Jonathan Kaplan on tue 24 sep 96
Recently there was a post from Ruth Ballou regarding pyrophyllite and kyanite.
Pyrophyllite is a hydrous aluminum silicate, having a formula of
Al20s*4SiO2*H20. It is a stable material and helps reduce shrinkage and
and expansion in firing. Pyrophyllite can be substituted for some or all
of the flint and feldspar in a body.
I have used this material for probably 15 years, and it has helped provide
me with very stable bodies throughout the temperature range. I have used it
in casting bodies, jiggering bodies, pressing, and throwing bodies.
There are different types available. I use the Prax brand from RT Vanderbilt.
Kyanite is an aluminum silicate 3Al2)3*3SiO2 and if calcined, becomes
mullite. Raw kyanite is mostly used in the refractories industry as it
gives mechanical strength when fired due to it's interlocking crystal
structure. Because it does convert to mullite when heated, kyanite
sometimes can be added to ceramic bodies to balance the shrinkage of the
clay (Ceramic Industry 1/96)
I'd be more inclined to use pyrophyllite.
Jonathan
Jonathan Kaplan
Ceramic Design Group Ltd./Production Services
PO Box 775112
Steamboat Springs CO 80477
(970) 879-9139*voice and fax * email jonathan@csn.net
"Show up, pay attention, be a good listener, tell the truth, don't be
attatched to the results!"
gshaffer on tue 24 sep 96
Jonathan Kaplan wrote:
>
> ----------------------------Original message----------------------------
> Recently there was a post from Ruth Ballou regarding pyrophyllite and kyanite.
>
> Pyrophyllite is a hydrous aluminum silicate, having a formula of
> Al20s*4SiO2*H20. It is a stable material and helps reduce shrinkage and
> and expansion in firing. Pyrophyllite can be substituted for some or all
> of the flint and feldspar in a body.
>
> I have used this material for probably 15 years, and it has helped provide
> me with very stable bodies throughout the temperature range. I have used it
> in casting bodies, jiggering bodies, pressing, and throwing bodies.
>
> There are different types available. I use the Prax brand from RT Vanderbilt.
>
> Kyanite is an aluminum silicate 3Al2)3*3SiO2 and if calcined, becomes
> mullite. Raw kyanite is mostly used in the refractories industry as it
> gives mechanical strength when fired due to it's interlocking crystal
> structure. Because it does convert to mullite when heated, kyanite
> sometimes can be added to ceramic bodies to balance the shrinkage of the
> clay (Ceramic Industry 1/96)
>
> I'd be more inclined to use pyrophyllite.
>
> Jonathan
>
> Jonathan Kaplan
> Ceramic Design Group Ltd./Production Services
> PO Box 775112
> Steamboat Springs CO 80477
>
> (970) 879-9139*voice and fax * email jonathan@csn.net
>
> "Show up, pay attention, be a good listener, tell the truth, don't be
> attatched to the results!"
Jonathan-I understand how pyrophillite replaces silica in a clay body
but do not see a relationship to feldspar. Can you explain this to me,
as I am working hard to formulate a good cone 9 white stoneware body.
Gary Shaffer
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