What do I need to know about printing on athleisure garments?
Plastisol inks are usually stretchy by nature, but adding a little bit of stretch additive can greatly improve its stretchability. This is especially true for performance and athletic fabrics, which often contain a high percentage of Lycra. Adding excessive amounts of a stretch additive, however, could reduce the opacity of the ink, so it is important to only add about one to five percent.
There are new inks on the market, such as performance inks, which have been specifically formulated for these next-generation performance fabrics. These inks have great stretchability and allow for lower curing temperatures (275 degrees F). The ability to cure at lower temperatures helps to control any potential dye migration issues.
Some of these materials and material colors may require you to print an underbase for your athletic graphics. When printing vibrant colors on black or dark garments it is often necessary to print a white underbase first. This is due to the fact that many plastisol inks do not have the opacity to cover well on dark garments. White is printed first to provide a base for the colored ink to rest on. The underbase is flash cured before the remaining colors are printed.
It's kind of like using a primer before adding the new color to your kitchen walls. The primer seals the surface which makes it nicer to paint on. Just as important as the ink itself, you also have to select the right screen.
This answer can be found in a longer blog from Texsource.