I frequently get asked if my glazes are lead free. They are, and so are the glazes used by any educated western potter. I’ll explain why.
We’ve all heard that glass is make of sand. Actually, it’s silica sand. But silica melts to form the glass at an extremely high temperature. So it’s common to add stuff to the silica to lower the temperature at which it melts. And a cheap, abundant material that will lower the temperature at which glass matures is lead. Yep, that’s lead crystal. Silica with lead added to lower the temperature.
So why am I talking about glass? Because glass and glazes in ceramics are eccentially the same thing. The difference is that glass is formulated to be fluid when molten, so it can be shaped into bottles and jars, and other shapes, while glazes are formulated to be stiff when molten so they stay on the side of the pot. So a ceramic glaze is a glass coating that is fused with the clay.
And just like the glass, the silica used in making the glass needs an additive to lower the temperature at which the glaze will melt in the kiln.
But there are many, many other materials the will work to lower the temperature of the glaze. They are mostly minerals, and have mineral names like sodium and calcium and boron.
The major danger in a lead glaze is not the person using the pottery after it’s been fired, but the potter using the leaded glaze in it’s raw state. Unlike many other minerals, lead does not flush out of the body. Lead can enter the body by breathing lead dust, orally (getting some of it on your soda can as you’re working), and even absorbed through the skin. And it will stay in the body until there is enough accumulated to cause lead poisoning. And it is because of this that you won’t find American potters using lead glaze. It’s too dangerous to the person making the pottery.
The most common danger from lead comes in lead paint. At one time in America it was required by law that paint contain lead, and children would eat the paint chips as they flaked off. And then there was the recent event where toys imported from China were painted with lead paint. But these were paints, not glazes.