Tom Sawyer on wed 18 apr 07
I am doing a considerable amount of "glaze layering". As most of us know
such a process effects the eutectic temperature of melt. How does this
affect food safety. I exclusively use food safe glazes on anything that
might serve edible or drinkable food but what if I use two food safe glazes
one on top of the other? A related question concerns the "Ox Blood Glaze"
recently discussed. What if one were to place a clear food safe glaze on
top? I have a gut response to these questions but wonder what those more
expert think. Thanks
Tom Sawyer
Lynn Goodman Porcelain Pottery on wed 18 apr 07
On Apr 18, 2007, at 5:10 AM, Tom Sawyer wrote:
> I am doing a considerable amount of "glaze layering". As most of us
> know
> such a process effects the eutectic temperature of melt. How does this
> affect food safety. I exclusively use food safe glazes on anything
> that
> might serve edible or drinkable food but what if I use two food
> safe glazes
> one on top of the other? A related question concerns the "Ox Blood
> Glaze"
> recently discussed. What if one were to place a clear food safe
> glaze on
> top? I have a gut response to these questions but wonder what those
> more
> expert think. Thanks
> Tom Sawyer
Layering two glazes produces a third glaze which can have very
different properties from the two original glazes. I would test any
combinations that you want to use.
Lynn
Lynn Goodman
Fine Porcelain Pottery
Cell 347-526-9805
www.lynngoodmanporcelain.com
John Hesselberth on fri 20 apr 07
On Apr 18, 2007, at 5:10 AM, Tom Sawyer wrote:
> I am doing a considerable amount of "glaze layering". As most of us
> know
> such a process effects the eutectic temperature of melt. How does this
> affect food safety. I exclusively use food safe glazes on anything
> that
> might serve edible or drinkable food but what if I use two food
> safe glazes
> one on top of the other? A related question concerns the "Ox Blood
> Glaze"
> recently discussed. What if one were to place a clear food safe
> glaze on
> top? I have a gut response to these questions but wonder what those
> more
> expert think. Thanks
Hi Tom,
While I have no data, I believe if you layer two stable glazes, the
resulting glaze will be stable. I have shown in my work that silica
and alumina levels are important to stability. If both glazes have
silica and alumina levels in the stable range, any mixture of the two
will also. The additional running you see with layering is due to
having better melting. It has been my experience that never hurts
stability. Undermelted glazes are the problem with stability.
So I say layer with impunity as long as both glazes are in the stable
range.
Regards,
John
Tom Sawyer on sun 22 apr 07
John,
Thank you so very much. I'm certain that this information will reassure many
other clayarters. I know from your book that some of your glazes are layered
but I was worried that the additional melt might somehow change the safety
level of the glazes otherwise designate as safe.
Tom Sawyer
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of John
Hesselberth
Sent: Friday, April 20, 2007 6:59 PM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Re: Cone 6 red glaze - layering and safety
On Apr 18, 2007, at 5:10 AM, Tom Sawyer wrote:
> I am doing a considerable amount of "glaze layering". As most of us
> know
> such a process effects the eutectic temperature of melt. How does this
> affect food safety. I exclusively use food safe glazes on anything
> that
> might serve edible or drinkable food but what if I use two food
> safe glazes
> one on top of the other? A related question concerns the "Ox Blood
> Glaze"
> recently discussed. What if one were to place a clear food safe
> glaze on
> top? I have a gut response to these questions but wonder what those
> more
> expert think. Thanks
Hi Tom,
While I have no data, I believe if you layer two stable glazes, the
resulting glaze will be stable. I have shown in my work that silica
and alumina levels are important to stability. If both glazes have
silica and alumina levels in the stable range, any mixture of the two
will also. The additional running you see with layering is due to
having better melting. It has been my experience that never hurts
stability. Undermelted glazes are the problem with stability.
So I say layer with impunity as long as both glazes are in the stable
range.
Regards,
John
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