Fabric, unlike paper, is a three dimensional structure and the ink and colorant requirements vary over a large range. Practical limitations exist on the range of fabrics and colors that can be produced with a single ink set. On some fibers that are absorbent, like wool and cotton, the ink is absorbed quickly and easily, so bleeding of the water-like ink jet ink is minimized even without a pretreatment. Unlike the thick, paste-like ink used in conventional screen-printing, these water-like inks will bleed badly on non-porous fibers like polyester and nylon. A mechanism to control bleeding must be incorporated to avoid the ink wicking along the non-porous fibers of the textile. This also is important in applications that require print through on the design to give nearly equal color on both sides of the fabric. In traditional printing this is controlled by the high viscosity of the inks used. With ink jet printing pre-heating the textile or addition of a fabric pretreatment may help control these effects. The binding mechanism of the pigment to the textile and the reaction of the dyes with the fibers usually require a complimentary pretreatment chemistry and/or post treatment to achieve the optimum result. The bottom line is that the ink, textile and the printing system must be designed to control bleeding while achieving the hand, correct color and fastness required by the intended application.

The operative here is "intended application." Printed textiles are sold to many different market segments for a variety of end uses, including fashion textiles, home textiles and soft signage (flag and banner). The target market and end use will ultimately determine the fabric, ink and post processing requirements.

Source: 3P InkJet Textiles

As printing technology advances, progress must and will be supported by ink chemistry improvements. The important trend to follow is the development of pigment systems or alternative chemistry for textiles. Pigment systems have not been easily adapted for the textile inkjet environment and early introductions have been criticized for color brilliance and fastness. For the sewn products industry, the pigment trend is significant for a couple of reasons. In contrast to dye based systems in which dye class must be matched with fiber type, pigments are substrate independent. They can be used for printing a wide range of fibers and fabrics including blends. This will have a great deal of interest for producers of home furnishings, bed linens, and certain apparel products. In addition, pigments and alternative chemistry that do not require steam fixation will simplify the path between printing and cutting. A dry fixation unit could potentially be mounted between a printer and single-ply cutting unit. In contrast, the steaming process required by dye-based systems presents a barrier to integration. Steaming requires a separate process and may cause changes in dimension and shape that make part recognition more difficult during the cutting procedure.

Spot v Process Color

There is not an issue more widely contested in the emerging digital textile printing market than the issue of spot v process colors. Each has its advantages and disadvantages, as outlined below. Some experts argue that the best solution will be one that supports the ability to print both spot and process colors, which will support no color gamut problems, perfect color matching, color gradation similar to screen printing, for spot tones and color gradation better than screen printing for halftones.

*	Ink Jet Process Colors	Screen Printed Spot Colors (analog printing)
Advantages	Theoretically 4 basic colors, actual use of 7-12 colors depending on print head	Higher productivity due to bigger drops
	A color change on the fabric does not require a physical color hange on the machine	Better coverage due to bigger drops
	Theoretically an unlimited number and range of colors for printing available.	Easy setting of desired color tones
	Less chemical/dyestuff usage	Normal work processes can be kept
	Environmentally friendlier	Exact color reproduction
		Wider tolerance permitted for fabric structure as well as for mechanical engineering
Disadvantages	Difficult color adjustment on “flat” colors	Colors must be premixed (color kitchen)
	Strong dependence on dye stuffs and fabric structure	Color change requires washing and changing of colors (environmental issue plus 40% ink waste in the wash).
	As the single color drops, it must be placed on the fabric at exact spots. Maximum preciseness is required for the printing machine manufacturer
	High resolution (up to 760 dpi) is required to avoid color areas from appearing granular and pixel-like. The resolution value however does not represent the delicateness actually achieved on the fabric, as several color drops together form “superpixels.”
	Higher resolution leads to lower output speed
	Penetration varies depending on how many process colors are used.

The Advantages of Digital Textile Printing

To date, the key drivers in adopting digital textile printing technology for traditional textile printers has been the reduction of sampling costs and time to market. In conventional textile screen printing, the development cost for stirke-offs and samples are $4,000-$8,000 (USD) per design, with the cost fluctuating based upon the number of spot colors used in a design. The development of these screens and strike-offs takes from 2 to 5 weeks. With digital textile printing there are no screen costs, and a sample can be printed upon demand.

However, with the textile industry using this technology only for strike-offs, while moving to conventional screen printing for their production needs, it is failing to incorporate many of the key benefits and design opportunities that the new technology provides. These benefits include the ability to use an unlimited number of colors, excellent reproduction of continuous tone images, unlimited repeat sizes and the ability to print engineered designs across multiple seam lines.

What Will Drive the Market?

By eliminating wet post processing, ink jet pigment printing has the potential to make "agile manufacturing" much more attractive. "Agile manufacturing" refers to an integrated, on demand, order and fulfillment process that includes the textile printing and product fabrication manufacturing processes. To implement "agile manufacturing" one must have the ability to print, cut, sew and ship immediately on demand. This capability can dramatically change the way sewn product and other printed textiles are produced.

Freedom from the requirement of using wet chemicals along with "agile manufacturing" will facilitate "distributed printing". "Distributed printing" refers to a small textile fabrication facility that receives the design and product information electronically, then produces product at or near the retail outlet. With these capabilities, along with the digital design, the potential cost savings in the supply chain and the reduction in inventory and design risk, the availability of digital ink jet pigment printing should drive conversion of some parts of the textile printing industry away from conventional screen printing.

Another key driver is printing speed. While all printers available on the market to date have been too slow to support mass production speed requirements, two recent product launches from BMT Technologies (dye sublimation/heat transfer printing) and Dupont boast digital textile printing speeds that can match the speeds of conventional rotary screen printing. While increasing speeds will certainly increase the likelihood of adaptation by the conventional printing industry, this solution merely supports the application of technology to existing business models, and provides no incentive to develop the mass customization business opportunities that the technology will support.

The greatest challenge to digital textile printing adaptation is the conventional textile printing industry itself, which continues to place analog restrictions on digital printing. They are looking at this new technology through the existing workflow and output of a 30 year old printing technology and trying to replace these analog processes and products with the digital ones. The result is a mind set that is focused more on what the digital technology can’t do than what it can do.

Implementing digital printing effectively means rethinking the overall system. It means designing different types of products that leverage the advantages of digital printing. It means sales and marketing strategies that leverage short run production. It means thinking about your business from the perspective of mass customization as opposed to mass production.

The single most costly element in today’s soft goods business is the holding of product and parts in anticipation of a sale. This process supports the maxim that the best way to create profit is to mass produce and discount the surplus. To make this gamble work the apparel delivery system has developed a cumbersome structure designed to stockpile the inventory in staged production surpluses, then to sell finished product in tiered discount and therefore reduce the risk for each participant. While this process has in fact lowered cost, it has also lowered profit and customer choice. In many ways this solution has made a badly weakened segment of the U.S. economy even weaker. The solutions to profit erosion and lack of consumer choice are the same ... individualized mass production and delivery. Digital textile printing offers the technology to deliver mass customized product.

And therein lies the heart of the problem ... as well as the opportunity. Screen printing was developed in the industrial age where the economies of scale demanded a mass production business model. The technology itself, with the tremendous time and cost of screen development, demanded large production runs. The economic models of the conventional printing industry are based upon the volume of yardage that can be printed each year. Digital printing, in its current state of development, does not support this business model.

However, when looked at from the perspective of the wide format printing industry, an industry which is based on short run, customized production, textiles represent nothing more than a new media and a new market. This industry doesn’t look at digital textile printing from the perspective of what it can’t do, but rather all of the new markets it will allow them to enter. The challenge to these people is in learning the textile industry, whereas the challenge to the textile industry is in learning both the digital printing technology as well as a new business model under which to sell their products.

Bottom line, digital printing for short run production requires thinking outside the box. It requires an entirely new approach with new products and new marketing strategies that leverage not just printing technology, but CAD systems, cutting systems, information systems and even the Internet. Since the traditional industry has repeatedly demonstrated its lack of desire to change its ways and its fear of new technology, digital textile printing applications are as likely to come from outside the industry as they are from the inside.