Fred Cook on thu 15 aug 02
When a clay recipe calls for stoneware clay as part of the mix...not ball
clay, not china clay, but stoneware clay....is it possible to substitute
some things.
I am having trouble finding a clay supplier who sells 50 lb bags of
"stoneware" clay. In most catalog listings under raw materials.."clay"
there are of course categories for ball clays, fire clays, Kaolins, red
earthenware... but not "stoneware".
Any suggestions?
Thank you for any help with this as well as for all the support of the list.
Fred Cook
Snail Scott on fri 16 aug 02
At 12:10 PM 8/15/02 -0400, you wrote:
>I am having trouble finding a clay supplier who sells 50 lb bags of
>"stoneware" clay.
I know that Laguna sells Goldart, which some
people categorize as a stoneware. They also
sell premixed dry claybodies in 50# bags.
-Snail
vince pitelka on fri 16 aug 02
> I am having trouble finding a clay supplier who sells 50 lb bags of
> "stoneware" clay. In most catalog listings under raw materials.."clay"
> there are of course categories for ball clays, fire clays, Kaolins, red
> earthenware... but not "stoneware".
Fred -
One of the most common dry stoneware clays is Cedar Heights "Goldart" clay,
and it is available from almost any clay supplier. Others are available as
well, and your clay supplier should be able to tell you which ones they
have.
When we talk about a "stoneware claybody," we are referring to a blended
claybody for making stoneware pottery, that fires dense, durable, and
low-porosity at high-fire temperatures. That usually involves a mix of
different kinds of raw clays, feldspar, grog or sand, and sometimes flint.
But when you are talking about dry raw materials, "stoneware clay" refers to
a variety of secondary clays (clays which have been transported by wind or
water away from the site of the parent rock), which contain a high
percentage of kaolinite, the essential clay mineral, plus some flux and
other contaminants. They usually have a fairly broad distribution of
particle sizes, giving high plasticity, and in firing they mature at
high-fire temperatures. But they rarely produce an ideal claybody without
other additions, as mentioned above.
Best wishes -
- Vince
Vince Pitelka
Appalachian Center for Crafts
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
Home - vpitelka@worldnet.att.net
615/597-5376
Work - wpitelka@tntech.edu
615/597-6801 ext. 111, fax 615/597-6803
http://www.craftcenter.tntech.edu/
Ron Roy on sat 17 aug 02
The definition I have always used for stoneware clay is - matures between
cone 6 and 10 - maybe 11 and has a shrinkage of about 12%. Makes it usable
as is for throwing pots if drying and firing characteristics suit.
Many of our so called ball clays have a shrinkage of about 14% and most
mature between cone 6 and cone 10 so they are "almost stoneware clays -
OM#4 would be an example. One of the problems with many of this type of
clay is the natural variation in maturing temperature and shrinkage.
If you could find a stoneware clay that was stable then a body could be
made of that clay but - where would you get the data to rely on and what
guarantee would you have that the next batch would be the same. What I am
trying to say is - use the ball clays and the fireclays and the kaolins to
make a body that you can adjust to what you want - my rule of thumb is
don't use any more than 25% of any one clay - and have at least 5 different
clays in a body - the natural variations will tend to cancel each other
out.
GoldArt - as someone pointed out - can be thought of as a stoneware clay -
but you will find it varies so not too much of it.
It is difficult for me to understand why the "stoneware" clay mentioned
does not have some data with it - does it mature at 6 or 10 for instance -
if there is say 25% of that clay in the body surely it will have an effect
on maturity.
I suggest you simply use any body recommendations as a starting point and
test them to see if they are suitable for the temperature and atmosphere
you plan to fire at. Test the clays you have available so you know how much
they shrink and how mature they are at the temperature you want to fire
them to. That way you can adjust your clay body to do what you want.
In "Clay and Glazes for the Potter" - by Dan Rhodes (currently rewritten by
Hopper) chapter 5 has a general description of kinds of clay. The chapters
on clay have helped me understand the different classifications of clays -
they are general but a decent foundation to build on.
RR
>When a clay recipe calls for stoneware clay as part of the mix...not ball
>clay, not china clay, but stoneware clay....is it possible to substitute
>some things.
>
>I am having trouble finding a clay supplier who sells 50 lb bags of
>"stoneware" clay. In most catalog listings under raw materials.."clay"
>there are of course categories for ball clays, fire clays, Kaolins, red
>earthenware... but not "stoneware".
>
>Any suggestions?
>
>Thank you for any help with this as well as for all the support of the list.
>Fred Cook
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
karen gringhuis on sat 17 aug 02
Fred -
You might be interested in Cushing's HANDBOOK which
includes 2 pgs. of individual clay compositions plus 9
pgs. of clay BODY recipes. One can learn a lot by
scanning through these. Plus it's a whole bookful of
good information.
Vince's explanation was right on.
=====
Karen Gringhuis
KG Pottery
Box 607 Alfred NY 14802
Personal e-mail to:
KGPottery@hotmail.com
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