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monona on food safety

updated sat 15 apr 00


Earl C. Brunner on tue 11 apr 00

Fine, shut down the kilns, pack up your equipment and send it to the dump.
Clay: Al2O3-2SiO2-2H2O
pay particular attention to the AL2O3 part = ALUMINA
that's the only aluminum that I know of that is going to get out of my
pots and
into anything. Tell me where the Aluminum is going to come from?????
Because if we are talking about Alumina then we can give it up

----------------------------Original message----------------------------
Actually, aluminum is suspected to be a contributing factor in Alzheimer's
many other diseases. It is certainly not innocuous.

Earl Brunner wrote:

> ----------------------------Original message----------------------------
> Hopefully people are becoming more aware of the
> responsiblities and precautions that they need
> to have and take while working with various materials, but
> How about water and oxygen? Isn't it amazing that we live
> at all?

"Common sense is not so common"
-- Voltaire

Earl Brunner
Lois Craig Elementary

Michael on fri 14 apr 00


All this about food safe is very interesting to me. I am a potter and I
develop my own glazes. I am very interested in safety and leaching. I have
an engineering background, and am currently an organic farmer... I better
stop there lest you think I have a bit of a multiple personality disorder!

Have your tests shown trends of safe vs high leaching from various glaze
recipes? Is there any difference between oxidation and reduction firings of
the same glaze? Is high silica content a way to trap and prevent leaching?

I have been adding extra silica and zirconium and firing at higher ox
temperatures trying to make harder and more food safe glazes. I do not yet
have a lab to do the metals testing but I do so rudimentary brute force
testing just for my own info - like boiling water immersion of pieces
frozen to 0F for glaze fit, microwave oven testing at high for 10 minutes
(will blow gold rims off if there is even a tiny crack) and my acid test
using full strength muriatic acid (HCl) and some lye tests (using NaOH). I
am looking at these extreme tests just for any visible change - so they are
pretty crude.

The prospect of doing sub ppm tests of leaching is intriguing and I can
already see several hundred tests I would run on multiple samples and this
seems expensive - maybe I need to build a lab next to the pottery. There
are so many variations I can see now that I will have a new test to run
with every line blend and firing experiment.

I ask all this because I have some intuition that higher fire higher silica
glazes are going to leach less, and this is in conflict with my
environmental economies of wanting to fire lower. I am at a cross roads of
development: to pursue moving glazes to lower temperatures or to pursue
making harder and more insoluble high temp glazes.

Thank you for your contributions!