Using discharge as an underbase for plastisol prints is an excellent way to achieve soft, vibrant designs on dark garments. This technique allows for a lightweight, breathable print while maintaining the bold colors of plastisol inks. In this new episode of Deep Dive with Colin, we will break down how to do it correctly, the key steps to ensure wash-fast results, and some professional tips to make your prints stand out.
WHY USE DISCHARGE AS AN UNDERBASE?
Instead of printing a traditional white plastisol underbase, discharge ink removes the dye from the fabric, creating a natural canvas for plastisol colors. This method keeps the print soft and reduces the heavy plastic feel of standard plastisol layering.
A discharge underbase creates a much softer print compared to a thick plastisol base. It also allows for more vibrant colors since the plastisol sits directly on neutralized fabric rather than on a layer of ink. Another advantage is that it makes the print more breathable, which is especially beneficial for large designs on dark garments.
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CHOOSING THE RIGHT SHIRT
Discharge printing only works well on certain garments. You need 100 percent cotton shirts with a high dischargeability rating. Some blends will work, but fabrics with a high percentage of polyester or synthetic fibers will not react to discharge ink properly.
For this print, we used Allmade black 100 percent cotton shirts, which are known to discharge well. Always test your fabric before production to ensure it reacts properly to discharge ink. Even within 100 percent cotton shirts, different dye types can affect how well the discharge process works.
INK AND MIXING SETUP
For this print, we used Zodiac Aquarius Discharge Base with 5 percent activator. Most shirts will discharge well with an activator ratio between 4 and 6 percent. It is important to mix thoroughly and let it sit long enough for the activator to disperse properly into the base before use.
For the plastisol inks, we used Rio National Red, a custom-mixed blue, lemon yellow, and black with an extender base to create a smoother CMYK-like effect. Using an extender base in black ink can help achieve a softer, more natural look while maintaining detail in the design.
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Keeping water-based inks covered while working is essential to prevent premature evaporation. Discharge ink dries faster than plastisol, so monitoring its consistency throughout the print run is necessary.
PRINTING PROCESS STEP-BY-STEP
WARMING UP THE PLATENS
Discharge inks are water-based and evaporate quickly. To keep the ink flowing smoothly, preheating the platens is a good practice, especially in colder environments. Honeycomb platens, in particular, tend to cool down quickly, which can affect how well the discharge ink prints and evaporates.
PRINTING THE DISCHARGE UNDERBASE
When printing the discharge underbase, applying firm pressure helps drive the ink into the fabric rather than letting it sit on top. A light flood stroke followed by a strong print stroke ensures good coverage and penetration.
Flashing the underbase properly is one of the most critical steps in this process. The ink must be fully dry before applying plastisol on top. Any remaining moisture will create adhesion issues, leading to plastisol ink washing out after curing. The best way to check if the underbase is flashed correctly is to feel the fabric. If any part of the design still feels damp, it needs more time under the flash unit.
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PRINTING THE PLASTISOL COLORS
Once the discharge underbase is completely dry, plastisol colors can be printed in sequence. Since this print is a simulated process design, color development will look slightly different compared to printing directly onto a white or solid underbase. Some colors may appear muted at first, but they will develop fully once the print is cured.
CURING THE PRINT PROPERLY
We ran our shirts through the Aeolus Dryer at 340 to 350 degrees Fahrenheit for 1 minute and 45 seconds to ensure a full cure. Because this print contains both discharge and plastisol inks, the curing process must be treated like a water-based print.
Discharge ink needs enough time for complete evaporation and bonding. If it is under-cured, the plastisol ink on top will not adhere properly and may wash out in the first wash. The key is making sure the ink layer reaches the proper curing temperature and holds there long enough for the discharge reaction to fully complete.
FINAL THOUGHTS AND TIPS
Using a discharge underbase is an effective way to create soft, breathable prints while maintaining the vibrancy of plastisol inks. The key to success is ensuring that the underbase is fully dry before printing on top and that the entire print is properly cured.
A high-quality forced-air dryer is the best option for curing these prints, as it helps with both evaporation and final ink curing. Testing different garment types, ink mixes, and flash times will help fine-tune the process and improve consistency.
Discharge printing is a great way to elevate the quality of screen prints, especially on dark garments. With proper technique and curing, this method can produce professional, high-quality prints that stand out.