Maridel Crawford-Brown on mon 14 sep 98
Would the following glaze recipe used with a commerical red underglaze
(leadfree) either over it or under it and fired to cone 6 be food safe? I
do not know the chemical analysis of the red undergalze only that it is
lead free.
soda feldspar 40.0
Gerstley borate 30.0
ball clay 20.0
flint 10.0?
I am concerned about how to ensure glazes are food safe and have a couple
of others I would like to post later for evaluation or comments.
Thanks
maridel
Lesley Alexander on tue 15 sep 98
Maridel, I just sent a bowl done with thick red/orange/yellow
inclusion pigments under a clear glaze, cone 10, to Alfred Analytic Lab to
be tested for cadmium. Will it leach through? I'll let you know when the
answer comes back! Lesley
Ron Roy on wed 16 sep 98
Hi Maridel,
Yes it is a food safe glaze - a bit short of silica but there are no strong
toxins present so - but if you started putting in enough problem materials
it may release some. It also has too much gerstly borate - its a variable
material and also may flocculate your glaze after a while. The first glaze
is a better version than the one you asked about - the second one is about
the same but with some of the GB replaced with frit 3134.
soda feldspar 40.0
Gerstley borate 30.0
ball clay 16.0
flint 14.0
Total 100.0
soda feldspar 36.0
Gerstley borate 14.0
Frit 3134 18.0
ball clay 18.0
flint 14.0
Total 100.0
Please let me know if you test these - I would like to know if they are
well behaved glazes - include the recipes when you report back.
>----------------------------Original message----------------------------
>Would the following glaze recipe used with a commerical red underglaze
>(leadfree) either over it or under it and fired to cone 6 be food safe? I
>do not know the chemical analysis of the red undergalze only that it is
>lead free.
>soda feldspar 40.0
>Gerstley borate 30.0
>ball clay 20.0
>flint 10.0?
>
>I am concerned about how to ensure glazes are food safe and have a couple
>of others I would like to post later for evaluation or comments.
>Thanks
>maridel
Ron Roy
93 Pegasus Trail
Scarborough, Ontario
Canada M1G 3N8
Tel: 416-439-2621
Fax: 416-438-7849
Web page: http://digitalfire.com/education/people/ronroy.htm
Carol Brody on wed 16 sep 98
let me know what they say, i'm considering testing the inclusion stains on
several cone 6 base glazes.
Bobbi Bassett on fri 18 sep 98
What are inclusion stains? Help?
Bobbi in PA
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