Wednesday, May 22, 2013
Spodumene and the Food Safe Controversy
Potters have known for a long time about lead (a bad word). Potters use lead because it is a great flux. It lowers the melting point and flows into a soft shinny coating on a piece of low fired pottery. A glaze is basically a coating of glass, melted onto a clay vessel to hold liquids and to look nice. Glass (silica sand) melts at a higher temperature than red clay, so a flux must be added to the mix so it will melt onto the clay pot without melting the pot itself. A red clay pot fired high enough to melt the silica sand without a flux, and you would have a molted mess.
So anyway, we use wood ashes, sodium, potassium, lithium, boron, calcium, magnsium, barium, strontium, lead, zinc and iron. These minerals lower the melting point of the glaze and also have different effects.. gloss, matt, etc.
We now avoid lead.
Spodumene also crops up in glaze formulas. I have some glazes that use spodumene in the formula. Spodumene is a lithium flux. Someone I know, has brought up spodumene many times in conversations, so when we recently went back to the Connecticut Antique Machinery Museum in Kent, I saw that they had samples of many rocks from our area including Spodumene. This got me interested in learning more about the mining and uses of Spodumene in my pottery.
It seems it is a controversal subject about food safety too. Here is an interesting article I found...
History. It's always interesting and you never know what you will turn up when you start looking into things.