Kendall deaton on sun 13 jul 03
I am working on a porcelain body recipe that has to meet several criteria:
1. Cone 10, Reduction and Soda
2. I want to use it for handbuilding (press molded platters over 18" and bottles 10"-14"ish) reference: Brother Thomas Bezanson
3. Medium to Large thrown work (platters and bowls 18" plus and vertical forms 10" plus)
4. It needs to be WHITE!!!! and relatively smooth ( no 30 mesh molochite), translucency is less of a concern.
I am considering starting with a fairly standard porcelain body, Grolleg 55, Custer 20, Flint 13, Pyrax 12 plus Vee Gum-T 2%. Adding to this a 120 mesh Molochite at 8-10%. I am not sure this will have the toughness and plasticity that I need.
Can I add ball clay and still maintain whiteness, if so which one?
Do I need Grolleg or can I use EPK since translucency is less of a concern, while maintaining whiteness and plasticity?
I know what I need to do is about a hundred tests but I am hoping I can get a little more insight to narrow my search. All thoughts are welcome. Thanks, Kendall Deaton
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David Beumee on sun 13 jul 03
Hi Kendall,
As I look at the criteria you have set, I think
the recipe you've chosen is a good place to start, since
you want the result to fire white, you want to work with
fairly large forms, and you want to hand build.
I have tested at least 35 different ball clays
and have not seen a fired result yet that wouldn't grey
this true porcelain recipe you are considering. True white
burning porcelain bodies include only kaolin, with no added
ball clay, and use a white burning plasticizer such as
Macaloid, a product called Bentone MA, and Veegum T.
All three appear the same as fired fusion buttons, but
Angela Fina says that as a gum, Veegum T eventually
rots out, so that recycled scrap does not make as plastic
a body as the original. It's very important, essential in fact
if you want to make good use of such plasticizers, that you
mix them wet. Use a five gallon bucket of warm water and
have someone else stir the water as you slowly add the Mac
or Bentone. Allow the water to break down the plasticizer
for at least a day, then stir the bucket and use it as an addition
to the water you use to mix the body. 1.5% should be enough.
Of course if you want maximum plasticity from the recipe, you
must mix the body as a slurry and make drying racks to dry the clay
to workable consistency, unless you have access to a filter press.
It is some work to set up, but the results are wonderful.
If translucency is less of a consideration, you can
substitute some or all of the Grolleg with EPK, as EPK is the
whitest burning domestic kaolin to my knowledge, and quite
comparable in fired color to Grolleg, Standard Porcelain, and Super Standard.
Also, I have found Macnamee kaolin to be another consideration.
Both EPK and Macnamee are high shrinkage, of comparible absorpton
and texture, both show lots of cracks as fired test bars,
and both have comparable fired color at cone 11 in reduction.
I think your're on the right track to add Molochite grog
for toughness, and in fact I am going down the same track in trying
to find a true porcelain body that will stand up tall on the wheel.
Michael Wendt, the potter connected with the production of
Helmer kaolin in Idaho, has true 125 mesh quartz silica, and this
might be another possibility for your consideration.
I'd really like to compare notes as we both progress
with this, and I'd like to post the results on Clayart.
David Beumee
Earth Alchemy Pottery
Lafayette, CO
7/13/03 2:51:00 AM, Kendall deaton wrote:
>I am working on a porcelain body recipe that has to meet
several criteria:
> 1. Cone 10, Reduction and Soda
> 2. I want to use it for handbuilding (press molded platters over 18" and bottles 10"-14"ish)
reference: Brother Thomas Bezanson
> 3. Medium to Large thrown work (platters and bowls 18" plus and vertical forms 10" plus)
> 4. It needs to be WHITE!!!! and relatively smooth ( no 30 mesh molochite), translucency is less of a
concern.
> I am considering starting with a fairly standard porcelain body, Grolleg 55, Custer 20, Flint 13, Pyrax 12 plus
Vee Gum-T 2%. Adding to this a 120 mesh Molochite at 8-10%. I am not sure this will have the toughness and
plasticity that I need.
> Can I add ball clay and still maintain whiteness, if so which one?
> Do I need Grolleg or can I use EPK since translucency is less of a concern, while maintaining whiteness
and plasticity?
> I know what I need to do is about a hundred tests but I am hoping I can get a little more insight to narrow
my search. All thoughts are welcome. Thanks, Kendall Deaton
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>
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>
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>settings from http://www.ceramics.org/clayart/
>
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>
Kendall deaton on mon 14 jul 03
Thanks to all for the thoughts, keep'em coming.
David, thanks for the encouragement that I might be headed in the right direction. I would like very much to share notes on our pursuit. I am working on getting some internet space allocated so I will even be able to post pictures of my tests. You mentioned a source for coarse mesh silica. Do you have any contact info for this person? I am already working with a 200 mesh silica and a combination of the two might work quite well to ensure a variety of particle sizes.
Kendall
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Craig Martell on mon 14 jul 03
At 03:51 AM 7/13/2003 -0500, you wrote:
>I am working on a porcelain body recipe that has to meet several criteria:
>
>4. It needs to be WHITE!!!! and relatively smooth ( no 30 mesh molochite),
>translucency is less of a concern.
>I am considering starting with a fairly standard porcelain body, Grolleg
>55, Custer 20, Flint 13, Pyrax 12 plus Vee Gum-T 2%. Adding to this a 120
>mesh Molochite at 8-10%. I am not sure this will have the toughness and
>plasticity that I need.
>Can I add ball clay and still maintain whiteness, if so which one?
Hello Kendall:
David Beumee has given you some great info already but I'll add a thing or two.
David is right on about epk being the best US kaolin for a white body. A
lot of the others are too high in titanium and will grey. Ball clays are
the same. I've used Hywite Magnum with ECC Standard porcelain and this
produces a nice workable white body. You can get these clays from Hammill
and Gillespie in NJ, or they can tell you of distributors.
I wouldn't use custer as the fluxing feldspar. I've used it for many years
and am much happier with fired results after switching to g-200. You get
more KNaO per gram with g-200 and more fluxing power. You might want to
use about 25% silica instead of a mix of silica and pyrophyllite. If you
use the wrong type of pyrophyllite it really greys the body and also
creates fit problems. The best one I've heard of for a white body is Pyrotrol.
David said that Angela Fina has some reservations about Vee Gum T "rotting
out" but I gotta tell you that she's mistaken. I don't know why they call
that material a "gum". There's no gum involed at all. It's a magnesium
alumino silicate material and is very fine grained and plastic. I've used
it for years and it's a great material. No problems at all. There's
nothing at all in Vee Gum T that will dissipate due to prolonged moisture
content. Vee Gum Cer is a different thing. That stuff DOES have
gum. It's not for body use. The advice David gave about blunging the
plasticizer is right on the money. It makes the final mix a lot better to
do this. I blunge the night before I mix and have buckets of water and
blunged Vee Gum ready to add to the dry in the mixer. Works great.
regards, Craig Martell Hopewell, Oregon
David Beumee on mon 14 jul 03
Hi Kendall,
Thanks very much for your willingness to share notes.
Michael Wendt can be reached at:
Idaho Clay & Glaze
Wendt Pottery
2729 Clearwater Ave.
Lewiston, Idaho 83501
208-746-3724
wendtpot@lewiston.com
1-800-554-3724
Since there always seems to be enough spar in porcelain recipes
to soak up super fine silica that is part of the 200 mesh that you are
using, or ejected silica from the decomposition of clay in the firing,
true 125 mesh shouldn't contribute to any potential cristobalite
problems. But alot of glazes I have used over the Babu body,
(which is the recipe you are starting with), craze because of the
low thermal expansion of this body. I am wondering if the substitution
or addition of 125 mesh silica will continue to lower the expansion
of the body. In the absence of a dilitometer, the yardstick that I use
is Jim Robinson's Glaze Test Series of 10 high to low expansion glazes.
If you know of an article by Peter Sohngen entitled "Cristobalite:The Hump"
New Data on Silica at Cone 10, The Studio Potter, Volume 28, Number 1,
December 1999, I recommend it. I get more out of it every time I read it.
Ron did the dilitometry for the article, and although it may not apply to
porcelain, I am very happy that a source for coarse mesh silica is available.
7/14/03 1:34:02 AM, Kendall deaton wrote:
>
>
> Date: Mon, 14 Jul 2003 02:34:02 -0500
>
> From: Kendall deaton
> Subject:Re: Porcelain Body advice needed
> To: CLAYART@LSV.CERAMICS.ORG
>
>
>
>
> Thanks to all for the thoughts, keep'em coming.
>
>
> David, thanks for the encouragement that I might be headed in the right
> direction. I would like very much to share notes on our pursuit. I am
> working on getting some internet space allocated so I will even be able to
> post pictures of my tests. You mentioned a source for coarse mesh silica. Do
> you have any contact info for this person? I am already working with a 200
> mesh silica and a combination of the two might work quite well to ensure a
> variety of particle sizes.
> Kendall
>
>
>
>
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> ______________________________________________________________________________
> Send postings to clayart@lsv.ceramics.org You may look at the archives for
> the list or change your subscription settings from http://www.ceramics.org/
> clayart/ Moderator of the list is Mel Jacobson who may be reached at
> melpots@pclink.com.
Michael Wendt on mon 14 jul 03
Kendall,
David referred to the Lane Mountain 125 mesh silica we stock. It is more =
expensive than sand but less costly than 200 mesh silica.
you also mentioned the need for a kaolin for porcelain and I use the =
following recipe which I also sell ready mixed to anyone who wants mixed =
clay:
Helmer 100
Custer 75
Neph Sye 25
125 mesh silica 40
200 mesh silica 25
translucent at cone 10 in thin sections. Fires to cone 11 or 12 without =
slumping but I fire very fast and cool quickly. A longer dwell time or =
slower cool would allow you to use less flux and silica and make the =
body more plastic.
fired color is white in ox and white in reduction, shrinkage wet to cone =
10 is 11.5% and the scaling factor is 1.13 . There is some slight =
roughness and discoloration induced by the 125 silica when compared to =
regular porcelain
Regards,
Michael Wendt
wendtpot@lewiston.com
Thanks to all for the thoughts, keep'em coming.
David, thanks for the encouragement that I might be headed in the right =
direction. I would like very much to share notes on our pursuit. I am =
working on getting some internet space allocated so I will even be able =
to post pictures of my tests. You mentioned a source for coarse mesh =
silica. Do you have any contact info for this person? I am already =
working with a 200 mesh silica and a combination of the two might work =
quite well to ensure a variety of particle sizes.
Kendall
Kendall deaton on mon 14 jul 03
If not Pyrax then how about Alumina Oxide @ 3%? I am looking for something that will toughen the body up some since I will be asking it to do things porcelain does not like to do. For something like Jeff Zamek's Revised J-body, Grolleg 49, G-200 19, Flint 29, Alumina Oxide 3 and Veegum-T.(which I got out of a very good article in CM Jan. 94 "Porcelain Bodies for Potters" which I just realized was written by David, I thought that name looked familiar.) I guess the Alumina takes out any translucency and gives density. I have used it in stoneware and seemed to notice a big jump in wet strength.
I will test Grolleg and EPK exclusively and in various combinations. I would like to try the other english kaolins, but I am a student and although I have the most supportive professor ever of my experimentation I would feel bad asking her to let me order another exotic material fom another distributor. Although I would like to try some of those british ball clays on stoneware as slips in salt, do they carry those Craig?
I am a big fan of Brother Thomas' work. His work in technique is very similar to what I am working on (large press molded pieces and largish thrown pieces) In his book "Creation out of Clay" (beautiful book, glazes I would give an extremity for) their is a section in the back that shows him working. His clay body is a darkish grey-brown wet but very white fired. I have never seen a Grolleg body that dark. It almost looks like it has ball clay in it but it fires very white. Anyone know what could cause the darkness or even better, know the recipe?
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Kendall deaton on tue 15 jul 03
David, Thanks very much for all your advice. I think I have a good idea of where to start. I am going to test Grolleg and EPK in varying combos and alone as well as pyrax and alumina alone and in concert. I will start with the Babu body and the aforementioned Pinnel body as opposite ends of the spectrum since everything is proportionate, besides those fillers, and work from both ends. I will use Custer and 200 mesh Silica as constants since those are well established in other recipes and Macaloid at 2%.
I will add molochite 120 mesh ( would a blend of 120 and 200 be useful or just redundant?) in 5%, 7.5% and 10% increments. I think I will even try a few ball clays( Did you test C&C? That is what Cushing reccomends.) and Bentolite (macaloid family is so expensive, I won't be in school forever). How does that sound?
As for testing, what are your mixing, forming and firing methods for tests? Still the same as laid out in that article? I want our tests to be comparable for consistencies sake when we go to compare findings. Anyways, thanks again for being a sounding board you have been very helpful.
Kendall
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Michael Wendt on tue 15 jul 03
David asked;
Hi Michael,
Could you explain what scaling factor means?
David Beumee
David,
The recent discussion centered around how much larger to make a wet pot than
the desired finished item and I said I use a scaling factor of 1.13 because
to get the size you want finished, you multiply the desired size by the
scaling factor. To get a 10'' pot, multiply 10 by 1.13 and make the wet pot
11.3'' accross.
If you want to know how large a wet pot will be, then the percentage of
shrinkage becomes useful so you multiply the 11.3'' wet pot by 0.885 which
is 11.5 percent subtracted from 1.
Regards,
Michael Wendt
7/14/03 9:54:01 AM, Michael Wendt wrote:
>fired color is white in ox and white in reduction, shrinkage wet to cone 10
is 11.5% and the scaling factor is 1.13
David Beumee on tue 15 jul 03
7/14/03 9:54:01 AM, Michael Wendt wrote:
>fired color is white in ox and white in reduction, shrinkage wet to cone 10 is 11.5% and the scaling factor is 1.13
Hi Michael,
Could you explain what scaling factor means?
David Beumee
>Kendall,
>
>David referred to the Lane Mountain 125 mesh silica we stock. It is more expensive than sand but less costly than
200 mesh silica.
>
>you also mentioned the need for a kaolin for porcelain and I use the following recipe which I also sell ready mixed
to anyone who wants mixed clay:
>
>Helmer 100
>
>Custer 75
>
>Neph Sye 25
>
>125 mesh silica 40
>
>200 mesh silica 25
>
>translucent at cone 10 in thin sections. Fires to cone 11 or 12 without slumping but I fire very fast and cool
quickly. A longer dwell time or slower cool would allow you to use less flux and silica and make the body more
plastic.
>
. There is some slight roughness and discoloration induced by the 125 silica when compared to regular porcelain
>
>Regards,
>
>Michael Wendt
>
>wendtpot@lewiston.com
>
>
>
>Thanks to all for the thoughts, keep'em coming.
>
>David, thanks for the encouragement that I might be headed in the right direction. I would like very much to share
notes on our pursuit. I am working on getting some internet space allocated so I will even be able to post pictures
of my tests. You mentioned a source for coarse mesh silica. Do you have any contact info for this person? I am
already working with a 200 mesh silica and a combination of the two might work quite well to ensure a variety of
particle sizes.
>Kendall
>
>______________________________________________________________________________
>Send postings to clayart@lsv.ceramics.org
>
>You may look at the archives for the list or change your subscription
>settings from http://www.ceramics.org/clayart/
>
>Moderator of the list is Mel Jacobson who may be reached at melpots@pclink.com.
>
David Beumee on tue 15 jul 03
We've been looking at the same book Kendall,
and I was just noticing the clay coming from
Brother Thomas pug mill as well. My guess is that he may
add a very small percentage of ball clay, but
getting his recipe may not be possible. It's obvious
Creation out of Clay is revealing few secrets, but who
knows? Maybe a connection with Brother Thomas
can be made.
You will also notice from the 1994 CM article
Pete Pinnell's porcelain body, which contains 2%
325 mesh alumina hydrate, useful to reduce
shrinkage, minimize warping and slumping, and give
the body strength.
20 Custer
2 325 mesh Alumina Hydrate
55 Grolleg
23 200 mesh silica
add: 2% Veegum T
You might also consider adding alumina In Addition to Pyrax.
David Beumee
Earth Alchemy Pottery
Lafayette, CO
7/14/03 11:45:43 AM, Kendall deaton wrote:
>
>
> Date: Mon, 14 Jul 2003 12:45:43 -0500
>
> From: Kendall deaton
> Subject:Re: Porcelain Body advice needed
> To: CLAYART@LSV.CERAMICS.ORG
>
>
>
>
> If not Pyrax then how about Alumina Oxide @ 3%? I am looking for something
> that will toughen the body up some since I will be asking it to do things
> porcelain does not like to do. For something like Jeff Zamek's Revised J-
> body, Grolleg 49, G-200 19, Flint 29, Alumina Oxide 3 and Veegum-T.(which I
> got out of a very good article in CM Jan. 94 "Porcelain Bodies for Potters"
> which I just realized was written by David, I thought that name looked
> familiar.) I guess the Alumina takes out any translucency and gives density.
> I have used it in stoneware and seemed to notice a big jump in wet strength.
>
>
> I will test Grolleg and EPK exclusively and in various combinations. I would
> like to try the other english kaolins, but I am a student and although I
> have the most supportive professor ever of my experimentation I would feel
> bad asking her to let me order another exotic material fom another
> distributor. Although I would like to try some of those british ball clays
> on stoneware as slips in salt, do they carry those Craig?
>
> I am a big fan of Brother Thomas' work. His work in technique is very
> similar to what I am working on (large press molded pieces and largish
> thrown pieces) In his book "Creation out of Clay" (beautiful book, glazes I
> would give an extremity for) their is a section in the back that shows him
> working. His clay body is a darkish grey-brown wet but very white fired. I
> have never seen a Grolleg body that dark. It almost looks like it has ball
> clay in it but it fires very white. Anyone know what could cause the
> darkness or even better, know the recipe?
>
>
>
>
>
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> ______________________________________________________________________________
> Send postings to clayart@lsv.ceramics.org You may look at the archives for
> the list or change your subscription settings from http://www.ceramics.org/
> clayart/ Moderator of the list is Mel Jacobson who may be reached at
> melpots@pclink.com.
David Beumee on tue 15 jul 03
Craig wrote,
> I've used Hywite Magnum with ECC Standard porcelain and this
>produces a nice workable white body.
I wondered how your tests of English ball clays had gone.
Very surprising to find that Hywite Magnum produced a white
burning porcelain body for you. My test of the clay shows a very
grey fired bar with black specks at cone 11 in reduction. Old Hickory
#5 and H.C. Spinks #5 are the whitest burning ball clays I have tested,
but both grey an all kaolin body using Grolleg, EPK, or Standard porcelain
in my experience.
I use a pyrophyllite called Pyrax and have not had trouble with
it coloring a porcelain body, but I'm glad to know about Pyrotrol.
G-200 does provide more fluxing power than Custer, and testing is necessary
to find out how much lower than 20% (Custer) in the Babu body will give
the absorption percentage you want. To me an absorption percentage of
zero is not particularly helpful because how far into zero have you gotten?
I like an absorption percentage 0.1 or 0.2, and then I know I have added
just enough spar and not too much. Also, getting a true absorption
percentage is tricky, and depends on your method of testing. Are you
boiling and soaking a thick test bar or a thin walled bowl? Did you get the
dry weight when the test was still warm from the firing, or not? Was the
test pressure - cooked or boiled, and for how long? Was the test allowed
to soak overnight, and how much drying of the test was done before
wet weight was measured? On and on it goes.
Glad to know about Veegum T. Angela
will be glad to know, and so am I.
David Beumee
Earth Alchemy Pottery
Lafayette, CO
7/14/03 9:16:57 AM, Craig Martell wrote:
>At 03:51 AM 7/13/2003 -0500, you wrote:
>>I am working on a porcelain body recipe that has to meet several criteria:
>>
>>4. It needs to be WHITE!!!! and relatively smooth ( no 30 mesh molochite),
>>translucency is less of a concern.
>>I am considering starting with a fairly standard porcelain body, Grolleg
>>55, Custer 20, Flint 13, Pyrax 12 plus Vee Gum-T 2%. Adding to this a 120
>>mesh Molochite at 8-10%. I am not sure this will have the toughness and
>>plasticity that I need.
>>Can I add ball clay and still maintain whiteness, if so which one?
Hello Kendall:
>
>David Beumee has given you some great info already but I'll add a thing or two.
>
>David is right on about epk being the best US kaolin for a white body. A
>lot of the others are too high in titanium and will grey. Ball clays are
>the same. You can get these clays from Hammill
>and Gillespie in NJ, or they can tell you of distributors.
>
>I wouldn't use custer as the fluxing feldspar. I've used it for many years
>and am much happier with fired results after switching to g-200. You get
>more KNaO per gram with g-200 and more fluxing power. You might want to
>use about 25% silica instead of a mix of silica and pyrophyllite. If you
>use the wrong type of pyrophyllite it really greys the body and also
>creates fit problems. The best one I've heard of for a white body is Pyrotrol.
>
>David said that Angela Fina has some reservations about Vee Gum T "rotting
>out" but I gotta tell you that she's mistaken. I don't know why they call
>that material a "gum". There's no gum involed at all. It's a magnesium
>alumino silicate material and is very fine grained and plastic. I've used
>it for years and it's a great material. No problems at all. There's
>nothing at all in Vee Gum T that will dissipate due to prolonged moisture
>content. Vee Gum Cer is a different thing. That stuff DOES have
>gum. It's not for body use. The advice David gave about blunging the
>plasticizer is right on the money. It makes the final mix a lot better to
>do this. I blunge the night before I mix and have buckets of water and
>blunged Vee Gum ready to add to the dry in the mixer. Works great.
>
>regards, Craig Martell Hopewell, Oregon
>
>______________________________________________________________________________
>Send postings to clayart@lsv.ceramics.org
>
>You may look at the archives for the list or change your subscription
>settings from http://www.ceramics.org/clayart/
>
>Moderator of the list is Mel Jacobson who may be reached at melpots@pclink.com.
>
Snail Scott on tue 15 jul 03
>7/14/03 9:54:01 AM, Michael Wendt wrote:
>>...shrinkage wet to cone 10 is 11.5% and the scaling factor is 1.13
>David wrote: Could you explain what scaling factor means?
It's the opposite of the shrinkage rate: the amount
of enlargement you need to make something bigger, in
order for it to shrink to a specified size.
A useful term, Michael!
-Snail
Craig Martell on wed 16 jul 03
David sez::
>Very surprising to find that Hywite Magnum produced a white
>burning porcelain body for you. My test of the clay shows a very
>grey fired bar with black specks at cone 11 in reduction.
Hi David:
I did fired samples of all the kaolins and ball clays before I started
blending and testing bodies. The Hywite produced a light grey bar with
specks at cone 10R. So, yes, I too was surprised at the results. A white
body with one or two iron spots thru the celadons.
> G-200 does provide more fluxing power than Custer, and testing is necessary
>to find out how much lower than 20% (Custer) in the Babu body will give
>the absorption percentage you want.
I like to get the porcelain bodies with cornish kaolins to zero percent
absorbtion. I usually go over the mark and then cut the % of spar until I
get between 0% and 1% and then I take the spar level back to the zero
point. It's good to do some tests on the final body composition for
pyroplastic deformation.
The thing that I prefer with regard to g-200 is that it will take less % of
the spar to vitrify the porcelain and you can add more clay to the
body. With Custer, you get less KNaO and more alumina and silica so you
need to add more spar to vitrify. I think we're better off getting that
extra alumina and silica from a plastic source, such as ball or
kaolin. Custer is a stiff spar and the silica is at about 7.0 to 1.0 fluxes.
>Also, getting a true absorption percentage is tricky, and depends on your
>method of testing. Are you
>boiling and soaking a thick test bar or a thin walled bowl? Did you get the
>dry weight when the test was still warm from the firing, or not?
I use a pinched out test mouse ala Jim Robinson style. They are weighed
right out of the kiln before they can absorb any atmospheric moisture. I
boil them all day long, about 10 to 12 hours, dry off the surface water and
weigh. I do 10 samples of each body and average the results. How am I
doing? :>)
regards, Craig Martell Hopewell, Oregon
David Beumee on wed 16 jul 03
7/16/03 1:14:31 PM, Craig Martell wrote:
>I use a pinched out test mouse ala Jim Robinson style. They are weighed
>right out of the kiln before they can absorb any atmospheric moisture. I
>boil them all day long, about 10 to 12 hours, dry off the surface water and
>weigh. I do 10 samples of each body and average the results. How am I
>doing? :>)
Ah! You're taking averages! Excellent! I hadn't thought of it.
David Beumee
>David sez::
>>Very surprising to find that Hywite Magnum produced a white
>>burning porcelain body for you. My test of the clay shows a very
>>grey fired bar with black specks at cone 11 in reduction.
>
>Hi David:
>
>I did fired samples of all the kaolins and ball clays before I started
>blending and testing bodies. The Hywite produced a light grey bar with
>specks at cone 10R. So, yes, I too was surprised at the results. A white
>body with one or two iron spots thru the celadons.
>
>> G-200 does provide more fluxing power than Custer, and testing is necessary
>>to find out how much lower than 20% (Custer) in the Babu body will give
>>the absorption percentage you want.
>
>I like to get the porcelain bodies with cornish kaolins to zero percent
>absorbtion. I usually go over the mark and then cut the % of spar until I
>get between 0% and 1% and then I take the spar level back to the zero
>point. It's good to do some tests on the final body composition for
>pyroplastic deformation.
>
>The thing that I prefer with regard to g-200 is that it will take less % of
>the spar to vitrify the porcelain and you can add more clay to the
>body. With Custer, you get less KNaO and more alumina and silica so you
>need to add more spar to vitrify. I think we're better off getting that
>extra alumina and silica from a plastic source, such as ball or
>kaolin. Custer is a stiff spar and the silica is at about 7.0 to 1.0 fluxes.
>
>>Also, getting a true absorption percentage is tricky, and depends on your
>>method of testing. Are you
>>boiling and soaking a thick test bar or a thin walled bowl? Did you get the
>>dry weight when the test was still warm from the firing, or not?
>
>
>regards, Craig Martell Hopewell, Oregon
>
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David Beumee on wed 16 jul 03
7/15/03 9:43:30 PM, Kendall deaton wrote:
>> I will add molochite 120 mesh ( would a blend of 120 and 200 be useful
> or just redundant?) in 5%, 7.5% and 10% increments. I think I will even
> try a few ball clays( Did you test C&C? That is what Cushing
> reccomends.) and Bentolite (macaloid family is so expensive, I won't be
> in school forever). How does that sound?
>
> As for testing, what are your mixing, forming and firing methods for
> tests? Still the same as laid out in that article? I want our tests to
> be comparable for consistencies sake when we go to compare findings.
> Anyways, thanks again for being a sounding board you have been very
> helpful.>
I'm confused. I didn't know Molochite came in 200 mesh.
Or perhaps you're suggesting substituting grog for silica? Didn't you
say 200 mesh silica would be a constant?
I'd suggest you also consider 30/80 mesh Molochite
for a handbuilding porcelain body.
Yes I have tested C&C ball clay, but you began by saying
you wanted a fired result that was white. But one person's
definition of white is different than another's, and there are lots of
potters who look at "porcelains" containing ball clay that call the
fired result white. If C&C is what is available to you, use it, but
there are much whiter burning ball clays available. Four that I know
of come from Old Hickory Clay Company in Kentucky; M-23, Taylor,
54-S, and #5. Their number is 270-247-1842, email : psp@oldhickoryclay.com,
website http://www.oldhickoryclay.com
Ron's had some trouble with specks in M-23. My test of the clay shows no specks.
If you can still get hold of bentolite, that's great. It's long gone around
Denver.
I think your program sounds good. I printed out a paper for you that I wrote,
with illustrations and directions to make the form for test bars (illustration #1). Look
under Mixing Procedures for directions and email me with questions. The wooden
form in illustration #1 is all you need for starters. I no longer use a test bar to
measure for absorption. I make 1500 grams for a claybody test, which gives
me enough clay to throw a bowl to test for absorption. Much better accuracy.
Send me your address and the info will be on it's way. Keep in touch.
David Beumee
Earth Alchemy Pottery
Lafayette,CO
>
>
>
>
>
>
>
>
>
>
> David, Thanks very much for all your advice. I think I have a good idea
> of where to start. I am going to test Grolleg and EPK in varying combos
> and alone as well as pyrax and alumina alone and in concert. I will
> start with the Babu body and the aforementioned Pinnel body as opposite
> ends of the spectrum since everything is proportionate, besides those
> fillers, and work from both ends. I will use Custer and 200 mesh Silica
> as constants since those are well established in other recipes and
> Macaloid at 2%.
>
>
>
>
> Kendall
>
>
>
>
>
> MSN 8 with e-mail virus protection service: 2 months FREE*
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> be reached at melpots@pclink.com.
Kendall deaton on wed 16 jul 03
David, Molochite does come in 200 mesh (Laguna), and I am using 200 mesh silica (as a constant ingredient but the amount will vary depending on pyrax and alumina in that particular sample) that is why I asked if it was redundant. I asked because I am thinking silica starts to soften at cone 10 and the molochite should not. With the 120 and 50/80 the 200 would assure a variety of particle sizes to improve my odds of the handbuilt stuff making it through the fire. My logic may be way off, the Silica may do the job. I have used 30 mesh before, it is really noticeable when you clean up seams and such on handbuilt. I am not sure I will even be able to use 50/80. For throwing, 30 mesh and 50/80 helps out alot, if you do not mind the texture. You can makes some big pots and throwing in sections I did not lose any to cracks. I choose not to use that blend anymore because I found that it broke up the luminosity of the surface detracting from the ethereal quality I am going for.
I got the idea from Bobby Silverman at a workshop. He was working on large tiles (2'x3') that he was firing on EDGE! cone 10 soda. The body was a 50-25-25 with paper and 10% 120 mesh and 20% 200. He said that he had pretty low success rate but did have some turn out. It does not get much more extreme than that.
Laguna still has Bentolite L-10 any oftheir distributors should be able to order it for you. How does it look in a Grolleg body? I have used it in an EPK body but also had 10% XX Sagger (pretty grey). I think I am going to start with pure grolleg and no ball clay at first (why go second best?) and only use the ball clay if all else fails. I have also ordered some Veegum-T. In your experience, do you have any preference between it and macaloid? All reference on the products say they are similar in properties but everyone who actually uses them seems to have preferences.
I am going to send you my contact info off list. Again, Thanks very much.
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