Jancy Jaslow on tue 2 mar 99
Although I have been potskying in clay for ---years, I have managed to avoid
much study of the chemistry, the science of the glazes & clay. The
discussions on clayart have helped answer many questions, and have (naturally)
helped inspire some.
What is truly food-safe? I blanched when I read a comment suggesting that
"well, of course, never put wood-ash glazes on a food-surface"....what am I
supposed to do with my beautiful ash glazed platters and pots...True, most of
them do appear to have the ash drip happening on the exterior, but not my
(richard aerni) platters. Hmmm?? And the (tongue-in-cheek) note that "Nobody
makes oj in a ceramic pitcher." ??? How about lemonade. Water from leaded
pipes? (or copper ones, from a recent thread of discussion).
Should all ware be labeled, Use At Your Own Risk.?
I have a raku platter,a wedding gift from gosh, 19 years ago. The
potter/clay-person/ included a note about raku process, yada yada yada, and
then in SMALL PRINT was a note that it was really not for food use. I doubt
the kind friends who purchased it for us read that far to know that their gift
was strictly decorative. We are happy to have it as a decorative, non-
functional piece, but we could have used a plate back then.
Barium: yes or no? How much ? Is this where Limits come in? Recipes include
it, some people say Replace with Strontium. That sounds a little cavalier.
If it is easily replaceable, why don't the recipes just say Strontium. And is
strontium o.k.? A few years ago I saw some remarkably radioactive looking
mugs and teapots by a regional potter. He blithely stated that he used barium
glazes, and worries about it were unfounded. But if someone uses those neon
bright pots as functional ware, will they end up glowing in the dark?
Sorry if I sound like a worry-wart. Nomenclature-wise I like Potter.
Jancy Jaslow
In Cincinnati (hoping to be in Columbus for Friday)
Jancy Jaslow on tue 2 mar 99
Although I have been potskying in clay for ---years, I have managed to avoid
much study of the chemistry, the science of the glazes & clay. The
discussions on clayart have helped answer many questions, and have (naturally)
helped inspire some.
What is truly food-safe? I blanched when I read a comment suggesting that
"well, of course, never put wood-ash glazes on a food-surface"....what am I
supposed to do with my beautiful ash glazed platters and pots...True, most of
them do appear to have the ash drip happening on the exterior, but not my
(richard aerni) platters. Hmmm?? And the (tongue-in-cheek) note that "Nobody
makes oj in a ceramic pitcher." ??? How about lemonade. Water from leaded
pipes? (or copper ones, from a recent thread of discussion).
Should all ware be labeled, Use At Your Own Risk.?
I have a raku platter,a wedding gift from gosh, 19 years ago. The
potter/clay-person/ included a note about raku process, yada yada yada, and
then in SMALL PRINT was a note that it was really not for food use. I doubt
the kind friends who purchased it for us read that far to know that their gift
was strictly decorative. We are happy to have it as a decorative, non-
functional piece, but we could have used a plate back then.
Barium: yes or no? How much ? Is this where Limits come in? Recipes include
it, some people say Replace with Strontium. That sounds a little cavalier.
If it is easily replaceable, why don't the recipes just say Strontium. And is
strontium o.k.? A few years ago I saw some remarkably radioactive looking
mugs and teapots by a regional potter. He blithely stated that he used barium
glazes, and worries about it were unfounded. But if someone uses those neon
bright pots as functional ware, will they end up glowing in the dark?
Sorry if I sound like a worry-wart. Nomenclature-wise I like Potter.
Jancy Jaslow
In Cincinnati (hoping to be in Columbus for Friday)
Tom Buck on wed 3 mar 99
Jancy J:
Let's be sensible about this business of possibly posioning
people. Your pots should NOT release an amount of metallic IONS (charged
atoms) that could end up in someone's stomach and cause health problems.
(As an aside, any potter who wishes to work with toxic susbtances is free
to do so; just don't involve anyone else).
Barium is an excellent flux for some glaze effects. Sadly Ba++ ion
is harmful to the human body. So, the question is: Does my glaze release
Ba++ ions to any food placed in the pot? There is really only one sure way
to know: have the fired pot tested by a recognized testing lab. Currently,
Dr Hale at Alfred University will perform such reliable tests for $10 (US)
per ion requested. This, BTW, is a Bargoon! of major size.
And do not for a second think that because you made the pot as a
vase, food-safety is not at issue; it is, because you have no control over
how the pot will be used by the buyer (or subsequent recipient). Last
year, an Alberta potter recounted the tragic tale of a Quebec mother who
unkowningly poisoned her young son (he died) by using a lead-glazed vase
to hold the daily supply of orange juice.
Among Clayart's list are chemically-alert potters who study glazes
and express opinions about them. And in Australia one potter Janet DeBoos,
performed a series of tests on glazes containing Barium. If I read her
conclusions correctly, she learned it is extremely difficult, perhaps
impossible, to predict whether a particular recipe, once fired, will
release Ba++ to acidic foodstuffs. Looking at the Seger Formula did not
lead to a prediction of safety.
There is no agreement on Ba++ safety among the experts. So do the
safe thing yourself. Either have your favourite Barium glazes tested by Dr
Hale, or replace the Barium Carbonate with Strontium Carbonate since Sr++
ion is handled safely by the human body. And yes SrO doesn't give the same
colours as BaO but it could safe-guard you from a lawsuit.
Til later.
Tom Buck ) tel: 905-389-2339 & snailmail: 373 East 43rd
St. Hamilton ON L8T 3E1 Canada (westend Lake Ontario, province of Ontario,
Canada).
Thonas C. Curran on thu 4 mar 99
Gurus all: I know that some schools have replaced Barium Carbonate with
Barium frits in their glaze recipes. Now that's great since it's
better not to have rat poisons around, but is there any literature on
barium frits? Things I have read about barium have usually been
fiercely pro or con and have not cleared up the question. OK, you make
a frit to render the soluble insoluble and to render harmless injurious
stuff, etc., but can't a fritted glaze still leach nasty things if
weirdly compounded? Inquiring minds want to know... cnc
Earl Brunner on fri 5 mar 99
I'm not a "Guru" but I think the primary factor in using the frits over the
raw barium carbonate is in the handling of the raw glaze. If the glaze is
still not within limits it will/may still leach. These are seperate issues.
Thonas C. Curran wrote:
> ----------------------------Original message----------------------------
> Gurus all: I know that some schools have replaced Barium Carbonate with
> Barium frits in their glaze recipes. Now that's great since it's
> better not to have rat poisons around, but is there any literature on
> barium frits? Things I have read about barium have usually been
> fiercely pro or con and have not cleared up the question. OK, you make
> a frit to render the soluble insoluble and to render harmless injurious
> stuff, etc., but can't a fritted glaze still leach nasty things if
> weirdly compounded? Inquiring minds want to know... cnc
--
Earl Brunner
mailto:bruec@anv.net
http://members.aol.com/brunnerec
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