peter coates on tue 17 apr 01
Hello All...
I have been researching some on making my own clay body. I haven't found =
much in the way of limit formulas or such... mostly I have found that =
the books tell you what the different components are, yadda yadda... and =
I found a allot of recipes for different bodies.
Here is an example...(Jeff Zamek's cone 9 white stoneware)
goldart 15
apg missouri fire clay 15
pioneer kaolin 10
epk kaolin 18
tenessee ball clay #10 20
custer feldspar 12
flint 200x 10
silica sand F-65 5%
How easily can you change ingredients such as tile #6 for pioneer with =
out having to reformulate it? (since I can't seem to figure out how to =
formulate a clay body)
how big a deal is it to remove the grog?=20
etc... etc...=20
even my Daniel Rhodes book only covers clay bodies from pages 22 to 46 =
and most of that doesn't say a whole lot. so any info, suggestions or =
stories would be very much appreciated.
Pete form Oklahoma...
David Hendley on wed 18 apr 01
Hi Pete, formulating claybodies is really not too similar
to formulating glazes. I don't know of any 'limit formulas'
for claybodies.
A lot of it just comes down to what your supplier carries
and asking other area potters what they use.
Others may disagree, but I would not use an ingredient that
no local supplier carries, and thus has to be shipped across
the country, just because it's in a recipe in a book or magazine.
Most cone 10 stoneware claybodies end up being variations
of your example. That is,
about 40 to 60% fireclay/kaolin/stoneware clay (Goldart),
about 20 to 40% ball clay,
about 12% feldspar,
about 10 200m silica,
and 0-5% grog or sand.
=46rom this starting point, you just adjust the recipe to
account for what's readily available, what kind of firing
properties you want, and handling, or forming, properties.
For example, use more kaolin if you want a light colored
body, don't use fireclay if you want a smooth-textured
clay, use more ball clay if you want more plasticity.
=46rom here, you can fine-tune the body by selecting the
best ball clay for your purposes, the particle size of grog
you desire, and so on.
Be sure to test small batches for glaze fit, vitrification,
shrinkage, warping, and so on, before you make big batches!
Take a look at Jonathan Kaplan's article about claybodies at:
http://digitalfire.com/education/clay/kaplan1.htm
--
David Hendley
Maydelle, Texas
hendley@tyler.net
http://www.farmpots.com/
----- Original Message -----
From: peter coates
To:
Sent: Tuesday, April 17, 2001 5:38 PM
Subject: formulating clay bodies
Hello All...
I have been researching some on making my own clay body. I haven't found
much in the way of limit formulas or such... mostly I have found that the
books tell you what the different components are, yadda yadda... and I fo=
und
a allot of recipes for different bodies.
Here is an example...(Jeff Zamek's cone 9 white stoneware)
goldart 15
apg missouri fire clay 15
pioneer kaolin 10
epk kaolin 18
tenessee ball clay #10 20
custer feldspar 12
flint 200x 10
silica sand F-65 5%
How easily can you change ingredients such as tile #6 for pioneer with ou=
t
having to reformulate it? (since I can't seem to figure out how to formul=
ate
a clay body)
how big a deal is it to remove the grog?
etc... etc...
even my Daniel Rhodes book only covers clay bodies from pages 22 to 46 an=
d
most of that doesn't say a whole lot. so any info, suggestions or stories
would be very much appreciated.
Pete form Oklahoma...
Pancioli on fri 20 apr 01
Pete:
It helps to understand a clay body by translating its "brand"
name components into their generic names; then you can consider
substitutions. For example in the Zamek body you gave:
Gold Art is a plastic stoneware clay firing to med high temp.
APG is a high temperature moderately plastic firecly.
Pioneer is a coarse kaolin (high temp.)
EPK is a plastic finer grained kaolin (high temp.)
Tennessee Ball is a very fine grained medium temp. ball clay
(high in silica).
Sand is one kind of coarse additive (use for "tooth",
to help the body stand up, and for good drying properties).
The variety of clays in this body are used to vary particle size,
be sufficiently plastic (but not flabby), and mature at the right
temperature. The feldspar and flint are added to increase
vitrification.
I personally would not use sand in place of grog, except for a salt fire
body. I also would not use more than 20 percent ball clay in any high
temp body because it is itself too low in temp and can make a body too
fat and flabby.
I hope this helps a little.
Diana
Craig Martell on sun 22 apr 01
Hello Pete:
There are two articles by Jim Robinson in Studio Potter that will give you
some direction. "Fear of Silica" in the June 1981 issue I think. Might be
June '82 though. The other one is "Body Building for Potters in the June
1988 issue. Both articles give some very good info on the nuts and bolts
mechanics of balancing bodies for vitrification, strength, and glaze
fit. Studio Potter has a web site and you can search for the issues there
and order them if you want. Where I live, the library has SP and you can
check out issues at the Reference Desk.
The basic approach to making a claybody is to first, decide on temp,
atmosphere, and clay type for that application. It's beneficial to go to
your supplier and get several different clays and fire the samples to see
what they will do with no blending or additions. Test them for plasticity,
workability, shrinkage, the whole shot so you can build your own personal
reference. Do some two and three clay blends and up to four and five as
you gain some insight into their properties. Once you arrive at some
possible clay blends that strike your fancy, blend in some potash spar to
bring them into the proper vitrification point. You figure this out by
testing them for absorbtion of water after they are fired to maturation
temp. About 2.5% absorbtion is ideal for a stoneware body. You don't want
to get stonewares too tight and brittle. Then comes the tough
part. Finding the correct amount of added quartz(silica) to promote good
glaze fit.
The reason I mentioned Jim's articles is that he gives recipes for 10
glazes that go from low to high expansion and he gives advice on how to use
these glazes to assess whether or not you have a balanced, well formulated
claybody. These glazes are a great tool for assessing clays and figuring
the correct additions of spar and silica.
I've just gone thru the bare minimum basics and I haven't talked about
stuff like grog to control plastic shrinkage and to give tooth and working
strength. Not enough time. The problem about doing any of this
formulating stuff now is that we have SO much stuff at our fingertips that
it's a full time job just becoming well versed in materials and what's
available. Anyway, I CAN recommend a good grog. North American
Refractories makes several mesh sizes of calcined kaolin grog that is very
good for clays. The brand name is "Ione".
hope this helps a bit, Craig Martell in Oregon
Brian Molanphy on sun 22 apr 01
diana wrote:
> I personally would not use sand in place of grog, except for a salt fire
> body.
>
>
thanks for your post. would you say more about why sand is appropriate for
salt firing, please. would this be true of any vapor-firing, including wood
firings with sufficient flyash?
Pancioli on wed 25 apr 01
Regarding using sand as grog in a clay body:
I was taught that it was bad to load a body with too much silica, and
sand, of course, markedly increases the silica content. The reason given
was that too much silica could cause dunting.
The only exception was its use in salt bodies, because the salt would
adhere to the sand particles at the surface and increase the intensity
of the orange-peel surface.
Diana
Snail Scott on thu 26 apr 01
At 09:38 PM 4/25/01 +0100, you wrote:
>I was taught that it was bad to load a body with too much silica, and
>sand, of course, markedly increases the silica content. The reason given
>was that too much silica could cause dunting.
>Diana
Sand behaves competely differently from
powdered silica; it does not completely
enter the melt. See 'Ceramic Technology
for Potters and Sculptors' by Cuff.
-Snail
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