 34 years.
The reason dye-based inks produce It’s worth noting that many fine art reproduction houses use Iris inkjet printers to produce “Giclee” prints, which are renowned for their longevity. All Iris printers use dye-based inks. more brilliant color is illustrated in Figure 4.

We see the colors of a print by the light reflected off the print’s surface. The particles in a dried pigment ink have a very rough surface, so the light reflected off the print tends to scatter (Figure 4a). On the other hand, dried dye ink has a smoother surface that reflects the light back more uniformly (Figure 4b).

Another favorite trick of inkjet marketers is to show color gamut comparison diagrams in promotional literature. These illustrations are two-dimensional diagrams showing how big a color space an ink has compared to a competitor. However, these 2-D charts only show the range of achievable colors that can be had from an ink set, and don’t show the brilliance level of the colors, which can only be represented in 3-D. Before writing this article, I conducted a very simple test. I took the leading OEM pigment ink set and a long-life dye-based ink set, and made 2- D color comparison charts using topend color measurement equipment (Figure 5). The dye ink had a slightly larger color space, but the color gamut of both inks was very similar. Then, I made prints on the same media using the same color print file. The results were vastly different. The dye-based print was more intense and brilliant. The point is that 2-D gamut comparison charts do not tell the whole story. The best way to make a true comparison is with the actual printed images.

The “archival” debate
If there were ever a more misused word in our industry, it would be “archival.” The dictionary defines this word as, “of, relating to, contained in, or suitable for archives.” It mentions nothing about lasting a long time on display. My industry is intent on branding every type of product , from inks to media, to laminates and protection lacquers - as “archival,” implying that they are long-lasting. The simple fact is that an inkjet print is a combination of several components - ink, media, protection spray or laminate, mounting material, matte board, framing material, etc. Each can have a dramatic effect on an image’s display life.
Two instances come to mind. One photographer I know produced a beautiful series of images using “archival” media and standard dye-based ink. He was led to believe that the media alone would make his prints fade-resistant. Another photographer used a well-respected, long-life ink set with a media from a different manufacturer. He experienced rapid color shift as the ink and media chemically reacted.
The only way to maximize a print’s fade resistance is to ensure that all components are tested together. This is why ink suppliers also sell media and protection sprays, which have been tested for longevity as a complete system. If an ink or media vendor doesn’t supply the complete tested package, they should be able to recommend products that have been longevity tested with their product.
The subject of longevity testing and the methods used is a minefield. Unfortunately, there is no internationally accepted standard for longevity testing of inkjet produced images. An American National Standards Institute (ANSI) working group composed of technical representatives from many major inkjet manufacturers has been working for years towards a testing standard, but it’s yet to be approved and published. That’s why you should ask for testing procedure details when choosing products with claimed longevity properties, and use common sense when interpreting the test results.
The only way to determine the life of an image (other than displaying it and waiting) is to accelerate the fading. Usually, this is done by exposing an image to a high intensity light source, then extrapolating the resulting fade over time. When doing this, it’s very important to control the environmental conditions, such as temperature and humidity, as these can have a dramatic effect on fade rates. It’s also logical that the type of light source used to accelerate the test should be similar to that where a print will be displayed. One common procedure, the “blue wool test,” uses a xenon light source to simulate sunlight. This test originally was created by the textile industry to determine the light fastness of textile dyes. However, it has been proven that the fading effect of artificial light can be very different than that of sunlight, and this test has proved to be somewhat inaccurate for predicting fade rates under indoor display conditions.
There are stranger test procedures out there. One pigment ink manufacturer actually dips prints into a bleach solution, then measures the resultant fade over a period of time. Their biased results show how much better their products are than dye inks. Any college chemistry student knows that dyes can be bleached faster than pigments.

Photo industry paradox
A paradox in the photo industry is the question of the longevity of traditional photo printing vs. digital output. We know that some excellent color print papers available from manufacturers such as Ilford and Fuji are accepted as the ultimate for long-life display material. These products use dye technology and produce stunning color. Longevity testing by independent test houses like Wil-helm put the estimated indoor display life of these papers in the 30–60 year range. Why, then, are the new digital technologies expected to exceed this? There are several dye-based ink sets available that rival traditional products in longevity and color quality, but they are dismissed because they lack a 100+ year expected life.
During a recent trip to Denver, I browsed many photo gallery stores that had wonderful color prints of the Rockies and the local wildlife. At one store, I bumped into the owner whose work was on display. I asked him why his prints were produced on long-life traditional papers, and weren’t digital. He replied that he would love to use inkjet because of the extra creative flexibility and enlarged media choice, but was disappointed with the color quality of available “archival” pigment inks. His eyes lit up when I told him there were dye-based inks available that would give the color he wanted, along with the longevity he sought. A false expectation gap exists between the old and new ways. I think that some manufacturers have pushed the longevity envelope too far, too quickly. While they supply long-lasting ink products, the inks disappoint in terms of color rendition.

Bulk ink feeders
With photo-quality inkjet printers now widely used for the commercial production of images, many third-party ink companies have introduced bulk-ink feed devices that provide a continuous ink supply (CIS) to the printer, eliminating the need to change cartridges. The potential reduction in consumable costs is enormous, equaling about a 70% savings over buying original cartridges. These devices are bad-mouthed by printer manufacturers because they take away a valuable revenue stream, and are claimed to be unreliable, difficult to install, and, worse yet, damage the printer. In some cases, this is true; there are some poorly made systems out there. However, I believe that a welldesigned bulk feed system can actually increase the printer’s reliability. The reason a printer requires several cleaning cycles after a cartridge change is because of air ingress into the print head. We’ve found that bulk feed attachments are more trouble-free since the need to run cleaning cycles is dramatically reduced.
Here are some tips when choosing a bulk ink feed system. First, find out if the system comes with pre-primed ink cartridges. A lot of these systems are supplied empty (the ink is sold separately), and the user must first fill the cartridges using syringes or a small suction pump.
Second, determine if installing the system requires any major modifications to the printer. Awell-designed system shouldn’t require any hole drilling or cutting of the printer covers. (Remember, you may one day need to return the printer for warranty repair.) Finally, don’t consider a bulk ink feed attachment unless you regularly do a fair amount of printing. If you only do a couple of prints a week, these systems are not for you since the ink in the reservoirs will go out-of-date before you use it. A good rule of thumb is, if you use more than a cartridge set each week, a bulk feed will save you money and work reliably.

Ask questions
Don’t be afraid to ask awkward questions when selecting a printer, an ink type or a media. Any reliable supplier should be able to answer most queries and back up their products with factual information. In summary, here are a few points to remember.
• Do not be misled by OEM publicity regarding poor quality third-party products. Remember these guys make a huge percentage of their profits from consumables.
• Choose between pigments and dyes wisely. The choice is a compromise between color quality and longevity. For extreme long life requirements, pigments are the way to go, but they have reduced color quality when compared to dyes. For very good life and great color, go with the dyes.
• Don’t be fooled by color gamut comparison charts. Ask to see direct comparison prints on the media you want to use. • Avoid using pigment inks in printers designed for dyes. It can work, but often ends in tears.
• For longevity, always use products matched as a “system” or have been tested together. Ask for details on the test methods used, and use that common sense when interpreting the results.

Some manufacturers have pushed the longevity envelope too far, too quickly. While they supply long-lasting ink products, the inks disappoint in terms of color rendition.

• Only use a bulk ink feed device if you regularly produce prints (e.g., exhaust a cartridge ink set weekly). Avoid systems that aren’t primed or that require major modifications to your printer.

Tony Martin is President of Lyson USA, based in Elk Grove Village, Ill. His email address is Tmartin@lysonusa.com
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