Dale A. Neese on mon 7 feb 00
I am confused! Several clay body recipes that I have been considering for
wood-firing has Missouri Fireclay as an ingredient. Next there maybe a
claybody
recipe listing A.P. Green Fireclay as the ingredient. The bags I have show
A.P Green Fireclay-Missouri Fireclay. And If I wanted to mix a Randy
Johnston claybody recipe calling for Missouri Fireclay, which flavor of
Missouri Fireclay do you guess he is using? Hawthorne or A.P. Green? Which
do you think would be "the Missouri Fireclay"?
When considering any formula for either a glaze or a claybody, from a
workshop or from a ClayArt message, it would be very helpful if everyone
would make sure to include the firing cone temperature and correctly
identify each ingredient and percentage.
Dale Tex
David Hendley on tue 8 feb 00
I can't state this as fact, because I've never been to
the clay pits in Missouri, but I've always been told
that AP Green fireclay and Hawthorne bond clay are
mined from the same deposit, across the road from
each other. They are, for all intents and purposes,
the same. I would be more concerned with the mesh
size of the grind than the company that bagged it.
BTW, my opinion, Dale, is that fireclay based claybodies
are not very pleasing for wood firing. The clay, when
flashed, just goes to a dark brown; none of that nice warm
toasty color.
--
David Hendley
Maydelle, Texas
hendley@tyler.net
http://www.farmpots.com/
----- Original Message -----
From: Dale A. Neese
To:
Sent: Monday, February 07, 2000 2:21 PM
Subject: Missouri Fireclays
| ----------------------------Original message----------------------------
| I am confused! Several clay body recipes that I have been considering for
| wood-firing has Missouri Fireclay as an ingredient. Next there maybe a
| claybody
| recipe listing A.P. Green Fireclay as the ingredient. The bags I have show
| A.P Green Fireclay-Missouri Fireclay. And If I wanted to mix a Randy
| Johnston claybody recipe calling for Missouri Fireclay, which flavor of
| Missouri Fireclay do you guess he is using? Hawthorne or A.P. Green?
Which
| do you think would be "the Missouri Fireclay"?
| When considering any formula for either a glaze or a claybody, from a
| workshop or from a ClayArt message, it would be very helpful if everyone
| would make sure to include the firing cone temperature and correctly
| identify each ingredient and percentage.
| Dale Tex
|
Stephen Grimmer on tue 8 feb 00
Dale,
You're not going to like hearing this, but there are really THREE
Missouri fireclays! Besides the A.P. Green and the Hawthorne, there's a
third called Chicago-Wellsville. In the past, the APG has had intermittent
problems with sulfur, lime, iron nodule, and coal contamination. The
company's response has been that the clay is intended as a brick mortar, not
a pottery clay. Says it on the bag. Hawthorne has had similar problems, but
not as severely nor as frequently. The producer, Christy Minerals, is small
and is willing to address potter's needs; they produce a 50 mesh fireclay
(as opposed to the standard 28 mesh) that is more plastic and seems to
eliminate most impurities. I don't know about the availability of the C-W
fireclay outside the Midwest. We used it at Kansas City and it seemed OK.
If you have access to both the APG and the Hawthorne, I guess I would
try each by itself and then a blend of the two. Either way, in my book it's
a big risk to try to make functional pots using a stoneware comprised
chiefly of fireclay. Not that people don't get away with it, but the track
record hasn't been so hot. I think a better starting place for a potting
stoneware is Goldart and Roseville stonewares from Ohio, balanced with a
little ball clay, some fine grog, and feldspar. Then again, I'm one of
those porcelain guys, so my taste runs toward a slick body (in clay, too!).
I understand Tom Turner is making pots with an equal parts blend of Goldart,
Roseville, and OM-4. I threw a little of it, and it's pretty smooth and
dense. Absorption is about 1% at cone 11. Cristobalite? It's a good bet!
Anyway, in 1992, Randy Johnston was using 50 Hawthorne, 50 Chicago
Wellsville, and 12 Custer Spar for his stoneware. It is a body developed to
approximate the clay he used at Shimoka's place in Japan. Not very plastic,
but it suits his pots, kiln, slips, and work style.
I'll stop now.
steve
--
Steve Grimmer
Bowling Green State University
Bowling Green, OH
----------
>From: "Dale A. Neese"
>To: CLAYART@LSV.UKY.EDU
>Subject: Missouri Fireclays
>Date: Mon, Feb 7, 2000, 2:21 PM
>
> ----------------------------Original message----------------------------
> I am confused! Several clay body recipes that I have been considering for
> wood-firing has Missouri Fireclay as an ingredient. Next there maybe a
> claybody
> recipe listing A.P. Green Fireclay as the ingredient. The bags I have show
> A.P Green Fireclay-Missouri Fireclay. And If I wanted to mix a Randy
> Johnston claybody recipe calling for Missouri Fireclay, which flavor of
> Missouri Fireclay do you guess he is using? Hawthorne or A.P. Green? Which
> do you think would be "the Missouri Fireclay"?
> When considering any formula for either a glaze or a claybody, from a
> workshop or from a ClayArt message, it would be very helpful if everyone
> would make sure to include the firing cone temperature and correctly
> identify each ingredient and percentage.
> Dale Tex
Tom Wirt on tue 8 feb 00
Dale....
Essentially AP Green and Hawthorne are the same clay. They come from the
same vein.
That said, The AP Green is mined for the firebrick industry. It is not
intended for use in clay bodies, although many, many people (myself included
right now) use bodies in which it is a main ingredient. The problem is that
the physical specs are all over the ball park. Very little control because
the brick industry doesn't need it.
The Hawthorne Bond, is, however, mined for the pottery industry as well as
the firebrick industry. So they screen more carefully, and take greater
care in handling.
The big question is why you want a fireclay in your clay body in the first
place. It is highly refractory material which is generally comparatively
non-plastic. Better to start with ball clays, add some kaolins and maybe a
little fireclay to get the large particles. You'll end up with a much
better handling body, and don't have to kick in as much nonplastic feldspar
to melt that high temp stuff.
As has been mentioned here before, when you are considering clays for
throwing, particle size is almost as important as the chemical make-up. It
is from the mix of particle sizes that you get your throwing strength,
drying characteristics, quality of the melt in firing, and much more.
Suggest reading the "Clay" heading in Hamer as well as associated topics.
Tom Wirt
----- Original Message -----
rom: Dale A. Neese
Subject: Missouri Fireclays
> I am confused! Several clay body recipes that I have been considering for
> wood-firing has Missouri Fireclay as an ingredient. Next there maybe a
> claybody
> recipe listing A.P. Green Fireclay as the ingredient. The bags I have show
> A.P Green Fireclay-Missouri Fireclay. And If I wanted to mix a Randy
> Johnston claybody recipe calling for Missouri Fireclay, which flavor of
> Missouri Fireclay do you guess he is using? Hawthorne or A.P. Green?
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