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Understanding Discharge Inks

(September 2007) posted on Wed Sep 19, 2007

Discharge inks are experiencing a renewed interest among garment screen printers. This article describes the types of ink systems available, proper use of these formulations, and the safety precautions you should employ when working with them.


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By Mike Ukena

A lot of printers are now discovering discharge inks and printing. Those of us who have been at this for more than a few years have to chuckle just a little about this so-called discovery. Discharge textile inks have been around for a long time and have gone through cycles of popularity just like a lot of other screen-printing inks. Discharge inks are experiencing what I would have to call a renaissance.

Sales of discharge inks are greater right now than they’ve been since the early 1990s. Back then, their popularity was fueled by the use of belt printers. Belt printers required the use of waterbased inks; therefore, the only way to use a belt press to print on dark fabric was to use discharge inks. When belt printing fell out of favor, discharge seemed to follow it down rather rapidly.

But discharge inks never went away. In fact, they just got better and more versatile. In addition, the garment manufacturers have become much more supportive of discharge printing through their use of discharge-friendly dyestuffs (more on that later). Discharge inks come in a wide array of types, including some that are actually combined with plastisol, which is used as the source of the replacement color.



 

How discharge works

Discharge inks work by extracting or bleaching out the dye from the fabric being printed. Some formulations replace the dye with the pigment (color) in the ink that is printed (Figure 1). The process seems a little magical to those who have never seen it, because discharge is a steaming process that actually takes place in the dryer. The print does not look very good when the fabric/garment is removed from the print platen, but it looks great after it’s properly cured (Figure 2). Additionally, discharge prints are among the most demonstrative of a complete cure. If the appearance after curing is right, the garment is most likely fully cured.


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