Monona Rossol on tue 6 jan 98
---------- Forwarded message ----------
> Date: Mon, 5 Jan 1998 10:47:02 EST
> From: Mark Sweany
> Subject: Re: vanadium
> Since I have been on the list, I've read a number of posts
> about using the various metals in glaze and I too would like to
> get some kind of difinitive answer as to their safe use. I know
> when we had the big deal about the lead compounds many years
> ago, the belief at that time was that their use in high fire
> glazes was safe, but at lower temperature firings, if the ware
> was used for food service, the lead could leech out of the
> glaze. Has that been proven wrong? <
Sure has.
> Does the lead leech out
> regardless of how it was fired? I'm also assuming that what
> holds true for lead is true for the other metals? Is that a bad
> assumption? Somewhere, someone has to have done a study on
> this. Can anyone help us out? <
*All* glazes fired to *all* temperatures leach *all* their ingredients into
food. It is only the rate at which glazes dissolve that define good glazes
from bad. And even a "good" glaze formula can be rendered bad if it is
fired too hot, too cold, too oxidized, too reduced, cooled too fast, not
mixed well enough, contaminated by other metals from clay bodies or fumes
from other pots, and more and more and more.
And no: there are not nearly enough studies on this for the potter. The
industrial ceramics makers have lots of data--not only on leaching, but on
dish washer performance, abrasive resistance, etc. They got this data on
their glazes by TESTING. That costs money, but if you sell stuff to people,
you owe them a safe product. And the only way to know how a glaze will
perform is to TEST.
Instead, potters get their information from:
1) small commercial glaze manufacturers who wont even tell us what is in the
glazes they sell;
2) glaze chemical distributors who don't provide MSDSs unless asked, who
rarely supply technical data such as batch and trace analyses, particle size
distribution charts, and other information which is very useful to good glaze
making;
3) text books that are old as the hills and full of misinformation or new
texts that "borrowed" technical information and glaze formulas from the same
old as the hills books; and
4) by our ceramic departments in universities who want graduate students to
write another damn paper on Bernard Leach rather than to study leaching.
We really need to get serious about this problem and about providing solid
technical education on ceramics in our art schools. Only a handful of
schools are addressing these problems at present.
There. I got that off my chest.
Monona Rossol, industrial hygienist
Arts, Crafts and Theater Safety
181 Thompson St., # 23
New York, NY 10012-2586 212/777-0062
http://www.caseweb.com/acts/
Gavin Stairs on wed 7 jan 98
At 12:06 PM 1/6/98 EST, Monona wrote:
....
>We really need to get serious about this problem and about providing solid
>technical education on ceramics in our art schools. Only a handful of
>schools are addressing these problems at present.
....
A while ago, I floated an idea about an Institute of Studio Ceramic
Technology. It seemed to me that Alfred was the ideal location, with both
esthetic and engineering ceramics in the same university. The person I
approached there did not give any evidence of interest beyond passing it on
to a colleague on the other side. I never heard from that person.
In my own, slow time, I am interested in setting myself up to do this kind
of work, but it will be painfully slow without help from the community.
Ron Roy and I batted a few ideas around at the time that a certain infamous
glaze was discussed on the list, but neither of us had the time or money to
do anything about it at the time.
What I wonder is whether there are people in the studio ceramics world who
are willing to pay for analysis services and research into glazes and other
ceramic questions. The instruments necessary for these studies are,
predictably, expensive and well used by other researchers for their own
programs. Gaining time on university lab equipment is not impossible, but
requires a significant investment in time and effort, as well as evidence
that the work is producing publications of worthy quality, as well as being
useful to a defined community.
I would be interested to hear what the list thinks about all of this.
Gavin Stairs
Suzanne Storer on wed 7 jan 98
So, Monica, what are the names and addresses of companies that will test
pottery for leaching. And what is an "acceptable" rate of leaching? And
will the information derived from testing allow a potter to conclude whether
or not their pottery is "safe" enough to sell as dinnerware?
I understand that a test must be run for each toxic substance in the pot.
Let's say a glaze is made up of colemanite, talc, dolomite, Kona f-4, neph
syn, whiting, zinc oxide, EPK and flint with additions of cobalt, copper and
iron oxide. Which ingredients should be tested for leaching? And how much
should I expect to pay per test on each of these substances?
Suzanne Storer
Monica said:
>*All* glazes fired to *all* temperatures leach *all* their ingredients into
>food. It is only the rate at which glazes dissolve that define good glazes
>from bad. And even a "good" glaze formula can be rendered bad if it is
>fired too hot, too cold, too oxidized, too reduced, cooled too fast, not
>mixed well enough, contaminated by other metals from clay bodies or fumes
>from other pots, and more and more and more.
Suzanne Storer on fri 9 jan 98
Gavin,
I am a studio ceramist and may be willing to pay for these services. Do you
envision this as being less expensive than through commercial labs?
Suzanne
>What I wonder is whether there are people in the studio ceramics world who
>are willing to pay for analysis services and research into glazes and other
>ceramic questions. The instruments necessary for these studies are,
>predictably, expensive and well used by other researchers for their own
>programs. Gaining time on university lab equipment is not impossible, but
>requires a significant investment in time and effort, as well as evidence
>that the work is producing publications of worthy quality, as well as being
>useful to a defined community.
>
>I would be interested to hear what the list thinks about all of this.
>
>
>Gavin Stairs
>
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