A few years ago, we looked at the production chain of a printed t-shirt and separated its impact into 3 categories:
- Where the shirts were made
- What the shirts were made of
- How they were printed
- Made in the US
- Made out of a sustainable fiber
- Printed with low-impact water-based or other PVC/phthalate-free inks
Traditional PrintingThere are two main formats of screenprinting ink – plastisol and waterbased. A typical screenprinter will take a dyed shirt (which is to say, a shirt that is already a color) and print it with plastisol inks. Plastisol inks are all-around nasty. They create a surface coating on the shirt that feels like plastic (surprise!) leaving the fabric covered with an uncomfortable, rubbery print that will eventually crack and peel off the shirt. These inks also almost always contain PVC and phthalates; the former emits dioxins (a very potent environmental toxin/pollutant) during manufacture/disposal and the latter are known to cause various negative health effects. Waterbased inks, on the other hand, soak into and become part of the shirt. They are more permanent, will never crack, peel, or fade, and leave the fabric completely breathable. They also contain no PVC or phthalates. So why is most printing performed with plastisol over waterbased inks? Because in order to print a light color on a dark shirt, a surface coating must be used. Analogously, consider watercolor paint vs. latex paint. If you have a black piece of paper and try to paint a light blue watercolor paint on it, the result is less than impressive. The paint will soak into the paper, but since the paint is translucent and does not sit on top of the paper, no color is perceived. On the other hand, if you paint that piece of paper with latex paint, a paint that is opaque and will sit on the surface of the paper, the color will be bright and vibrant. But you’ll also be able to feel that surface coating, and could chip it away with your fingernail if you tried. This is essentially the same difference between waterbased and plastisol inks. So while waterbased inks feel better and are more environmentally-friendly, they don't work well on color shirts. On the other hand, plastisol is less comfortable and harsher to the environment, but easier to work with and more versatile. REHANCE is the solution to this problem.
The SolutionThe REHANCE process utilizes a specially-formulated waterbased ink that resists dye, which means we must print white shirts and then dye them a color (rather than printing on a shirt that is already a color). Using our example above, we would take white shirts, print them with the REHANCE chemistry, and then garment dye the shirts black. The printed ink will essentially ‘seal’ the area it’s printed on and prevent the color from dyeing or staining that area. As a result, a white print is visible on the shirt. However, this white print is not a surface coating – it is simply the lack of black dye. Think of it as using painters tape before painting a wall. Tape over the area you don’t want to paint, then peel the tape off afterward and voila! No color. REHANCE essentially works the same way, except there’s nothing to peel off afterward.
The SpecificsReactive dyes chemically attach to cellulosic compounds (e.g. cotton) on the molecular level by creating a covalent bond between the dye molecule and the hydroxyl groups of the cellulose molecule. On the wild off-chance that you have no idea what that means, I’ll explain in a bit more detail. When I say “hydroxyl groups,” I’m referring to a single oxygen atom bonded to a single hydrogen atom. In the diagram below of a cotton molecule, the hydroxyl groups are everywhere you see OH.
During the dye process, reactive dyes will bond to these hydroxyl groups to create a permanent color on the shirt. The chemist who developed REHANCE refers to these hydroxyl groups as “dye sites.” The REHANCE chemistry bonds to those hydroxyl groups before the dyes have a chance to. Take away the dye sites in a printed pattern, and no color will bond to the areas printed.
Even BetterSo what I’ve just described allows us to achieve a white print on a dark shirt without using a surface coating. But what if I want, say, a light blue print on a dark shirt? Never fear! The REHANCE chemistry can be printed over a waterbased ink to protect that ink from the color the shirt will eventually be dyed. So first: print ink color, second: print REHANCE over ink color. From there, it works exactly the same way as described above, except that the fabric has an ink printed on it before the REHANCE chemistry bonds to the dye sites. If you’re asking yourself “How can ink be printed in the same place as the REHANCE chemistry and they don’t conflict with each other?” then worry not, for I will make all things clear. Inks, unlike dyes, are affixed to cotton in a completely different way. Normal inks do not bind to hydroxyl groups, so there is no conflict among the inks and REHANCE chemistry for dye sites.
AdvantagesNo PVC; no phthalates; no cracking, fading, or peeling; no petroleum products; no rubbery, sticky print across your chest. Just a completely breathable, permanent, colorful print. You could even iron the shirt if you were so inclined (though why anyone would iron a t-shirt is beyond me). It’s also worth noting that REHANCE printing leaves less stuff on the shirt in general. REHANCE works by stopping stuff from being put on the shirt, whereas plastisol printing adds stuff (ink) on top of the shirt to cover up even more stuff (dye).
Not DischargeFor those familiar with textile printing, it’s important to know that REHANCE is not discharge. Discharge works by taking an already-dyed shirt and printing zinc formaldehyde sulfoxylate to blast that dye out of the shirt. Rather than our method, which prevents dye from bonding to the shirt in the first place, discharge uses harsh chemicals to eliminate the color after it’s already affixed to the cotton.
Learn MoreREHANCE is the technology that allows us to stop dye from sticking to fabric in a targeted manner. To learn more about the waterbased inks we use to print the design colors, check out this page. Read More
Here at TS Designs, we are currently working on a project with Dow Corning to test their silicone inks in automatic printing. We at TS Designs want to support anyone who is interested in developing more environmentally friendly products and we're excited to contribute to the development of a cutting-edge environmentally-friendly printing technology. We are interested in anything with an environmental story and Dow Corning came to us because they knew we would have an open mind. The silicone inks have similar properties to plastisol inks, but they are a much more environmentally friendly option because they do not contain PVCs or phthalates (both of which have harmful effects when they are washed into the water supply and become a part of the ecosystem). Dow Corning, a multinational corporation specializing in silicone-based technologies came to us because of our close proximity to their location in Greensboro, NC, as well as our environmental interests. We rented them the equipment in our facility as well a production employee so that they could test the inks in a multi print, production environment. So far, they have completed one day of trials, and we anticipate that there will be more to come in the future as they continue to develop their inks.Read More