of Discharge Ink (in Screen and Inkjet Printing)
By Terry Combs
This article is referring to printing white ink on dark garments.
Note: The T-Jet™ line of printers do not and will not use discharge
ink to print white on dark garments.
has been available to garment decorators for many years. As with other
technologies that come and go in our industry, discharge printing is
being tossed about yet again as a brand new concept. (My first article
on discharge ink was written back in 1993. And the process was introduced
many years earlier.) It's back again, and being touted as an all new
The first time
garment decorators see the discharge print result, they will react with
surprise and excitement. No heavy underbase, and an ultra soft-hand
print is the promise. "Great idea! Why hasn't anyone thought of
But, the excitement
and anticipation wear off quickly when the details are exposed. Details
such as the harsh chemicals involved, our employees' reactions to the
risks and the odor, and the limited availability and expense of the
actual garments required. Over the years, discharge inks have been repeatedly
destined for the lonely shelf of passing fads in our shops.
The term "discharge" refers to a chemical reaction that destroys
the ability of certain dyes to reflect a color. In simple terms, the
discharge agent in the ink breaks down or bleaches the dye out of a
specially prepared garment, leaving white, undyed fabric in the print
area. When printed, discharge inks are almost transparent on the garment,
activating only during the curing process.
Discharge ink is a water-based formulation (or a plastisol/water-based
hybrid) that includes a discharge-activating agent to make it work.
The activator used in most systems is zinc formaldehyde sulfoxylate
(ZFS). That's right, discharge ink contains a formaldehyde compound!
and curing of discharge inks, formaldehyde and sulphur dioxide develop
as by-products of the discharge process. Therefore, it is extremely
important that you properly exhaust your work area. As a safety precaution,
you should have your shop's air quality tested to be certain that any
formaldehyde levels are within permissible government limits.
To avoid liability,
garment decorators who use discharge inks will commonly label shirts,
recommending end users thoroughly wash the product before wearing. This
home washing is meant to eliminate the residual formaldehyde and discharged
dye on the fabric. The alert label on the shirt may be a deterrent to
consumers, especially when buying children's garments.
While owners and managers decide to give discharge ink a try, it is
often the production staff putting an unceremonious end to the plan.
The MSDS sheet alone, explaining the formaldehyde component in the ink,
is the first large red flag to employees. And then, the distinctive
odor of rotten eggs will accelerate the flow of employee complaints.
More often than not, coupled with the availability and limitations of
specially prepared garments, this is enough to bring a great new idea
to an inglorious end.
Not all textile dyes are dischargeable, and garments woven from blends
of natural and synthetic fibers can further complicate the matter. In
50/50 garments, each type of fiber requires the use of a different family
of dyestuffs. When attempting to use discharge ink on 50/50 shirts,
the result will not offer the dynamic, bright effects that you can achieve
on properly prepared 100% cotton garments.
If you choose
to use your standard 100% cotton garments, the best result is a return
to the original greige goods (before dying) color, which is not a true
white. Pre-dyed traditional garments are usually a shade of grey, pink
or yellow, rather than the white that most of us assume. Process ink
colors (as used in current inkjet technology) applied onto this unbleached
cotton stock will take on the color of the original pre-dyed fabric.
And the end result will vary from batch to batch, often changing from
size to size during a print run.
For best results,
you must use discharge ready 100% cotton garments. These garments have
the added step of being bleached white before being dyed to a dark color.
Most if not all dark garments that you currently buy to decorate with
screen printing or inkjet technology are NOT discharge ready. Using
discharge inks on traditional 100% cotton garments will rarely give
you an acceptable, salable finished product.
step in the dying process adds substantially to the cost, making discharge
printing more like sublimation transfer printing - a special garment
required at a much higher cost than traditional garments. And, you are
limited in your selection to the garments and colors specifically processed
and sold as discharge ready. Printing on customer garments will rarely
if ever be possible, since most consumer goods are not available with
this pre-bleaching process before being dyed.
While discharge ink is an interesting concept that comes and goes, the
drawbacks and limitations continue to make it simply a footnote upon
the garment decorating industry, both as a direct screen printing process
and as a component in the new inkjet technology.