Screen Printing: Production

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July 23, 2019

If you’ve bought into water-based ink’s hand-feel, longevity and sustainability advantages, then you’ve probably also heard about the challenges of transitioning from a plastisol to water-based ink system. While there’s a lot of trial and error inherent in the learning process, you’ll learn some tips here for printing success with water-based ink.

If you’ve ever wanted to try printing with water-based inks, a kit is a good starting point. Every screen printer has different equipment and preferences, and each kit will expose you to different products. As a rule, any kit will work if you use it correctly.

If you’ve tried a kit and it didn’t work, there are two possible (and pretty obvious) reasons. First, you may not have used it correctly. It’s easy to default to plastisol-printing techniques, or skip steps or instructions, when using water-based ink, especially if you’re an experienced printer. Because of factors involved, it’s important to approach this as a student, not a master.

Another reason your kit may not have worked is that you may have used a bad kit. This is common, as vendors will get samples or kits that sit on their shelves for quite some time, possibly drying out. The pigments harden and separate from their encapsulation. To determine whether this happened to your kit, feel the bottom of the bottle. If it’s hard or feels like a hockey puck, it should be replaced.

Regardless of the reason, keep trying. Printing with water-based inks is a journey of trial and error; if you can’t welcome the challenge, it may not be ideal for you.

However, if you’re still interested, here are some things to know before you get started:

The Screen: Make sure your dual-cure emulsion is fully exposed before use. Using a single-cure photopolymer emulsion isn’t recommended, although it can work with a hardener. Still, this is not advised if you’re a novice water-based ink printer.

Choose an emulsion with a decent diazo additive, and don’t allow too many bubbles when activating it. This gives it a shelf life, so be sure to understand how much time is needed to let it set and how long it will last. Quart samples are easy to get from your vendors for free; just reach out to them and ask directly.

Once the cure is good, it’s ready to be set up on the press. You don’t need a high emulsion over mesh (EOM), but you should coat 2×2 with the scoop coater’s round edge, as dual-cure emulsions are not as thick as single-cure ones.

The Method: Double strokes help tremendously. Don’t use slow strokes as you would with plastisol ink; rather, use faster double strokes with medium pressure. Using one stroke is too inconsistent and adds risk.

When printing with water-based inks, flood the front of the screen, as it helps save time and keeps the mesh loaded with ink. It also is important not to let the ink dry. When testing, remember that you need the correct amount of ink for the number of shirts you’re printing.

Inks
Understand the ink system you’re using. Abide by your kit’s rules and remember that no two systems are alike. Following is an overview of different ink options.

Discharge: On the appropriate garments, this ink type performs like a dream. However, it can have a high strike-off rate if quality control isn’t in check. It’s very aggressive on emulsion and prints are hard to see before going through the dryer. Cure times must be met; otherwise, they won’t have proper evaporation, which is important with all water-based printing, but most apparent with discharge ink.

This ink type also stays in the screen well, can print a wide range of art and is used wet-on-wet with no bases. One of the easier ink systems to learn to use, beginning with discharge ink will provide a sense of accomplishment. However, it’s important to understand which products will and won’t be compatible with this ink type, as not all 100% cotton shirts are equal.

Also, screens and quality control must be in place. Don’t cut any corners, allow proper time for the activation process and ensure the correct cure times. Gray or burned-out discharge ink means longer cure time is needed.

High-Solid Acrylic (HSA): This is the most difficult ink type with which to print. It requires flashing after almost every color, especially on vector art. HSAs dry quickly in the screen if humidity is low, so there can be a higher margin for error.

At the moment, wet-on-wet printing with HSAs is impossible. New systems are being developed with their own sets of rules and complications.

If flashing after every color doesn’t sound ideal for your shop, then you should avoid this ink system. However, when used correctly, it results in phenomenal prints, a great hand and almost no dye migration.

Low-Solids: These inks are limited to use on white or light-colored garments, as they use very little white pigment in the mixtures. They have a great screen time — hours, not minutes — and can be used to print a wide range of art.

Low-solids inks leave no-hand-feel prints on garments and have no opacity, so they will not print on dark garments. Because of the lack of opacity, color matching can be difficult. However, this ink type is easy to use on the right garments.

Medium-Solids: These inks have medium opacity and can be printed directly on some dark garments. A base is required with discharge or high-solids white inks to print on navy, black or any truly dark color.

When running a job, be sure to warm platens, double-stroke and flash after every couple of colors. This system has more opacity than discharge and low-solids ink types, but not as much as HSA inks. Two colors — and as many as three, depending on the art style — typically can be printed wet-on-wet. Medium-solids inks have better screen time than HSA inks, but not as good as low-solids varieties.

Wet-on-Dry, Wet-on-Wet Systems: These inks still are being developed and can be challenging. They rely on hot pallets for wet-on-wet printing and are suited for smaller presses, so up to three colors can be printed before flashing again. These inks are harder to master because of small print-time windows. However, as these systems are perfected, they will have an industry-changing capacity.

The most important thing to remember is that none of the aforementioned inks print like plastisol. Experiment in adjusting squeegee angles, pressures and flood thicknesses with each ink or kit. Document everything so that you know what to try or avoid next time.

Another important nuance about water-based printing is the variation in effects between garment types. Different blends will yield different results; sometimes, the only way to figure out what will work is to try different garments.

For guaranteed success on your first run, get a gallon of discharge super white and some activator and search the garment manufacturer’s discharge rating. Pick the one with an “A” rating; learning to print with water-based inks on such garments will allow you to discharge anything you want.

No one has definitively mastered water-based printing, but there’s beauty in the trial-and-error method of learning how to do it. Once you’ve adopted this mindset, prepare to have fun exploring this rewarding printing process.

Nathan Foster has been in the screen-printing industry for nearly 20 years. He has worked in every aspect of screen printing, from production to sales. He is now the vice president of production at Fayetteville, Arkansas-based B-Unlimited, where he has led a transition from using plastisol to nearly all water-based ink. For more information or to comment on this article, email Nathan at nathan.foster@b-unlimited.com.