In order to get bright waterbased prints on dark fabrics we need to add a discharge agent to the ink. It is this agent that facilitates the ‘bleaching’ effect, allowing the inks to yield a bright print. Discharge inks use a zinc-formaldahyde formulation in order to work their magic and may exhibit a slight sulfurous odor. Although the majority of this checmical becomes a gas and is cooked off during the curing process, we still encourage customers to wash these garments before wearing.
It should be noted that some ink manufacturers offer a non-formaldahyde based discharge ink. We tried one once and everyone in the shops eyes were burning so we went back to the ZFS formulation that we knew how to deal with quickly.
Regarding the ZFS (Zinc Formaldahyde Sulfoxylate) additive, this is a fairly safe chemical when handled properly. More technical info can be found on Wikepedia.
Particularly, they detail the Risk and Safety factors involved with ZFS as the following:
- R36: Irritating to eyes
- R37: Irritating to respiratory system
- R38: Irritating to skin
- S26: In case of contact with eyes, rinse immediately with plenty of water and seek medical advice
- S36: Wear suitable protective clothing
We wear gloves and goggles when handling the activator (mixing it into ink) and then properly vent our forced air gas dryer to the outside to remove any fumes.
More Notes About ZFS
Here is some additional info about the activator, this time courtesy of an old article from Union Ink:
Environmental Concerns Regarding ZFS
The following excerpt is directly from a federal EPA letter concerning zinc formaldehyde sulfoxylate which is the discharge agent used in DSPCH-1000.
“A review of the current office of water activities reveals that there are no current regulations specifically controlling zink formaldehyde sulfoxylate (ZFS). Also according to the Office of Pesticides and Toxic Substances Hot Line, which has a computer based Federal Register (FR) data base, there have not been any FR notices/publications over the past ten years discussing, proposing, or promulgating rules for ZFS. Further, we are not aware of any situation where state or local officials have established controls for ZFS or banned the release of ZFS into water..”
As the above excerpt from the letter is dated June 11, 1991, the Toxic Substance Hot Line and Federal EPA have been asked to keep us advised of any changes in the status of ZFS and we will call them to check every few months. If anyone wants to check the accuracy of the above statement and to make sure there has been no change for themselves, the telephone numbers are:
Federal EPA- 1-202-260-7120 Toxic Substance Hot Line- 1-202-554-1404
Giving the CAS# for ZFS (24887-06-7) along with the name (ZFS) will expedite matters. Even though there are no specific laws against putting ZFS into water it should not be taken as an invitation to dump it down a drain. All chemicals should be disposed of as specified by local laws and your MSDS.
Health and Safety Concerns Regarding ZFS
According to the Material Safety Data Sheets for ZFS, qualified experts and results of actual monitoring; formaldehyde in ZFS is not set free prior to, during or after the discharge reaction. Nevertheless, as an added precaution, a scavenger has been built into all UNION discharge bases to capture any possible free formaldehyde.
Possible products of decomposition include carbon monoxide, carbon dioxide, sulfur dioxide and zinc oxides.
Govenment guidelines use the following terms for measuring relative danger of these chemicals:
- PEL – Permissible Exposure Limit
- TLV – Threshhold Limit Value
- STEL – Short Time Exposure Limit
PEL and TLV for sulphur dioxide is 2 ppm in any eight period (STEL is 5 ppm). Sulfur dioxide can cause irritation of the respiratory tract.
TLV for zinc oxide is 5 Mg/m to the third power in any eight hour period. Zinc oxides could theoretically cause metal fume fever.
Any fumes generated in a well ventilated oven should pose no problems. Adequate ventilation recommended for any shop area should be sufficient enough for a good air exchange rate. Air blowing directly on the screens should be avoided as this will cause the inks to dry in the screen.
Union DSPCH-1000 Discharge Underbase White is solvent free and made with the safest possible ingredients. However, prolonged contact could cause skin irritation in sensitive individuals especially after the ZFS is added. Additionally, dried prints contain chemicals that could irritate the skin of sensitive individuals if the garment is worn prior to washing. Prolonged contact with the ink or unwashed prints should be avoided.
Discharge and Kids?
We have yet to find any specific technical info regarding discharge agent and children. The chemical itself has a scary sounding name but is fairly harmless when used in inks since the majority of it is cooked off in the curing process. Some of the agent may remain in the print and can cause minor skin irritations in some people. Any residue will come out in the first wash, so we find many of our children’s clothing clients will have everything bulk laundered and then pressed before going to retail with it.