Craig Clark on mon 30 jan 06
Janie, the risks of using lead based glazes are tremendous! It is my
belief that anyone who suggests otherwise is either foolish, misinformed
or mean. Don't use lead based glazes!!!! They are toxic!!!!!! And yes,
the kiln that was used to fire lead based glazes is contaminated.
I'm not trying to sound harsh, just leaving no room for
misinterpreting what my thoughts are on lead based glazes. For the life
of me, I cannot understand why in the name of providence anyone would
want to knowingly use, or advise anyone to use, lead based glazes
anymore. The jury is no longer out on this one. We know what lead does,
and it ain't good!!
Rant Over
Craig Dunn Clark
619 East 11 1/2 St
Houston, Texas 77008
(713)861-2083
mudman@hal-pc.org
janie wrote:
>I hope this isn't a stupid question......If once you use leaded glaze in
>your kiln does it contaminate it from there on out?? What risks am I
>taking by using a lead base glaze?? Any???
>
>TIA
>
>______________________________________________________________________________
>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.
>
>
>
janie on mon 30 jan 06
I hope this isn't a stupid question......If once you use leaded glaze in
your kiln does it contaminate it from there on out?? What risks am I
taking by using a lead base glaze?? Any???
TIA
Steve Slatin on mon 30 jan 06
Janie --
Actually a very good question -- lead melts at 621 F, volatizes at about
1100 F (heat gun temperature, which is why removing lead-based paint
with a heat gun is so dangerous) , way below firing temps for most of
us. Lead vaporizes at such low temps that lead-core candle wicks
have been banned in many countries -- the heat from a single candle
flame is sufficient to volatize the lead.
Once it's volatized, it's really just a question of where it goes. Your
kiln (and kiln furniture) will have some lead residue, which will re-volatize
when next you fire. This is the reason why I find lead glaze use so
problematic -- you might be a very careful person and fire lead glazes
only in a safe process or only on non-functional ware, but who knows
what the lead will get into -- and leach out of -- the next time you fire?
Unless you intend to stick with commercially mixed glazes, all of
which are tested for lead safety, using a kiln for lead firing puts a
big safety question mark over it.
The pro-lead faction will beat up on me for this, but unless you are
willing to test everything you do AFTER you do a lead-glaze firing,
you're taking a chance with the health of your clients,
no matter how small. And even if you think this level of risk is
acceptably low, how will your clients feel?
Are you ready to put 'lead-bearing' disclaimers on everything
you make from here on? And will you take on
the danger of a liability lawsuit following any issue involving lead
after using your kiln for such a firing? Imagine a jury's thoughts
as you expound on how your lead use isn't so much and isn't
so bad while a jury watches a neurologically child twitch in its
chair ... the CDC's standards on 'acceptable' level of lead in
blood has gone from 40 mcg/dl to 10 mcg/dl.
Sorry for the rant -- Steve Slatin
janie wrote:
I hope this isn't a stupid question......If once you use leaded glaze in
your kiln does it contaminate it from there on out?? What risks am I
taking by using a lead base glaze?? Any???
Steve Slatin --
In watermelon sugar the deeds were done and done again
as my life is done in watermelon sugar.
---------------------------------
Bring words and photos together (easily) with
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Gayle Bair on tue 31 jan 06
Anyone not sure about the lead issue can do an
claart archive search with my name & the subject "lead".
e.g. see:
http://www.potters.org/subject71095.htm
Craig's answer was tactful.... my rant would not have been.
You could also contact Monona Rossel see:
http://www.artsafety.org/links.html
Also see:
http://www.nsc.org/ehc/nlic/lifall97.htm
Gayle Bair - oye .... don't get me started
Bainbridge Island, WA
Tucson, AZ
www.claybair.com
-----Original Message-----
From: Craig Clark
Janie, the risks of using lead based glazes are tremendous! It is my
belief that anyone who suggests otherwise is either foolish, misinformed
or mean. Don't use lead based glazes!!!! They are toxic!!!!!! And yes,
the kiln that was used to fire lead based glazes is contaminated.
I'm not trying to sound harsh, just leaving no room for
misinterpreting what my thoughts are on lead based glazes. For the life
of me, I cannot understand why in the name of providence anyone would
want to knowingly use, or advise anyone to use, lead based glazes
anymore. The jury is no longer out on this one. We know what lead does,
and it ain't good!!
Rant Over
Craig Dunn Clark
619 East 11 1/2 St
Houston, Texas 77008
(713)861-2083
mudman@hal-pc.org
janie wrote:
>I hope this isn't a stupid question......If once you use leaded glaze in
>your kiln does it contaminate it from there on out?? What risks am I
>taking by using a lead base glaze?? Any???
>
>TIA
>
>___________________________________________________________________________
___
>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.
>
>
>
____________________________________________________________________________
__
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.
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janie on tue 31 jan 06
Thanks guys, I'm glad I asked, am new to all this. Hate to admit it but my
husband was right.......(just hate that)
Joseph Herbert on tue 31 jan 06
Jane,
At lower temperatures a certain amount of the lead vaporizes; at higher
temperature it all vaporizes. What is worrisome is the fact that the lead
(lead oxide) condenses. There are cooler parts of the inside of your kiln
that are below the condensation temperature of the lead. The edges of the
door leading to the outside certainly will be. So, if you fire lead glazed
ware in your kiln, there will be some parts of it that will receive a
coating of lead by condensation. You will not be able to tell exactly where
and you won't know when you get in on your hands, clothes, etc.
There is a problem with arsenic in coal-fired generation stations. Arsenic
comes in with the coal at parts per million concentrations. The coal is
burned, vaporizing the arsenic. Parts of the furnace and the fly ash inside
it are cooler than the condensation temperature of the arsenic. Many of the
surfaces inside the furnace ( after millions of pounds of coal have passed
through) have quite a lot of arsenic on them. Enough to require precautions
for workers going inside to clean or do maintenance.
Lead in glazes is kind of the same. If you fire load after load of lead
glazed ware, the vapor deposition of the lead on the cool parts of the kiln
increases. How much scattered lead oxide are you comfortable with in your
environment? Be sure and tell your friends about it so they can decide for
themselves and you might want to keep you cat away from the kiln, too.
Joseph Herbert
Paul Lewing on tue 31 jan 06
I just wanted to point out that this volatilization thing doesn't happen
with china paints, even though they are lead-based. Fritted lead (which
all china paints are made with) does not begin to volatilize until a higher
temperature than that. I found that information in two very reliable
sources, and tested it myself. I got a lead test kit for surfaces that
will detect only 1-2 micrograms of lead on any surface. It detected no lead
on the inside of my kiln, nor on a tile setter that's been fired 1000 or so
times with china paint.
Of course we all know that lead is harmful, but before you conclude that a
kiln is contaminated, I suggest you test it and find out for sure. The test
kits are not expensive.
Paul Lewing, Seattle
Paul Lewing on wed 1 feb 06
on 1/31/06 10:31 PM, Ron Roy at ronroy@CA.INTER.NET wrote:
> If you have been using lead glazes I recommend you have a blood test done
> to find out how much you have in you already.
I'd be really interested to know the results if anyone has ever done this.
And if you do this, keep in mind that lead leaves the blood fairly quickly,
but it then deposits in your bones, where it stays. There is another test
that will measure how much lead you have in your bones, but the blood test
results can vary according to how recently you've been exposed.
I had my blood tested as part of my research into china paint. I had a blood
lead load of 5 micrograms per liter, after 20 years of using china paints.
The level that FDA considers hazardous is 20, although the level would be
much lower if I were a child of a woman of child-bearing age.. The average
for Americans who are not exposed to lead in work or home is 1.6.
Paul Lewing, Seattle
Ron Roy on wed 1 feb 06
Hi Janie,
Listen to Steve and Craig - they are right - don't use lead glazes unless
you have them tested - lead is a controlled substance for potters in North
America and many other countries - you have to be under the prescribed
limits of leaching.
Even if you only do functional ware once in a while or occasionally - the
lead in your kiln will contaminate even none lead bearing ware in future
firings.
Even if you do buy commercial glazes - you can still wind up with lead
leaching out of them - because lead is easily reduced - which does happen
in electric kilns - it is even more susceptible to fuming.
I'm surprised there are still lead glazes recommended for functional ware -
many suppliers simply don't sell lead compounds any more.
If you have been using lead glazes I recommend you have a blood test done
to find out how much you have in you already.
RR
>I hope this isn't a stupid question......If once you use leaded glaze in
>your kiln does it contaminate it from there on out?? What risks am I
>taking by using a lead base glaze?? Any???
>
>TIA
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Bonnie Staffel on fri 3 feb 06
When I started out in clay oh so many years ago, lead glazes were the
norm and of course I used them in my firing. I think I worked with lead
glazes for a number of years, but only took personal care by wearing a
mask when mixing glazes. I never had heard that the fumes from kiln
were also dangerous nor that the lead remained in the kiln.
No wonder I can't lose any weight, I have lead in my bones!!!
Paul Lewing wrote:
>There is another test that will measure how much lead you have in your
bones
http://webpages.charter.net/bstaffel/
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