Dori Grandstrand on wed 20 apr 05
I have a glaze recipe (C6) called Floating Red -- can anyone tell me if it is foodsafe? I wondered about the high RIO content, but a few glazes listed in The Glaze Book by Stephen Murfitt have similar high percentages of RIO (20%) and the author lists those glazes as suitable for domestic use. Here's the recipe for Floating Red:
Gerstley Bor. 55
Talc 15
Silica 30
Add: RIO 22
Thanks for your input! --- Dori Grandstrand
Cindy in SD on thu 21 apr 05
I have tested this glaze, I think. Or at least one with the same name
and similar recipe. It was really interesting with pools of red floating
(literally) on a black field. I thought it gorgeous, but didn't see it
as a suitable glaze for utilitarian vessels of any kind. I suspect that
acrylic paint with a good sealer would be more durable. Still, if you
have artistic pieces that would look good coated in lava, this might be
your glaze.
Best wishes,
Cindy in SD
James and Sherron Bowen on thu 21 apr 05
This looks like one of the recipes from the Ceramics Monthly (April-1990)
article on Cone 5 Iron Reds.
I don't have the article anymore, but I have a bowl glazed with it that has
seen daily use ( I mean that!) for ten years now that shows no change and no
damage despite heavy use with the microwave, and vegetables having been
stored in it in the fridge. Interesting glaze, but very thickness and firing
sensitive. There is a Minnesota potter whose name escapes me right now that
just nails this glaze in his work. He made my bowl and gave me the recipe
and the CM reference. There is much in the Clayart archives on this glaze.
The gurus always say the same thing. "Not food safe, not durable." I will
continue to use my bowl.
JB
John Hesselberth on thu 21 apr 05
Hi Don,
This glaze is probably not be very durable (I don't use the term food
safe because there is no agreed-on definition for it) because it has
almost no alumina and a very low level of silica. It is hardly a
glaze--more of a surface treatment. I would not use it on functional
work unless it passes a 3 day vinegar test.
Regards,
John
On Wednesday, April 20, 2005, at 05:32 PM, Dori Grandstrand wrote:
> I have a glaze recipe (C6) called Floating Red -- can anyone tell me
> if it is foodsafe?
John Hesselberth on thu 21 apr 05
On Wednesday, April 20, 2005, at 05:32 PM, Dori Grandstrand wrote:
> I have a glaze recipe (C6) called Floating Red -- can anyone tell me
> if it is foodsafe?
Ooops, sorry! It was Dori, not Don. Hadn't had my first cup of coffee
and was still a little bleary eyed.
John
David Berg on thu 21 apr 05
There are companies that will test your glaze for a fee. See the info at
John Hesselberth's website:
http://www.frogpondpottery.com/glazetest.html
David
Dori Grandstrand on fri 22 apr 05
Thanks to all who have been responding -- actually, I asked this question before I had the results of my glaze firing, but with what I saw come out of my kiln, I won't even consider using this glaze again. My initial tile/tester looked promising -- the glaze was rather smooth, with lots of iron/rust coloring, but my subsequent "full" test on a small vessel looked like something to come out of a volcano. Might be nice on 'something', but definitely not on my functional/decorative wares. thanks for responding, though! Proof of the value of testing on one or two items before you do a kiln load - and a tile tester is vastly different from finished ware ;) --- Dori Grandstrand, Sultanarts Studio
> I have tested this glaze, I think. Or at least one with the same name
> and similar recipe. It was really interesting with pools of red floating
> (literally) on a black field. I thought it gorgeous, but didn't see it
> as a suitable glaze for utilitarian vessels of any kind. I suspect that
> acrylic paint with a good sealer would be more durable. Still, if you
> have artistic pieces that would look good coated in lava, this might be
> your glaze.
>
> Best wishes,
> Cindy in SD
>
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