Read this tip to make your life smarter, better, faster and wiser. LifeTips is the place to go when you need to know about OH&S and other Ceramics topics.
Toxicity in pre-fired form (liquid or dry)
Commercial glaze manufacturers label their glazes using ASTM D-4236. All their glazes are either AP Non-toxic, which means non-toxic in liquid or dry form, or CL Cautions Required, which means it has proper labeling of ingredients for health and safety. In this sense, non-toxic only refers to lead and cadmium.
All glazes sold in K-12 schools must be AP Non-toxic. This is to reduce the risk of harm if a child drinks the glaze. You don't want a lead based glaze in the classroom for example. You will see the AP Non-toxic label on the glaze bottle; a circle with an AP inside.
Remember, all glazes in DRY form are unsafe for breathing, and you should use a good mask whenever dealing with dry glazes. There are chemicals such as manganese which are known to be a health hazard when breathed in dry form, but are not believed to be a problem after being fired. And even clay particles with no toxicity get trapped inside lungs and thus are bad for potters to breathe.
Hello, my compliments for your nice website!