BETTER OPTIONS
Discharge Printing
Discharge printing is similar to traditional water-based ink, except that “ink” is actually formulated to remove the original dye from the garment being printed. Discharge printing involves discharging (or removing) the dye in a textile substrate and is often followed by a traditional screen-printing of color on the resulting natural (pre-dyed) color of the fabric. These printing systems only work on garments dyed with dyestuffs that are compatible with discharge systems. However, the oven time for water-based inks — including discharge — is longer than for plastisol inks, slowing production times. Typical oven conditions are one to two minutes at over 300 F. Discharge requires a heater or dryer that can evaporate all of the water in the time that it takes the textile to pass through the system. Water-based only discharge involves a lot more water to get rid of than the plastisol/water-based combination systems. Discharge inks require an activator or catalyst to function. The most popular system relies on zinc formaldehyde sulfoxylate (ZFS) as its active ingredient. The newer system uses thiourea dioxide chemistry as its active ingredient. Discharge ink has a limited pot life once the activator is added- typically one workday. Discharge ink can be “recycled” after once activated as a normal ink on light colored textiles. Waste discharge inks, like all inks in a liquid state, are considered a hazardous waste
Pros • No or lower VOCs • Non PVC method to print on dark shades • Fewer chemicals/solvents involved in clean-up • Thiourea dioxide systems have no/low formaldehyde issues
Cons • Zinc-formaldehyde-sulfoxylate (ZFS) based chemistry produces formaldehyde (a known human carcinogen) as a by-product • Can use more energy to power oven/heaters used to evaporate water • Can still have toxic ingredients and additives • Some consider it to be the worst of both worlds since the garments must be dyed first and then printed, when in some cases just printing could suffice
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