Jeffrey James on wed 26 aug 98
Hello
I think I need some help. I just got hired as the pottery derictor at a
local fine arts center. The clay body that the center has been using is
giveing me problems. This is the body
Cone 04-10 OX or RED.
5 scoops Goldart
2 scoops Ball clay (ten.)
1 scoop fire clay(Harthorn
3/4-1 scoop corderite
once a month 1/4 scoop fine grog
once a month 1 cup Bentonite
This is mixed dry (layered) first, then mixed in a Soldner with water
till firm. The clay is used within a week of being mixed, I do not have
room to store the clay to allow it to age ( the last director did not
think it helped much) and do not have a pugmill. Now the problem the
clay is short when throwing and not very plastic, as I said I do not
have the room to store the clay for long, one - two weeks at the most.
Does anyone have any ideas for helping the throwing qualties of this
body. We are fireing a gas reductoin kiln ^ 10.
Thank You
Jeff
Craig Martell on thu 27 aug 98
Jeff says:
>The clay body that the center has been using is
>giveing me problems. This is the body
>
> Cone 04-10 OX or RED.
>5 scoops Goldart
>2 scoops Ball clay (ten.)
>1 scoop fire clay(Harthorn
>3/4-1 scoop corderite
>
>once a month 1/4 scoop fine grog
>once a month 1 cup Bentonite
Jeff:
This claybody, understating things a bit, is probably very unbalanced .
Sorry, I don't mean to be a jerk or "know it all" but this body really needs
some work.
Is the 04 to 10 temp rating a typo? There are no known claybodies that will
be suitable throughout a wide temp range such as this.
If you are firing this one to cone 10, do an absorbtion test to determine
the level of vitrification that you are getting. I would bet this body is
quite porous due to no added feldspar. It should be less than 4%. Are any
of your glazes shivering? Bodies with no spar can develop a lot of
cristobalite, which will cause glazes to shiver and will also exhibit
cracking due to thermal shock. If you don't see shivering etc. it's probably
due to the fact that Hawthorne will contribute some natural fluxes, micas I
think, which helps to neutralize some of the cristobalite. A fast cooling
will also retard cristobalite development. Also, the corderite content will
impart some thermal shock resistance and will flux the body as well but
corderite bodies are real tricky, and sometimes have a real short and tight
firing range which strengthens the idea that the 04 to 10 rating you give
the clay is wishful thinking. The fact that your receipe calls for 3/4 to 1
scoop of corderite to the claybody leads me to believe that a more careful
approach to formulation and mixing would be approproate. If it were me, I
would dump the corderite and use feldspar and silica. If you want some good
info on corderite bodies, read Ceramic Science for The Potter by Lawrence
and West.
I would suggest mixing by weight rather than by volume especially if you are
going to continue using corderite. Different clays have different molecular
weights and you really don't know what the percentages and molecular
contributions of silica, alumina, and other oxides are. Most clays can be
quite workable with 20% or so of ball clay but you have no idea what the
percentage in this case is. You could start by weighing the volumes that
you are now using and put these weights into a percentage formula in order
to get an idea of the percentage composition of this body. The types of
clays that you are using may be just fine but you will probably have to
adjust them a bit to get the kind of workability you want. You will have to
add some spar for strength and fusion, or adjust the corderite content, and
probably add some ground silica for glaze fit etc. Formulate the body to
work at the temp you normally fire to, and don't try to achieve an 04 to 10
body. It just doesn't work well.
You might want to look at Studio Potter, June 1988, Bodybuilding for Potters
by Jim Robinson, for some good information on claybody formulation and dynamics.
regards, Craig Martell-Oregon
John K. Dellow on thu 27 aug 98
Jeffrey, try adding 10% vinager to the water when makeing up the body.
John Dellow
Grimmer on thu 27 aug 98
Jeff,
Right off the bat, I would suggest reversing the mixing order; start with
water in the mixer, then add clay, fluxes, and fillers as the mixer turns.
This way, you ensure thorough wetting of the clay platelets. Adding water to
dry clay tends to make the clay particles clump together in little balls.
Bentonite, especially, is prone to this. And, yes, clay straight out of the
mixer can be pretty short!
Now, on to the body you are using. From what I am able to gather, cordierite
is a magnesium silicate, related to talc, used in flameproof bodies and kiln
furniture. Bodies made with cordierite have very narrow firing ranges. I
don't know why the previous director put that in a shop stoneware.
I would suggest the following as a more workable and reliable general
purpose stoneware body:
34 lbs H2O (this may have to be adjusted; keep a record of how much you use
each time.)
30 lbs Tenn. Ball. A very plastic clay. Helps workability.
30 lbs Goldart or Roseville stoneware. A somewhat coarser clay. Still
plastic.
20 lbs Hawthorne Bond. Medium grain Fire clay. plastic as these clays go.
Helps with standing power on the wheel. Now we have a nice distribution of
particle sizes.
12 lbs Custer Feldspar. Predictable, slow-acting flux. Low in solubles.
8 lbs Silica. Opens up the body a wee bit and helps glaze fit.
3 lbs fine grog. Opens the body for good drying characteristics and helps
the clay stand up on the wheel.
1 lb medium grog.
Put the water in the mixer and add the ingredients in the order listed. If
the clay seems to be getting too stiff as you add ingredients, you can spray
in some water. If you get done and its too soft, sprinkle in some goldart.
Mixing clay a bit on the soft side helps plasticity, too.
Hope this helps.
steve grimmer
marion illinois
----------
>From: Jeffrey James
>To: CLAYART@LSV.UKY.EDU
>Subject: Clay body help Please
>Date: Wed, Aug 26, 1998, 8:19 AM
>
>----------------------------Original message----------------------------
>Hello
>I think I need some help. I just got hired as the pottery derictor at a
>local fine arts center. The clay body that the center has been using is
>giveing me problems. This is the body
>
> Cone 04-10 OX or RED.
>5 scoops Goldart
>2 scoops Ball clay (ten.)
>1 scoop fire clay(Harthorn
>3/4-1 scoop corderite
>
>once a month 1/4 scoop fine grog
>once a month 1 cup Bentonite
>
>This is mixed dry (layered) first, then mixed in a Soldner with water
>till firm. The clay is used within a week of being mixed, I do not have
>room to store the clay to allow it to age ( the last director did not
>think it helped much) and do not have a pugmill. Now the problem the
>clay is short when throwing and not very plastic, as I said I do not
>have the room to store the clay for long, one - two weeks at the most.
>Does anyone have any ideas for helping the throwing qualties of this
>body. We are fireing a gas reductoin kiln ^ 10.
> Thank You
> Jeff
Tom Wirt on fri 28 aug 98
>I would suggest the following as a more workable and reliable general
>purpose stoneware body:
>34 lbs H2O (this may have to be adjusted; keep a record of how much you use
>each time.)
>30 lbs Tenn. Ball. A very plastic clay. Helps workability.
>30 lbs Goldart or Roseville stoneware. A somewhat coarser clay. Still
>plastic.
>20 lbs Hawthorne Bond. Medium grain Fire clay. plastic as these clays go.
>Helps with standing power on the wheel. Now we have a nice distribution of
>particle sizes.
>12 lbs Custer Feldspar. Predictable, slow-acting flux. Low in solubles.
>8 lbs Silica. Opens up the body a wee bit and helps glaze fit.
>3 lbs fine grog. Opens the body for good drying characteristics and helps
>the clay stand up on the wheel.
>1 lb medium grog.
>
>Put the water in the mixer and add the ingredients in the order listed. If
>the clay seems to be getting too stiff as you add ingredients, you can
spray
>in some water. If you get done and its too soft, sprinkle in some goldart.
>Mixing clay a bit on the soft side helps plasticity, too.
>Hope this helps.
>
>steve grimmer
>marion illinois
Hi Steve,
Appreciate the notes. I happened to be reading Tichane's Clay Bodies and
noted that if you mix dry first, he recommends putting in the coarsest
materials first, then the fine particled ingredients.
Also, what meshes are you recommending? e.g., Hawthorne has 2 meshes, the
coarser of which apparently has calcium bit problems (from previous list
discussions). Tichane also talks about the melt rates for various
grinds....finer being faster. Any thoughts on all this?
TIA
Tom Wirt
Clay Coyote Pottery
Hutchinson, MN
claypot@hutchtel.net
Milton Markey on fri 28 aug 98
Steve,
Thanks for the corrected mixture, for Jeff's mystery clay body. Could you tell
us, the color of the clay, when it is fired for either reduction or oxy? What
is the firing range of the corrected mixture?
Thanks!
Milton MiltonsLin@AOL.COM
Jeffrey James on sat 29 aug 98
Hi everyone
First off sorry if I wrote it wrong but we put wet slop and water in the
mixer first then add the dry clay mixture. As for the corderite... the
last director told me that he started useing it when his normal clay
supplier stoped carrying grog ant told him to use this instead, my
understanding was he used to use 3/4-1 scoop of fine grog. I will try
and keep everyone posted on what I try and what works.
Thank You
Jeff
Grimmer on sat 29 aug 98
Tom and Milton,
I have never tried the finer Hawthorne, so I can't address that from
personal experience. Can anyone add to this? I haven't had any problems with
Hawthorne before, but I don't use much stoneware, so my sample size is
small. Another solution is to use the mixer for reclaim and just buy a good
stoneware premixed and pugged.
This is a pretty light stoneware, grey in reduction; lighter on ox, I
suppose. I fire to a cool cone 10 in reduction. I confess I haven't done
porosity tests on this body, so it may fire higher with no problems at all.
I read the Tichane book some time ago but don't recall most of it right
now. He is right, though, about finer particles. Think about melting a pound
of snow versus a pound block of ice.
steve grimmer
marion illinois.
----------
>From: Tom Wirt
>To: CLAYART@LSV.UKY.EDU
>Subject: Re: Clay body help Please
>Date: Fri, Aug 28, 1998, 9:23 AM
>
>----------------------------Original message----------------------------
>
>>I would suggest the following as a more workable and reliable general
>>purpose stoneware body:
>>34 lbs H2O (this may have to be adjusted; keep a record of how much you
use
>>each time.)
>>30 lbs Tenn. Ball. A very plastic clay. Helps workability.
>>30 lbs Goldart or Roseville stoneware. A somewhat coarser clay. Still
>>plastic.
>>20 lbs Hawthorne Bond. Medium grain Fire clay. plastic as these clays go.
>>Helps with standing power on the wheel. Now we have a nice distribution of
>>particle sizes.
>>12 lbs Custer Feldspar. Predictable, slow-acting flux. Low in solubles.
>>8 lbs Silica. Opens up the body a wee bit and helps glaze fit.
>>3 lbs fine grog. Opens the body for good drying characteristics and helps
>>the clay stand up on the wheel.
>>1 lb medium grog.
>>
>>Put the water in the mixer and add the ingredients in the order listed. If
>>the clay seems to be getting too stiff as you add ingredients, you can
>spray
>>in some water. If you get done and its too soft, sprinkle in some goldart.
>>Mixing clay a bit on the soft side helps plasticity, too.
>>Hope this helps.
>>
>>steve grimmer
>>marion illinois
>
>
>Hi Steve,
>
>Appreciate the notes. I happened to be reading Tichane's Clay Bodies and
>noted that if you mix dry first, he recommends putting in the coarsest
>materials first, then the fine particled ingredients.
>
>Also, what meshes are you recommending? e.g., Hawthorne has 2 meshes, the
>coarser of which apparently has calcium bit problems (from previous list
>discussions). Tichane also talks about the melt rates for various
>grinds....finer being faster. Any thoughts on all this?
>
>TIA
>
>Tom Wirt
>Clay Coyote Pottery
>Hutchinson, MN
>claypot@hutchtel.net
Jarita Thomson on sat 29 aug 98
Dear Steve,
I haven't mixed clay before, but I would like to save this recipe
should I need to. Your explanations for each component seem reasonable.
Only, when I pull this up later to actually make use of it, what temp
would be its ranges? Also what color does it fire to at each end of its
scale or does it remain consistent? Thank you.
Sincerely,
Jarita
On Thu, 27 Aug 1998 09:22:21 EDT Grimmer writes:
>----------------------------Original
>message----------------------------
>Jeff,
> Right off the bat, I would suggest reversing the mixing order; start
>with
>water in the mixer, then add clay, fluxes, and fillers as the mixer
>turns.
>This way, you ensure thorough wetting of the clay platelets. Adding
>water to
>dry clay tends to make the clay particles clump together in little
>balls.
>Bentonite, especially, is prone to this. And, yes, clay straight out
>of the
>mixer can be pretty short!
>Now, on to the body you are using. From what I am able to gather,
>cordierite
>is a magnesium silicate, related to talc, used in flameproof bodies
>and kiln
>furniture. Bodies made with cordierite have very narrow firing ranges.
>I
>don't know why the previous director put that in a shop stoneware.
>I would suggest the following as a more workable and reliable general
>purpose stoneware body:
>34 lbs H2O (this may have to be adjusted; keep a record of how much
>you use
>each time.)
>30 lbs Tenn. Ball. A very plastic clay. Helps workability.
>30 lbs Goldart or Roseville stoneware. A somewhat coarser clay. Still
>plastic.
>20 lbs Hawthorne Bond. Medium grain Fire clay. plastic as these clays
>go.
>Helps with standing power on the wheel. Now we have a nice
>distribution of
>particle sizes.
>12 lbs Custer Feldspar. Predictable, slow-acting flux. Low in
>solubles.
>8 lbs Silica. Opens up the body a wee bit and helps glaze fit.
>3 lbs fine grog. Opens the body for good drying characteristics and
>helps
>the clay stand up on the wheel.
>1 lb medium grog.
>
>Put the water in the mixer and add the ingredients in the order
>listed. If
>the clay seems to be getting too stiff as you add ingredients, you can
>spray
>in some water. If you get done and its too soft, sprinkle in some
>goldart.
>Mixing clay a bit on the soft side helps plasticity, too.
>Hope this helps.
>
>steve grimmer
>marion illinois
>
>
>----------
>>From: Jeffrey James
>>To: CLAYART@LSV.UKY.EDU
>>Subject: Clay body help Please
>>Date: Wed, Aug 26, 1998, 8:19 AM
>>
>
>>----------------------------Original
>message----------------------------
>>Hello
>>I think I need some help. I just got hired as the pottery derictor at
>a
>>local fine arts center. The clay body that the center has been using
>is
>>giveing me problems. This is the body
>>
>> Cone 04-10 OX or RED.
>>5 scoops Goldart
>>2 scoops Ball clay (ten.)
>>1 scoop fire clay(Harthorn
>>3/4-1 scoop corderite
>>
>>once a month 1/4 scoop fine grog
>>once a month 1 cup Bentonite
>>
>>This is mixed dry (layered) first, then mixed in a Soldner with water
>>till firm. The clay is used within a week of being mixed, I do not
>have
>>room to store the clay to allow it to age ( the last director did not
>>think it helped much) and do not have a pugmill. Now the problem
>the
>>clay is short when throwing and not very plastic, as I said I do not
>>have the room to store the clay for long, one - two weeks at the
>most.
>>Does anyone have any ideas for helping the throwing qualties of this
>>body. We are fireing a gas reductoin kiln ^ 10.
>> Thank You
>> Jeff
>
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bmshelton.uky on sun 30 aug 98
The formula given is really similar to the one printed in Ceramics Monthly
last year in an article by a guy named Zamek. I'm thinking his name was
Jeff but my memory has been known to fail me. I've tried this type of body
and it works very well. I simplified the formula to fit the materials I had
on hand and came up with
40 goldart
25 Hawthorn bond 35 mesh
15 OM4 ball clay
10 flint 325
7 Custer spar
97 total parts
I hate grog and red clay so I left them out and it throws well straight out
of the mixer.
It might be fun to mix both and try them out,Ben
----------
> From: Grimmer
> To: CLAYART@LSV.UKY.EDU
> Subject: Re: Clay body help Please
> Date: Thursday, August 27, 1998 9:22 AM
>
> ----------------------------Original message----------------------------
> Jeff,
> Right off the bat, I would suggest reversing the mixing order; start
with
> water in the mixer, then add clay, fluxes, and fillers as the mixer
turns.
> This way, you ensure thorough wetting of the clay platelets. Adding water
to
> dry clay tends to make the clay particles clump together in little balls.
> Bentonite, especially, is prone to this. And, yes, clay straight out of
the
> mixer can be pretty short!
> Now, on to the body you are using. From what I am able to gather,
cordierite
> is a magnesium silicate, related to talc, used in flameproof bodies and
kiln
> furniture. Bodies made with cordierite have very narrow firing ranges. I
> don't know why the previous director put that in a shop stoneware.
> I would suggest the following as a more workable and reliable general
> purpose stoneware body:
> 34 lbs H2O (this may have to be adjusted; keep a record of how much you
use
> each time.)
> 30 lbs Tenn. Ball. A very plastic clay. Helps workability.
> 30 lbs Goldart or Roseville stoneware. A somewhat coarser clay. Still
> plastic.
> 20 lbs Hawthorne Bond. Medium grain Fire clay. plastic as these clays go.
> Helps with standing power on the wheel. Now we have a nice distribution
of
> particle sizes.
> 12 lbs Custer Feldspar. Predictable, slow-acting flux. Low in solubles.
> 8 lbs Silica. Opens up the body a wee bit and helps glaze fit.
> 3 lbs fine grog. Opens the body for good drying characteristics and helps
> the clay stand up on the wheel.
> 1 lb medium grog.
>
> Put the water in the mixer and add the ingredients in the order listed.
If
> the clay seems to be getting too stiff as you add ingredients, you can
spray
> in some water. If you get done and its too soft, sprinkle in some
goldart.
> Mixing clay a bit on the soft side helps plasticity, too.
> Hope this helps.
>
> steve grimmer
> marion illinois
>
>
> ----------
> >From: Jeffrey James
> >To: CLAYART@LSV.UKY.EDU
> >Subject: Clay body help Please
> >Date: Wed, Aug 26, 1998, 8:19 AM
> >
>
> >----------------------------Original message----------------------------
> >Hello
> >I think I need some help. I just got hired as the pottery derictor at a
> >local fine arts center. The clay body that the center has been using is
> >giveing me problems. This is the body
> >
> > Cone 04-10 OX or RED.
> >5 scoops Goldart
> >2 scoops Ball clay (ten.)
> >1 scoop fire clay(Harthorn
> >3/4-1 scoop corderite
> >
> >once a month 1/4 scoop fine grog
> >once a month 1 cup Bentonite
> >
> >This is mixed dry (layered) first, then mixed in a Soldner with water
> >till firm. The clay is used within a week of being mixed, I do not have
> >room to store the clay to allow it to age ( the last director did not
> >think it helped much) and do not have a pugmill. Now the problem the
> >clay is short when throwing and not very plastic, as I said I do not
> >have the room to store the clay for long, one - two weeks at the most.
> >Does anyone have any ideas for helping the throwing qualties of this
> >body. We are fireing a gas reductoin kiln ^ 10.
> > Thank You
> > Jeff
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