Wes Rolley on tue 5 nov 02
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I have some personal prejudices about glaze safety. Any glaze the either=20
leaches badly or otherwise discolors, changes surface, etc. when subjected=
=20
to either acid attack or the alkaline effects of detergents does not belong=
=20
on food surfaces. Any glaze that shows knife marks does not belong on a=
plate.
I also believe the there are some who take the idea that a crazed surface=20
can grow germs like a petri dish to an extreme. As "da mayuh" once said,=20
just send me all of your crazed, pin-holed Arakawa tea bowls or rough=20
textured Hal Riegger trays, I will keep the public safe.
Often it is hard to get people to take the step from acceptance of the idea=
=20
to doing the actual analysis and testing required to assure safe=20
glazes. The result of often an overkill to the other side. The recent=20
discussion of barium glazes is an example. When there is a relatively easy=
=20
method of testing for barium leaching, it seems reasonable that one should=
=20
not automatically discount using barium on functional ware. The proviso=20
here, and it is a big one, is that you know what you are doing and have=20
done the testing.
The recent political campaigns, especially here in California, demonstrate=
=20
that negativity works. Say something negative often enough and people are=
=20
read to believe almost any cockamamie conspiracy theory. So, I would like=
=20
to gather in some anecdotal evidence of the fact that lack of attention to=
=20
glaze safety has affected a potter's business negatively, either through=20
some action by a litigious zealot or just the simple fact of having to give=
=20
some one their money back or replace an item.
If you don't want to reply in public, send me something off line. The=20
purpose of this exercise is to gather anecdotes for a newsletter item for=20
our guild.
"I find I have a great lot to learn =96 or unlearn. I seem to know far too=
=20
much and this knowledge obscures the really significant facts, but I am=20
getting on." -- Charles Rennie Mackintosh
Wesley C. Rolley
17211 Quail Court
Morgan Hill, CA 95037
wrolley@charter.net
(408)778-3024
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Ron Roy on thu 7 nov 02
Two comments on this,
First of all - I think most potters don't do the testing because they
simply would not know what to do to improve a glaze and keep the same look.
Once again - our collective ignorance conspires to put another shot into
our collective foot.
I also think this is starting to change - we are - as a group - getting
smarter - inspite of the objections of those who insist on doing it the old
way. - er - I mean doing nothing - er trying to shout down anyone who says
there is a better way. Still we are making headway - and to those who are
not convinced - it's a facinating journey.
Barium has to be there only for those copper turquoise and electric blue
smooth mattes - and it has to be there in high amounts - it will always
leach from those glazes because there is so much there to start with - the
question is - how much leaches out in use and is it a problem? As I have
stated repeatedly - those glazes are going to change colour in use - so
even if there is no danger - what will your customer think when they see
that? And what will they think when they find out there is a toxicity issue
Barium is completely unecessary in a white shiny glaze for instance -
absolutly no reason to have it there. It's toxic, expensive and promots
grazing. Again - the reason is lack of understanding on the part of glaze
makers who use line blending and choose by looks alone.
Strontium is a good sub for middle temperature fluxing and works as an
anticraze, whiting is even better because it is cheaper - all we need to do
is get curious enough to understand some of the basics of our craft.
>Often it is hard to get people to take the step from acceptance of the idea
>to doing the actual analysis and testing required to assure safe
>glazes. The result of often an overkill to the other side. The recent
>discussion of barium glazes is an example. When there is a relatively easy
>method of testing for barium leaching, it seems reasonable that one should
>not automatically discount using barium on functional ware. The proviso
>here, and it is a big one, is that you know what you are doing and have
>done the testing.
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
iandol on fri 8 nov 02
Dear Ron Roy=20
You are right on the mark with your summary. I wonder how many of us =
realise the deeper implications of your conclusions.
To me it seems very clear that we know almost nothing about the =
Chemistry of Glazes and Glazing even though there are suggestions that =
the Chemistry of Glazing is being taught in institutions of higher =
education, by private teachers and at workshops.
Recent insights offered to Clayart show that there is need for some real =
analytic work, both quantitative and qualitative, to be done to find out =
what happens to the materials we mix and melt.
Best regards,
Ivor Lewis. Redhill, South Australia.
Wes Rolley on fri 8 nov 02
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At 12:05 AM 11/7/02 -0500, you wrote:
>First of all - I think most potters don't do the testing because they
>simply would not know what to do to improve a glaze and keep the same look.
>Once again - our collective ignorance conspires to put another shot into
>our collective foot.
While I agree with this, I am looking for anecdotal evidence, true=20
confessions, etc. of cases where unsafe glazes have truly cost some potter=
=20
revenue, got them into a law suit, or otherwise made their lives miserable.
So far, I have not gotten any such response. I conclude that no one wants=20
to "fess up" rather than that it never really happened.
If, as early as 1988, there were three companies in the United States=20
selling home kits to test ceramics for the presence of lead, there must be=
=20
a market for such products and a reasonable fear on the part of the public.
Wes
"I find I have a great lot to learn =96 or unlearn. I seem to know far too=
=20
much and this knowledge obscures the really significant facts, but I am=20
getting on." -- Charles Rennie Mackintosh
Wesley C. Rolley
17211 Quail Court
Morgan Hill, CA 95037
wrolley@charter.net
(408)778-3024
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iandol on sat 9 nov 02
Dear Wes Rolley,=20
Your second posting on this topic jogged my memory,
Fifteen years or so ago when I was hell bent on Salt glazing everything. =
I made a lot of Port Wine Jugs with wood spigots. I had a good clay =
which vitrified well and the coarse salt I used gave very good texture =
and colour on the surface. Sold Kilns Full.=20
Then one came back to haunt me. First thing was that the booze rotted =
the wooden spigot. Replaced that FOC, no argument. Then the Chap =
complained that the body was seeping, seeping good vintage Tokay. OK, =
give you a swap, no worries.
He turned up about two months later with another "Weeper". Asked him how =
much he had paid and gave him an immediate refund. Never done another =
salt firing since then. Lost confidence in the process. You have to have =
a well vitrified clay, a totally reliable liner glaze and absolutely =
consistent firings. Big trouble is that salt glaze is always crazed so =
there is no back up when the other two seals fail.
Changed my ceramic life. Went on to develop Soda Felspar glazes that do =
not craze.
Best regards,
Ivor Lewis.=20
Ron Roy on sun 10 nov 02
Hi Wes,
I did not respond to your original for two reasons - it might appear that I
was trying to justify my position on toxins in glazes - and my "stories" go
back a long way and involve lead - which I hope and pray - is no longer an
issue here.
In a major Canadian city there was a case of lead poisoning - from imported
ware I think - got into the press - some potters noticed a decrease in
sales right after that.
In another incident there was some international coverage of some folks in
the US who had brought back some dinnerware from Italy - they were being
poisoned by it over there - it took months for the dinnerware to catch up
with them - they noticed they were starting to feel worse when they started
using it again - the problem was lead.
For years after that - potters selling at shows were asked - continually -
any lead in your glazes.
My contention is - we are not dealing with logical people most of the time
- when the hysteria settles in it takes a long time to get rid of a reason
to not buy hand made pots. I could say - because we are not regulated - it
works against us. Any of us can do whatever we want - except for Lead and
Cadmium - and no one is checking.
It means that those who do not take responsibility for the stability of
their ware can damage the market place for all of us - including suppliers.
Frankly I'm more concerned with glazes changing colour, pots breaking in
use and leaking than the toxicity issue. I also feel the toxicity issue has
a possibility of blowing up in our collective faces.
I don't hold much hope if a certification program being put in place - but
I do think it would be wonderful if - those potters who are trying to do it
right - would get some sort of advantage in the market place. I also think
- those suppliers who are trying to do it right - should get some
advantage. Actually they are - slowly but surely.
RR
>At 12:05 AM 11/7/02 -0500, you wrote:
>>First of all - I think most potters don't do the testing because they
>>simply would not know what to do to improve a glaze and keep the same look.
>>Once again - our collective ignorance conspires to put another shot into
>>our collective foot.
>
>While I agree with this, I am looking for anecdotal evidence, true
>confessions, etc. of cases where unsafe glazes have truly cost some potter
>revenue, got them into a law suit, or otherwise made their lives miserable.
>
>So far, I have not gotten any such response. I conclude that no one wants
>to "fess up" rather than that it never really happened.
>
>If, as early as 1988, there were three companies in the United States
>selling home kits to test ceramics for the presence of lead, there must be
>a market for such products and a reasonable fear on the part of the public.
>
>Wes
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Kathy on mon 11 nov 02
Hi Ivor,
Is there such a thing as absolutely consistent
firings? I'd be glad to admit that some kilns fire
more evenly that others. Still, if a potter can tell
that some firings give better glaze and clay results
than others, then those firings are not consistent.
How many potters can claim that their glazes and clays
never surprise them?
I agree with your general idea; but aspiring to the
perfect firing, every time, seems an unattainable
solution.
You wrote:
> You have to have a well vitrified clay, a totally
> reliable liner glaze and absolutely consistent
> firings. Big trouble is that salt glaze is always
> crazed so there is no back up when the other two
> seals fail.
Yours,
Kathy
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