The search for sustainability pushes many screen printers to rethink their production methods and consumables choices. Read on to learn why water-based inks are a viable solution and discover how you can use the latest formulations to produce unique effects on garments.
By Ed Branigan
One reason why some turn to water-based inks is because the inks are cheaper than plastisol and are a great cost-saving device, especially when printing longer runs on light garments. They also are easy to manufacture in house. Printers can purchase the raw materials separately and easily mix them in an ink room. Manufacturing in house is another good money-saving solution, as the mixed ink does have a much shorter life than plastisol ink. The hand also is very soft, and the inks can be reduced easily with water, giving an even softer hand—although this is only possible on white shirts, where color fastness or opacity is not a critical issue.
Traditional issues with water-based inks
Opacity has always been a downside to using water-based inks. Their typically low solids content (sometimes as low at 30%) prevents successful use on colored garments, never mind black or navy. Moisture evaporates during curing, leaving a very thin ink film that’s extremely transparent. As mentioned already, this is often not an issue for white shirts, and with some creativity and imagination, the inks could be used effectively on colored garments—but darks are often ruled out. Add to this the fact that the inks themselves dry up in screens very rapidly, which makes long production runs either very frustrating or almost impossible. The addition of retarders sometimes helps, but the rapid drying on the screens remains a problem.
One way to offset the problem of printing on darks is using a discharge underbase; however, you can rule out its use as an environmentally friendly product due to a high formaldehyde content. The extremely unpleasant odor of discharge underbase also makes it very difficult to use. Many printers simply refuse to get involved with it.
However, great strides have been made in recent years in the development of discharge inks. The formaldehyde levels have been lowered, and the odor has been greatly diminished. In some newer products, the primary discharge agent, zinc formaldehyde sulphate, has been replaced by a sodium-based equivalent, but the jury is still out on its effectiveness. It is an important step though, and the hope is that with further deve-lopment and the encouraging trend towards greener products, the mometum will keep going.
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