User login

The Mystery of Fibrillation

(December 1999) posted on Sun Dec 19, 1999

Hedge identifies the causes of fibrillation and how to overcome it.


By Steve Hedge

It's Friday afternoon and you've finished working on a difficult design for a valued customer. You have mastered perfect image reproduction and are awaiting final customer approval. The phone rings and you answer with great anticipation. Your customer says, "I just received my wash-test results and the ink is coming off." You think to yourself, "It can't be. I know these shirts are fully cured." Your customer says that the garments appear washed out, and you agree to evaluate the prints firsthand. On your way to meet the customer, you begin to review the job processes for what could have caused the problem. You know that your dryer settings were more than adequate because you had just checked ink-film temperatures that morning. You also rule out the inks because you know of a dozen other good jobs printed with them. After examining the washed garment, you can see a definite difference in the appearance of some colors before and after washing. You also notice that the ink looks washed out in an even manner over the entire print. Because you are a professional, you know that washout due to uncured ink appears in a spotty, almost random fashion across a design. Since this print looks evenly washed out, you realize that you have a new mystery to solve. This scenario is becoming more and more common among textile screen printers who use plastisol inks every day. Since quality imprinted products are the lifeblood of these companies, identifying the cause of this fading is critical. Unfortunately, these cases involve plastisol inks from every major ink manufacturer and garments from every major mill. Combined, the variety of inks, application processes, and substrates makes it extremely difficult to pinpoint the cause of this condition. The fact is that the apparent color loss is not the result of plastisol inks being washed out of the garment. Instead, the color fading is caused by fibrillation, a condition that occurs when substrate fibers break loose from the ink film due to washing. As the fibers break through the film, high contrast between the loose fiber ends and the ink film causes the print to have a faded, hairy appearance. Fibrillation vs. ink washout As mentioned previously, washed out prints are faded in spotty, uneven patterns across the print. On the other hand, when a color looks somewhat washed out or faded in an even manner over the entire print, you are probably experiencing fibrillation. If any ink appears washed out in certain areas only, it is the result of undercured ink. The topic of ink-cure parameters is too involved to discuss here, but suffice it to say, you should be familiar with the necessary dryer conditions required to ensure proper cure of the ink you use. The most important issues are why and how fibrillation unexpectedly occurs. By the end of this article, you will become a certified sleuth in detecting the causes of this condition. With some knowledge about the key factors that affect fibrillation, you will know exactly where to begin your investigation into the specific cause for your particular job. Once you can predict the outcome of using certain ink/substrate combinations, you will be prepared to intelligently advise your customer up front and offer alternatives. Otherwise, your customer may experience fibrillation and become so displeased that he or she refuses to pay you for the job. Demands of the market Fibrillation is one consequence of attempting to meet the demands of the increasingly sophisticated imprinted-sportswear market. Customers today often request particular qualities or attributes in their finished product, usually beginning with the soft, supple feel of 100% cotton. In addition, everyone wants prints with rich, bright colors and an ultra-soft hand on both light and dark garments. Advances in high-tech equipment and modern printing techniques are making it easier than ever to meet these criteria. However, the rapid development of new equipment, substrates, and inks to meet the market's needs has created some compatibility problems. When screen printers don't refine their processes in response to the new materials and technology, fibrillation may occur. What are the effects of washing and drying? To avoid fibrillation, you first need to understand how it occurs. Washing and drying create a rubbing action against the print and can cause fibrillation by raising loose yarn-fiber ends from the ink film. To see an example of the effect, take two garments with the same print, turn one inside out, and wash and dry them together. After examining the prints, you will see that one washing/drying cycle results in a minimal change in appearance. In fact, you may not notice a difference at all. Repeat the washing/drying process four more times. You will now be able to detect an obvious difference in appearance, with the garment turned inside out having the least amount of fibrillation. How can you predict a job's outcome, choose the right substrate and ink system, and avoid having to face a disappointed customer? Unfortunately, the answer is test, test, test, and test some more. You need to prepare a series of test prints and examine the ink film deposited under normal printing conditions for each type of garment material you intend to offer. This point cannot be over emphasized. The time you invest for testing will be paid back many times by savings in the cost of product returns. The exact same press setup will produce dramatically different results on a variety of substrates made by the same mill. Yarn type, yarn count, fabric content, and fabric construction all have an impact on the washability of the applied ink system. Let's begin our investigation by setting up the test-printing parameters and discussing some application and ink options. To make testing and examination of prints easier, you'll need a magnifier or microscope with a magnification of 30x or more. These are available in many electronics and hobby stores. Set up your initial tests To prepare the test prints, set up your press with a screen that has a mesh count typically used in your shop. Ideally, you should set up on an automatic press and prepare all test prints on the same print head with the same screen. Using an automatic press will help you maintain the same squeegee angle and pressure on all test prints. Remember, the whole point of the testing is to compare identical ink deposits on different substrates. You may want to repeat these tests in the future, so think about requirements for duplication and consistency. Record the particular press, print head, squeegee durometer and edge, pressure settings, and any other variables you can control and duplicate. Use a graphic (or prepare a special test pattern) with a print area of solid coverage and a 50% dot pattern. The dot pattern will give you an idea of the results you may obtain when printing four-color process jobs. Make the image large enough that you can actually cut the cured print in half, keeping one half unwashed and using the other half for the wash test. Always maintain one half of your print as the unwashed control, which you will need to compare results before and after washing. Select the ink you normally use, prepare three prints for each substrate type, and cure thoroughly. Be sure to properly identify each test print by substrate and ink type. The purpose of multiple prints is to allow you to use one set for comparison after one wash, one set after two washes, and the third set after five washes. These wash-cycle test levels are typical of what your customer might perform on your garments. To get a good feel for what may happen when you use different substrate/ink combinations, start with dark-colored ink on white shirts. Remember that the whole trick to preventing fibrillation is to get the substrate fibers matted down with the ink film so that they stay there after multiple washings. This is easy to say, but often difficult to accomplish, especially when you have to maintain an ultra-soft hand in the print. Keep in mind that fibrillation can occur in many combinations of ink color and substrate color. The problem can be as evident with light-blue ink on a red garment as with black ink on a white garment. The degree to which fibrillation becomes apparent depends on the contrast between the shirt color and ink color. Therefore, fibrillation will be much less noticeable (if noticeable at all) with yellow ink on white shirts or red ink on berry shirts. Fibrillation will still occur, but the contrast between ink and fibers will not be obvious to the eye. Nevertheless, you can conduct tests and evaluate any ink color on any substrate color using the same methods outlined here. Here's where the fun begins. Get out your magnifier and look closely at the ink-film deposit on your initial test prints. The prints may take on a wide variety of appearances. When you examine the prints and compare the washed and unwashed halves, you will probably see some dramatic differences in the appearance of the ink films on some of the substrates you tested. In some cases, you may see loose, white fibers sprouting from the ink film even before you wash the fabric. This initial print quality will continue to deteriorate when subjected to abrasion during washing and drying. Initially, you may see that all fibers are matted down with your ink deposit and that only a small number break loose after washing. But multiple washings generally cause more and more fibers to break free from the main ink film. You will be able to see any degenerating print quality by comparing the three levels of wash-test results. Also, notice the effect washing has on the dot pattern. When the print area diminishes to the size or length of the loose fiber ends, the risk of yarn fibers breaking free increases. Simply put, there just isn't as much area of ink coverage by the dots, and the fibers tend to break away easier. Since your ultimate objective is to give your customer that ultra-soft hand with rich, bright colors, you will most likely need to continue your tests, altering one variable at a time. First, determine if your original setup will give you acceptable results on any of the substrates. If so, record the setup specifics for those substrate(s). Next, evaluate any unsatisfactory results for loose surface-fiber ends with that particular ink type. Obviously, the more loose surface-fiber ends, the greater the fibrillation. Application options If you feel your initial ink deposit doesn't effectively combat fibrillation on some substrates, try decreasing your mesh count and duplicating all the initial tests. You should also print those substrates that had satisfactory results on the initial tests so you can compare the change in ink-film structure, especially after washing. Heavier ink deposits will increase your chances of matting down loose fibers and holding them down after washing. Continue your testing with decreasing mesh counts until you reach the point where the fibrillation becomes acceptable. Remember, though, heavier ink deposits result in a harsher hand. If the fibrillation level is acceptable on a substrate but achieving a softer hand is your goal, try the reverse approach to the previous steps: Repeat the tests with increasing mesh counts. This will help you define your limits for acceptable fibrillation with soft hand. Ink system options An alternative for attacking fibrillation is to consider the particular ink system you are using. Not all ink systems are equal in filler content and, subsequently, their effectiveness against fibrillation also varies. Most process inks and fast-fusion inks, for instance, have little or no fillers. All-purpose or multipurpose inks generally have moderate levels of fillers. High-opacity or super-opaque inks have very high levels of fillers. Generally, the higher the filler content, the better the mat-down characteristics. The exceptions to this rule are fast-fusion inks, which tend to maintain very good ink-film structure after washing. But in general, remember that higher filler content means harsher hand on the printed garment and that adding extender bases to filled-ink systems will reduce their mat-down capability. Check with your ink supplier for details on the particular ink system you are using. If your testing seems to suggest that you should change or modify your ink system, then proceed with the second series of tests using the new inks with the same setup parameters as before. Chart 1 gives a brief overview of various ink-system concerns that affect fibrillation. Chart 1 * Ink type Filler level Mat-down capability Print hand * Process Little/none Poor Soft * All purpose Moderate Fair Fair * Fast fusion Little/none Good Fair * Super opaque High Good Harsh When you have completed the testing as described, you will have a firm grasp of the results you can expect to achieve after subjecting the garments to washing and drying. If you maintain a file on all the print controls and wash-test samples, you can even present the expected results and provide other options to your customer when you negotiate the sale. How to improve your results Here is where you have to use your ingenuity and creativity. You have to keep in mind the delicate balance between your equipment's capabilities, the attributes of the ink system you're using, and your goal of matting down the loose fiber ends and getting them to stay there. You must be willing to go beyond your standard application processes and the test procedures previously outlined. Here are some ideas you may want to try: 1. With high mesh counts (160-280), apply a wet base (leave it wet, do not flash) consisting of clear base, balanced extender, or a combination of these blended with fast-fusion clear base. The application of this wet ink will help matte down the fibers and allow the overprint to form a secure surface film, which will resist the abrasion of washing and drying. Also try this technique on dark garments using similar variations with your white underbase. 2. With varying mesh counts, apply: * a flashed base of a fast-fusion ink. A fast-fusion underbase will provide an initial ink film that will help hold down the loose fiber ends during multiple washing and drying cycles. Use a clear fast-fusion ink except where you need an underbase of white on dark garments. Mixing a flash additive into the fast-fusion underbase will help improve the after-flash tack. * a printable adhesive, normally used for transfer backing. A printable adhesive will help hold down loose fibers by gluing them in place. The deposit will require a coarser mesh in the range of 110-125T and will result in a harsher hand. 3. Alter your ink deposits by combining * greater stencil thickness and higher mesh count. * lower stencil thickness and lower mesh count. * softer, slightly rounded-edge squeegees with less pressure. 4. Change your ink system to * a blend of fast-fusion inks and filled inks. Here you want to take advantage of the fiber mat-down capability of the filled system and combine it with the improved washability of the fast-fusion ink. Blend these in varied ratios and compare the results after washing. * a hot-split transfer system. A hot-split transfer provides good fiber mat down with a very soft hand. Using a transfer powder or printable-adhesive backer will help promote long-term fiber mat down and washability. * a mixture of image ink and transfer powder. The transfer powder will improve the ability of the ink film to maintain its integrity and keep fibers matted down during washing and drying. T-shirt considerations A number of factors in T-shirt manufacturing can contribute to fibrillation. Not all of them are under your control, and you probably aren't interested in all the minute details of T-shirt manufacturing. But you should understand some basic concepts of fabric construction that can contribute to the fibrillation phenomenon. Yarn type Cotton and blended yarns are produced by a variety of spinning techniques. The most common of these are referred to as open end and ring spun. Without going into how these yarns are manufactured, you should have some insight into the differences between the two and a general understanding of some yarn factors that influence fibrillation. Open-end yarns have a considerable number of fibers loosely wrapped around a twisted center core and are more even, without thick and thin places. They have greater elongation potential (stretch capability), but less strength than ring-spun yarns. With ring-spun yarns, the majority of the cotton fibers are twisted along the longitudinal axis of the yarn. All of these fibers contribute to the overall strength of the yarn. Why is this an issue? Some contend that one type of yarn is more prone to fibrillation than the other, but we've seen the condition in both. Actually, the "hairiness" of both yarns is a result of spinning. It is inversely proportional to the size or fineness (count) of the yarn and the length of the individual fibers. The more coarse the yarn, the hairier it is and when combined with a thin ink deposit, the more prone it will be to fibrillation. Yarn count To distinguish differences in their size and weight, yarns are given size numbers referred to as "count." For typical cotton and blended yarns, 840 yd of yarn per pound is the industry standard. If 840 yd of yarn weigh 1 lb, then the count is #1. If it takes 8400 yd to weigh a pound, the count is #10, and so on. The higher the numerical count, the finer the yarn. The finer the yarn, the less problem you're going to have. In other words, a lightweight cotton T-shirt will be less susceptible to fibrillation than a heavyweight cotton T-shirt. 100% cotton vs. blends and 100% synthetics Yarns that contain at least a portion of polyester fibers are less prone to fibrillation than 100%-cotton yarns. For instance, 67/33 blended poly/cotton yarns are less hairy than 50/50 poly/cotton yarns, which are less hairy than 100% cotton. Likewise, 100% polyester yarns are less hairy than poly/cotton blends. However, 100% acrylics and acrylic/cotton blends are similar to 100% cotton in hairiness. Fabric construction Given the many combinations of yarn type and size discussed above, the possible range of fabric constructions is endless. The more common products supplied to our industry are 50/50 fleece, 50/50 jersey, and 100% cotton jersey. For 50/50 fleece, the yarn count is typically 28. For 50/50 jersey, the yarn count is in the range of 22-26. The 100%-cotton jersey ranges from 18-22. For all construction variations, the stitch density of the fabric knitting controls the ink's ability to bridge the individual knitted ribs. The stitch density is the product of the number of stitches in each fabric dimension: the course (the row of stitches across the knitted fabric) and the wale (the chain of loops that run lengthwise). A stitch density of at least 1000 is desirable for adequate ink bridging. For example, a typical lightweight cotton jersey may be made with 22-count, open-end yarn and have 35 courses per in. and 36 wales per in. equaling a stitch density of 1260. The smaller the yarn count for any stitch density, the heavier the garment weight. This is due to the fabric having more yarn bulk per square area. However, remember that the yarn hairiness increases as the yarn count decreases. In general, a stitch density greater than 1000 is desirable in reducing the likelihood of fibrillation. Conclusion With the rapid development of new ink systems, printing equipment, and garment substrates, fibrillation is occurring more frequently than ever before. To prevent this condition from affecting your prints, test different ink/substrate combinations and carefully monitor press-setup parameters. Research the substrates you commonly use and determine what yarn characteristics make them good or poor choices for particular jobs. Use a magnifier to investigate test prints after washing and drying. Record important data about the press setup, ink type, garment type, and test results. And use this data to help you identify jobs with a potential for fibrillation before you begin printing. Don't allow fibrillation to be an unsolved mystery in your shop.


Terms:

Did you enjoy this article? Click here to subscribe to the magazine.