There’s never been a better time to hop aboard the water-based inks train.
By Lon Winters
Once the job is running, these inks will keep the image open unless it stops flooding, so be sure to keep the screens wet with ink. HSA inks have a tendency to move to the sides of the squeegee, so it’s important to have a person tend the screens and use winged flood bars to keep ink in the center of the screen. Refresh ink in the screen by moving it into the print area and adding new ink. One common problem is overloading the screen with ink, as it can dry out. Misting the ink with water can help, but a more effective method is using a fogging type of system that utilizes vapor rather than airborne water.
Squeegee pressure is another variable to consider. The first screen seals the garment so the pressure on that screen should be the highest. The subsequent screens need to build opacity, so use as little pressure as possible on them. Typically, double-stroke printing is necessary to clear the ink completely from the mesh openings.
We want the flood bar to hover above the screen mesh and not force it into the stencil. As the ink runs, it will be going through an evaporation process. Depending on the humidity level, this process may be fast or slow.
The combination of heat and airflow promotes water evaporation, which is the key to flashing these inks. Controlling the ink film and platen temperature is critical, however. The heat you need to properly set the ink at the flash station is totally unwanted at the press, where it can cause print performance problems including accelerated drying in the screen. Using flash time, temperature control, distance, upper limits, and all the other tools on the flash, we can achieve that delicate balance of controlling the heat and ink film temperature.
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