- Ceramic pigments, commonly referred to as stains, are blends of metal and ceramic oxides that have been fired and reground into a fine powder. Stains are sold as a solid powder or liquid. Stains can be used as an underglaze, overglaze, glaze and slip1. Stains are desired since they maintain their color before and after firing.2 Most stains work best with low firing temperatures; as temperatures increase, colors may begin to change.
- Stains are a mix of metal oxides that are ground into a powder. Many ceramic stains are proprietary, so recipes for colors are unavailable. Stain compositions vary per color and per company. Companies indicate the composition of stains with a naming system.
- Stains require extraction of nonrenewable earth metals. Stains commonly contain rare metals such as chrome, iron, cobalt, aluminum, zinc, tin, nickel, copper, manganese and more.5 Mining metals, requires a lot of energy and causes damage to wildlife and water systems.6
- Stains contain a heavy metals and hazardous materials. Stains can “leach” or pass trace amounts of toxic metals from the piece to the user if used as an eating or drinking vessel.Leaching should be tested for if ceramics are used for food purposes.7
Safe Use and Exposure
- Upon firing, stains can release carbon monoxide and hazardous metal fumes.9 When firing, use a downdraft or overhood to avoid inhalation of fumes. Skin absorbs chemicals and pigments so when mixing stains use a utensil to stir and wear gloves. Wash hands after use and before eating, drinking or smoking. 8 Always wear a respirator if working around dry stain dust.
- Do not pour any liquid stain down the drain. To dispose, pour unwanted glazes into a larger “slop bucket”. Glaze can be dried and discarded in the hazardous waste bin. If spilled, soak up with a rag and discard in hazardous material bin.3 Donate any unwanted ceramic stains to givetake.
- Avoid stains that are marked with a CA Proposition 65 or CL Caution Label, which indicate toxic contents.9
- “Ceramic Stains”, About.com, http://abt.cm/2gNreLq
- “How to Add Color to Your Ceramic Art: A Guide to Using Ceramic Colorants, Ceramic Stains, and Ceramic Oxides”, Ceramic Arts Daily, http://bit.ly/2h4pcCH
- French Green Leadless Earthenware Glaze MSDS, http://bit.ly/2gF2PCV
- Chappell, James. “Stains”, The Potter’s Complete Book of Clay and Glazes. 147-151.
- “Mining and Refining – Process”, Aluminum For Future Generations, http://bit.ly/1MBSmTZ
- Chappell, James. “Stains”, The Potter’s Complete Book of Clay and Glazes. 147.
- “Are Your Glazes Food Safe or are They Leachable?”, Digital Fire, http://bit.ly/2g1N09W
- “Hazards in Ceramics”, goshen.edu, http://bit.ly/2he74Kl
- Mason Color Cobalt Zinc Silicate Blue Phenacite MSDS, http://bit.ly/2hzWPO0