What are some considerations for choosing UV-safe bulbs, and how important are they for my screens? This was a question posed by a Printwear reader, and here is Kieth Stevens’ response:
I prefer to use Rubylith film to cover my bulbs to make sure I have prevented any possibility of light contamination. Some amber covers do not sufficiently block all the UV light that can expose the coated screens, especially if the screens are being kept in the darkroom for any length of time in preparation for future use. Even the emulsion in the container can be slowly exposed if left uncovered for extended periods.
Kieth Stevens is the Western regional sales manager for International Coatings. He has been teaching screen printing for more than 10 years and is a regular contributor to International Coatings’ blogs.
…from gloomy Southern California.
In an article that was recently featured in Screen Printing Magazine’s October/November 2016 issue, and on Screenweb.com, Kieth Stevens gives us some tips on printing on today’s modern fabrics. Here is Part 3 of the article.
Popular, profitable, and often a pain in the neck to print, the latest fashion fabrics can present quite a challenge to shops accustomed to printing standard plastisols on all-cotton garments.
Typical plastisol inks cure between 315 and 330 degrees Fahrenheit, which isn’t a problem when printing on cotton substrates. With synthetic performance fabrics, however, such temperatures might be an issue. Beyond dye migration, the garments may even shrink or become deformed. A low-cure additive will allow you to reduce the curing temperature to around 280 degrees Fahrenheit to give you some breathing room.
Always test a garment before a full production run, first to make sure an unfamiliar fabric can withstand the curing temperature, but also to ascertain that the ink is fully cured. A wash test is an ideal indicator of how well the ink is cured. Under-cured ink will wash off – if not entirely, then surely in several spots, most likely in the center of a design. In addition, the ink shouldn’t crack when the fabric is stretched. This could be a sign of under-curing, though with the newer low-cure inks for performance fabrics, it could be a sign that the curing temperature was too high.
Another type of print flaw might not be apparent to consumers until they try the garment on. Many of the newer fabrics being used today, especially for athletic wear, can’t hold up the weight of a standard print like the old cotton standbys. Some garments are so light that even a small print can make the decoration hang or drape stiffly. For these garments, use finer meshes with higher quality inks to reduce the weight of the ink deposit. This makes the design not only look better, but also feel more comfortable when worn.
Heavier garments, on the other hand, may be more prone to a defect known as fibrillation, in which yarn fibers from below the ink surface come through the ink film after washing, making the print appear fuzzy. Certain types of yarn, notably 100-percent cotton but also 100-percent acrylic and acrylic/cotton blends, are more prone to fibrillation than others. The best way to control it is to make sure the ink is fully cured and consider using a slightly coarser mesh count to deposit more ink. Using a matte-down screen after flashing the underbase will also help keep the fibers down and the surface of the print smooth.
Work uniforms present different considerations. More companies today have their logos or slogans screen-printed onto their uniforms rather than embroidered – a nice source of new business for some shops. However, uniforms must withstand an industrial washing process that is far more aggressive than what a standard consumer garment requires. Using a nylon-style catalyst when printing uniforms can dramatically improve the durability of the ink deposit, enabling it to withstand many industrial washes.
Garments with irregular or bumpy surfaces, such as zippers and hoodies, pose unique challenges when these features must be printed over. Often, printers have to improvise a solution in order to get the job done, and it may mean creating a custom platen that conforms to the irregular surface. I once made a platen out of quarter-inch aluminum to fit bobby socks so I could print designs like poodles and dice on the cuffs. Some strategically placed cardboard may also help minimize the bump caused by zippers and buttons.
Finally, fabrics designed to hold up in outdoor conditions can be problematic. Typically, printers use catalysts to help bond the ink to nylon fabrics, but many don’t know that catalysts can also help with especially difficult substrates such as certain polyester outerwear materials and the synthetics used for backpacks. Test it when you’re dealing with a problem fabric to see if it works. Another tip when you’re working with water-repellent fabrics: Try dabbing a little rubbing alcohol over the area to be printed. This may remove some of the water-repellent coating so that the ink with the catalyst can better adhere to the garment.
Test, Test, Test
Here is my motto for delivering the best possible outcome for your customer: Thoroughly test all prints and shirts before committing to costs and production methods. Never relax and assume that everything will run like the last time, even for a repeat job. A printer once told me that their customer supplied them with the same nylon jackets as a previous order, yet this time the jackets bled through the white print. What the customer did not tell them was that they had switched manufacturers, so instead of printing nylon again, the shop was dealing with a dyed polyester fabric. That turned out to be a costly mistake, as the bleeding was not discovered until several days after they had completed the job.
Everyone is looking out for themselves and you should be no different. A good customer will understand and appreciate your caution. They may even refer you to others because your service stands out.
In a recent article published by Impressions magazine, Mark Brouillard shares with us some of his knowledge regarding ink and light refraction.
Sheen is the reflection of light from a surface. The smoother the surface, the easier the light reflects, giving it a glossy-sheen look. The more angular or rough a surface is, the harder it is for light to reflect, thus giving it a dull or matte sheen.
Most ink comes in either a matte or glossy finish. You can take a glossy ink finish and add a dulling agent to make it a lower gloss or matte. However, it is difficult to make matte-finish ink look glossy without the addition of a clear gloss coat to smooth out the surface.
So, the real question is how many screens you want to use versus how many additives you want to use. If you have a matte ink and want to make it not so matte, you are going to need an extra screen to overprint clear gloss ink. If you have a gloss ink and want to make it lower sheen, most companies offer a dulling/matte additive (or a puff additive) that can be added to the ink. The dulling additive will, in effect, roughen up the surface of the ink giving it a lower light refraction and thus a lower sheen.
Typically, dulling agents are added to ink at around 5-7% by weight. What is important to note is that when making lower-sheen ink, you should write down the recipe and label the leftover ink. Also note what percentage the dulling agent was used on the job sheet in case of a re-order, or so that it doesn’t get used on another job where that effect is not desired.
Mark Brouillard is our Western Regional Product Manager and has years of experience in the industry.
International Coatings Blog | Forum for Screen Printing Tips, Ideas, Thoughts
From all of us at International Coatings!
International Coatings manufactures a complete line of Centris™ non-Phthalate screen printing inks, including a wide variety of whites, specialty inks, special effects inks,color matching systems, additives and reducers. In addition, International Coatings also manufactures a line of AXEON™ non-Phthalate, non-PVC special effects inks. For more information on our products, please visit our website at www.iccink.com.
It’s International Coating’s 60th Anniversary! Join us at ISS Long Beach 2017 and participate in our daily raffles to win an ink kit of your choice – either a color mixing system starter kit or a special effects kit for the lucky daily winner.
All California-based entries will be eligible for a Grand Prize – An Expert Print Shop Makeover. One of our print shop experts will travel to your business for an in-depth consultation on how your shop can run more smoothly and productively!
Our print shop expert will help the winning shop troubleshoot problems and suggest ways it can maximize its capabilities.
So be sure to come by Booth #2041 and enter to win!
For a FREE pass to the show, enter promo code INTERCOAT.
Here is Part 2 of an article that was recently featured in Screen Printing Magazine’s October/November 2016 issue, and on Screenweb.com, Kieth Stevens gives us some tips on printing on today’s modern fabrics:
Giving Up the Ghost
As I mentioned above, it’s always important to use the right ink for the fabric you’re printing. Using low-bleed inks when they aren’t needed is a good example of what can go wrong. If you print them on 100-percent cotton and some 50/50 fabrics, you can encounter a phenomenon known as ghosting, where an image of the print may inadvertently transfer to the back of a garment stacked on top of it. This happens because the reactive dyes used for some cotton colors can react with the low-bleed bleaching agents in the ink. The ink coming off the dryer is still hot and reactive, the moisture from the shirt may not have completely evaporated, and the stacking creates a hot, humid environment – perfect for the ink to react with the dye in the shirt stacked on top, thus creating an unwanted “ghost” image of the print. If you have a short dryer outfeed or you’re running at a fast belt speed, you may be more likely to see this problem.
Two tips: Be sure to cool each shirt completely before stacking or packing them. And instead of having just one stack of shirts at the end of the dryer, consider creating several to give the garments a chance to cool down before another goes on top.