Charles on mon 14 jan 08
I can't begin to answer the question, but it makes me want to ask another one. There is a lot of published help available out there for learning how to formulate, modify and correct glazes, but as far as I know, all the instructions dealing with clay bodies are side notes in glaze books. Is there a definitive source out there for information of formulating, modifying and correcting clay bodies? Inquiring minds want to know :)
-Charles
--- On Mon, 1/14/08, arthur gruner <grunerap@YAHOO.COM> wrote:
From: arthur gruner <grunerap@YAHOO.COM>
Subject: [CLAYART] Looking for help formulating a cone 6 throwing body
To: CLAYART@LSV.CERAMICS.ORG
Date: Monday, January 14, 2008, 9:18 PM
I'm a beginning potter but thought I'd take a shot at mixing my own clay
body. It would be for throwing, mainly, and fired to cone 6 oxidation. I'm
mainly having trouble figuring out how much flux I need, and which fluxes work
best.
I started with a recipe from Chappell, modified it a little (added some
fireclay) and came up with this:
OM-4 Ball Clay 32
Hawthorn Bond 20
EPK 24
Silica 13
Talc 7
Neph Sy 4
add 10% grog.
It seems to work OK on the wheel, but I haven't fired any yet. When I
plugged this recipe into Insight, it came up with a very low expansion rate.
I'm a little worried that most glazes will craze on this body. I think
I'll fire some unglazed, just to see how porous it is.
I decided I wanted to try a brown colored body, and Redart has a higher
expansion rate, so I came up with a second recipe:
Redart 24
Hawthorn Bond 19
OM-4 Ball Clay 19
EPK 20
Silica 6
Neph Sy 10
Talc 2
Add 10% grog
Does this recipe look good? Has anyone used a similar formula?
Thanks,
Paul Gruner
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arthur gruner on mon 14 jan 08
I'm a beginning potter but thought I'd take a shot at mixing my own clay body. It would be for throwing, mainly, and fired to cone 6 oxidation. I'm mainly having trouble figuring out how much flux I need, and which fluxes work best.
I started with a recipe from Chappell, modified it a little (added some fireclay) and came up with this:
OM-4 Ball Clay 32
Hawthorn Bond 20
EPK 24
Silica 13
Talc 7
Neph Sy 4
add 10% grog.
It seems to work OK on the wheel, but I haven't fired any yet. When I plugged this recipe into Insight, it came up with a very low expansion rate. I'm a little worried that most glazes will craze on this body. I think I'll fire some unglazed, just to see how porous it is.
I decided I wanted to try a brown colored body, and Redart has a higher expansion rate, so I came up with a second recipe:
Redart 24
Hawthorn Bond 19
OM-4 Ball Clay 19
EPK 20
Silica 6
Neph Sy 10
Talc 2
Add 10% grog
Does this recipe look good? Has anyone used a similar formula?
Thanks,
Paul Gruner
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Ben Shelton on tue 15 jan 08
Paul,
I cannot comment on the particular body formulas you have quoted but I can
say that body formulation results are only results when you test them.
Theoretical opinions are only good as a starting point. test, test, test
What I can suggest is a method that may help you out.
The calculated expansions derived by softwares are great starting places for
comparison but you actually need to test the clay for both absorption and
expansion. In "Mastering Cone 6 Glazes" there is a method described for
using a series of glazes, each with a slightly higher expansion than the
previous, to test expansion of a clay body. I really like this method. It
has taught me tons about glaze fit and body expansion. You glaze and fire a
series of test pieces and monitor them for crazing over the next couple of
weeks. Don't forget to mark each tile as to which test glaze it has on it.
Freeze the samples over night then pour boiling water over them and let them
cool to room temp. Look for crazing. do this every couple of days for a
couple weeks or a month. Color the glaze sample with a sharpie marker then
wipe it off with rubbing alcohol. If there are cracks in the glaze the
marker will stain them and make them easier to see. Then line up the tiles
and it will easy to see which tiles are crazed and which are not. Compare
this to the calculated expansion for the glazes and you will have a pretty
solid idea of where that clay bodies expansion is.
MC6G also describes a method for testing absorption. If you can't buy the
book, contact your local library, they can probably get it through inter
library loan.
Also, there are some GREAT articles along this line published in Studio
Potter magazine. "Body Building For Potters" by Jim Robinson is the name of
one. Also look for an Author named David Beumee I believe.
Ah look what I found
http://www.davidbeumee.com/ceramic-monthly.pdf
http://www.davidbeumee.com/beumee-article.pdf
These articles are great and right on topic.
I usually make my test tiles by extruding them. They are shaped like an
upside down letter T and I use a number stamp to stamp them when wet. Each
tile is then marked with the type of clay the tile is made form. It is too
hard to tell otherwise.
I guess that is all off the top of my head.
Ben
Michael Wendt on tue 15 jan 08
Paul,
May I suggest much more flux.
Just for comparison, the Alfred
recipe for cone 10 porcelain
is:
25 Kaolin
25 Ball clay
25 Feldspar
25 Silica
I started here but wanted
a more reactive surface
because I fast fire (in by
10:00 am- cone 10 by 5:00 pm)
I use:
50 Helmer Kaolin
12.5 Feldspar
12.5 Nepheline Syenite
25 Silica
Porosity is near zero
shrinkage is 12.5%
low warping or slumping
fired color is very white in oxidation.
I would start with your recipe
as one end of a line blend.
Mix a second version with
much more flux as the other
end. Mix 10-20 lbs of each.
Bar test both samples to cone 6
with a protective sheet under them
and rolled rods of a cone 10 clay
supporting each end so that you can
assess slumping as well.
Ideally, we want an overfluxed version
at one end of the line blend and an
underfluxed version at the other end.
If you do porosity, shrinkage and
slump tests and find a recipe the first
time out, congratulations.
If one body is overfluxed and the
other is underfluxed, you can create
intermediate blends using stack and
slam wire wedging 40 doublings.
Weigh the proportions of each recipe
something like this:
1:4, 2:3, 3:2, 4:1
Once a candidate range has been found,
further refinement can be made by
using the two end points in the range
as starting points and increasing the
level of detail by another decimal
point. say the proportions 2:3 and
3:2 turned out to be over and under
matured.
Then do:
55:45, 50:50, 45:55... (3:2 can be
expressed as 60:40)
Additional refinement can be made
with a third line bend to 3 decimal
places like this:
550:450, 545:455, 540:460,...
you can see why it is easy this way
because you made two initial batches
that were large enough to permit
many blend trials to zero in on the
desired characteristics for the clay body.
I developed this blending method during
my term as a research assistant for the
University of Idaho's Research Foundation
in the early 70s and have used it for both
clay body and glaze development over
the years.
One final note:
once you settle on a recipe, mix the
recipe from fresh ingredients at least
twice using the calculated
values to see if you get the same results
as the stack and slam trials.
Then be sure you test every batch you
make before you commit many hours
to making work with it. With your
new found understanding of how clay
bodies respond to more or less flux,
silica and refractories, you will nor fear
to adjust a batch that may have been
made wrong.
Regards,
Michael Wendt
Wendt Pottery
2729 Clearwater Ave.
Lewiston, Id 83501
U.S.A.
208-746-3724
wendtpot@lewiston.com
http://www.wendtpottery.com
http://UniquePorcelainDesigns.com
Paul wrote:
Redart 24
Hawthorn Bond 19
OM-4 Ball Clay 19
EPK 20
Silica 6
Neph Sy 10
Talc 2
Add 10% grog
Does this recipe look good? Has anyone used a similar
formula?
Thanks,
Paul Gruner
Ron Roy on thu 17 jan 08
Hi Paul,
I've compared the first one with a white stoneware from Tuckers - looks
like you should try one with the talc at 6 instead of 7 and you better add
some Epsom salts to counter the defloccing action of the Neph Sy. You don't
need much - 0.2 lbs per 100 lbs of dry clay - make sure it's completely
dissolved before you add it to the water.
The second one has way too much flux - remember that Red Art has a lot of
flux in it. Try one without the talc and only 2.5 Neph Sy.
Let me know if you need more on this - would you like me to send my clay
testing instructions?
RR
>I'm a beginning potter but thought I'd take a shot at mixing my own clay
>body. It would be for throwing, mainly, and fired to cone 6 oxidation.
>I'm mainly having trouble figuring out how much flux I need, and which
>fluxes work best.
>
> I started with a recipe from Chappell, modified it a little (added some
>fireclay) and came up with this:
>
> OM-4 Ball Clay 32
> Hawthorn Bond 20
> EPK 24
> Silica 13
> Talc 7
> Neph Sy 4
> add 10% grog.
>
> It seems to work OK on the wheel, but I haven't fired any yet. When I
>plugged this recipe into Insight, it came up with a very low expansion
>rate. I'm a little worried that most glazes will craze on this body. I
>think I'll fire some unglazed, just to see how porous it is.
>
> I decided I wanted to try a brown colored body, and Redart has a higher
>expansion rate, so I came up with a second recipe:
>
> Redart 24
> Hawthorn Bond 19
> OM-4 Ball Clay 19
> EPK 20
> Silica 6
> Neph Sy 10
> Talc 2
> Add 10% grog
>
> Does this recipe look good? Has anyone used a similar formula?
> Thanks,
> Paul Gruner
>
>
>
>
>
>
>
>---------------------------------
>Looking for last minute shopping deals? Find them fast with Yahoo! Search.
>
>______________________________________________________________________________
>Clayart members may send postings to: clayart@lsv.ceramics.org
>
>You may look at the archives for the list, post messages, or change your
>subscription settings here: http://www.acers.org/cic/clayart/
>
>Moderator of the list is Mel Jacobson who may be reached at melpots2@visi.com
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Paul Gruner on fri 18 jan 08
Ron,
Yes, please send instructions on testing clay. I did see a method for
testing absorption, but I'd like your particular method. I've got your
book, so I have the recipes for different expansion glazes to test glaze
fit.
Neph Sy causes defloccing in bodies? I think I'll stick to G-200 from now
on.
Do you have any advice for Silica and Alumina levels in bodies? Or Si:Al
ratios? Is magnesium an effective body flux at cone 6 bodies? I think I
read in the archives that you said people should use mostly potassium and
sodium.
-Paul
On Thu, 17 Jan 2008 19:33:57 -0500, Ron Roy wrote:
>Hi Paul,
>
>I've compared the first one with a white stoneware from Tuckers - looks
>like you should try one with the talc at 6 instead of 7 and you better add
>some Epsom salts to counter the defloccing action of the Neph Sy. You
don't
>need much - 0.2 lbs per 100 lbs of dry clay - make sure it's completely
>dissolved before you add it to the water.
>
>The second one has way too much flux - remember that Red Art has a lot of
>flux in it. Try one without the talc and only 2.5 Neph Sy.
>
>Let me know if you need more on this - would you like me to send my clay
>testing instructions?
>
>RR
>
>
>>I'm a beginning potter but thought I'd take a shot at mixing my own clay
>>body. It would be for throwing, mainly, and fired to cone 6 oxidation.
>>I'm mainly having trouble figuring out how much flux I need, and which
>>fluxes work best.
>>
>> I started with a recipe from Chappell, modified it a little
Ron Roy on sat 19 jan 08
Hi Paul,
Neph Sy has some soluble sodium - clay is OK at the beginning but can
slowly deflocc - the Epsom salts work fine - and you will have trouble
melting white clays at cone 6 without it - unless you use talc. I use a
combination of Neph Sy and G200 to keep the cone 6 porcelains balanced.
The ratios are all over the place for clay bodies so they are not that
useful. The amount of Alumina and Silica in relation to the fluxes is the
important thing. I use the Seger formula all the time to adjust clay bodies
- it works just fine - do you use a calculator? Where are you?
I do think Talc is an effective body flux at cone 6 - but a little can make
a big difference so learn to weigh it properly. There is some concern about
some talc's being carcinogens by the way - make sure you don't breath clay
dust anyway.
I'll send the clay testing instructions directly - it's rather a long document.
RR
>Ron,
>
>Yes, please send instructions on testing clay. I did see a method for
>testing absorption, but I'd like your particular method. I've got your
>book, so I have the recipes for different expansion glazes to test glaze
>fit.
>
>Neph Sy causes defloccing in bodies? I think I'll stick to G-200 from now
>on.
>
>Do you have any advice for Silica and Alumina levels in bodies? Or Si:Al
>ratios? Is magnesium an effective body flux at cone 6 bodies? I think I
>read in the archives that you said people should use mostly potassium and
>sodium.
>
>-Paul
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Paul Gruner on sun 20 jan 08
>The ratios are all over the place for clay bodies so they are not that
>useful. The amount of Alumina and Silica in relation to the fluxes is the
>important thing. I use the Seger formula all the time to adjust clay
bodies
>- it works just fine - do you use a calculator? Where are you?
>
Ron,
I'm in Annapolis Maryland. I'm using Insight - I actually like using it
to compare different glaze recipes, reformulate them or make adjustments.
In fact, I plugged some of the throwing body recipes from Chappell's book
into Insight just to see what they look like in the Seger formula. I got
some wildly varying numbers, but that might be because I didn't have data
for all the clays cited in Chappell - I just made some substitutions based
on wild guesses. (I would post the results here, but I think my guesses
make the data pretty worthless.)
I just bisque-fired some bars of my clay, including some with Redart
blended in. (I know you said my clay was probably over-fluxed, and it'll
be even worse with the Redart, but I already had the clay mixed before I
read your post). Well, we'll see what happens. I'll post the test results
after I fire them.
-Paul
PS - Congratualtions to you and John Hesselberth. The current issue of
Pottery Making Illustrated had a poll of readers' favorite books and MC6G
was number one.
Lee on sun 20 jan 08
On Jan 16, 2008 12:40 PM, Michael Wendt wrote:
> I started here but wanted
> a more reactive surface
> because I fast fire (in by
> 10:00 am- cone 10 by 5:00 pm)
> I use:
> 50 Helmer Kaolin
> 12.5 Feldspar
> 12.5 Nepheline Syenite
> 25 Silica
> Porosity is near zero
Michael, do you add epsom salts or is 12.5% Neph Sye not a problem?
THis sounds like a good soda body.
--
Lee in Mashiko, Tochigi Japan
http://mashikopots.blogspot.com/
"Tea is nought but this: first you heat the water, then you make the
tea. Then you drink it properly. That is all you need to know."
--Sen No Rikyu
"Let the beauty we love be what we do." - Rumi
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