Sheryl VanVleck on sat 9 mar 02
I am using CT-3, low fire clay from Mile Hi in Denver and glaze firing it to
cone 2.
It has a beautiful white color at that range.
I am formulating my own glazes. Much of the work I do is functional, thrown
lidded forms, cups, bowls, etc with sculptural additions, so I am concerned
about toxicity. I have the Ceramic Spectrum by Robin Hopper which states
that Manganese Dioxide, Cobalt, Chrome and Copper Oxides are all Toxic. I am
presuming this is not just in their raw/powder state. Is there a book out
there for cone 2 glazes? I am wondering if the toxicity is ?neutralized? by
firing? I am far from a chemistry major, as you can tell.
Thanks all for any information.
Sheryl in Wyoming
It's off for my first visit to NCECA we go, the contingent from Casper
College, so perhaps I will find some answers there.
Snail Scott on sat 9 mar 02
At 05:34 PM 3/9/02 EST, you wrote:
...Manganese Dioxide, Cobalt, Chrome and Copper Oxides are all Toxic. I am
>presuming this is not just in their raw/powder state. Is there a book out
>there for cone 2 glazes? I am wondering if the toxicity is ?neutralized? by
>firing?
Not neutralized, per se, but entrapped.
Many of our materials are toxic, but when bound up
in a properly melted, stable glaze, they will not
be released to the user of the finished pottery.
Hazard from ingestion and inhalation of raw powder
can be controlled by consistent use of a dust mask
and gloves, and by keeping your glaze-mixing area
dust-free. Hazard from inhalation of the vapors
during firing is a different concern. If you must
hang around the kiln during firing, use a mask
rated for fumes, not just mists and dust.
I recall Chappell's book has a few glazes in your
temp range. Stability for food use is never
guaranteed, though. You need to test them for
yourself. The vinegar test and lemon-slice test
are probably good starting points.
-Snail
Martin Howard on mon 11 mar 02
Sheryl in Wyoming
If you stick with cone 2, like me, you will be one of a very small group.
As far as I know, there is no book for this range. I aim for 2 but touch 3
occasionally, using a high firing red earthenware.
Colours come from the pigments you mention.
So put the colour in the slip. Then cover with a clear glaze which is food
safe and protects the underlying slip colourants leaching through.
That seems to be the simple answer to this riddle.
Martin Howard
Webbs Cottage Pottery
Woolpits Road, Great Saling
BRAINTREE, Essex CM7 5DZ
01371 850 423
martin@webbscottage.co.uk
http://www.webbscottage.co.uk
Updated 3rd March 2002
Tom Buck on tue 12 mar 02
Sheryl:
Cone 2 is seldom used by other potters. But Richard Zakin has some
Cone 3 glazes in his "Electric Kiln Ceramics" so you could check that out.
Be aware that you likely will need some frits to help a feldspar/clay mix
melt at C2.
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, 9 Mar 2002, Sheryl VanVleck wrote:
> I am using CT-3, low fire clay from Mile Hi in Denver and glaze firing it to
> cone 2.
> It has a beautiful white color at that range.
>
> I am formulating my own glazes. Much of the work I do is functional, thrown
> lidded forms, cups, bowls, etc with sculptural additions, so I am concerned
> about toxicity. I have the Ceramic Spectrum by Robin Hopper which states
> that Manganese Dioxide, Cobalt, Chrome and Copper Oxides are all Toxic. I am
> presuming this is not just in their raw/powder state. Is there a book out
> there for cone 2 glazes? I am wondering if the toxicity is ?neutralized? by
> firing? I am far from a chemistry major, as you can tell.
>
> Thanks all for any information.
> Sheryl in Wyoming
> It's off for my first visit to NCECA we go, the contingent from Casper
> College, so perhaps I will find some answers there.
>
> ______________________________________________________________________________
> 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.
>
scott lykens on mon 18 mar 02
From what i have heard about commercial stain production. the materails are
generally fritted and then become something that is not leachable in the
same way that manganese is in your glaze. Call your favorite manufacturer
to double check. They have Phds sitting around that will be glad to talk to
you in a breif way. Have some questions written down before you call. they
often have a way of talking that can put one in a fog if your not acustome
to speaking to chemical engineers.
But I would say, a well balanced glaze with reasonable additions of stain is
the food safe way to go. just make sure you dont sacrifice too much silica
in exchange for your boron.
Scott
>From: Tom Buck
>Reply-To: Ceramic Arts Discussion List
>To: CLAYART@LSV.CERAMICS.ORG
>Subject: Re: Cone 2 glazes
>Date: Tue, 12 Mar 2002 00:42:49 -0500
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>
>Sheryl:
> Cone 2 is seldom used by other potters. But Richard Zakin has some
>Cone 3 glazes in his "Electric Kiln Ceramics" so you could check that out.
>Be aware that you likely will need some frits to help a feldspar/clay mix
>melt at C2.
>
>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, 9 Mar 2002, Sheryl VanVleck wrote:
>
> > I am using CT-3, low fire clay from Mile Hi in Denver and glaze firing
>it to
> > cone 2.
> > It has a beautiful white color at that range.
> >
> > I am formulating my own glazes. Much of the work I do is functional,
>thrown
> > lidded forms, cups, bowls, etc with sculptural additions, so I am
>concerned
> > about toxicity. I have the Ceramic Spectrum by Robin Hopper which
>states
> > that Manganese Dioxide, Cobalt, Chrome and Copper Oxides are all Toxic.
>I am
> > presuming this is not just in their raw/powder state. Is there a book
>out
> > there for cone 2 glazes? I am wondering if the toxicity is
>?neutralized? by
> > firing? I am far from a chemistry major, as you can tell.
> >
> > Thanks all for any information.
> > Sheryl in Wyoming
> > It's off for my first visit to NCECA we go, the contingent from Casper
> > College, so perhaps I will find some answers there.
> >
> >
>______________________________________________________________________________
> > 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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Bun Bun on sat 10 may 03
This ain't black but its the only cone 2 glaze I actually found in my
resources. Can't even say how it might work our, never tried it.
Cone 2 Colemanite
8.2 Calcined zinc oxide
38.5 Potash Feldspar
17.55 Colemanite
6.8 Barium Carbonate
6.45 Steatite (talc)
22.5 Flint
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Bun Bun on sat 10 may 03
This ain't black but its the only cone 2 glaze I actually found in my
resources. Can't even say how it might work our, never tried it.
Cone 2 Colemanite
8.2 Calcined zinc oxide
38.5 Potash Feldspar
17.55 Colemanite
6.8 Barium Carbonate
6.45 Steatite (talc)
22.5 Flint
_________________________________________________________________
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