becky schroeder on sat 5 jan 02
i've got to agree with earl on this one. (when he wrote the post about dr
laura some while ago i thought i'd never agree with him EVER). my very best
friend for some years was an african grey parrot named Vader. he met his
demise one day when he sat on my shoulder and ate my barrett which had lead
paint on it. who would have thought. only a few very tiny flakes. i still
miss him terribly. now i just have dogs and as we all know they can eat
anything (use your imagination) and still survive.
becky schroeder
>Sorry Marsha, I think your advice is a little irresponsible. Any glaze
>that has lead in it is obviously using it as a material in the glaze for
>a reason.
_________________________________________________________________
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Marsh Pottery on sat 5 jan 02
Hi Liz,
Please don't freak out over lead in the glaze - It is ONLY a problem if it
is put on LOW fired dinnerware and then used for acidic foods like tomatoes,
citrus, vinegar, or potatoes..
It's a bit dangerous to work with because you can absorb it thru your
skin, so wear gloves. But the infinitesimal amounts you might get are
nothing. It takes large amounts and prolonged exposure to cause harm.
Your kiln is NOT contaminated - If you fired to ^6 or higher, the lead is
locked in chemically & won't leach out even with acidic foods.
If it really bothers you alot, turn those pieces in plant containers and
trays.. Then use it strictly as an outside glaze on flower pots & garden
decorations.
Marsha Koenig
----- Original Message -----
From: "Liz Gowen"
To:
Sent: Saturday, January 05, 2002 1:34 PM
Subject: Labeling leaded dry glaze mixes
After reading all the info on clayart regarding safe glazes I
decided to buy a liner glaze until I could make one to my liking for
pottery used for food. I had purchased 5 lb.of a translucent cone 6
glaze several years ago, I assume, from looking at a sample of
something glazed in a show room and decided to use some this year.
Looks great smooth on porcelain. Went back to make sure it was still
available and found out it was a LEADED glaze. This was pointed out
by the owner of my supply place. I am freaked to say the least.
Yes it is marked in the catalogue as leaded but I didn't order
it from the catalogue. I don't remember what I have used it on
though since the bag is pretty full and I only tried it a few months
ago I hope not too much. The few in my kitchen I have pulled from
the shelves. Have I now screwed up and contaminated my kiln for
other work? Where do I get rid of the rest of this glaze. How do I
remember what else I used it on!
I really think putting translucent 533 on a bag of leaded glaze
is not enough! For glazes with cadmium and lead I feel it should be
clearly marked on the bag contains lead. Perhaps this is my medical
background coming through but my memory just can't keep all these
numbers on its hard drive (Think I need another memory chip) but
seriously I don't think asking for better labeling or even a sticker
that says contains lead. is too much.
Frazzled
Liz Gowen NJ USA
____________________________________________________________________________
__
Send postings to clayart@lsv.ceramics.org
You may look at the archives for the list or change your subscription
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Earl Brunner on sat 5 jan 02
Sorry Marsha, I think your advice is a little irresponsible. Any glaze
that has lead in it is obviously using it as a material in the glaze for
a reason. Where did you get the idea that ONLY low fired lead was a
risk? Lead is one of the most serious environmental concerns of our
times. Just because we quit putting it in gasoline (and from there into
our air) doesn't mean the problem has gone away. You cannot assume that
this is the only source of lead one might or has been exposed to and you
cannot assume that the maker of a pot can control how or with what it
may be used. And how on earth would you know with such authority if the
kiln was contaminated or not?
Earl Brunner
mailto:bruec@anv.net
http://coyote.accessnv.com/bruec
-----Original Message-----
From: Ceramic Arts Discussion List [mailto:CLAYART@LSV.CERAMICS.ORG] On
Behalf Of Marsh Pottery
Sent: Saturday, January 05, 2002 11:33 AM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Re: Lead scare
Hi Liz,
Please don't freak out over lead in the glaze - It is ONLY a problem
if it
is put on LOW fired dinnerware and then used for acidic foods like
tomatoes,
citrus, vinegar, or potatoes..
It's a bit dangerous to work with because you can absorb it thru your
skin, so wear gloves. But the infinitesimal amounts you might get are
nothing. It takes large amounts and prolonged exposure to cause harm.
Your kiln is NOT contaminated - If you fired to ^6 or higher, the lead
is
locked in chemically & won't leach out even with acidic foods.
If it really bothers you alot, turn those pieces in plant containers
and
trays.. Then use it strictly as an outside glaze on flower pots &
garden
decorations.
Marsha Koenig
----- Original Message -----
From: "Liz Gowen"
To:
Sent: Saturday, January 05, 2002 1:34 PM
Subject: Labeling leaded dry glaze mixes
After reading all the info on clayart regarding safe glazes I
decided to buy a liner glaze until I could make one to my liking for
pottery used for food. I had purchased 5 lb.of a translucent cone 6
glaze several years ago, I assume, from looking at a sample of
something glazed in a show room and decided to use some this year.
Looks great smooth on porcelain. Went back to make sure it was still
available and found out it was a LEADED glaze. This was pointed out
by the owner of my supply place. I am freaked to say the least.
Yes it is marked in the catalogue as leaded but I didn't order
it from the catalogue. I don't remember what I have used it on
though since the bag is pretty full and I only tried it a few months
ago I hope not too much. The few in my kitchen I have pulled from
the shelves. Have I now screwed up and contaminated my kiln for
other work? Where do I get rid of the rest of this glaze. How do I
remember what else I used it on!
I really think putting translucent 533 on a bag of leaded glaze
is not enough! For glazes with cadmium and lead I feel it should be
clearly marked on the bag contains lead. Perhaps this is my medical
background coming through but my memory just can't keep all these
numbers on its hard drive (Think I need another memory chip) but
seriously I don't think asking for better labeling or even a sticker
that says contains lead. is too much.
Frazzled
Liz Gowen NJ USA
________________________________________________________________________
____
__
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.
william schran on sun 6 jan 02
Marsha - I hate to disagree, but lead becomes volatile at cone 6, can
gas out of the glaze and become part of the kiln interior. This can
then contaminate other glazes in subsequent firings. You are right
about handling lead or materials containing lead - that may be the
best reason to avoid it all together.
Bill
F.Chapman Baudelot on mon 7 jan 02
Birds are very sensitive where lead and other toxic materials are=20
concerned: One of my beautiful parrots died about 20 years ago from=20
pecking at an unpeeled apple in the fruit bowl (pesticides), and canaries=20
were used in both coal mines and Spanish folk potteries. If anything were=20
amiss, the canary was the first to die. I wonder how many wild birds are=20
now being unwittingly poisoned by the use of herbicides, chemical=20
fertilizers, pesticides etc.
Fran=E7oise in Spain.
(I have updated my website)
Becky wrote:
>i've got to agree with earl on this one. (when he wrote the post about dr
>laura some while ago i thought i'd never agree with him EVER). my very=
best
>friend for some years was an african grey parrot named Vader. he met his
>demise one day when he sat on my shoulder and ate my barrett which had lead
>paint on it. who would have thought. only a few very tiny flakes/snip
http://indalopottery.tripod.com
Steve Mills on tue 8 jan 02
In message , F.Chapman Baudelot writes
>Birds are very sensitive where lead and other toxic materials are=3D20
>concerned: One of my beautiful parrots died about 20 years ago from=3D20
>pecking at an unpeeled apple in the fruit bowl (pesticides), and canaries=
>=3D20
>were used in both coal mines and Spanish folk potteries. If anything were=
>=3D20
>amiss, the canary was the first to die. I wonder how many wild birds are=
>=3D20
>now being unwittingly poisoned by the use of herbicides, chemical=3D20
>fertilizers, pesticides etc.
Far too many! and it's not just chemicals; in this country habitats are
being destroyed as well. The Common House Sparrow ain't so common now!
--
Steve Mills
Bath
UK
iandol on wed 9 jan 02
Dear Steve Mills,=20
You say
Got a big flock in our front garden, and a flock of Blackbirds and there =
are several giant flocks of Starlings around the district. To that add =
the rabbits which are proliferating, like the proverbial, in this =
vicinity after the release of that wonder virus which was supposed to =
wipe them out.
Now, if you wish to restock those Islands of yours with your indigenous =
species I feel sure we could assist. Best regards,
Ivor
Steve Mills on thu 10 jan 02
How kind, how kind!
:-)
Steve
Bath
UK
In message <000101c1998f$81bb66c0$5c7d38cb@oemcomputer>, iandol
writes
>
> Dear Steve Mills,
>
> You say
>
> Got a big flock in our front garden, and a flock of Blackbirds and
> there are several giant flocks of Starlings around the district. To
> that add the rabbits which are proliferating, like the proverbial,
> in this vicinity after the release of that wonder virus which was
> supposed to wipe them out.
>
> Now, if you wish to restock those Islands of yours with your
> indigenous species I feel sure we could assist. Best regards,
>
> Ivor
--
Steve Mills
Bath
UK
Ron Roy on fri 11 jan 02
None of the following is true.
> Please don't freak out over lead in the glaze - It is ONLY a problem if it
>is put on LOW fired dinnerware and then used for acidic foods like tomatoes,
>citrus, vinegar, or potatoes..
> It's a bit dangerous to work with because you can absorb it thru your
>skin, so wear gloves. But the infinitesimal amounts you might get are
>nothing. It takes large amounts and prolonged exposure to cause harm.
> Your kiln is NOT contaminated - If you fired to ^6 or higher, the lead is
>locked in chemically & won't leach out even with acidic foods.
> If it really bothers you alot, turn those pieces in plant containers and
>trays.. Then use it strictly as an outside glaze on flower pots & garden
>decorations.
Lead can leach out of any unstable glaze no matter what temp it's fired to
- it can volatilize at very low temperatures when reduced - a common
situation at different stages even in an electric kiln. Most foods are
acidic by the way. Some glazes will leach with common tap water.
They say it is no use using lead above cone 6 because it has all vaporized
by then.
Inhalation and ingestion are the common ways of absorption.
Your kiln will be contaminated when firing lead glazes - how much depends
on several factors including how high you fire, how much lead is in the
glaze, how stable the glaze is and how well ventilated you kiln is.
I do recommend freaking out over lead - it's one of the worst materials we
have to deal with - best not to mess with it at all.
RR
> Please don't freak out over lead in the glaze - It is ONLY a problem if it
>is put on LOW fired dinnerware and then used for acidic foods like tomatoes,
>citrus, vinegar, or potatoes..
> It's a bit dangerous to work with because you can absorb it thru your
>skin, so wear gloves. But the infinitesimal amounts you might get are
>nothing. It takes large amounts and prolonged exposure to cause harm.
> Your kiln is NOT contaminated - If you fired to ^6 or higher, the lead is
>locked in chemically & won't leach out even with acidic foods.
> If it really bothers you alot, turn those pieces in plant containers and
>trays.. Then use it strictly as an outside glaze on flower pots & garden
>decorations.
Ron Roy
RR# 4
15084 Little Lake Rd..
Brighton,
Ontario, Canada
KOK 1H0
Residence 613-475-9544
Studio 613-475-3715
Fax 613-475-3513
Paul Herman on fri 11 jan 02
Greetings all,
Unless I am mistaken, almost all of the commercial china and
institutional ware manufacturers use fritted lead glazes. Any comments?
Paul, from out in the sagebrush
----------
>From: Michael Banks
>To: CLAYART@LSV.CERAMICS.ORG
>Subject: Re: Lead scare
>Date: Fri, Jan 11, 2002, 3:08 PM
>
> Lead has only a very few, very restricted, useful applications in ceramics
> today. These include the formulation of certain low fire art glazes (e.g:
> lead-chromium reds, oranges, yellows and greens), and as a smoothing agent
> in low-fire commercial clear glazes.
Michael Banks on sat 12 jan 02
Ron is absolutely correct here.
Lead has only a very few, very restricted, useful applications in ceramics
today. These include the formulation of certain low fire art glazes (e.g:
lead-chromium reds, oranges, yellows and greens), and as a smoothing agent
in low-fire commercial clear glazes.
Anyone who does not know the true properties of lead well, should not use
it. Lead poisoning is still far too common in our community, and the
brain/nerve damage from lead intoxication is permanent.
Michael Banks
Nelson,
NZ
----- Original Message ----- -
Ron Roy wrote:
> Lead can leach out of any unstable glaze no matter what temp it's fired to
> - it can volatilize at very low temperatures when reduced - a common
> situation at different stages even in an electric kiln. Most foods are
> acidic by the way. Some glazes will leach with common tap water.
>
> They say it is no use using lead above cone 6 because it has all vaporized
> by then.
>
> Inhalation and ingestion are the common ways of absorption.
>
> Your kiln will be contaminated when firing lead glazes - how much depends
> on several factors including how high you fire, how much lead is in the
> glaze, how stable the glaze is and how well ventilated you kiln is.
>
> I do recommend freaking out over lead - it's one of the worst materials we
> have to deal with - best not to mess with it at all.
John Hesselberth on sat 12 jan 02
on 1/12/02 12:48 AM, Paul Herman at potter@PSLN.COM wrote:
> Unless I am mistaken, almost all of the commercial china and
> institutional ware manufacturers use fritted lead glazes. Any comments?
Hi Paul,
They may; however I think a number of them are moving to lead-free glazes.
When large scale manufacturers (at least those in the developed part of the
world) do use lead they have the resources to assure they are handling it
safely and that their glazes don't leach. I would bet that they leach test
at least a few samples from every batch or lot. They also have
significantly better control of their kilns than we do. They don't use
nonuniform ingredients like Gerstley Borate. New colors are thoroughly
tested, etc, etc.
Studio potters just don't have the resources (money, time and knowledge) to
assure they are using lead safely. It takes quite a bit of all 3.
Regards,
John
web sites: http://www.masteringglazes.com and http://www.frogpondpottery.com
EMail: john@frogpondpottery.com
"It is, perhaps, still necessary to say that the very best glazes cannot
conceal badly shaped pots..." David Green, Pottery Glazes
iandol on sat 12 jan 02
Dear Ron Roy,
I am waiting for someone to confirm the suggestion I put forward that =
the vapour pressure of Lead Monoxide at cone 6 was about the same as =
water at less than 50 deg Celsius.
Now if you pour a litre of water onto a hot pavement it evaporates =
pretty quickly in this part of the world, which seems as good a way as I =
can think of for illustrating the volatility of at least one Lead =
compound.
Best regards,
Ivor
Tom Buck on mon 14 jan 02
Ivor:
You are on the right track. PbO (lithage, lead monoxide) melts at
888 degrees Celsius (1630 deg F). By the time you hit Cone 6 or 1230 C
(2250 F) any dissolved lead oxide not bound to the glass matrix will have
long gone as vapour. and bound PbO at that temperature would likely be a
quite small amount.
You might see if you can access Am Ceramic Soc archives for
specific numbers.
til later. be well. peace. Tom
Tom Buck ) tel: 905-389-2339
(westend Lake Ontario, province of Ontario, Canada).
mailing address: 373 East 43rd Street,
Hamilton ON L8T 3E1 Canada
On Sat, 12 Jan 2002, iandol wrote:
> Dear Ron Roy,
>
> I am waiting for someone to confirm the suggestion I put forward that the vapour pressure of Lead Monoxide at cone 6 was about the same as water at less than 50 deg Celsius.
>
> Now if you pour a litre of water onto a hot pavement it evaporates pretty quickly in this part of the world, which seems as good a way as I can think of for illustrating the volatility of at least one Lead compound.
>
> Best regards,
>
> Ivor
>
> ______________________________________________________________________________
> 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.
>
iandol on tue 15 jan 02
Dear Tom Buck, <>
Makes the idea that it will happen a bit more accessible to =
understanding when you look at it that way. I leave it to interested =
parties to do the research. Left the lead glaze pathway about thirty =
five years ago.
All the best.
Ivor.
Ron Roy on wed 16 jan 02
Hi Ivor,
My server has been crippled for about 5 days so I am just out of limbo.
I don't know about "pressure" but tell me if I understand this much - the
"pressure" gradually increases till very strong at cone 6 - so strong there
is not much point in using lead above that temp because it leaves? More
importantly - when does the lead start to vaporize from this pressure?
Then there is what happens when lead oxide is reduced to the metal - and it
starts to boil when? Keeping in mind that even firings that are "oxidized"
so have periods of reduction from LOI sulphur and wax during certain
stages.
So - as you see I cannot confirm your assertion but have to go on what I
read - being chemically - basically ignorant.
RR
>Dear Ron Roy,
>
>I am waiting for someone to confirm the suggestion I put forward that the
>vapour pressure of Lead Monoxide at cone 6 was about the same as water at
>less than 50 deg Celsius.
>
>Now if you pour a litre of water onto a hot pavement it evaporates pretty
>quickly in this part of the world, which seems as good a way as I can
>think of for illustrating the volatility of at least one Lead compound.
>
>Best regards,
>
>Ivor
Ron Roy
RR# 4
15084 Little Lake Rd..
Brighton,
Ontario, Canada
KOK 1H0
Residence 613-475-9544
Studio 613-475-3715
Fax 613-475-3513
iandol on thu 17 jan 02
Dear Ron,
Looking at the Tables of Vapour Pressure and Boiling Points allowed me =
to make that assessment.
From the same source, Metallic Lead seems to be about one fifth as =
volatile as Lead oxide around same cone six temperature. In health =
terms, this seems to be an insignificant reduction. So the stuff is =
still bad news. So, as you say, even mild passages of reduction will not =
change the basic concepts.
Best regards,
Ivor.=20
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