Ah, the smell of discharge in the morning! One of my personal favorite shop aromas. What is that smell anyway? What your nostrils are cringing at is the discharge agent ZFS or zinc formaldehyde sulfoxylate. It's the active ingredient in the ink tonic that kicks off the bleaching reaction associated with this style of printing.
The discharge printing process allows us to dye fabric to a natural color to achieve a bright underbase to print on, achieving a soft hand and vibrant prints. While the name might sound a little scary, the process is regarded as relatively harmless and shouldn’t cause any discomfort or negative side effects when handled properly. Below are some tips to ensure you are using the products safely.
Ventilation is probably the most important safety precaution shops can take when printing with discharge inks. Printing with this method should only be done on a well-ventilated dryer that has a decent air exchange rate. The gasses burned off during the curing process while regarded as harmless are not something you want you or your team breathing in on a regular basis. While considered safe it’s still an irritant to skin, lungs, and eyes; and from personal experience cause some wicked headaches if your shop is not ventilated properly. Weather permitting, opening any doors or windows to help any excess gases escape is a good idea as well.
Another clever idea is using a respirator whenever handling discharge agent or mixing ink to avoid any airborne particles coming in contact with the lungs or eyes. Gloves should also be worn to avoid contact with skin.
Also, be sure to let the shirts dwell long enough in the dryer at the right temperature to keep the gassing process contained to the heat chamber of the dryer. If your shirts are coming out of the dryer with a billow of smoke, they haven’t had enough heat and/or time to properly complete the discharge process.