Dreamweavers III: The Material World

Fabric printing has its own unique set of consumables or basic materials, each of which has an important role to play in the imaging process.

April 5, 2016
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The choice of transfer paper can mean the difference between a high-quality, washfast image and a low-quality image that washes out in a short period of time.

Consumables—the materials used for printing—are an important element in the process. These include ink and substrate, but intermediary materials such as plates or—if you have been around for a long time—film also contribute to the overall quality of the final printed image.

Fabric printing has its own unique set of consumables or basic materials, each of which has an important role to play in the imaging process, including one that often gets neglected: transfer paper.

Ink and Fabric

There are many different kinds of inks for printing on fabrics, the primary difference being that they are compatible with different kinds of fabrics. The reason for this is basic chemistry; just as ink on paper printing is the result of physical and chemical interactions between ink and substrate, so, too, is ink on fabric printing.

The general classes of digital inks for fabric printing are:

  • Reactive dye inks—Also known as “fiber-reactive dye inks,” the dyes in these inks react chemically with natural cellulose fibers like cotton, and become physically part of those fibers. This imparts strong washfastness, among other desirable traits.
  • Acid dye inks—Like disperse inks, acid dye inks chemically react with the fibers in the substrate, in this case the most compatible being natural or synthetic polyamide fibers, like silk, wool, or nylon.
  • Disperse dye inks—These are the inks we are usually referring to when we talk about dye-sublimation. These dyes become gaseous when heated to high temperature and the gas will penetrate into the fibers of the fabric. These work pretty much exclusively with polyester fibers.
  • Pigment inks—Generally, pigment inks can print on virtually any fabric, and cure easily via heat or ultraviolet (UV) light. One snag with pigment inks is that the inks require a bonding agent. Another is that, for a given quantity of ink, the more color (aka pigment) it contains, the less of the bonding agent, and thus the less washfast it is. On the the hand, the more bonding agent, the more washfast, but the less vibrant or colorful.

According to Michele Riva, Sales and Marketing Director for EFI Reggiani in his keynote presentation at last February’s EFI Connect, pigment inks represent a “good opportunity” for fabric printers thanks to the versatility and large number of applications for which the inks can be used.

As for the fabric itself, textiles can be made from virtually anything, natural and synthetic, and the choice of fabric will be a function of what kind of product you’ll be printing, as well as the type of printing equipment you are using. The dye-sublimation inkjet printers that have been emerging en masse and are targeted at commercial printers or specialty shops looking to add textile printing require polyester-based fabrics, and there are thousands to choose from. We saw in the last installment of this series that up-and-coming inkjet dye-sub printers print direct-to-fabric, a process that requires pretreated polyesters to optimize ink holdout and minimize dot gain, wicking, and other defects that can occur when you are jetting a liquid ink into an absorbent substrate. While it’s true that direct-to-fabric is the Holy Grail of textile printing, at the moment, transfer-based dye-sublimation is the most common and versatile solution for fabric printing, especially at the entry level.

Transfer-based dye-sublimation offers a lot more variation in the types of fabrics that can be printed, but there is one critical yet often overlooked element in transfer printing.

Transfer Paper

Transfer paper often gets short shrift in fabric printing conversations, and yet it’s arguably the most important part of the process. We often refer to transfer paper in passing, saying little more than “transfer printing requires transfer paper,” as if that referred to one single thing.

Dye-sub printing on transfer paper has the same challenges as inkjet printing on any paper: the transfer paper needs to be compatible with the ink being used. It’s not a case of going out to Staples and buying Acme Transfer Paper, feeding it into the printer, and then sublimating it to the fabric.

“One of the biggest questions I get is, ‘Can I use bond paper’?” said Lily Hunter, Product Manager, Textiles and Consumables, for Roland. Roland offers the Texart line of transfer dye-sublimation printers for both entry-level and high-volume textile printing applications. This may seem like (or even a prerequisite of) Textile Printing 101, but “transfer paper” is specially treated paper with a coating that is designed to hold the ink during printing and then release it onto the fabric under heat and pressure during sublimation. The thing is, said Hunter, “not all transfer papers are created the same. Like any product, you have different levels of quality. You can have cheap transfer paper that doesn’t do a good job of holding the ink or releasing it.”

Part of the problem is that inks can vary greatly. As we know from Ink 101, inks consist of two basic elements: the colorant (a dye or pigment) dissolved or dispersed in a vehicle (mostly water in the case of dye-sub inks, or solvents in other kinds of wide-format inks). It’s the job of the vehicle, as the term suggests, to transport the colorant to the substrate. Different inks can have different dye-to-vehicle ratios, or “dye loads.” Inks with higher dye loads don’t need as much total ink laid down to get vibrant colors, while more watery inks that have lower dye loads do.

“If it’s a lower dye content, you’re going to really have to load the paper up to get the color that you need,” said Hunter. “If you use a paper that’s too thin or has a poor coating, you’re going to get wrinkling and buckling of the paper. Then you’re going to have issues with printing and crashing the printheads.”

That’s just getting the ink onto the paper. Then there’s the process of getting it off. The transfer paper coating should optimally release 90 percent of the ink onto the fabric. (There’s no precise way to measure this aside from eyeballing it and seeing how much or how little ink remains on the paper after sublimation.) If you find you’re releasing less than that, you may need to adjust your color profile—or choose another paper.

This is also where the two types of transfer paper are important: tack and non-tack. Tack paper, as the term suggests, is tacky (the heat of the press activates the adhesive), which means that the paper will stick slightly to the fabric so it doesn’t move during sublimation. (This is opposed to some of the apparel we print and wear, which can also be described as “tacky,” albeit in a different sense. We continue.) When should you use tack vs. non-tack transfer paper? It will be a function of both the heat press you’re using for sublimation, and the fabric itself.

“If you have a flatbed [heat] press, and you’re using fabric that may shrink a little bit, you can use tack paper to prevent ghosting,” said Hunter. “If you’re using a rotary calender heat press, you don’t really need tack paper.” The only time you would need a tack paper on a rotary heat press would be if the fabric to which you’re sublimating is highly elastic or subject to substantial shrinkage.

As you can tell, balancing the ink, the paper, and the fabric can be a bit of a challenge, but effective color profiling can help manage all of these variables. But only up to a point.

“You can have the best color profile in the world but if you have cheap inks and cheap paper that don’t perform well, you’re going to have problems,” said Hunter.

What is cheap vs. non-cheap? A good transfer paper will run about 10 cents a square foot. When you’re looking at two to five cents a square foot, that’s where you should be cautious.

“Go with someone reputable that your dealer or even manufacturer recommends,” said Hunter. “We have our paper [Roland Texart Sublimation Transfer Paper] to make it easy for someone who is starting out, but we work with different companies that have good products.” Coldenhove and Beaver Paper are two sublimation paper producers that Roland works with. As always, Hunter advised, “Test it and see who gives you the best results.”