I have penned a few articles on the subject of discharge printing over the years; the last one about five years ago. Back then, it was still widely regarded as an unviable process, prone to result in disastrous results. Sure, there were some (primarily larger) shops printing with water-based inks but that was mostly for large volume retail. Then, very slowly, we started to see other print shops experimenting with discharge under bases and having some success.
Right around the same time, the hybrid plastisol/discharge systems came out and many were achieving successful results with these. Soon after, small- to mid-size shops started testing the waters with full color discharge and bang—almost all of them were amazed how easy it truly was. Not only were they achieving the soft hand, but many colors were more vivid, prints were crisper, halftone resolution was increased and, often, the presses ran faster. Moreover, when many ran the numbers, they found it was less expensive.
Flash forward to now; scrolling through employment sections on the industry forums, the ads for print practitioners and supervisors almost always mention that knowledge of this process is a prerequisite, or a plus at the very least.
We will touch on all of this and explore much, much more but first, let’s take a look at what happened and how we got to where we are now. Grab your coffee, shut your office door and buckle up; it’s going to be quite the ride.
A History Lesson
So how did we get here so fast? Well, several factors contributed, really. First, the larger shops, both domestic and offshore were printing discharge for retail. At first, the higher-end boutique shops were requiring it but, as always, retail trickles downward and it was showing up at outlet stores and large volume discount destinations. We all began to buy and wear apparel decorated with water-based inks. And we liked it.
Test prints are imperative when taking on the task of water-based and discharge prints. Be sure to record all different results, and make sure those results are available to the art department.
It was inevitable that customers would eventually walk into shops with a discharge shirt and exclaim “this is what we want!” Of course, that was quickly followed by the question “can you do this.” Very often, the answer was no, and that was fine for quite a while. But the pressure was on and not long after, the “guy down the street” started doing it and many lost appreciable business.
Meanwhile, while this trend was growing legs, ink manufacturers started to pay attention. More brands of ink started popping up. And, one of the biggest hang-ups for printers began to be addressed: color formulation. Five years ago, there were only companies that were working on it. Today there are at least three that have Pantone formulas.
Simultaneously, garment manufacturers were stepping up their game in two main directions. More dischargeable reactive dyes were becoming the staple. In fact, many were even beginning to rate the discharge-ability of their fabrics. The second direction was garment construction. Fine gauge ring-spun cotton began to be all the rage (and shows no signs of slowing down). Slapping a plastic, heavy print on the soft garments seemed contradictory. Soft, strong fabric simply yearns for soft decoration.
Lastly, the Internet happened to the industry. Industry forums were popping up, affording a new culture of interactive information-sharing. Many turn to the forums to both give advice and share frustrations. Solutions were bantered about. Printers began to get excited and suddenly, almost daily, there were picture posts showing off results. This stirred the pot and the subject grew wings. That’s where we are now. Discharge is no longer taboo or voodoo, just another aspect of the industry. So let’s get to the nuts and bolts of it.
Options and experiments
For those who have never tried printing with discharge inks, the first decision to make is which product to buy. Now more than ever there are many purchasing options. Most involve a base (also known as a binder) and a series of pigment concentrates—this is a PC system. There are a few ready for use (RFU) systems. Both perform equally well.
It’s primarily a personal preference—some like that RFU formulas are more forgiving, meaning you don’t have to worry if your measurements are off by .02 grams. On the other hand, the pigment concentrates are quite concentrated indeed, but some brands can flake and settle, so watch for this. The other ingredient in the mix is the activator (zincformadehydesulfoxalate, thankfully referred to as ZFS). Many like to say this “bleaches out” the dye, but the chemically correct word is displace. The ink displaces the dye, replacing it with pigment.
If an RFU seems like the right way for you, consider the following exercise. Take a small amount of each of the primary mixing colors and activate them right out of the bucket at 6 percent. Using a test screen, draw down each color on black or dark fabric. Next, try cutting them with different base-to-ink ratios starting at a 50 percent base to 50 percent color.
Continue to increase the base-to-color ratio—the colors will get lighter and brighter as you do. Print each on a test square until you have as many as you like. These will vary in strength but will be single pigmented, very clean formulas. Before you know it, you’ll have dozens of samples. Some will match the Pantone books, others may not. Find a way to categorize the samples, along with their formulas, in a binder. Of course, make at least one extra book for the art department.
This same experiment will work for a pigment concentrate (PC) system as well, but the ratios will be very different. For most PC systems, eight percent is the maximum. Start there and then cut it in half to four, then again to two.
This accomplishes several things. First, you will have a very simple set of color formulas to start with. Second, it allows you to observe the properties of each color, which will aid in developing new colors. Sure, many systems have the Pantone color formulas, but this project is very helpful.
A note on formulas—try to stay away from using white pigments or ink in discharge printing. It can dull and flatten the colors. For you artists out there, think in terms of paint: water-based inks for lights and discharge inks for darks behave much like watercolors. Many watercolor purists do not use white and rely on their transparent properties to achieve the desired hues. The same applies here.
Now that we know a few things about the ink itself, let’s talk about the application aspects. Will you need to do certain things differently? A resounding yes here. Let’s talk screen prep first. While there may be some photopolymer emulsions that resist water, I have yet to find one I trust. Most good, old-fashioned diazos work quite well. The emulsion companies have stepped up lately and almost all of them carry a discharge emulsion. Most of these work quite well and it appears most of these are diazo.
Ink manufacturers are paying attention to the discharge trend. More brands of ink are available and they address one of the biggest hang-ups for printers: color formulation.
It’s best to coat as close to the edges of the frame as your trough will permit and as close to the top as possible. If you get serious with this, you might want to buy a wider coating trough. The screen needs to be as hermetically sealed as possible, as tape can actually cause more harm than good.
We all will deny it but we all have used screens with holes in a pinch. Don’t try this with discharge; the risk of a screen leak is too great. Coat and expose in the normal manner, taking care to use leftover emulsion for blockout. Be sure to post-expose the screens after this step.
When new to the process, many are often scared silly about leaks and will apply a whole roll of tape to prevent them. But this can actually cause leaks.
The stencil needs to “breathe” water ever so slightly. The tape prevents this and the emulsion begins to get saturated, the resulting problem is that water, with traces of discharge activator, can come through to the print side, almost always in the form of a thin tape line. Compounding the problem is that this leak is often invisible until the garments exit the dryer, causing multiple misprints.
Lastly, hardeners are available for long production runs. I use them for insurance and peace of mind. Consult with your vendor or chemical supplier about these. Some can cause the screen to be difficult to reclaim.
As for production? That’s a whole other article… or series of articles. We’ll get to that. But, for now, get familiar with the products and the way they work at different ratios. Make some test prints, and stay tuned for more.