Betty Burroughs on fri 24 jan 97
First of all, I have to tell all of you how much I am enjoying Clayart! I am
new (since November) to this list, and to owning a computer, but I am
learning fast! There is so much great information here and already I feel
I've got a world full of new friends! I hope I can contribute something of
value one of these days.
In the meantime, I would appreciate anyone's input about raku clay
bodies. I'd like to find a ready-made white body that is smooth when fired.
Living on the west coast, I can choose from Plainsman, Seattle, Laguna,
Imco, Fairey Hy-Bond and Tacoma clays. Can anyone recommend a good one? I
tried Industrial raku but the body is pinkish and does not look as great as
a white clay when sprayed with ferric chloride (I think that's correct) for
a horesehair firing. I've heard of using porcelain for raku. Any comments on
that?
Betty Burroughs
869 Cunningham Road,
Victoria, BC V9A 4M7
250-382-0974
Keith Chervenak on sat 25 jan 97
Betty,
I am very pleased with Laguna/Miller Industrial raku. If this is
what you are using also, I have not found it to be pink after raku firing
but it certainly is after the bisque fire.
Keith
Keith Chervenak
kac2@po.cwru.edu
Case Western Reserve University
Cleveland, Ohio U.S.A.
vpitelka@Dekalb.Net on sat 25 jan 97
>I'd like to find a ready-made white body that is smooth when fired.
Betty -
The standard West Coast low-fire sculpture body, which is 50-50 ball clay
and talc, makes a pretty good raku body. The high talc content makes it
very thermal-shock-resistant. It fires smooth and white. There are of
course variations from one manufacturer to another. I have used one of
Laguna's talc-ball clay bodies, but I cannot remember which one. I
recommend you call Laguna in City of Industry, CA (LA Area) and ask them to
recommend which talc-ball clay body gives highest thermal-shock resistance.
Good luck.
- Vince
Vince Pitelka - vpitelka@Dekalb.Net
Phone - home 615/597-5376, work 615/597-6801
Appalachian Center for Crafts
1560 Craft Center Drive, Smithville TN 37166
Tony Hansen on sun 26 jan 97
> The standard West Coast low-fire sculpture body, is 50-50 ball clay
> The high talc content makes it very thermal-shock-resistant.
Unless I am mistaken talc is added to increase thermal expansion
so the body should be less thermal-shock-resistant? The secret of
good thermal shock bodies is grog and low expansion materials like
kyanite, pyrophilite, etc.
--
=================================================================
Tony Hansen, IMC - Get INSIGHT 5 beta or The Magic of Fire II at
http://digitalfire.com or http://www.ceramicsoftware.com
Martin Butt on mon 27 jan 97
Betty;
Re. your search for a smooth white raku body; I have used Laguna's WS-5 with
great success for raku and horsehair firing. Fairly smooth, and white;
survives better than most similar textured bodies. You asked about raku
firing with porcelain; definitly possible, but your loss rate will probably
go way up. You might want to try B-Mix (Laguna) as an in between; not quite
a true porcelain, but very smooth and white. Works for me most of the time,
especially on smaller, closed forms, and looks great with terra sig and
horsehair.
Martin Butt
Coyote Craft School
Albuquerque, NM
http://members.aol.com/martinb888
Vince Pitelka on mon 27 jan 97
>Unless I am mistaken talc is added to increase thermal expansion
>so the body should be less thermal-shock-resistant? The secret of
>good thermal shock bodies is grog and low expansion materials like
>kyanite, pyrophilite, etc.
>Tony Hansen, IMC - Get INSIGHT 5 beta or The Magic of Fire II at
>http://digitalfire.com or http://www.ceramicsoftware.com
Tony -
I can't argue with the expert, but I have used the talc-ball clay body in
raku with good results. But I am curious. If magnesium in general is
characterized by very low thermal expansion, then why would magnesium
silicate (talc) be added to give higher thermal expansion?
- Vince
Vince Pitelka - vpitelka@Dekalb.Net
Phone - home 615/597-5376, work 615/597-6801
Appalachian Center for Crafts
1560 Craft Center Drive, Smithville TN 37166
Tony Hansen on mon 27 jan 97
> I would appreciate anyone's input about raku clay bodies.
> I'd like to find a ready-made white body that is smooth when fired.
> Living on the west coast, I can choose from Plainsman, Seattle, Laguna,
> Imco, Fairey Hy-Bond and Tacoma clays. Can anyone recommend a good one?
Check out the Plainsman web site at http://digitalfire.com/plainsman
The Raku97 body is brand new and will be shipping in a couple of weeks.
Every body has detailed information and you can register with each page
so that when it changes you get automatic email notice.
We will be adding current changes for each body in the next few weeks.
For example, if a body has a little more speckle than usual, the code
numbers will be noted and if you are registered for the page you will
receive notice.
=================================================================
Tony Hansen, Plainsman Clays
Tony Hansen on tue 28 jan 97
> Vince said: I have used the talc-ball clay body in
> raku with good results. But I am curious. If magnesium in general is
> characterized by very low thermal expansion, then why would magnesium
> silicate (talc) be added to give higher thermal expansion?
Talc is used as a low fire body addition to encourage conversion of excess
free quartz to cristobalite to increase body expansion which reduces
crazing. It is also used to produce thermal shock resistant stoneware
bodies where it acts as a low expansion flux which reduces body expansion
by converting available quartz mineral to silicates of magnesia. Cordierite
bodies used in kiln furniture and flameware extend this concept so that all
free quartz is used up.
--
=================================================================
Tony Hansen, IMC - Get INSIGHT 5 beta or The Magic of Fire II at
http://digitalfire.com or http://www.ceramicsoftware.com
Bryan Hannis on tue 28 jan 97
Betty Burroughs wrote:
>
> ----------------------------Original message----------------------------
> First of all, I have to tell all of you how much I am enjoying Clayart! I am
> new (since November) to this list, and to owning a computer, but I am
> learning fast! There is so much great information here and already I feel
> I've got a world full of new friends! I hope I can contribute something of
> value one of these days.
> In the meantime, I would appreciate anyone's input about raku clay
> bodies. I'd like to find a ready-made white body that is smooth when fired.
> Living on the west coast, I can choose from Plainsman, Seattle, Laguna,
> Imco, Fairey Hy-Bond and Tacoma clays. Can anyone recommend a good one? I
> tried Industrial raku but the body is pinkish and does not look as great as
> a white clay when sprayed with ferric chloride (I think that's correct) for
> a horesehair firing. I've heard of using porcelain for raku. Any comments on
> that?
>
> Betty Burroughs
> 869 Cunningham Road,
> Victoria, BC V9A 4M7
> 250-382-0974I use laguna raku # 548 and also Coleman raku for my horsehair pot
these bodies are then TS on bisque they are then ok for spraying with
ferric chloride. If yu need more info email me at my net address.
Bryan
COOPJ@aol.com on tue 28 jan 97
Vince-
Talc (Magnesium Silicate) is very common in low fire bodies and helps to
sinter
or stick things together in the firing. At low fire temperatures it is a high
expansion material which helps glaze fit which is especially difficult at
earthenware temperatures. Talc is at the same time, a low expansion material
at high temperatures when it is in a vitreous state. Silica acts the same
way. In crystalline form (quartz) silica flour and sand it is a high
expansion material yet the same material added to a glaze is a low expansion
oxide when it is in a galass or glaze.
Jim Cooper
Vince Pitelka on wed 29 jan 97
>Talc is used as a low fire body addition to encourage conversion of excess
>free quartz to cristobalite to increase body expansion which reduces
>crazing.
>==========================================================
>Tony Hansen
Tony -
OK, my turn again. I have always been under the impression that
Cristobalite only forms above 2250 Fahrenheit. Am I right? And if so, how
could talc encourage cristobalite formation in low-fire bodies?
- Vince
Vince Pitelka - vpitelka@Dekalb.Net
Phone - home 615/597-5376, work 615/597-6801
Appalachian Center for Crafts
1560 Craft Center Drive, Smithville TN 37166
Tony Hansen on thu 30 jan 97
> OK, my turn again. I have always been under the impression that
> Cristobalite only forms above 2250 Fahrenheit. Am I right? And if so, how
> could talc encourage cristobalite formation in low-fire bodies?
Wow, I never thought of that, always just assumed. Let me look into it.
=================================================================
Tony Hansen, IMC
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