Screen-printed water-based ink utilizes water as its solvent and sometimes contains a petroleum-based cosolvent to reduce the time needed to evaporate the ink’s vehicle. Total evaporation must occur before the remaining pigments or dyes can set at approximately 300-330 degrees F. However, rapid evaporation does not begin until the screen-printed ink reaches 212 degrees F. So, a portion of the garment’s dwell time in the dryer is spent raising the water temperature boiling point. Another part is spent holding it at the boiling point until all water/solvent has evaporated, and only the final few seconds are spent actually curing the pigments or dyes remaining on the garment.
Water-based direct-to-garment white ink can be even more challenging to dry because it is inkjet-printed over typically dark fabric, pretreated with a solution that prevents the water-laden ink from soaking into the garment. Since water sitting on top of pretreatment has less surface area than wetted fabric, DTG printed white ink takes even longer to evaporate before curing can occur.
The answer to rapid curing of all water-based coatings is to specify a conveyor dryer with separately controlled heating zones explicitly intended for this application. The first zone should be intensely hot, sending the ink temperature to a boiling point within only several inches of conveyor travel. This setup allows the second zone to hold the ink at the optimum boiling point over a correspondingly longer amount of time, reducing the total time needed for the coating to reach 300-330 degrees F. This allows for maximizing of conveyor belt speeds and output for any textile screen printed or DTG-printed with water-based products.
—Vastex International
