Ivor and Olive Lewis on tue 13 dec 05
Dear Jim,
You say ....<needle-like Mullite
crystals [during thermal decomposition] which is not-so-good for =
"translucency". Of course, there are kaolin-based porcelain recipe =
exceptions!
Whereas, a Halloysitic-based "porcelain" - like Southern Ice - would =
have
different crystal growth behaviour, presumably with LESS Mullite.>>....
I take it that you have checked this out and are certain Halloysite =
clays do not decompose and reform in the same manner that Kaolinitic =
materials do. The chemistry of these two minerals suggests they might =
produce identical final products given identical environments.
Given that there may be less than 1.0% glass phase remaining in a Glass =
Ceramic system after nucleation and precipitation it seems doubtful that =
a Glass Ceramic would have optical properties differing much from those =
of a white translucent porcelain. This family of materials certainly has =
a complex science and technology.
I am not sure if this makes sense to those people who are using Southern =
Ice or one of its imitators
David Beumee on tue 13 dec 05
Jim,
Speaking of alternative fluxes as to McCarty's research, any idea where to obtain zinc borate in the US?
David Beumee
-------------- Original message ----------------------
From: Ivor and Olive Lewis
> Dear Jim,
>
> You say ....<> Mullite
> crystals [during thermal decomposition] which is not-so-good for "translucency".
> Of course, there are kaolin-based porcelain recipe exceptions!
> Whereas, a Halloysitic-based "porcelain" - like Southern Ice - would have
> different crystal growth behaviour, presumably with LESS Mullite.>>....
>
> I take it that you have checked this out and are certain Halloysite clays do not
> decompose and reform in the same manner that Kaolinitic materials do. The
> chemistry of these two minerals suggests they might produce identical final
> products given identical environments.
>
> Given that there may be less than 1.0% glass phase remaining in a Glass Ceramic
> system after nucleation and precipitation it seems doubtful that a Glass Ceramic
> would have optical properties differing much from those of a white translucent
> porcelain. This family of materials certainly has a complex science and
> technology.
>
> I am not sure if this makes sense to those people who are using Southern Ice or
> one of its imitators
>
> ______________________________________________________________________________
> 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.
Jim Murphy on tue 13 dec 05
Hi David,
U.S. Borax may be able to point you in the right
direction.
I know they supply Zinc Borate in their FireBrake line of flame retardant
materials .
Hope this helps.
Jim Murphy
on 12/13/05 12:24 PM, David Beumee at claybuds@ATT.NET wrote:
,
> Speaking of alternative fluxes as to McCarty's research, any idea where to
> obtain zinc borate in the US?
Jim Murphy on tue 13 dec 05
Hi Ivor,
Most everybody is familiar with the Orangish-Brown transparent Visions=AE lin=
e
of domestic cookware [Corning, developed by Beall et al].
Often mistaken for a "glass", Visions=AE is actually a perfect example of a
transparent "glass-ceramic" [Beta-quartz solid-solution]. I believe the
glassy-phase is more like 65% (by wt%).
The "glass-ceramics" field is a wide one. Whether "transparent" or
"translucent", i.e., higher glassy-phase %, the principles are the same -
efficient nucleation and control of a slow crystal growth to make fine
nanocrystalline materials.
If "Southern Ice" were to use a high-Titania Kaolin [as opposed to its
ultra-white low-Titania halloysite clay], I'd expect an "opaque" [less
translucent] white porcelain body.
All we really need to understand is the role certain materials play in
"nucleation" [like Titania or "low-Titania"] and control of crystal growth
[dependent on total flux & Alumina levels].
So ...... I'm just sayin' Magnesium Carbonate [as suggested by you] 'could'
be used to develop a more translucent porcelain, but, the "mechanism" may
very well be due to control of crystal growth [rather than as an aux. flux]=
.
;o)
Best wishes,
Jim Murphy
on 12/12/05 10:33 PM, Ivor and Olive Lewis at iandol@WESTNET.COM.AU wrote:
=20
> Given that there may be less than 1.0% glass phase remaining in a Glass
> Ceramic system after nucleation and precipitation it seems doubtful that =
a
> Glass Ceramic would have optical properties differing much from those of =
a
> white translucent porcelain. This family of materials certainly has a com=
plex
> science and technology.
>=20
> I am not sure if this makes sense to those people who are using Southern =
Ice
> or one of its imitators
David Beumee on thu 15 dec 05
Excellent Jim!
What's the secret of Corning Ware, and how do I begin producing pots that are safe for use as flameware?
David Beumee
Lafayette, CO
-------------- Original message ----------------------
From: Jim Murphy
> Hi Ivor,
>
> Most everybody is familiar with the Orangish-Brown transparent Visions® line
> of domestic cookware [Corning, developed by Beall et al].
>
> Often mistaken for a "glass", Visions® is actually a perfect example of a
> transparent "glass-ceramic" [Beta-quartz solid-solution]. I believe the
> glassy-phase is more like 65% (by wt%).
>
> The "glass-ceramics" field is a wide one. Whether "transparent" or
> "translucent", i.e., higher glassy-phase %, the principles are the same -
> efficient nucleation and control of a slow crystal growth to make fine
> nanocrystalline materials.
>
> If "Southern Ice" were to use a high-Titania Kaolin [as opposed to its
> ultra-white low-Titania halloysite clay], I'd expect an "opaque" [less
> translucent] white porcelain body.
>
> All we really need to understand is the role certain materials play in
> "nucleation" [like Titania or "low-Titania"] and control of crystal growth
> [dependent on total flux & Alumina levels].
>
> So ...... I'm just sayin' Magnesium Carbonate [as suggested by you] 'could'
> be used to develop a more translucent porcelain, but, the "mechanism" may
> very well be due to control of crystal growth [rather than as an aux. flux].
> ;o)
>
> Best wishes,
>
> Jim Murphy
>
>
>
> on 12/12/05 10:33 PM, Ivor and Olive Lewis at iandol@WESTNET.COM.AU wrote:
>
> > Given that there may be less than 1.0% glass phase remaining in a Glass
> > Ceramic system after nucleation and precipitation it seems doubtful that a
> > Glass Ceramic would have optical properties differing much from those of a
> > white translucent porcelain. This family of materials certainly has a complex
> > science and technology.
> >
> > I am not sure if this makes sense to those people who are using Southern Ice
> > or one of its imitators
>
> ______________________________________________________________________________
> 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.
Jim Murphy on thu 15 dec 05
David,
The "secret" is Beta-Quartz Solid-Solution ........ Shhhhhhhhh, don't tell a
soul! :o)
Jim
on 12/14/05 11:22 PM, David Beumee at claybuds@ATT.NET wrote:
> What's the secret of Corning Ware, and how do I begin producing pots that are
> safe for use as flameware?
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