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Wednesday, May 22, 2013

Spodumene and the Food Safe Controversy

My real job is making pottery.  Over the years now, 30 or something, I have been traveling down different clay paths.  I liked yellow ware pots, so I worked out the formulas and fit to make that type of ware and sold a lot of wholesale. Yellow ware is a historical pottery, made in England in the late 1700s and here in the USA till around 1920.  Some of us can't ever get enough history, so I also learned about red wares and since I am from New England, mostly red clay is found here... a lot, I got interested in bricks, and old red ware. 

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.

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