Wesley C. Rolley on wed 13 jun 01
Maybe this is a start for another discussion on glaze safety.
We have an UME tree in our yard. While some call it a Japanese Plum, it is
really another species in the family that has apricots and plums. In any
case, having successfully made a tonic from the green ume and honey and
also made ume-shu (a typical Japanese drink - really a white liquor
flavored by soaking the ume) she now wants to make umebushi, a typical
Japanese pickled ume flavored with red oriental basil, and I just threw the
crock (lots of time, since this year's crop is all used up).
While I know that most American pickling crocks were salt glazed, that is
out of the question as I only have an electric. Am I correct that any good
high-silica clear that fits my stoneware body is going to be OK? The brine
is very, very salty.
Wes Rolley
Wes Rolley
"Happiness is to be fully engaged in the activity that you believe in and,
if you are very good at it, well that's a bonus." -- Henry Moore
http://www.refpub.com
Paul Lewing on wed 13 jun 01
Wesley C. Rolley wrote:
Am I correct that any good
> high-silica clear that fits my stoneware body is going to be OK?
You're on the right track here, Wes. You do want high SiO2, but you
also want high Al2O3. This will result in a very hard glaze, fairly
certain to be food-safe, especially if it's uncolored, and probably will
be a decent fit as well. But don't just go by the recipe. Make sure
you have enough of those two oxides on a molecular analysis basis. I'd
try to get more than 0.3 moles of Al2O3 and more than 3.0 moles of SiO2.
Good luck,
Paul Lewing, Seattle
John Hesselberth on wed 13 jun 01
on 6/13/01 11:19 AM, Wesley C. Rolley at wrolley@REFPUB.COM wrote:
> While I know that most American pickling crocks were salt glazed, that is
> out of the question as I only have an electric. Am I correct that any good
> high-silica clear that fits my stoneware body is going to be OK? The brine
> is very, very salty.
You are pretty close Wes. I'd add a couple things and be a little more
specific. I'd pick a glaze that had silica over 3.0 and alumina over 0.35
and make sure it really is melting thoroughly, i.e. it really is a glaze
that matures at whatever temperature you're firing at. As you say, it
should probably be clear; although I have found that adding about 6% rutile
improves acid stability every time I have tested with and without. I'm sure
you know, but I'll say it for any newcomers to glaze formulation that I'd
make sure the glaze contained only clays, feldspars, silica, whiting or
wollastonite, talc, and/or barium/lead-free frits--the same list that Ron
Roy and I published our Sept 2000 CM article.
That will give you a glaze that is about as stable as it can be. Whether or
not it would last for months of exposure to vinegar, I don't know, but I'm
betting it would. Usually if vinegar is going to do much to a glaze it does
it within a day or two.
Regards,
John
Web site: http://www.frogpondpottery.com Email: john@frogpondpottery.com
"The life so short, the craft so long to learn." Chaucer's translation of
Hippocrates, 5th cent. B.C.
Wesley C. Rolley on wed 13 jun 01
Thanks. I will start from the ^10 glossy base on the digital fire WWW
site. My body is ^10 and that has seemed to fit OK.
Otherwise going offline for a while.
Wes
At 05:13 PM 6/13/01 -0400, you wrote:
>on 6/13/01 11:19 AM, Wesley C. Rolley at wrolley@REFPUB.COM wrote:
>
>> While I know that most American pickling crocks were salt glazed, that is
>> out of the question as I only have an electric. Am I correct that any good
>> high-silica clear that fits my stoneware body is going to be OK? The brine
>> is very, very salty.
>
>You are pretty close Wes. I'd add a couple things and be a little more
>specific. I'd pick a glaze that had silica over 3.0 and alumina over 0.35
>and make sure it really is melting thoroughly, i.e. it really is a glaze
>that matures at whatever temperature you're firing at. As you say, it
>should probably be clear; although I have found that adding about 6% rutile
>improves acid stability every time I have tested with and without. I'm sure
>you know, but I'll say it for any newcomers to glaze formulation that I'd
>make sure the glaze contained only clays, feldspars, silica, whiting or
>wollastonite, talc, and/or barium/lead-free frits--the same list that Ron
>Roy and I published our Sept 2000 CM article.
>
>That will give you a glaze that is about as stable as it can be. Whether or
>not it would last for months of exposure to vinegar, I don't know, but I'm
>betting it would. Usually if vinegar is going to do much to a glaze it does
>it within a day or two.
>
>Regards,
>
>John
>Web site: http://www.frogpondpottery.com Email: john@frogpondpottery.com
>
>"The life so short, the craft so long to learn." Chaucer's translation of
>Hippocrates, 5th cent. B.C.
>
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Wes Rolley
"Happiness is to be fully engaged in the activity that you believe in and,
if you are very good at it, well that's a bonus." -- Henry Moore
http://www.refpub.com
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