Typically when printing on dark garments, achieving a soft hand and a detailed design can be a challenge. This is often attributed to the need for an underbase layer, adding an additional deposit of ink. Although there are many methods to achieve a high quality design on a black shirt, one of the most effective means of doing so is through discharge water based printing.
Discharge printing is a process where the base, after being activated, releases the dyes in the garment, eliminating the need to use an underbase print on dark textiles. The best results are achieved by printing on 100% cotton garments. Some tri-blends and 50/50 shirts can discharge, but testing these before production is highly recommended. Discharge will not work on 100% Polyester or sublimated textiles.
For the print featured in this article, I used Magna AB AW Clear Discharge Base with Magna ECO Pigments. The AB AW Discharge Clear Base is a conventional ZFS based discharge system, which gives very bright colors and an excellent feel. It is as if no ink was even printed on the shirt! Keep in mind that the use of a water resistant emulsion is also required when printing with discharge inks. Since they are waterbased, they will breakdown any emulsions that are designed for plastisol printing.
When printing with discharge, the ink needs to penetrate into the garment, which may require squeegee angle, pressure and speed adjustments. The design should be printed wet on wet, eliminating the need for flash curing. A 60 or 60/90/60 (or medium) durometer squeegee is recommended for best ink penetration results. Unlike traditional plastisol printing, and since there is no need to underbase the design, it is recommended to print your white layer last to avoid any ink pick up on the underside of the screens. Because of the viscosity of the ink, you can take advantage of a higher mesh count, allowing for better print detail. Cure temperature is recommended at 330-340 degrees for 3 minutes, so a gas dryer is the best choice for waterbase and discharge because of the airflow and larger heat chambers.
Discharge printing has many clear advantages over traditional plastisol. Although it requires some trial and error, the results are well worth the time invested, and you will be able to provide customers with dark t-shirt designs that last and feel soft.