Eileen Streeter on thu 13 jan 00
need an assist... did try to find this info and it wasn't addressed in any
of the books i have on hand...
so... we are thinking of purchasing electric kilns that were used to fire
low temp LEAD glazes over a period of time... the issue is that functional
ware will be a good portion of our work and we are concerned that the ead now
in the bricks could contaminate future firings... especially at higher
temps.... anyone out there that could help us with this....
many thanks...
eileens
John Hesselberth on fri 14 jan 00
Eileen Streeter wrote:
>----------------------------Original message----------------------------
>need an assist... did try to find this info and it wasn't addressed in any
>of the books i have on hand...
>
>so... we are thinking of purchasing electric kilns that were used to fire
>low temp LEAD glazes over a period of time... the issue is that functional
>ware will be a good portion of our work and we are concerned that the ead now
>in the bricks could contaminate future firings... especially at higher
>temps.... anyone out there that could help us with this....
>
>many thanks...
>eileens
Hi Eileen,
You are right to be worried about this. The simplest way to test for
this problem is to buy one of the lead testing kits for sale in most
hardware and paint stores. Their primary use is to test for lead paint
in homes however they will work well on ceramic surfaces too. They cost
about $10 for 3 or 4 tests last time I checked. If you don't find any
lead on the interior surfaces of the kiln, fine. If you do then you have
a difficult decision to make. You could test fire some pots in the kiln
and test them for lead contamination. You could also try to purge the
kiln of lead by firing it empty for several firings at least a couple
cones above the temperature where you plan to use it and then retest. If
you do this, do it with LOTS of ventilation. You would have to
volatilize the lead and flush it out of the kiln with lots of air when
the kiln is near peak temperature. I have no idea how well this would
work or how long it would take. But you can test after each firing with
the lead test kits.
Personally, I'd challenge the current owner to prove to me the kilns were
lead-free before I bought them. Let him/her do the purging while you do
the testing.
Let us know how this turns out. We are always interested in real data on
this subject and their is precious little. Good luck.
John Hesselberth
Frog Pond Pottery
P.O. Box 88
Pocopson, PA 19366 USA
EMail: john@frogpondpottery.com web site: http://www.frogpondpottery.com
"It is time for potters to claim their proper field. Pottery in its pure
form relies neither on sculptural additions nor on pictorial decorations.
but on the counterpoint of form, design, colour, texture and the quality
of the material, all directed to a function." Michael Cardew in "Pioneer
Pottery"
Earl Brunner on fri 14 jan 00
My understanding is that lead from repeated firings with lead glazes does in fac
get deposited into the brick and will in fact "fume" out in later firings. Give
that you are planning to fire at higher temperatures, I believe you will compoun
the problem. It doesn't sound like a good risk to me. Sorry
Eileen Streeter wrote:
> ----------------------------Original message----------------------------
> need an assist... did try to find this info and it wasn't addressed in any
> of the books i have on hand...
>
> so... we are thinking of purchasing electric kilns that were used to fire
> low temp LEAD glazes over a period of time... the issue is that functional
> ware will be a good portion of our work and we are concerned that the ead now
> in the bricks could contaminate future firings... especially at higher
> temps.... anyone out there that could help us with this....
>
> many thanks...
> eileens
--
Earl Brunner
http://coyote.accessnv.com/bruec
mailto:bruec@anv.net
Charles G Hughes on fri 14 jan 00
I was thinking about this issue last year when a friend was shopping for a
used kiln. Since lead volatizes (at what point, I can't remember, cone
6???), any firing done at or above the volatization point of lead would be
potentially contaminated, but a firing done below that point would not, or
so it seems to me. Anyone else have a thought, or know for sure? Personally
I wouldn't want to risk it for functional ware without knowing for sure.
Charles
----- Original Message -----
From: Eileen Streeter
To:
Sent: Thursday, January 13, 2000 4:37 PM
Subject: Re: residual lead in kiln
> ----------------------------Original message----------------------------
> need an assist... did try to find this info and it wasn't addressed in
any
> of the books i have on hand...
>
> so... we are thinking of purchasing electric kilns that were used to
fire
> low temp LEAD glazes over a period of time... the issue is that
functional
> ware will be a good portion of our work and we are concerned that the ead
now
> in the bricks could contaminate future firings... especially at higher
> temps.... anyone out there that could help us with this....
>
> many thanks...
> eileens
Tuckers Pottery Supplies on fri 14 jan 00
Hi Eileens,
Several times over the years I have run into this problem.
There is no question that the lead in the bricks will end up in the ware.
I have had customers test glazed ware and unglazed ware and lead was
detected .
It follows that lead would be in the room atmosphere also.
I would suggest that you look for another kiln.
Frank Tucker
Tucker's Pottery Supplies Inc.
1-800-304-6185
At 04:37 PM 1/13/00 EST, you wrote:
>----------------------------Original message----------------------------
>need an assist... did try to find this info and it wasn't addressed in any
>of the books i have on hand...
>
>so... we are thinking of purchasing electric kilns that were used to fire
>low temp LEAD glazes over a period of time... the issue is that functional
>ware will be a good portion of our work and we are concerned that the ead now
>in the bricks could contaminate future firings... especially at higher
>temps.... anyone out there that could help us with this....
>
>many thanks...
>eileens
>
>
Tuckers Pottery Supplies
1800-304-6185
Ray Aldridge on fri 14 jan 00
I wish we had some actual data, but that's probably not forthcoming, so
I'll speculate (but please don't take my word for anything.)
The fact that lead glazes have been fired in the kilns should not
necessarily mean that the kilns are saturated with condensed lead. Most
lead glazes are matured well below the volatization point of lead oxide,
beginning approx. 1100 degrees C. according to Hamer (about Cone 02.)
But even if testing reveals some contamination of the refractories with
lead, it might not be a disaster. If the kilns are intended to fire C6
midrange clays, for example, it's difficult to see how any significant
amount of lead could be deposited on these wares, since the firing range
would be so much higher than the volatization point of lead oxide.
Again, I emphasize that this is only speculation on my part, but the
converse view, that such kilns represent a danger to users of pottery fired
in them, is equally speculative-- and I haven't heard a plausible rationale
for how this latter speculation might be a real possibility.
I don't use lead in my glazes, but lead has assumed a demonized character
in the eyes of many folks that it does not deserve. It's not technically
difficult to produce a lead glazed pot that is perfectly safe-- the
tableware industry does it all the time. Most of the pottery-related
incidents of lead poisoning in this country in the last 50 years or so have
involved imported pots fired at very low temperatures, using raw lead
glazes, or lead-based enamels, also fired at very low temps.
The idea that enough lead to be measurable might cling to the surface of a
pot fired well above lead's volatization point strikes me as highly
unlikely. I might well be wrong, but I probably won't be convinced by
anything other than hard data.
Ray
Aldridge Porcelain and Stoneware
http://www.goodpots.com
Earl Brunner on sat 15 jan 00
If the lead isn't a problem at lower temperatures, how did it get off the
surface of the pot and onto/into the bricks of the kiln in the first place?
Surely you aren't suggesting that people glazed the inside of their kilns
with lead glazes?
Charles G Hughes wrote:
> ----------------------------Original message----------------------------
> I was thinking about this issue last year when a friend was shopping for a
> used kiln. Since lead volatizes (at what point, I can't remember, cone
> 6???), any firing done at or above the volatization point of lead would be
> potentially contaminated, but a firing done below that point would not, or
> so it seems to me. Anyone else have a thought, or know for sure? Personally
> I wouldn't want to risk it for functional ware without knowing for sure.
>
> Charles
> ----- Original Message -----
> From: Eileen Streeter
> To:
> Sent: Thursday, January 13, 2000 4:37 PM
> Subject: Re: residual lead in kiln
>
> > ----------------------------Original message----------------------------
> > need an assist... did try to find this info and it wasn't addressed in
> any
> > of the books i have on hand...
> >
> > so... we are thinking of purchasing electric kilns that were used to
> fire
> > low temp LEAD glazes over a period of time... the issue is that
> functional
> > ware will be a good portion of our work and we are concerned that the ead
> now
> > in the bricks could contaminate future firings... especially at higher
> > temps.... anyone out there that could help us with this....
> >
> > many thanks...
> > eileens
--
Earl Brunner
http://coyote.accessnv.com/bruec
mailto:bruec@anv.net
John Post on sat 15 jan 00
Every time I hear about this issue of residual lead in a kiln, it makes me
wonder whether or not ITC sprayed over the top could stop the lead from
fuming off of the walls.
I have a raku kiln made from an electric kiln that was taken from the
dumpster of a local elementary school. The walls of this kiln looked like
they had seen all kinds of stuff fume off onto them. I sprayed it with
ITC and now they look brand new. The ITC is holding up very well. I
wonder if those on the list with a more scientific approach to things could
shed any light on whether or not this is a viable idea worth testing...
John Post
Sterling Heights, Michigan
rp1mrvl@moa.net
Alex Wilson on sun 16 jan 00
In a message dated 01/14/2000 3:51:20 PM Central Standard Time,
pbwriter@fwb.gulf.net writes:
<< lead has assumed a demonized character
in the eyes of many folks that it does not deserve. It's not technically
difficult to produce a lead glazed pot that is perfectly safe-- the
tableware industry does it all the time. >>
Here, here! You're quite right, but oddly enough, the floor-tile industry is
not allowed to use lead of any form in their products.
It's a queer country this (U.S.), where you're allowed to buy guns
willy-nilly, but can't buy lead-bisilicate for love nor money. An odd sense
of what is safe and what is not.
Only this Scotsmans' Humble Opinion, of course.
Alex, The Scottish Potter
Phyllis E. Tilton on sun 16 jan 00
Residual lead in the kiln was something that I never considered when I bought
a used electric kiln. I guess ignorance is bliss--and I fired the kiln many
times. I did get an Orton vent at the same time so I hope the fumes made
their exit from the house but it could have affected the ware. The lady that
owned the kiln did molded greenware firing and glazing. I have no idea about
the use of lead containing glazes and she is living elsewhere now, so I can't
ask. One of my questions: Over a period of time, would not the lead fume out
until it is not a serious factor or will it always be a problem? Another
question: Seems that I have read that there are other chemicals that will
stay in the kiln and affect some of the glaze firings. What are they?
I have a nice collection of ceramic books and have kept and reread issues of
ceramic magazines. Those and this wonderful list have certainly educated
me--and it is never ending for someone that changed careers late in life.
Thanks to all--we are blessed to have this resource!!
Phyllis
Daisypet@aol.com
Charles G Hughes on mon 17 jan 00
Only the original owner of the kiln knows to which temperatures they took it
and after firing what?? Surely glaze drips, multiple temperature firings
with multitemperature kiln shelves could have produced contamination. I
don't know...and that's why I threw in my two cents and asked for other
opinions.
----- Original Message -----
From: Earl Brunner
To:
Sent: Saturday, January 15, 2000 9:38 PM
Subject: Re: residual lead in kiln
> ----------------------------Original message----------------------------
> If the lead isn't a problem at lower temperatures, how did it get off the
> surface of the pot and onto/into the bricks of the kiln in the first
place?
> Surely you aren't suggesting that people glazed the inside of their kilns
> with lead glazes?
>
> Charles G Hughes wrote:
>
> > ----------------------------Original message----------------------------
> > I was thinking about this issue last year when a friend was shopping for
a
> > used kiln. Since lead volatizes (at what point, I can't remember, cone
> > 6???), any firing done at or above the volatization point of lead would
be
> > potentially contaminated, but a firing done below that point would not,
or
> > so it seems to me. Anyone else have a thought, or know for sure?
Personally
> > I wouldn't want to risk it for functional ware without knowing for sure.
> >
> > Charles
> > ----- Original Message -----
> > From: Eileen Streeter
> > To:
> > Sent: Thursday, January 13, 2000 4:37 PM
> > Subject: Re: residual lead in kiln
> >
> > > ----------------------------Original
message----------------------------
> > > need an assist... did try to find this info and it wasn't addressed
in
> > any
> > > of the books i have on hand...
> > >
> > > so... we are thinking of purchasing electric kilns that were used
to
> > fire
> > > low temp LEAD glazes over a period of time... the issue is that
> > functional
> > > ware will be a good portion of our work and we are concerned that the
ead
> > now
> > > in the bricks could contaminate future firings... especially at
higher
> > > temps.... anyone out there that could help us with this....
> > >
> > > many thanks...
> > > eileens
>
> --
> Earl Brunner
> http://coyote.accessnv.com/bruec
> mailto:bruec@anv.net
Paul Lewing on mon 17 jan 00
Alex Wilson wrote:
> It's a queer country this (U.S.), where you're allowed to buy guns
> willy-nilly, but can't buy lead-bisilicate for love nor money. An odd sense
> of what is safe and what is not.
Alax, I'd agree with the first and the last parts of your statement, but
not the middle part. I have no trouble buying lead bisilicate here in
Seattle.
Paul Lewing
John Hesselberth on mon 17 jan 00
Phyllis E. Tilton wrote:
> One of my questions: Over a period of time, would not the lead fume out
>until it is not a serious factor or will it always be a problem? Another
>question:
Probably, but the problem is no one knows. You have a chance to
contribute some data here. Get one of the lead testing kits from your
hardware store, test your kiln and tell us the results.
John Hesselberth
Frog Pond Pottery
P.O. Box 88
Pocopson, PA 19366 USA
EMail: john@frogpondpottery.com web site: http://www.frogpondpottery.com
"It is time for potters to claim their proper field. Pottery in its pure
form relies neither on sculptural additions nor on pictorial decorations.
but on the counterpoint of form, design, colour, texture and the quality
of the material, all directed to a function." Michael Cardew in "Pioneer
Pottery"
Ron Roy on tue 18 jan 00
My understanding of this is - the lead will be there - it starts to
volitize way before cone 6 and - when it is reduced it happens even sooner.
There is lots of reduction going on in electric kilns so my guess is there
is probably lots of lead in those kilns.
Some states have higher standards than others - and they keep bumping them up.
Chances are you will have lead condenced on the surfaces of pots - and I
don't know when it will stop - if ever. Make sure you don't try to sell em
in California unless you have them tested first.
This is not a case of what is right and wrong - or if lead is safe or not -
the law is the law and there have been reports of government purchasing
ware at sales to take back and test.
I say get a clean kiln.
RR
>----------------------------Original message----------------------------
>need an assist... did try to find this info and it wasn't addressed in any
>of the books i have on hand...
>
>so... we are thinking of purchasing electric kilns that were used to fire
>low temp LEAD glazes over a period of time... the issue is that functional
>ware will be a good portion of our work and we are concerned that the ead now
>in the bricks could contaminate future firings... especially at higher
>temps.... anyone out there that could help us with this....
>
>many thanks...
>eileens
Ron Roy
93 Pegasus Trail
Scarborough
Ontario, Canada
M1G 3N8
Evenings 416-439-2621
Fax 416-438-7849
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