Testing Your High-Performance Substrates
Davis explains why determining how a high-performance polyester garment will behave on press and in the dryer is a critical part of a successful print run.
Each fabric in garment screen printing presents the printer with a unique challenge. Understanding the printing characteristics of the fabrics we use is a critical part of the business, whether we work with 100% cotton, 50/50 cotton/poly blends, polyester knits, nylon, or Lycra. Only when we have a command over the variables that come with printing onto these types of materials can we really meet our customers’ demands.
The manufacture of today’s garments includes more and more 100%-polyester performance fabrics for every type and style of apparel. Because almost all of these fabrics are now woven, dyed, and assembled overseas, it becomes the garment screen printer’s responsibility to know and understand how these fabrics will perform on press and after they’re printed, as well as how heat affects them during the curing process.
Another consideration for determining fabric printability is that as the licensed market has changed and the need for mass contract printing has decreased, many large contract printers are now looking back at the custom-printing market as a production source. If you’re a contract printer and your business is strong, determining fabric printability offers a greater challenge. After all, you desire to offer the client the greatest degree of printing quality, regardless of the garments they supply.
Garment screen printers decorate a wide variety of textiles, and while discovering how each fabric prints and reacts in production can take a lot of time and effort, the journey is definitely worth it. All fabrics are knitted, bleached, dyed, and sewn in different methods, depending on the manufacturer and type of fabric. One very important factor that you need to keep in mind is the type of dye used in the dying process and the content of that dye within the finished fabric.
Almost all of the current performance fabrics offered today are 100% polyester and have been dyed and treated with compounds to enhance moisture-wicking capabilities and soil/stain resistance. The issue that that these types of garments present to the garment screen printer is how the ink will perform on the fabric from the standpoint of bleed resistance and elasticity. Again, these factors are based on the construction and knitting/weaving of the fabric in question. I’ve had experiences with some fabrics that are on the market today dyed with inexpensive polyester dyes that are not properly set, which can make the printing process impossible without some degree of bleeding, regardless of the bleed-resistance quality and curing parameters of the ink being printed. It is here that some testing is required to ensure that you’ll be able to properly print the fabric without the worry about dye migration or sublimation.
Unfortunately, one of the greatest challenges of determining a fabric’s printability is something that you can’t really control in your facility: acquiring sample fabric from the garment manufacturer that you can test before going into production. The performance fabrics offered today are typically too expensive for most printers to order samples in the name of testing, although this may be required as a last resort in order to ensure a fabric’s printability.
Once you have acquired either the sample fabric or garment, you need to print test swatches. You should always use your best bleed-resistant inks and tightest printing techniques. In some cases, printers achieve good bleed resistance on 50/50 fabrics by simply double stroking the fabric. Others will print/flash/print. In either case, you will need to do pick the appro-ach that works best for you, given your inks, equipment, and experience, and set the fabric aside for at least six to ten days to ensure that the print is properly cured and migration is not an issue. It’s true that such a lengthy test period may cause some tension between your shop and the customer, but you are better off testing these fabrics prior to production than having to replace the run due to poor print results.
While you’re at it, take a moment to call the garment manufacturer directly and ask what printing parameters and products they suggest to properly decorate and finish the fabric. The response you get may range from detailed instructions on each step of production and suggested applications to the far extreme of, “The fabric was not intended to be imprinted.”
Heat sensitivity is a huge consideration when screen printing fabrics. Typically, 100%-polyester fabrics are heat set to 360°F to ensure that the fabric will be fade resistant during washing. This may not always be the case, depending on the fabric manufacturer’s dyeing and heat-setting applications.
One case I experienced just this year was excessive shrinkage of the garment during the curing process. In most cases you can lose a half of an inch in length or width when the garments pass through the dryer. But in this particular situation, I had a garment style that lost six inches in length and an inch in width when the printed apparel passed through the dryer. I was lucky in this case, because the manufacture was aware of the issue and accepted a return of the garments. Here again, it is a good idea to inquire as to a fabric’s sensitivity to heat to avoid such disasters. Obviously, issues with dye migration only apply to dark to medium fab-ric colors, whereas the shrinkage issue can apply to any color of performance fabric.
Minimize the ink film
From an application standpoint, always remember that more is not necessarily better. Do not go into your performance testing with the assumption that laying more ink down can solve your potential bleeding issues. Thicker ink films require a greater dwell time in the dryer chamber, thus exposing the fabric to high temperatures for a greater period of time than necessary. Doing so can, in this case, create more problems than it may solve.
You’re better off printing such fabrics with screens tensioned as high as you can support and by depositing as little ink onto the fabric as possible in order to minimize the amount of time needed to properly cure the ink film. Another option worth consideration is working with low-temp/fast-fusion inks—high-opacity inks that allow you to cure at lower temperatures and decrease the potential issues that the higher temperatures may cause.
Why you must test
None of the suggestions I’ve described is an absolute. The situation changes with each 100%-polyester fabric and with each man ufacturer. Also keep in mind that a majority of these fabrics are most likely produced in Asia, under questionable quality-control standards. That, perhaps, is among the biggest reasons why you must always test the fabrics you print.
Rick Davis is the president of Synergy Screen Printing in Orlando, FL. A 27- year veteran of the textile-printing industry, Davis is a member of the Academy of Screen Printing Technology and has a background that spans production management, artwork engineering, application testing, and industry consulting. He is a frequent contributor to trade publications and a speaker at industry trade events.