Vince Pitelka on fri 12 feb 99
>Cordierite is notoriously sensitive to temperature. Plus or minus a few
>degrees and you are in trouble. I would not suggest this approach.
Stephen -
Could you elaborate on your warning above? Cordierite bodies are highly
refractory and thermal-shock-resistant, and are used for making kiln shelves
and furniture.
- Vince
Vince Pitelka - vpitelka@DeKalb.net
Home 615/597-5376, work 615/597-6801, fax 615/597-6803
Appalachian Center for Crafts
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
stephen baxter on sat 13 feb 99
Vince:
I remember reading about oven ware and cordierite, I think it was in cardew
but I'm not sure -about the temperature needed to form codierite. The clay
has to be soaked at that temperature for the crystals to form, once formed
they are stable. According to what I read there is a small window of
temperature above and below which the codierite will not form. Commercial
manufacturers have pretty good quality control so I wouldn't worry about
shelves and such. I will try and find the reference.Someone with a book on
phase diagrams could look it up. Perhaps someone else has heard about
this????
Steve
----------
> From: Vince Pitelka
> To: CLAYART@LSV.UKY.EDU
> Subject: Re: Cordierite Body
> Date: Friday, February 12, 1999 7:36 AM
>
> ----------------------------Original message----------------------------
> >Cordierite is notoriously sensitive to temperature. Plus or minus a few
> >degrees and you are in trouble. I would not suggest this approach.
>
> Stephen -
> Could you elaborate on your warning above? Cordierite bodies are highly
> refractory and thermal-shock-resistant, and are used for making kiln
shelves
> and furniture.
> - Vince
>
> Vince Pitelka - vpitelka@DeKalb.net
> Home 615/597-5376, work 615/597-6801, fax 615/597-6803
> Appalachian Center for Crafts
> Tennessee Technological University
> 1560 Craft Center Drive, Smithville TN 37166
Vince Pitelka on sun 14 feb 99
>I remember reading about oven ware and cordierite, I think it was in cardew
>but I'm not sure -about the temperature needed to form codierite. The clay
>has to be soaked at that temperature for the crystals to form, once formed
>they are stable. According to what I read there is a small window of
>temperature above and below which the codierite will not form.
Steve -
Yes, I agree it is impractical to expect cordierite to form in normal studio
ceramics firing processes. Below about cone 9, as I understand it, what you
get is a magnesium silicate with very high expansion, instead of cordierite,
a magnesium aluminum silicate with very low expansion. And if you soak
above cone 9 you are risking formation of crystobalite, unless you are very
sure of the disposition of all free silica in the body. But cordierite grog
is readily available, which I have always assumed would decrease thermal
expansion of the claybody. Am I right in that assumption? I am ashamed to
say that I have completely lost track of the intent of the original post on
this thread. Sometimes that happens.
- Vince
Vince Pitelka - vpitelka@DeKalb.net
Home 615/597-5376, work 615/597-6801, fax 615/597-6803
Appalachian Center for Crafts
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
John Britt on mon 15 feb 99
Stephen,
You may want ot read Chapter 14 and 15 of "Ceramic Science for the
Potter" by Lawrence and West ISBN 0-8019-7155-1.
Chapter 14 is on Thermal Shock Theory and Chapter 15 is on Thermal
Shock Bodies. In there he refers to the approximately 9 degree F
temperature range.
Good Luck,
--
Thanks,
John Britt claydude@unicomp.net
Dys-Functional Pottery
Dallas, Texas
http://www.dysfunctionalpottery.com/claydude
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