pdp1@EARTHLINK.NET on tue 4 jan 05
Hi Joanne,
Are you saying that the Pot which was tested, did not in
itself contain any Lead bearing materials, but that it's
Glaze had absorbed Lead from being fired in a Kiln which had
Lead contamination in it?
If so, I wonder if one could do some fireings with an
intended atmosphere for drawing out residual Lead, and then
coat the Kiln's interior with ITC? Or even line the interior
with a suitable Koawool?
Would this be able to help things?
Phil
in chilly el ve
----- Original Message -----
From: "Joanne D. Phillips"
> Had a piece of pottery sent for testing. The test came
back .10 mg/L. The
> test of done by Absorption Spectrophotometry. EPA states
that action level
> for lead is 20 ppb (.02 mg/L). So, looks like I will be
parting with the
> kiln soon as I had hoped to do funcation pottery. It's a
Cress B-23-H (no
> limit timer) with lots of kiln furniture, (and I live in
Indianapolis.) If
> interested, email joannephillipsindy@yahoo.com.
>
> Joanne Phillips
Paul Lewing on wed 5 jan 05
on 1/4/05 8:52 PM, pdp1@EARTHLINK.NET at pdp1@EARTHLINK.NET wrote:
> Are you saying that the Pot which was tested, did not in
> itself contain any Lead bearing materials, but that its
> Glaze had absorbed Lead from being fired in a Kiln which had
> Lead contamination in it?
>
>
> If so, I wonder if one could do some fireings with an
> intended atmosphere for drawing out residual Lead,
I was wondering the same thing. And I also wondered how many times the kiln
was fired since it had any lead glaze in it.
Paul Lewing, Seattle
Joanne D. Phillips on wed 5 jan 05
Are you saying that the Pot which was tested, did not in
itself contain any Lead bearing materials, but that it's
Glaze had absorbed Lead from being fired in a Kiln which had
Lead contamination in it?
********Reply******
That is correct.
The glaze did not have any lead in it, so the contamination is coming from
the kiln. The kiln bricks themselves test positive for lead with a home
lead test swab (the kind that turn pink if there is lead present.)
Joanne
Louis Katz on thu 6 jan 05
I wonder about home test kits and what could possible create false
psoitives with this test kit? If it turned out to be lead I would not
be surprised. If it turned out that it was some other substance in the
glaze it would not surprise me either.
Skeptical that I am really a skeptic
Louis
On Jan 5, 2005, at 11:49 PM, Paul Lewing wrote:
> on 1/4/05 8:52 PM, pdp1@EARTHLINK.NET at pdp1@EARTHLINK.NET wrote:
>
>> Are you saying that the Pot which was tested, did not in
>> itself contain any Lead bearing materials, but that its
>> Glaze had absorbed Lead from being fired in a Kiln which had
>> Lead contamination in it?
>>
>>
>> If so, I wonder if one could do some fireings with an
>> intended atmosphere for drawing out residual Lead,
> I was wondering the same thing. And I also wondered how many times
> the kiln
> was fired since it had any lead glaze in it.
> Paul Lewing, Seattle
>
> _______________________________________________________________________
> _______
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your subscription
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>
> Moderator of the list is Mel Jacobson who may be reached at
> melpots@pclink.com.
>
>
Louis Katz
http://www.tamucc.edu/~lkatz
Fredrick Paget on thu 6 jan 05
This is something that has been lurking out there for some time.
Since there are low fire glazes still being sold out there with lead
in them, is it a valid assumption that any second hand kiln may be
contaminated?
Before we can prove it, there are holes in the logic of the test
that was run to show the kiln was at fault. Your experiment lacks a
"control".
Has the glaze itself to be used on the test pot been tested for
lead separately? There might be accidental contamination of the glaze
before it is used.
Two pots should be made, covered with the same glaze, firing one as
a control in a clean kiln and the second in the kiln with lead. Both
should be tested at the same facility to check the facility and the
glaze.
If the pot from the contaminated kiln comes back positive from the
test and the first (the control) is clean you have made your case.
Then try firing the contaminated kiln to cone 10 with a kiln vent on
and soak for 1 hour. After it cools run the test again and let us
know if we should worry. There is a supposition that the lead will
volatilize at high temperature and since there is a finite amount in
there, it should go out the exhaust and be eliminated.
Fred
--
From Fred Paget, Marin County, California, USA
fredrick@well.com
Charter Member Potters Council
John Hesselberth on thu 6 jan 05
Hi Louis,
I think you must have missed the first part of this thread. Joanne used
the hardware store test first as a screen and then had the actual pot
lab tested specifically for lead. This is an excellent data point that
confirms what many of us have been saying for several years. Lead
glazes can contaminate a kiln and then that contamination can be
transferred to lead free glazes in subsequent firings. Many thanks to
Joanne for reporting this very valuable data.
And it makes good sense to me. The lead that has migrated to the kiln
walls and shelves will not start to move again (at least not in a
significant way) until the kiln is hot enough that the new glaze is
sealed over. Therefore it will deposit itself mainly on the surface and
not be well integrated into the new glaze.
I do believe, however, that such a kiln can eventually be
decontaminated with enough lead free firings--No data to prove that,
but it should happen. Of course we don't have any data on how long that
takes and you have the issue of lead-contaminated pots to deal with in
the meantime.
Regards,
John
On Thursday, January 6, 2005, at 08:28 AM, Louis Katz wrote:
> I wonder about home test kits and what could possible create false
> psoitives with this test kit? If it turned out to be lead I would not
> be surprised. If it turned out that it was some other substance in the
> glaze it would not surprise me either.
> Skeptical that I am really a skeptic
pdp1@EARTHLINK.NET on thu 6 jan 05
Hi John,
Certainly one could fire any number of non-potable-intended
items, such as various kind of Tiles, small Sculpture,
out-door Ornaments or Wind Chimes or Candle-Holders or
whatever, which will offer no regrets if small amounts of
Lead were to be somehow in them...in their Glaze.
It seems to me also, that with each fireing, some percentage
of ambiently available Lead should deposit itself on the
Wares...diminishing whatever content of Lead the Kiln could
imaginably hold or have. Maybe the more surface area those
Wares offer, the larger percentage of the Kiln's ambiently
volotized Lead may be obtained for there then, to be just
that much less remaining.
Or, in oxidation, to merely fire it a few times high...and
let it leave with the normal exhaust-effluvium up the
spout...
...just wondering on it...
Phil
el ve
----- Original Message -----
From: "John Hesselberth"
> Hi Louis,
>
> I think you must have missed the first part of this
thread. Joanne used
> the hardware store test first as a screen and then had the
actual pot
> lab tested specifically for lead. This is an excellent
data point that
> confirms what many of us have been saying for several
years. Lead
> glazes can contaminate a kiln and then that contamination
can be
> transferred to lead free glazes in subsequent firings.
Many thanks to
> Joanne for reporting this very valuable data.
>
> And it makes good sense to me. The lead that has migrated
to the kiln
> walls and shelves will not start to move again (at least
not in a
> significant way) until the kiln is hot enough that the new
glaze is
> sealed over. Therefore it will deposit itself mainly on
the surface and
> not be well integrated into the new glaze.
>
> I do believe, however, that such a kiln can eventually be
> decontaminated with enough lead free firings--No data to
prove that,
> but it should happen. Of course we don't have any data on
how long that
> takes and you have the issue of lead-contaminated pots to
deal with in
> the meantime.
>
> Regards,
>
> John
>
> On Thursday, January 6, 2005, at 08:28 AM, Louis Katz
wrote:
>
> > I wonder about home test kits and what could possible
create false
> > psoitives with this test kit? If it turned out to be
lead I would not
> > be surprised. If it turned out that it was some other
substance in the
> > glaze it would not surprise me either.
> > Skeptical that I am really a skeptic
>
>
____________________________________________________________
__________________
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your
subscription
> settings from http://www.ceramics.org/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached
at melpots@pclink.com.
Louis Katz on thu 6 jan 05
Thanks John,
I have been close to lurking lately. Also our servers have been up and
down over the break here. They went down right before the snow fall the
25th and then again. Nothing like getting five days of Clayart at once
to make you miss stuff. Its important to recognize that the fumes
coming off the kiln should continue to be considered lead bearing until
proven otherwise. I recently put some antennas together with lead free
solder just to avoid fumes. With all of the pipe organ stuff I have
done I am worried about lead exposure. Time to get the MD's to run my
blood for heavy metals again. I will be offline for a few days unless I
can get to a machine on my trip to Phoenix.
Louis
KE5CVK
On Jan 6, 2005, at 10:25 AM, John Hesselberth wrote:
> Hi Louis,
>
> I think you must have missed the first part of this thread. Joanne used
> the hardware store test first as a screen and then had the actual pot
> lab tested specifically for lead. This is an excellent data point that
> confirms what many of us have been saying for several years. Lead
> glazes can contaminate a kiln and then that contamination can be
> transferred to lead free glazes in subsequent firings. Many thanks to
> Joanne for reporting this very valuable data.
>
> And it makes good sense to me. The lead that has migrated to the kiln
> walls and shelves will not start to move again (at least not in a
> significant way) until the kiln is hot enough that the new glaze is
> sealed over. Therefore it will deposit itself mainly on the surface and
> not be well integrated into the new glaze.
>
> I do believe, however, that such a kiln can eventually be
> decontaminated with enough lead free firings--No data to prove that,
> but it should happen. Of course we don't have any data on how long that
> takes and you have the issue of lead-contaminated pots to deal with in
> the meantime.
>
> Regards,
>
> John
>
> On Thursday, January 6, 2005, at 08:28 AM, Louis Katz wrote:
>
>> I wonder about home test kits and what could possible create false
>> psoitives with this test kit? If it turned out to be lead I would not
>> be surprised. If it turned out that it was some other substance in the
>> glaze it would not surprise me either.
>> Skeptical that I am really a skeptic
>
> _______________________________________________________________________
> _______
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your subscription
> settings from http://www.ceramics.org/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at
> melpots@pclink.com.
>
>
Louis Katz
Flamin Pipe Organ (needs Quicktime and high speed acess):
http://www.tamucc.edu/~lkatz/cs/
Joanne D. Phillips on sat 8 jan 05
Thanks for the replies! They have given me several things to consider.
That is a good point about the control piece for the glaze that should be
tested in someone else's kiln.
I will keep you updated on my findings and decisions: keep/sell the kiln, to
more firings, firing with nepheline syenite, doing more test pieces in my
kiln and someone elses, to test the glaze itself.
If nothing else, adding to the database of this issue will hopefully help
other potters in the future.
Joanne D. Phillips
moonshadowpottery.tripod.com
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