elizabeth l gowen on sat 20 mar 99

I like the idea of using some of the found materials and have started to dig
some nice clay deposits out of my driveway that with some added chemicals is
coming up close to one of my favorite Albany slip glazes. My dilemma is are
there things in the clay that are not food safe? Perhaps lead or arsenic
since I live near peach orchards that get sprayed. There was a development
within the state that recently had high levels of arsenic and it was built
on an old orchard. What happens to arsenic when fired if it is present? What
other chemicals should one test for and will one sample be the same as the
next unless you dig a large quantity, mix it and sample near everything from
it?
-----Original Message-----
From: Joseph Herbert
To: CLAYART@LSV.UKY.EDU
Date: Friday, March 19, 1999 4:57 PM
Subject: Glazes - test and calculate


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>Glaze Calc vs Tri-Axial Blends
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>C. A. Sanger wrote: <>recipes I used there, with some occasional need for adjustment. Now I
>wonder if I'd be better off biting the bullet and doing massive triaxial
>blends first, and just formulate my own base glazes and forget using the
>recipes I have. >>
>
>Calculation is not a total substitute for testing but allows you to aim
>your efforts. Doing calculation and testing to adjust the base glazes
>you are familiar with will certainly be more productive than the
>shotgun, try everything approach.
>
>If you wish to truly get away form the old school glazes, consider using
>local materials, clays, ash, rock dust, screened road dust, anything -
>as the major constituents of your glazes. Since the composition of
>these are not usually known, you could do as many triaxial blend tests
>as you could stand. There is a lot of Loess deposited around Kansas
>City that makes a fair glaze when mixed 50/50 with Custer Feldspar.
>(Look for vertical yellow cliffs with initials carved in them)
>
>There is also a book about using the native clays of Kansas. Published
>in the "70 s I believe - check the libraries, maybe a college geology
>library.
>
>Go for the local materials. You may find one that is your perfect glaze
>all by itself.
>
>Joseph Herbert
>Joseph.Herbert@att.net
>