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A Positive Reaction

 

Textile Printers Look to Ink and Media

 

By Cassandra Carnes

 

Part 1 of 2

 

Textiles provide a premium medium for print. These flexible substrates are available in a variety of lightweight and durable offerings. With this soft and durable media, print service providers (PSPs) are able to present a variety of looks for a range of applications. The choice of print method, material, and ink influence the look, feel, and quality of a textile print. Continuing on the theme of textiles found in the July print issue, this two-part Web-exclusive series focuses on the role of ink in direct to fabric and dye-sublimation (dye-sub) textile printing.

 

Digital Output covers three common methods of wide format textile printing, dye-sub transfer, direct dye-sub, and direct digital printing. Before selecting a method, PSPs consider many factors. The application and its end use determine potential water contact, UV light exposure, and durability—all conditions that influence media and consumable selection. Depending on the print method, material may require pre or post treatment. The type of fibers a textile is composed of, as well as the chemical composites of a treatment, influence the reaction of the ink’s dye or pigment on the material when printed.

 

Means to an End

Graphics produced on fabric are attractive to many industries, including fashion and sports apparel, hospitality, and theater. Each application requires its own set of specifications, which determine the best materials and processes for the job. For example, graphics that are meant to be viewed from far away may not need the same crisp output as those designed to be viewed up close. Additionally, clients may require jobs be run on either natural or man-made fibers, which would dictate the method used to print on them to ensure proper ink adhesion.

 

Fabrics printed using a direct to substrate process—not necessarily dye-sub direct—often require a coating, which can become costly unless the company is large enough to pre-coat its own material. “The actual printing process is the easy part, the pre- and post- processing is what can be costly, time consuming, and requires a bit of know-how,” says Ralph Terramagra, eastern regional sales manager, Mutoh America, Inc.

 

Mutoh does not manufacture or distribute textile inks, but the company partners with Sawgrass Technologies, Inc. and their line of sublimation inks.

 

Depending on the ink and materials used, post-processing methods differ. Printing on natural fibers such as nylon and cottons, requires a steaming process followed by washing to remove the coating. In comparison, direct dye-sub applications require heat activation, while dye-sub transfer requires both heat and pressure.

 

Ink is an important part of the equation as ink manufacturers use different dyes and carriers in their products. For example, Hilord Chemical Corp., a supplier of direct and transfer dye-sub inks in water, oil, and solvent systems, designs its inks to work with specific printers.

 

Acid, reactive, disperse, and pigment ink are all options for direct to textile printing. Acid dyes are designed for use on silk, nylon, and wool. They require steaming and washing to finish. Reactive dyes are for cotton, rayon linen, and silk. They also require steaming and washing. Disperse, or dye-sub, dyes are used for polyester and require steam or heat press fixation. Depending on end use, washing may also be required. Pigment inks are not fiber specific. They are typically used for cotton and cotton-blends and require dye heat to fix binders to fabric.

 

It is important for PSPs to consider their target market before selecting which textile printing process to bring on. “Each process involves multiple steps, and it is best to determine what the customers’ needs may be prior to jumping in to one specific ink technology,” suggests Marty Silveira, sales manager, DigiFab Systems, Inc.

 

For example, PSPs producing show graphics might not need to print to cottons, silks, or nylons, as there are many polyester alternatives that allow for direct sublimation or the use of transfer paper. On the other hand, PSPs working with home furnishings or apparel may need sublimation, acid, reactive, and pigment inks. Alternatively, Silveira notes that someone looking to print nylon flags may decide that using acid inks gives them a competitive advantage over a sublimation flag manufacturer that transfers or prints onto polyester.

 

DigiFab manufactures and distributes a number of textile inks under its DigiDye label. They are compatible with a variety of digital printing equipment.

 

Dye-Sub Inks

Dye-sub is performed in two processes—transfer and direct. The traditional transfer dye-sub process requires printing on transfer paper, which is then applied to fabric using a heat press. Many believe the dye-sub transfer process provides a more detailed print, although the direct dye-sub process continues to advance. Direct dye-sub eliminates the need for transfer paper, as images are sublimated directly onto the fabric.

 

Sublimation inks are water-, solvent-, or oil-based. For transfer printing, water-based inks are known to cause issues such as ink soaking and paper cockling. Therefore, solvent- or oil-based inks are a good fit. However, solvents may contain hazardous air pollutants and oil-based inks are thick and may cause printheads to clog.

 

“In direct to textile sublimation, and when reliability, easy maintenance, and environmental issues are considered, water-based inks become much better solutions,” notes Amir Shalev, future product manager, Hewlett-Packard (HP) Scitex.

 

HP produces direct dye-sub inks for existing owners of the HP Scitex XL 1500 printer with the Dye Sublimation Upgrade installed. The company also produces HP Latex Inks for direct to substrate textile printing.

 

Water-based inks are best for dye-sub direct because of output quality, reliability, speed, and low environmental impact, says Larry Salomon, VP wide format, GS/inkjet division, Agfa. He explains that aqueous dye inks sublimate uncoated materials and become fused after the heat/press stage.

 

Chuck Payne, channel development manager, digital, Nazdar, agrees, noting that solvent-based dye-sub inks are generally found in printers configured to print with standard solvent inks—for applications such as banners and wraps—or sublimation solvent inks. “The only real advantage to solvent-based sublimation ink is that it is chemically miscible with standard solvent ink,” says Payne.

 

Nazdar manufactures water-based dye-sub transfer ink and direct to fabric dispersed-dye ink.

 

The dye-sub process is largely dependent on fabric choice and PSP’s goals. For printing on polyester, dye-sub direct or dye-sub transfer technology is key. Inks are based on textile dyes that are designed specifically for this type of substrate.

 

“More end users opt to print direct, rather than use heat transfer paper, to simplify the printing process,” notes Michael E. Compton, national sales manager, Mimaki USA, Inc. The company manufactures and sells inks for direct to substrate, dye-sub direct, and dye-sub transfer processes. Additionally, Compton adds that today’s printers—such as the Mimaki Tx400 series—offer variable drop size printhead technology for detailed direct print output.

 

Keep in mind, polyester fabric typically requires a pre-treated coating for direct dye-sub printing, which isn’t necessary for the dye-sub transfer process.

 

Direct Digital Printing

In addition to the dye-sub process, many inkjet printers are equipped to print on select fabrics. Both reactive and acid dye products are applicable to direct to fabric printing. Comparing the two products is difficult as application requirements differ and ink set is determined by fabric type, explains Payne.

 

“Over the years, ink manufacturers and digital printing equipment companies have tried to be all things to all users in an effort to capture as much of the digital printing business as possible,” notes Compton. He suggests that the direct to textile printing process use direct to textile inks, as they are typically water-based and made from traditional textile dyes. “I would no sooner attempt to print on vinyl substrates with textile inks as I would print on textile substrates with solvent inks,” he says.

 

“In my experience, when printing natural fabrics such as cotton, it is best to use reactive dyes, when printing man-made fabrics such as nylon, it is best to use acid dyes, and of course dye-sub is best for polyester,” says Terramagra.

 

Emmanuel Swolfs, manager, inkjet field marketing international, EFI, says UV inks are appropriate for non-absorbing textiles if the feel of the material is not important. This is because it does not require a post-printing process. He explains that this method does affect the feel of real textile to some extent. Swolfs also notes that an intermediate white layer is needed for night and day applications.

 

HP’s alternative to dye-sub for direct to textile printing with its HP Latex Inks. Printers designed for use with the latex inks include integrated heaters that dry and cure so that prints come out fully dried and ready to ship or display. According to Shalev, it’s a very simple process and there is no separate calendar, heat press, or transfer paper required. The inks are water based and can print on both coated and uncoated polyester fabrics, as well as some natural fibers such as cotton and linen.

 

Think Ink

Inks are made specifically for different substrates, end products, and equipment. For textile applications, a number of factors—including ink selection—should be considered and tested up front. Determine where and to whom the final product is going before deciding which process, ink, and material should be used for the application. “Inks feature different limitations and the PSP must know this before striking out into fabric,” notes Nazdar’s Payne.

 

Runnability is also a consideration. Inks are generally designed to work on specific applications for select printers. “We’ve seen many dye-sub inks cause printhead nozzle loss after a short time. Users must set automatic cleanings on the printers at specific intervals, which leads to loss of production and ink,” he adds.

 

PSPs strive to know their business, in turn they help promote the best use of their technologies. Fabric printing is one appealing service, but it must be tackled with knowledge. Reade more about ink’s role in fabric printing in part two of this series. Additionally, the July printed issue of Digital Output digs deep into the ins and out of digital textile printing.


Click on the link above to get more information on the vendors mentioned in this article.

Jul2011, Digital Output  DOTI0711

 

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