Why Dye?

Athough an established money-maker in the European and Asian markets, digital textile printing has been slow to take root in the U.S. However, during the past few years that trend has changed.

“Here in the U.S., until maybe two years ago, we hadn’t seen more than two percent penetration by textile printing,” says Chuck Sharp, president of textile printer developer TexPress. “Now fabric printing makes up twenty to twenty-five percent of tradeshow products. And, unlike other technologies developed in the U.S., where we were the guinea pig, this media was tested overseas, and now we just have fully-capable applications.”

Driving this increase is the current generation of robust textile printers, with a range of capabilities that fit the needs of nearly any sized shop. Still, many print providers get puzzled looks on their faces when the word “textile” comes into play. To battle through that fog, let’s cover some basics.

TEXTILE WHO?
Textile printing has been around for centuries, and was most recently dominated by the screen-printing business. Just as digital printing has taken over the short-run screen- printed graphics industry, next in line comes fabric, for a number of reasons.

“So far, no digital printing or dye sublimation on textiles is as stable as screen printing. However, the range of colors and complexities of the design are far greater with non-screen-printing techniques,” says Jean Dilworth, textile design professor at Eastern Illinois University.

One main question to address when discussing digital textile printing is “just what is a textile?

“People use the word textile for a number of different things,” says Keith Faulkner, president of print system developer Splash of Color. “I think you have to pin them down when they say textile printing. Some people call vinyl banners textile. They take a lot of liberty with the definition.”

Textiles represent a desirable printing option because they offer “something soft, something flowing, something more elegant than vinyl,” states Marty Silveira, sales manager for textile media supplier Digifab.

For printing purposes, textiles can be broken into two categories: natural and synthetic fibers. Of course, the complexities grow from there.

Excluding aqueous and solvent pigments, and UV-curable inks, which several manufacturers have begun marketing for textiles, there are actually three types of dye-based textile inks: reactive, acid and disperse dye.

Reactive dye works best with cotton and like natural fibers, while acid dye is best for silk, nylon and wool. Acid dye requires the “wet” step of steaming to finish, which also requires washing. Disperse dyes are the inks traditionally thought of by digital printer owners and are sometimes referred to as dye-sublimation inks. Disperse dye inks interact with the chemical make-up of synthetic fibers such as polyester and dissolve into the fiber.

Most dye inks have water- or oil-based carriers. However, Hilord Chemical manufactures a solvent-based sublimation ink. This disperse dye ink uses solvent as a carrier, and the solvent (and VOCs) evaporate during the finishing steps.

Aqueous dye-sub inks are the most popular because they exhibit the highest color gamut and deepest blacks for textile printing, according to Nick Constable of U.S. Sublimation. Pigment inks are the least popular, as they exhibit poor color, and because pigments don’t penetrate the material as well and are less permanent.

Silveira says Digifab has been carrying a line of cotton fabrics for 12 years, but has only added a polyester line in the last four years. This increase is largely due to the increase in disperse dye inkjet printers.

HERE A PRINTER THERE A PRINTER
While transfer sublimation printing has been a reality nearly since the inkjet revolution - with users converting Xerox and 3M Scotchprint electrostatic machines to apply dye toners to transfer paper - several factors today make direct-printing technology more attractive.

“It’s revolutionary to be able to print and transfer in one step. It saves space, it saves time, and it saves money,” says Melissa Ackerman at NuSign, distributor of the d-gen Telios direct-to-textile printer.

Unlike the traditional transfer sublimation process, direct textile printers have special feed systems designed to accept and ink directly onto rolls of textile material. This eliminates the traditional transfer step of printing onto a receptive paper then running the paper and fabric through a heat press to transfer the image, wasting up to 30 percent ink during the process.

The Telios, available in 102" and 74" widths, is one of many four-color direct-to-fabric printers on the market today. Most feature a built-in heat fixer and use disperse dye inks.

Other direct textile options include US Sublimation’s Velotex, a 64" Mimaki JV5 printer converted for fabric stabilization. The dual-four-color direct-printer uses disperse dye ink and has a 400 degree heating unit attached.

Splash of Color has married the Roland FP-740 with an onboard heated calender and sublimation unit to create the DFP-74 Heat Wave. The roll-to-roll dual-four-color machine prints directly onto fabric up to 74" wide.

Then there’s the Texpress DSS1800, a 74" or 104", four-color, 12-channel direct textile printer developed from the Roland SolJET print engine. The TexPress won the textile “Product of the Year” award at the recent SGIA show, according to Sharp.

Mimaki USA offers the TX2-1600 direct-to-textile printer, an eight-color, 64" machine. “If the university had the budget for it, we would own a Mimaki TX2 textile printer,” says Dilworth. “It’s still my very favorite.” Mimaki also offers the direct printing TX3-1600, a 12-color version.

EFI VUTEk makes the FabriVu, a direct-to-textile printer that employs oil-based inks designed for fabric applications.

Gandinnovations offers the Jeti 3324 AquaJet, a 3-meter wide direct-printing unit equipped with water-based disperse dyes.

Hewlett-Packard offers the Scitex XL1500 DS, an upgrade to its XL1500 solvent printer, that allows for easy switching between solvent and dye-sublimation transfer printing.

Introduced to the U.S. at the 2007 SGIA show, Hollanders Printing Systems manufactures the Colorbooster, a production-level, eight-color (CMYK, Orange, Green, Dark Red and Blue) machine that uses an infra-red heat fixer. Both acid and reactive dye inks are also available for the printer, allowing it to print to a wide variety of substrates.

Although direct-textile printers are surging in popularity, traditional dye-sublimation transfer printing is still alive and well. Many water-based printers can be converted into textile printers with proper inks (such as those produced by Sawgrass), transfer paper and a heat press.

PROS AND CONS
As with any inkjet technology, getting the printhead closer to the substrate correlates to more accurate dot control. This logic applies to fabric printing.

“When you go direct to fabric, you can’t run the head as close because the fabric can move,” explains Sharp. As with all inkjet printing, head strikes equate to ruined prints and possible head damage. To compensate, direct printing must be done with a greater head height.

“If you’re looking for the absolute finest resolution, transfer is still going to be the best solution. That’s its major advantage, plus it’s still economical to do one image. However, when you want to do lots of images, transfer becomes very labor intensive,” Sharp acknowledges.

On the other hand, “One of the advantages about printing directly onto fabric is we can actually accomplish the sublimation process at a lower temperature than when using transfer paper, since the image is already on the fabric. You’ll experience less shrinkage because of that,” says Faulkner.

Textiles have a tendency to shrink under heat, Faulkner adds. Meanwhile, transfer paper is dimensionally stable and doesn’t shrink. This introduces the potential for artifacts, also known as ghosting.

“Transfer print quality is great, but transfer runs a greater risk because of shifting or ghosting,” says Silveira.

Another direct-print issue that Dilworth points out is head contamination. “Fabrics have small fibers that sometimes ‘wind off’ at the ends and wrap themselves on the spindle.Keep watching, and avoid this at all costs, otherwise the only solution is a slow and careful removal with tweezers.”

Luckily for both processes, Dilworth sees no effect on material hand. “Throughout time, all printing fabrics have to be processed by methods that set the dyes to the fabrics and rinse off the excess. During the process, as the rinsing removes excess dyes/inks and the remaining adhesives from the fabric, there are changes. Dye sublimation/transfers leave a film that remains around the design for 5-6 washings, which creates a stiffer area.”

“There are definitely benefits for each, depending on what the customer is looking to achieve,” says Constable. So what is it that textile customers are looking for?

AS SEEN ON TV
Textile applications seem to be popping up everywhere - flags, banners, tradeshow booths and even on television. Because fabric weighs less than printed graphics, it’s less expensive to ship, tends not to curl, and stays fresher looking after repeated packing and unpacking. But there are plenty of under-developed niche areas where textile can still cause ripples, such as apparel prototyping and in retail settings.

Finally, Dilworth recommends a few preventive measures for textile printer operators:

As with all materials, pay careful attention to temperature control. Every fabric has a different melting point.

Run the printer every day to discourage ink drying on the heads.

When not in use, place a guitar humidifier ($11 self-contained sponge) on the inside near the heads.