Rediscovering Discharge Printing...

Tony Pepitone has held technical and production-management positions in some of the country’s top apparel-decorating operations. He is currently technical director for Atlanta-based Gagwear, a full-service package apparel group.

I surf around the industry chat rooms now and then and I’ve got to tell you, it can be pretty entertaining. While there is quite a bit of useful and accurate information out there, you will also find some amusing (if not alarming) mis-information and dis-information on topics across the board.

This is certainly true when it comes to water-based inks, discharge ink systems in particular. I’ll be the first to say that, as of this writing, reliable and thorough information has been more readily available than in the past; however, putting it to use will still require research. Unfortunately, some of the individuals who post in the chat rooms on the subject are rather less than qualified to give advice. While certainly everyone has a right to his or her opinion, sometimes these opinions are based on lack of experience and misinformation. Indeed, much of the negative commentary I’ve read about water-based and discharge systems involves printers who tried it once or twice and gave up. Frustrated and bewildered, they advise others not to even try.

Bad day at the office

Like this one guy several months back. (And, like you see on late-night TV, the following is a “DRAMATIZATION. Names have been changed to protect the . . . well, “innocent” is probably as good a word as any.) So let’s call this guy Tom. . . .

Tom seemed to think he had done his homework and was ready to try discharge printing: something like 500 shirts, a multicolor design, some halftones, nothing too challenging. Almost immediately, though, his crew developed leaks in the screens that went unnoticed until the shirts exited the dryer. Mucho misprints already. Next, while they were frantically taping the screens, the ink began to dry there. After hurriedly wiping the screens they were able to resume printing . . . only to have the leaks return. After 200 misprints Tom gave up and got some beer for his frustrated and angry crew. They cursed water-base inks and hoisted their mugs to good ol’ plastisol, then came in hung-over the next morning and went back to their plastisol ways. And now, if anyone in Tom’s place even mentions discharge printing they get a written warning!

Or so he tells the story in the chat rooms to any and all who will listen, emphatically advising that this approach is a waste of time and money. And invariably, every time he does, someone else mentions that he tried printing discharge in his basement, stunk up the place (no ventilation), and finally threw the stuff in the garbage!

Simple truths

But wait a minute. . . . Discharge and water-based decorated garments are everywhere at retail. So some people must have figured it out! You shop some urban chic-fashionista stores and you’ll find more water-based garments than plastisol these days. What’s the deal?

The deal is that printing with discharge and any water-based products is (a little) more difficult than with plastisol; especially in the beginning. Let us take a minute and examine some simple truths:

  • there are no guarantees from the apparel companies of their garments’ dischargeability;
  • there are no formulas for color matching (at this writing); therefore, discharge colors must be “eyeballed” and tested;
  • screen making requires different chemistry and techniques;
  • many of the ingredients in the ink are not regulated chemicals; therefore, disposal of waste product must be addressed;
  • the inks themselves require more attention on the shop floor;
  • inks activated with ZFS (zinc formaldehyde-sulfoxilate) will take on a sulphurous odor; thus, a properly ventilated production area is necessary.

Then there is the inevitable learning curve out in that production area. Let’s face it: There’s going to be at least one or two salty employees in most plants who won’t want it to work just because its different and smells funny. Well, as with most things in life, there are answers and solutions to all of the above (even the old salts).

Simple solutions

I have to wonder about our friend Tom. Without actually being in his shop its impossible to know exactly what was going on—I only added the beer part for dramatic effect—but we can at least look at what problems he was experiencing, and offer solutions. First problem he had was related to ink leaking through his screens: a very common problem but not difficult to overcome. First, you must use an emulsion designed for printing with water-based products. Sure, some emulsions designed for plastisol can work with water-based inks, but why gamble?

Second, use this same emulsion as blockout when prepping for press and be sure to post-expose at twice the light units as normal. In addition, I apply a second taping to the underside of the screens being sure to tape as close to the design as possible. This second taping is sort of an insurance application. Be sure to be neat when applying the tape, as well. In the event that you may need to wipe the underside of the screens, any folds and wrinkles will trap very small traces of ink that may not appear (with discharge) till the garments exit the dryer.

While trying to solve this problem on the press, another quickly arose for Tom. The inks began to dry in the screens. Yes, you can re-wet the mesh with a damp rag; however, dried water-based inks can freeze up the image if left unattended too long. The trick is not to let it happen in the first place. Most of the new water-based products are engineered to resist this tendency; however, it certainly will happen if you invite it.

Ask for as many samples of ink as possible. While most brands of plastisol contain the same chemical foundation as one another, this not necessarily so with water-based products. I stay away from the thin, runny products, and stick with brands that have more body to them (you can always thin with water if necessary); these will evaporate more slowly.

Always leave the screens flooded with 1/64˝ clearance between the floodbar and the mesh. This will result in an optimum ink film over the open mesh area. It’s worth repeating that fans should not be directed at screens or press, as they will accelerate evaporation. (The best way to diffuse any odors—if that’s your aim—is to keep the fans at the back of the dryer.) Yes, you may mist water over the screens; however, I have found this step unnecessary. With practice you can leave the screens unattended for 30 minutes or so. Afterward, throw a few test-print shirts on the press, switch the print mode to double stroke, the inks will clear just fine and you can resume printing.

Color theory

What about those other issues, such as color formulation? Well, there is at least one major ink company working on color formulation as I write. Meanwhile, you can formulate old-school style. One hint: I use a particular ink company’s PC formulas for plastisol as a guideline for my discharge color formulation. This company modeled its water-based PCs after the plastisols and, thus, the hue properties are very close. This definitely works for strong bright colors. Off shades may take a little longer till you get used to the strength and properties of the pigments. I save all formulas on a spreadsheet as well as print them out and keep a hard file with a color swatch attached. Also remember that the percentage of activator (ZFS) can affect the cured color. Deep hues generally require two to four percent activator while bright shades will require six to eight percent.

And remember that some dyestuffs discharge better than others. I carry a few “opaque-discharge” colors that contain up to 50 percent discharge-white ink mixed with 50 percent base, and then maximize their pigment load (usually eight percent). This works great for colors such as lemon yellow on garments that do not discharge 100 percent. The finished print may have a slightly stiffer hand but, after the first wash, that will diminish.

Getting the goods

While we’ve not seen formal claims about the dischageability of dye stuffs from the apparel companies I would not be surprised if this will soon change. It’s a fact they cannot ignore as the decorating industry heads in the discharge direction. I’ve heard rumors about RFD (ready-for-discharge) clothing lines and talked to many blank manufacturers who have admitted that discharge compatibility is a hot topic for them. More and more reactive-dyed products are discharging consistently these days; particularly on finer-gauge fabrics. Suffice it to say sourcing dischargeable garments is not the huge issue it once was.

As for the ink itself, remember that pigmented base may keep indefinitely (in the summer its best to cool-store) but activated color has a shelf life that depends on the pigment(s) used and the amount of activator. Its best to be conservative with the batch amount when activating—that is, less is better. It only takes 60 seconds to activate fresh ink and, when it comes to the end of the run, you’ll want as little leftover product as possible.

Which brings us to the issue of disposal of leftover product. Since ZFS and other components are not regulated by any agency known to me, the best way to handle this is to have the ink tested by a local hazardous waste company and let them suggest proper handling. Some companies stockpile the ink in a drum and have it hauled away every few months (this should only cost a few dollars a day). Other big users install sophisticated water filtration systems which, in theory, eventually pay for themselves. It should also be noted that at least one manufacturer offers a non-ZFS activator that does not exhibit the sulphurous odor.

Speaking of odors and other unpleasant aspects . . . I’ve often been asked whether to charge more for discharge printing. Interesting question. Print speed is the same or faster since there is no flash (which also saves electricity). The ink costs are generally comparable assuming the waste ink is controlled. That said, I still try to add 25 cents or so per print, just to account for the learning curve. Also consider the perceived added value. Customers request apparel decorated with water-based ink because they prefer it. What reason, then, to give away the added value?

Hybrid inks

A lot of head scratching with hybrid ink products—that seek to combine the best of plastisol and discharge worlds—as well. Essentially multi-part systems, these were engineered for those printers unwilling to set up a whole new water-base system. They start with a finished plastisol color. The second additive is an aqueous liquid which “waters down” the plastisol enough so that it can absorb the activator (typically ZFS). Typically the ratio of finished color to liquid additive is 50/50 by weight. Again, up to eight percent activator may be now added to this slurry. Once activated this ink will take on the same shelf life as any pure discharge ink.

Benefits? Well, there are no worries about added carrying costs and space to set up a water-base color kitchen. Disadvantages? Since the finished color is diluted by 50 percent it is difficult to obtain bright and vibrant colors on dark grounds, and there is still the waste-product issue. And don’t forget to prepare the screens as you would for water-based printing!

Some savvy printers have taken white plastisol and converted it using the above steps, then used it as an underbase for high-mesh plastisol overlay colors. You’ll need to test your white inks as some of them contain too much filler and will not work. When it does work, the results are pretty impressive. Understand that transparent overlay colors don’t do very well, so I prefer full-strength plastisol overlays that are not “based back.” Be careful when flashing! Large areas of the hybrid underlay ink can begin to steam and you may have adhesion problems.

And one last item: Always, always, always check your cure after exiting the dryer. All of these processes will require adjustments for final cure, and all ovens cure at different rates.

New H20

We’ve run out of space this time, but stay tuned for another installment featuring some recent water-based innovations on which I’ve been doing a bit of R&D—such as burnout chemistry, wicking, staining and pre-dye treatments that are quite unique and are only just starting to sizzle at retail. Thanks for reading and don’t forget to stay active in those chat rooms. There’s a wealth of free information there . . . just remember to keep an open mind!

—tp