u1004425@warwick.net on tue 10 sep 96
Hi all,
First let me please thank everyone for your generosity and for all the
very wonderful info i've learned from all of you. I have two glaze
questions that i'm hoping someone, or many someones can answer.
1) Is silicon carbide a glaze ingredient that is safe to use on vessels
that are destined for food use? What are the hazards associated with this
material?
2) My friend, Jeanette, formulated this glaze recipe. We are wondering
about its safety in food related vessels, or any hazards we might not
have thought about.
^6 oxidation."Nettie's Nougat"
KONA F4.................30
SPODUMENE ..............20
TITANIUM................10
EPK.....................10
DOLOMITE................15
ZINC OXIDE..............15
Thanks in advance for any advice!
Marilyn
BobWicks@aol.com on fri 13 sep 96
Hi Marilyn:
Your glaze formula looks good and there is nothing that I can see that would
prevent you from using it on food dishes. Spodumene has lithium carbonate in
it so you will experience a wide firing range. Other than that I would be
very intertested to see how it turns out.
Bob
Gail Dapogny on fri 5 apr 02
I have a question about the lemon or vinegar "home" test for glaze
leaching: Is it more or less foolproof, or are there some more subtle
glazes that show leaching only when tested for real in a lab?
---Gail
Gail Dapogny
1154 Olden Road
Ann Arbor, MI 48103-3005
(734) 665-9816
gdapogny@umich.edu
John Hesselberth on sat 6 apr 02
on 4/5/02 11:56 PM, Gail Dapogny at gdapogny@UMICH.EDU wrote:
> I have a question about the lemon or vinegar "home" test for glaze
> leaching: Is it more or less foolproof, or are there some more subtle
> glazes that show leaching only when tested for real in a lab?
HI Gail,
It is a test that will pick out the very worst of glazes. I have
occasionally seen a glaze that passes the vinegar test that still leaches
quite a bit. The only sure way to know is with lab testing.
John
web sites: http://www.masteringglazes.com and http://www.frogpondpottery.com
EMail: john@frogpondpottery.com
"Pots, like other forms of art, are human expressions: pleasure, pain or
indifference before them depends upon their natures, and their natures are
inevitably projections of the minds of their creators." Bernard Leach, A
Potter's Book.
Autumn Downey on fri 2 mar 12
Could this be why a "lobster" Mason stain actually smells fishy in an
engobe mixture?
I use it sparingly, and not on food surfaces.
Autumn Downey
Paul Lewing wrote:
> On Mar 2, 2012, at 3:27 PM, Des & Jan Howard wrote:
>
> Ron
> Smell "it"! What is the "it" you are smelling?
> Could be an organic stain binder, a preservative, a
> plasticiser in the container. Don't just drop "it"
> among the nervous nellies of the pottery world.
>
> The "it"is sulphur. I also am of the opinion that not all of the
> cadmium gets encapsulated, because of the sulphur smell.
> What makes the cadmium colorant so fugitive and hard to work with, and
> what makes it different from every other colorant, is that it is not
> an oxide. It's a mixture of cadmium sulphate and cadmium selenate, or
> cadmium sulpho-selenate. The cadmium selenate is red and the cadmium
> sulphate is yellow. That's how they get the range of colors from
> yellow to red, by mixing the two. Both of those really want to be
> oxides, though. I never can remember which is which but either
> cadmium oxide or selenium oxide is black and the other is white, and
> reduction causes one of them to go to the oxide form and oxidation
> makes the other one go to an oxide. This is why if you don't get the
> atmosphere exactly right, you get white or grey.
> Paul Lewing
> www.paullewingtile.com
> www.paullewingart.com
>
>
>
Ben Morrison on fri 2 mar 12
Speaking of safety in glazes, has anyone done real testing on cadmium inclu=
sion glazes for food safety? I ask because I have seen a lot of cadmium inc=
lusion stains popping up in the marketplace as of late. A woman was selling=
some mugs which were under glazed with cadmium inclusion stains. One was t=
hat cadmium orange that mimics the good ole bright lead oranges, and one wa=
s the fire engine red cadmium stain. I've not personally done testing of my=
own on cadmium, because it's listed as a toxic chemical by the FDA. To my =
knowledge the only other chemical they regulate in food ware is lead. Near =
as I can tell they aren't as concerned with barium or manganese as all of u=
s are, but maybe that's only because no one is paying them to be.
-Ben
Steve Mills on fri 2 mar 12
Ben,=3D20
Speaking from my perspective as the one-time compiler of MSDS for our compa=
n=3D
y in the UK, this may help.=3D20
What is not normally known is that a substance listed (as a pure product) a=
s=3D
toxic, can be downgraded to virtually harmless by dilution. Thus a Cadmium=
c=3D
olorant incorporated into an Underglaze paste or diluted with medium or wat=
e=3D
r at up to 10% inclusion becomes classified only as "Harmful" I.e. No worse=
t=3D
han Clay! Even at a higher % inclusion it is still the same classification=
.=3D
Cover that with glaze, and it technically doesn't need to be listed (provi=
d=3D
ed of course the glaze is low/no risk). =3D20
Barium and Manganese are (or were) not listed as Harmful over here when I w=
a=3D
s doing that job, but I chose to employ American standards as I felt they w=
e=3D
re more realistic as far as Barium was concerned, as there was a fad of usi=
n=3D
g High Barium Matt glazes at the time, some of it on food bearing pots.=3D2=
0
Manganese was not on our radar at the time.=3D20
So you see: Dilution is extremely important!
Steve M
Steve Mills
Bath
UK
www.mudslinger.me.uk
Sent from my iPod
On 2 Mar 2012, at 08:39, Ben Morrison wrote:
> Speaking of safety in glazes, has anyone done real testing on cadmium inc=
l=3D
usion glazes for food safety? I ask because I have seen a lot of cadmium in=
c=3D
lusion stains popping up in the marketplace as of late. A woman was selling=
s=3D
ome mugs which were under glazed with cadmium inclusion stains. One was tha=
t=3D
cadmium orange that mimics the good ole bright lead oranges, and one was t=
h=3D
e fire engine red cadmium stain. I've not personally done testing of my own=
o=3D
n cadmium, because it's listed as a toxic chemical by the FDA. To my knowle=
d=3D
ge the only other chemical they regulate in food ware is lead. Near as I ca=
n=3D
tell they aren't as concerned with barium or manganese as all of us are, b=
u=3D
t maybe that's only because no one is paying them to be.
>=3D20
> -Ben
ronroy@CA.INTER.NET on fri 2 mar 12
Hi Ben,
I am sure there is still some free cadmium when it comes encapsulated
- I have seen micro photographs of the crystals and there appears to
be some unencapsulated cadmium there as well as incomplete crystals.
I have no idea how much or if it is a worry - but you can smell it
when you take the cover off a container of it.
I think you are wise not to use it - and you would still have to have
your ware tested to prove there was not enough released as required.
RR
Quoting Ben Morrison :
> Speaking of safety in glazes, has anyone done real testing on
> cadmium inclusion glazes for food safety? I ask because I have seen
> a lot of cadmium inclusion stains popping up in the marketplace as
> of late. A woman was selling some mugs which were under glazed with
> cadmium inclusion stains. One was that cadmium orange that mimics
> the good ole bright lead oranges, and one was the fire engine red
> cadmium stain. I've not personally done testing of my own on
> cadmium, because it's listed as a toxic chemical by the FDA. To my
> knowledge the only other chemical they regulate in food ware is
> lead. Near as I can tell they aren't as concerned with barium or
> manganese as all of us are, but maybe that's only because no one is
> paying them to be.
>
> -Ben
>
Edouard Bastarache on fri 2 mar 12
Encapsulated cadmium is certainly quite less toxic than the older
preparations,,,
To learn more about cadmium, check this out :
http://smart2000.pagesperso-orange.fr/Cadmium.htm
Plejkore,
Edouard Bastarache
Spertesperantisto
Sorel-Tracy
Quebec
http://www.flickr.com/photos/30058682@N00/
http://edouardbastarache.blogspot.com/
http://smart2000.pagesperso-orange.fr/bloggs_edouard.htm
http://www.facebook.com/edouard.bastarache
----- Original Message -----
From:
To:
Sent: Friday, March 02, 2012 3:23 PM
Subject: Re: Glaze Safety
> Hi Ben,
>
> I am sure there is still some free cadmium when it comes encapsulated
> - I have seen micro photographs of the crystals and there appears to
> be some unencapsulated cadmium there as well as incomplete crystals.
>
> I have no idea how much or if it is a worry - but you can smell it
> when you take the cover off a container of it.
>
> I think you are wise not to use it - and you would still have to have
> your ware tested to prove there was not enough released as required.
>
> RR
>
>
>
> Quoting Ben Morrison :
>
>> Speaking of safety in glazes, has anyone done real testing on
>> cadmium inclusion glazes for food safety? I ask because I have seen
>> a lot of cadmium inclusion stains popping up in the marketplace as
>> of late. A woman was selling some mugs which were under glazed with
>> cadmium inclusion stains. One was that cadmium orange that mimics
>> the good ole bright lead oranges, and one was the fire engine red
>> cadmium stain. I've not personally done testing of my own on
>> cadmium, because it's listed as a toxic chemical by the FDA. To my
>> knowledge the only other chemical they regulate in food ware is
>> lead. Near as I can tell they aren't as concerned with barium or
>> manganese as all of us are, but maybe that's only because no one is
>> paying them to be.
>>
>> -Ben
>>
>
Lee on fri 2 mar 12
And not every glaze is going to be used inside your orange juice cup!
On Fri, Mar 2, 2012 at 3:25 PM, Edouard Bastarache wro=
=3D
te:
> Encapsulated cadmium is certainly quite less toxic than the older
> preparations,,,
>
> To learn more about cadmium, check this out :
> http://smart2000.pagesperso-orange.fr/Cadmium.htm
>
>
> Plejkore,
>
> Edouard Bastarache
> Spertesperantisto
>
> Sorel-Tracy
> Quebec
>
> http://www.flickr.com/photos/30058682@N00/
> http://edouardbastarache.blogspot.com/
> http://smart2000.pagesperso-orange.fr/bloggs_edouard.htm
> http://www.facebook.com/edouard.bastarache
>
>
>
>
>
>
>
>
>
>
> ----- Original Message -----
> From:
> To:
> Sent: Friday, March 02, 2012 3:23 PM
> Subject: Re: Glaze Safety
>
>
>> Hi Ben,
>>
>> I am sure there is still some free cadmium when it comes encapsulated
>> - I have seen micro photographs of the crystals and there appears to
>> be some unencapsulated cadmium there as well as incomplete crystals.
>>
>> I have no idea how much or if it is a worry - but you can smell it
>> when you take the cover off a container of it.
>>
>> I think you are wise not to use it - and you would still have to have
>> your ware tested to prove there was not enough released as required.
>>
>> RR
>>
>>
>>
>> Quoting Ben Morrison :
>>
>>> Speaking of safety in glazes, has anyone done real testing on
>>> cadmium inclusion glazes for food safety? I ask because I have seen
>>> a lot of cadmium inclusion stains popping up in the marketplace as
>>> of late. A woman was selling some mugs which were under glazed with
>>> cadmium inclusion stains. One was that cadmium orange that mimics
>>> the good ole bright lead oranges, and one was the fire engine red
>>> cadmium stain. I've not personally done testing of my own on
>>> cadmium, because it's listed as a toxic chemical by the FDA. To my
>>> knowledge the only other chemical they regulate in food ware is
>>> lead. Near as I can tell they aren't as concerned with barium or
>>> manganese as all of us are, but maybe that's only because no one is
>>> paying them to be.
>>>
>>> -Ben
>>>
>>
>
--=3D20
--
=3DA0Lee Love in Minneapolis
http://mingeisota.blogspot.com/
=3DA0"Ta tIr na n-=3DF3g ar chul an tI=3D97tIr dlainn trina ch=3DE9ile"=3D9=
7that is, =3D
"The
land of eternal youth is behind the house, a beautiful land fluent
within itself." -- John O'Donohue
Ben Morrison on fri 2 mar 12
The problem I see with cadmium inclusion stains is that cadmium is toxic at=
a very low quantities, and there is no treatment. The health effects are q=
uite terrible from exposure either acutely or long term. For the potter the=
re is a significant risk, let along for the recipient.
________________________________
From: "ronroy@CA.INTER.NET"
To: Clayart@LSV.CERAMICS.ORG
Sent: Friday, March 2, 2012 12:23 PM
Subject: Re: Glaze Safety
Hi Ben,
I am sure there is still some free cadmium when it comes encapsulated
- I have seen micro photographs of the crystals and there appears to
be some unencapsulated cadmium there as well as incomplete crystals.
I have no idea how much or if it is a worry - but you can smell it
when you take the cover off a container of it.
I think you are wise not to use it - and you would still have to have
your ware tested to prove there was not enough released as required.
RR
Quoting Ben Morrison :
> Speaking of safety in glazes, has anyone done real testing on
> cadmium inclusion glazes for food safety? I ask because I have seen
> a lot of cadmium inclusion stains popping up in the marketplace as
> of late. A woman was selling some mugs which were under glazed with
> cadmium inclusion stains. One was that cadmium orange that mimics
> the good ole bright lead oranges, and one was the fire engine red
> cadmium stain. I've not personally done testing of my own on
> cadmium, because it's listed as a toxic chemical by the FDA. To my
> knowledge the only other chemical they regulate in food ware is
> lead. Near as I can tell they aren't as concerned with barium or
> manganese as all of us are, but maybe that's only because no one is
> paying them to be.
>
> -Ben
>
Paul Lewing on fri 2 mar 12
On Mar 2, 2012, at 3:27 PM, Des & Jan Howard wrote:
Ron
Smell "it"! What is the "it" you are smelling?
Could be an organic stain binder, a preservative, a
plasticiser in the container. Don't just drop "it"
among the nervous nellies of the pottery world.
The "it"is sulphur. I also am of the opinion that not all of the
cadmium gets encapsulated, because of the sulphur smell.
What makes the cadmium colorant so fugitive and hard to work with, and
what makes it different from every other colorant, is that it is not
an oxide. It's a mixture of cadmium sulphate and cadmium selenate, or
cadmium sulpho-selenate. The cadmium selenate is red and the cadmium
sulphate is yellow. That's how they get the range of colors from
yellow to red, by mixing the two. Both of those really want to be
oxides, though. I never can remember which is which but either
cadmium oxide or selenium oxide is black and the other is white, and
reduction causes one of them to go to the oxide form and oxidation
makes the other one go to an oxide. This is why if you don't get the
atmosphere exactly right, you get white or grey.
Paul Lewing
www.paullewingtile.com
www.paullewingart.com
Birgit Wright on sat 3 mar 12
Hi Ben this is what I recently replied to another clayater about this same =
=3D
question=3D2C=3D20
My experience with questions Regarding mason stains is this=3D2C I have=
c=3D
hecked out the encapsulated cadmium and gotten a positive go ahead using ^=
=3D
6 and a moderate percentage of stain=3D2C but if you go to FAQ's on the m=
as=3D
on stain website http://www.masoncolor.com/faq.htm =3D2C they have a lot o=
f =3D
answers. and if you call their 1-800 # and ask for tech. support they are =
=3D
very helpful. I had a red cup with tested at=3D2C http://www.bsclab.com/=
=3D
=3D2C Not that costly. You can see the sample at=3D2C http://www.birgits=
pots=3D
.blogspot.com/ =3D2C at the bottom of the page. Cheers=3D2C Birgit Wright=
=3D20
> Date: Fri=3D2C 2 Mar 2012 00:39:37 -0800
> From: potterpdx@YAHOO.COM
> Subject: Glaze Safety
> To: Clayart@LSV.CERAMICS.ORG
>=3D20
> Speaking of safety in glazes=3D2C has anyone done real testing on cadmium=
i=3D
nclusion glazes for food safety? I ask because I have seen a lot of cadmium=
=3D
inclusion stains popping up in the marketplace as of late. A woman was sel=
=3D
ling some mugs which were under glazed with cadmium inclusion stains. One w=
=3D
as that cadmium orange that mimics the good ole bright lead oranges=3D2C an=
d =3D
one was the fire engine red cadmium stain. I've not personally done testing=
=3D
of my own on cadmium=3D2C because it's listed as a toxic chemical by the F=
DA=3D
. To my knowledge the only other chemical they regulate in food ware is lea=
=3D
d. Near as I can tell they aren't as concerned with barium or manganese as =
=3D
all of us are=3D2C but maybe that's only because no one is paying them to b=
e.
>=3D20
> -Ben
=3D
Elisabeth Maurland on sat 3 mar 12
I make mugs kind of like the ones you mention, and I have had one tested =
=3D
at a lab (Brandyvine). The leaching was a fraction of what is allowed in =
=3D
California, which has the strictest rules. Now, working with the stains =3D
might be a different story, I suppose.....
Elisabeth
On Mar 2, 2012, at 2:39 AM, Ben Morrison wrote:
> Speaking of safety in glazes, has anyone done real testing on cadmium =3D
inclusion glazes for food safety? I ask because I have seen a lot of =3D
cadmium inclusion stains popping up in the marketplace as of late. A =3D
woman was selling some mugs which were under glazed with cadmium =3D
inclusion stains. One was that cadmium orange that mimics the good ole =3D
bright lead oranges, and one was the fire engine red cadmium stain. I've =
=3D
not personally done testing of my own on cadmium, because it's listed as =
=3D
a toxic chemical by the FDA. To my knowledge the only other chemical =3D
they regulate in food ware is lead. Near as I can tell they aren't as =3D
concerned with barium or manganese as all of us are, but maybe that's =3D
only because no one is paying them to be.
>=3D20
> -Ben
Elisabeth=3D20
www.elisabethmaurland.com
Paul Lewing on sat 3 mar 12
On Mar 2, 2012, at 9:29 PM, Autumn Downey wrote:
Could this be why a "lobster" Mason stain actually smells fishy in an
engobe mixture?
Yes. And you thought it was because they used actual lobsters?
Paul Lewing
www.paullewingtile.com
www.paullewingart.com
Des & Jan Howard on sat 3 mar 12
Ron
Smell "it"! What is the "it" you are smelling?
Could be an organic stain binder, a preservative, a
plasticiser in the container. Don't just drop "it"
among the nervous nellies of the pottery world.
Des
On 3/03/2012 7:23 AM, ronroy@CA.INTER.NET wrote:
> I have no idea how much or if it is a worry - but you
> can smell it
> when you take the cover off a container of it.
>
> I think you are wise not to use it - and you would
> still have to have
> your ware tested to prove there was not enough released
> as required.
--
Des & Jan Howard
Lue Pottery
Lue NSW
Australia
2850
02 6373 6419
www.luepottery.hwy.com.au
-32.656072 149.840624
Des & Jan Howard on sat 3 mar 12
Ben
I occasionally hand people a container, stating, "This
is the reaction product of a corrosive, poisonous
yellow-green gas & an explosive, soft, silver-white metal."
After I get the expected aversive shudders I add, "Just
wait 'til I tell you about it's chicken flavouring".
Des
On 3/03/2012 10:30 AM, Ben Morrison wrote:
> The problem I see with cadmium inclusion stains
> is that cadmium is toxic at a very low quantities,
> and there is no treatment. The health effects are quite
> terrible from exposure either acutely or long term.
> For the potter there is a significant risk, let along for the recipient.
--
Des & Jan Howard
Lue Pottery
Lue NSW
Australia
2850
02 6373 6419
www.luepottery.hwy.com.au
-32.656072 149.840624
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