John Kudlacek on wed 23 jun 04
Shino Gurus,
I have used a number of shinos over the years, most containing
substantial amounts of soda ash. Not a glaze chemist( flunked glaze calc)
why have I never encountered a shino that ran?
Humbly,
John in Topeka
Hank Murrow on wed 23 jun 04
On Jun 23, 2004, at 7:51 AM, John Kudlacek wrote:
> Shino Gurus,
> I have used a number of shinos over the years, most containing
> substantial amounts of soda ash. Not a glaze chemist( flunked glaze
> calc)
> why have I never encountered a shino that ran?
Dear John;
Probably because all shinos get their color from relatively high
amounts of Alumina in their Seger formulas. Mine run around
AL2O3 = 1.593 SiO2 = 5.246 for a Si/Al ratio of 3.29/1
So check your recipes for their Alumina content.......anything over .8
will be unlikely to run.
Cheers, Hank.......back in Eugene
Paul Herman on wed 23 jun 04
Him John,
Short answer... because they are all high in alumina.
best,
Paul Herman
Great Basin Pottery
Doyle, California US
http://www.greatbasinpottery.com/
----------
>From: John Kudlacek
>To: CLAYART@LSV.CERAMICS.ORG
>Subject: Yet Another Shino Question?
>Date: Wed, Jun 23, 2004, 7:51 AM
>
> Shino Gurus,
> I have used a number of shinos over the years, most containing
> substantial amounts of soda ash. Not a glaze chemist( flunked glaze calc)
> why have I never encountered a shino that ran?
> Humbly,
> John in Topeka
Ivor and Olive Lewis on thu 24 jun 04
Dear John Kudlacek,
You ask..<>
If your Shino Glazes were based on very high proportions of Felspar
this seems an acceptable observation.
Molten Felspars are known to retain a very high viscosity even when
their mineral structure has been destroyed in the heating process.
Shino style glaze are also low in those elements known to promote
fluidity in a glaze formulation. Even though Sodium oxide is added, in
the form of Soda Ash, it seems there is insufficient to make much
difference.
Best regards,
Ivor Lewis.
Redhill,
S. Australia.
Lee Love on thu 24 jun 04
John Kudlacek wrote:
>Shino Gurus,
> I have used a number of shinos over the years, most containing
>substantial amounts of soda ash. Not a glaze chemist( flunked glaze calc)
>why have I never encountered a shino that ran?
>
>
To get the typical red coloring, they have to be high alumina.
Lee
--
in Mashiko, Japan http://mashiko.org
http://journals.fotki.com/togeika/Mashiko/ Commentary On Pottery
Jim Murphy on thu 24 jun 04
Hi all,
Following Ivor's comment on a Shino Glaze based on high proportion of
Feldspar, which in general has large amounts of Alkali, Alumina and Silica,
I wonder how we may properly divvy-up the credit to "run-prevention" (read
also as high-viscosity).
[Sidebar] I believe most Ash Glazes have lots of Alkali - but most Ash
Glazes "run".
Shino Glazes also have lots of Alkali - typically from Feldspar and/or
Nepheline Syenite. Perhaps, in Shino Glazes, the combination of both large
proportion of Alumina AND Silica may be the key. The high Alumina level
would limit the "AMOUNT" of glass formed while the high Silica level should
help maintain a highly viscous Silica-saturated glass during firing.
Best wishes,
Jim Murphy
on 6/23/04 11:10 PM, Ivor and Olive Lewis at iandol@WESTNET.COM.AU wrote:
> Dear John Kudlacek,
> You ask..<>
> If your Shino Glazes were based on very high proportions of Felspar
> this seems an acceptable observation.
> Molten Felspars are known to retain a very high viscosity even when
> their mineral structure has been destroyed in the heating process.
> Shino style glaze are also low in those elements known to promote
> fluidity in a glaze formulation. Even though Sodium oxide is added, in
> the form of Soda Ash, it seems there is insufficient to make much
> difference.
Jim Murphy on mon 28 jun 04
Hi Ivor,
"
Thanks for the Singer and Singer" reference. Perhaps "Deformation Eutectics"
is the scientific area where alkali diffusion rates in an Alumina/Silica
environment are discussed (theorized) ?
> In spite of their apparent high R2O content and a 1/6 Al2O3/SiO2
> ratio, few true felspars apparently melt to form a free flowing
> vitreous liquid. some will retain their shape heated beyond ^12.
Understood. Maybe - in Shino Glaze - a "free flowing vitreous liquid" isn't
formed since the Alumina is going into solution and creating crystal growth
(mullite-needles, etc.) which eventually halts the formation of "glass", or
as would be the case with Shino - a less-glossy glaze.
A common definion for glass is "a homogeneous material with a random,
liquidlike (non-crystalline) molecular structure. The manufacturing process
requires that the raw materials be heated to a temperature sufficient to
produce a completely fused melt, which, when cooled rapidly, becomes rigid
without crystallizing." [Source: Corning Museum of Glass]
Alkali diffusion rate, Alumina-solubility, and quartz (Silica) dissolution
levels in the "glass-phase" of porcelain bodies is thoroughly being studied.
Some research (Alfred U.) suggests "constant mullite indicates constant
Alumina in glass". So, it is Alumina which dictates mullite formation - in
the tested porcelain bodies.
I'll ask rhetorically, in a high-Alkali high-Alumina high-Silica feldspathic
Shino, does Alumina-solubility inhibit crystal growth, or does crystal
growth inhibit Alumina-solubility ..... ??
Best wishes,
Jim Murphy
Ivor and Olive Lewis on tue 29 jun 04
Dear Jim,
Not being a Shino Maker (Though I ought. There are features in the
Environment in this area that shout out for a strong orange/white
carbon trap Shino with well defined linear elements) I am not quite
sure how to answer the issues you raise.
You suggest... <liquid" isn't formed since the Alumina is going into solution and
creating crystal growth (mullite-needles, etc.) which eventually
halts the formation of "glass", or as would be the case with Shino - a
less-glossy glaze.>> Thinking this way presupposes that abstract
elemental oxides behave as individual entities within a melting
mineral. That is a viewpoint I would find hard to support.
Seems to be a good definition of the term "Glass". For greater
elaboration have a look in Charles Bray, "Dictionary of Glass.
Materials and techniques" ISBN 976-6910-89-5
<porcelain bodies.>> It would seem that Mullite is a reaction compound
created through a solid state reaction during the thermal
decomposition of Kaolinite in the range 1000=BA- 1100=BA C. There is a
good account of the chemistry of this process in W. E Brownell, a text
I have mentioned before.
You ask...<< I'll ask rhetorically, in a high-Alkali high-Alumina
high-Silica feldspathic Shino, does Alumina-solubility inhibit crystal
growth, or does crystal growth inhibit Alumina-solubility ..... ?? >>
To sort this out you would need to do an full analysis of the
ingredients you are using then relate these to the quaternary phase
diagrams (Al2O3-FeO-K2O-SiO2 : Al2O3-FeO-Na2O-SiO2 :
Al2O3-K2O-Na2O-SiO2 ) and assume that during processing a full
solution is created. Then you would have to follow this up with some
thermal and mineralogical analyses of real life examples.
Why not just accept that Shino is a word for organised, controlled
Chaos
Best regards,
Ivor Lewis.
Redhill,
S. Australia.
Jim Murphy on tue 29 jun 04
Hello Ivor,
<< Thinking this way presupposes that abstract elemental oxides behave as
individual entities within a melting mineral.>>
Not trying to redefine "melting behavior" as we understand it, Ivor. Just
attempting - in an apparently incoherent manner - to propose
Alumina-solubility and subsequent mullite-needle crystal growth in
high-Alumina Shino prevents "running" and may even be responsible for Iron
precipitation (the mullite-needle crystals "push" the Iron to the glaze
surface.)
I offer no empirical data or evidence to support my Shino beliefs and accept
your "organised, controlled Chaos" suggestion.
Best wishes,
Jim Murphy
Lee Love on tue 29 jun 04
Ivor and Olive Lewis wrote:
>You suggest... <>liquid" isn't formed since the Alumina is going into solution and
>creating crystal growth (mullite-needles, etc.) which eventually
>halts the formation of "glass", or as would be the case with Shino - a
>less-glossy glaze.>> Thinking this way presupposes that abstract
>elemental oxides behave as individual entities within a melting
>mineral. That is a viewpoint I would find hard to support.
>
>
A friend sent me a shino teabowl that arrived yesterday.
Looking at it, I can see two different examples of how materials can be
aggregated in a glaze. Number one, it looks like two different shinos
are used. I am guessing they have two different kinds of feldspars in
them. The bottom glaze is pinker than the whitish mat top glaze.
Secondly, looking closely, you can see in the top layer of glaze,
which is mostly mat, glossy speckles that are a little greenish. I
think these speckles are from coarse, non-refined feldspar used in the
glaze.
Yesterday, I also read an essay on Matsuzaki's shinos (Ivor
doesn't like it when I quote, so I won't share any of it here with him.
;-) ) He layers different kinds of feldspars on the same pot:
hiratsu, Indian and yagumo feldspars) and also uses iron slip underneath
the glazes. He also uses unrefined, coarse feldspar. One of the
things glaze calculation normally does not deal with is the particle
size of the materials uses. I think that it isn't a big factor when
all materials used are refined. But in unrefined materials of mixed
texture are used, larger particle size is going to require more heat
energy to melt.
I'll put up some closeups of the teabowl when I can.
--
Lee in Mashiko, Japan http://mashiko.org
http://journals.fotki.com/togeika/Mashiko/ Commentary On Pottery
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