Continuous advancements in fabrics, inks and printers, have made the wide-format textile printing market one of the fastest growing segments in digital printing today. It is estimated that the volume of graphics printed on fabric will more than double from 2011 to 2014. And most of that printing will be done through dye sublimation.
This is the second in our five-part series that explores the intricacies of dye sublimation with guest expert Michael Syverson, Director of Special Projects at Louisville, Colo.-based PrinterEvolution. Mike has been in the printing industry more than 20 years, and was an applications specialist on the VUTEk project team when it unveiled its first grand-format dye sub printer in 2001. In this article, we will delve into the world of substrates, primarily fabric, from polyester to natural fibers to other materials.
Subsequent articles will address heat presses, finishing, marketplace economics and workflow. We asked Mike the following questions:
With the Evo33 from PrinterEvolution, fabric images can be created printing direct or via transfer paper using environmentally friendly AquaSub33 water based dye sublimation inks. The unit features 10pL, variable drop, greyscale printheads, and offers production speeds of up to 1,200 sq. ft/hr.
Q: Aside from fabric, what are some other substrates that can be used?
A: Most anything can be sublimated, but it has to have a polyester coating. Dyes are formulated to penetrate polyester. When polyester gets heated, the molecules expand, allowing the dye to seep in. Poly-coated mugs, ceramics, wood, glass, specially prepared mouse pads, and many other similar types of products can be printed with dye sublimation technology. There are several websites dedicated to providing these coated “blanks” for companies producing these types of products. By far, fabric is the most widely used, offering the industry many textures and finishes, versatility and flexibility that provide customers with high quality results.
Q: Tell us about the different types of fabrics and their applications.
A: Basically there are two types of fabric, woven and knit. Woven fabric is more stable in terms of its stretch characteristics, but tends to fray making finishing more difficult. Woven fabrics generally do not have much stretch unless they are woven with elastic or spandex type thread. Knit fabrics will have a bit more stretch by nature than a woven fabric and they do not fray which eases the finishing, but knitted fabrics can be more expensive because they are more labor intensive.
A very common material for hanging signs and banners that need weight is poplin. Poplin is usually a knit fabric, although some manufacturers have a woven version. Poplin drapes nicely and tends to be slightly heavier. Soft knits are typically of a lighter weight and have more stretch to them, making them ideal for overhead signage, tension fabric applications like exhibition graphics, and framed signage for a smoother look and feel. Flag material has an open weave so air passes through it. Flag is typically used for outdoor applications, such as a teardrop display or actual flags. Generally, this material is printed so that ink will pass through to the back side (strike-through) so the graphic is mirrored on the reverse side for double-sided applications. Because of the need for strike-through, it is usually printed directly to the fabric as opposed to transferred. If a customer wants a lightweight double-sided sign or banner, this would be a good choice.
Recent advancements in fabrics, inks and printers, have helped grow the burgeoning wide-format textile printing market.
Satin is a closed, tighter weave with a gloss or sheen to it. It drapes beautifully but can be expensive. Satin is most often used for P.O.P. displays and indoor applications. PolySilk is a versatile, light weight material that is growing in popularity for its translucent, draping applications. It can be bold and bright but it’s not as durable as the heavier materials due to its lightweight weave. Gaming felt is another type of fabric used for specialty applications like pool tables or poker tables with graphics.
This is only a small sampling of the different fabrics that are available. There are several manufactures that make many different products for virtually any application (see chart, at bottom of page).
Q: What are the trends in new fabrics?
A: The macro-trend in general is a fabric that is becoming the preferred choice over rigid or vinyl substrates for large and grand format applications. Fabrics are versatile, lightweight, have a wide range of applications and provide a high-quality look and feel. They are easier to install and remove and they are more cost effective to ship. Fabric manufacturers and suppliers are continually evolving their products to meet customer demand for environmentally friendly, flame-resistant fabrics that have excellent stretch and recovery characteristics and little to no shrinkage.
When selecting transfer paper, you must first make sure the paper’s coating is compatible with the ink technology being used. Different papers that are compatible with either oil, solvent or water based inks.
Some fabricators are actually designing fabric for clients based on how they want it to look and feel, stretch attributes, shrink level and opacity. This is especially true in the big box retail arena where companies want eco-friendly fibers woven into their fabrics with customized specifications. There’s also a growing trend in specialty upholstery projects and interior design elements. Everyone from architects to hotels to mom-and-pop interior decorators are using fabric for custom-printed furniture, draperies, shades, wall hangings and other indoor applications.
Q: What are some tips for working with various fabrics?
A: The endless fabric choices make working with them confusing. They all have different characteristics that need to be addressed when printing and sublimating through the calendar. For example, fabrics with a great amount of stretch need special attention on the setup of the printer in order for the material to flow through the machine with consistent surface tension. Flag materials are typically direct printed to maximize the strike-through to the reverse side of the material. When transferring to flag, it is virtually impossible to get over 50-75 percent strike-through. By printing direct, you can easily achieve 90-100 percent. It is important to control the amount of ink printed on the fabric as too little will not penetrate deep enough and too much can cause the ink to bloom on the fabric (dot-gain).
Many knit fabrics are relatively easy to print, whether transferred or direct. Again, ink load is critical for direct print. When sublimating fabrics, it is important to have your settings dialed in at the calendar (contact time, temperature and blanket pressure). Once these settings are in place, make sure they are maintained as changes in these calibrations can alter how the dyes are sublimated and affect color.
Q: Are there certain media transport systems that work better with different fabric types?
A: There are different philosophies as to media transport, each with their own advantages depending on the application. Many systems use a single nip for the material as it is loaded into the printer. This is a very sound system and can handle a wide array of fabrics and paper, but it lacks the robustness of larger, more industrial systems.
The large number of fabric choices make working with them confusing. Each has different characteristics that need to be addressed.
Some of the more industrial systems use a dual pinch roller system with tension applied to the material so it can feed very evenly and consistently through the printer. When direct printing to fabric, these systems can have some difficulties.
A third system utilizes a flat sticky belt (similar systems are seen on some flatbed UV printers). This works great for direct-to-fabric solutions, but often times cannot be used with the transfer method of sublimation as the sticky belt can tear the transfer paper.
Q: What are the most important considerations when selecting fabric?
A: The most important thing in choosing a fabric is to understand how it will be used. What’s the application? Do you need it to be translucent? How will it be lit? Will it be hanging, draped or stretched? You want to avoid fabrics that curl and consider the shrinkage factor. Suppliers should have a good consistent shrinkage rate for their materials and it shouldn’t exceed 1-2 percent. Cost is another factor and sometimes buying the less expensive option could end up costing more because the quality of the fabric may be inferior. There may be more dirt spots, or runs in the fabric. In addition, it may not be pre-shrunk or flame-retardant. Finally, lower cost options could have much more unpredictability from lot to lot.
Q: How does printing equipment affect fabric selection?
A: Your equipment can also influence the choices in fabrics. If you have a printer that can only print direct to textile, for example, you need to be very aware that some fabrics may not print well, (especially at wider widths) even though they may be available with a direct to textile coating. It is important to speak with your suppliers about your applications and your equipment so they can recommend the best solution for your needs.
Q: Are there specific inks that work better with fabric than others for both direct and transfer printing?
A: Dye sublimation is designed to work around polyester materials. When printing to a different material, such as silk, cotton, nylon or linen, other ink technologies need to be considered.
The newer water- based, eco-friendly textile inks offer improved depth of color and consistency.
Cottons and linen for example, require reactive dye-based inks. The chemical properties in the dyes and the cotton or linen fibers create a very strong bond for wash fastness and color fastness. After printing, the fabric needs to be steamed and washed for the ink to bond to the fabric.
Silk, nylon and wool require acid dye inks. These are printed in a very similar fashion and also require steaming and washing after printing to affix the colorant to the textile. Both of these technologies yield very good results in terms of color brightness and maintaining the hand of the fabric. An alternative to these technologies is printing with a pigment-based ink (such as latex, UV curable or solvent-based pigmented ink). Pigmented inks provide great flexibility as you can print on most any of the fabrics, however, some of them may need to be coated (in the case of solvent, for example). Additionally, pigmented inks will change the hand of the final product, which may be very important, especially in the case of a stretch fabric application.
Q: What should a print shop owner look for in choosing a dye sub transfer paper?
A: There are several things to consider when choosing a transfer paper. First, make sure the coating is compatible with the ink technology being used. Many manufacturers make different papers that are compatible with either oil, solvent or water based inks. The goal of coating is to minimize ink absorption in the paper by holding as much ink as possible in the coating. The better coatings can hold more ink during printing and release more of that ink into the fabric when sublimated. Generally this yields more color vibrancy, but it is somewhat subjective.
Another thing to look for when choosing a paper is how it runs through the printer. You want a paper that doesn’t cockle and will run through the printer smoothly. If the paper cannot absorb much ink, it will tend to cockle, potentially causing a head strike. Large shifts in humidity can also cause problems with the paper by making it unstable on the printer and more prone to wrinkling on the heat press. It is important to keep humidity levels stable within your facility. Most of the printer and heat press manufacturers have a lot of experience with different papers. When choosing one, they should be able to help by recommending products they have tested on their equipment.
Q: How have printing and ink technologies contributed to the growth of digital textile printing?
A: There’s been an increasing demand for printing equipment particularly in the 10ft. wide textile market. Manufacturers have started providing more options to customers interested in direct and transfer printing with equipment that can offer both and is faster and more efficient. Print heads have improved significantly in the past several years. Print heads with a fixed, binary droplet of 80 picoliters (pL) have been replaced with variable drop heads with droplets as small as 6-10 pL. This has resulted in greater sharpness and detail, finer lines, and overall, better image quality with excellent color gamut.
The newer water- based, eco-friendly inks are more widely available for grand format printers. These inks have also improved in depth of color and consistency. Advances have also been made in coating technologies for direct printing. There seems to be more communication between the mills and the ink manufacturers in how they develop effective coatings for fabrics. The various manufacturers of printers, supporting devices and consumables are constantly innovating in all of these areas as this is a fast-growing segment of the textile printing business.
To continue to Part 3, Click Here.
To read Part 1 of this series, Click Here.