Paul on wed 2 jul 03
Hello,
I am testing some cone 10 stoneware formulas and hope to be making all of my
own clay soon, after using a manufactured clay for several years. So i am no
expert on stoneware formulas, and have a question about the use of Redart
clay in them. Some of the recipes i am looking into call for 10 percent
redart, and i was wondering what the function of this low-fire clay would be
in a high-fire body. Is it generally for color or does it act as a body flux
in some way? Is there a way to eliminate it from the body without affecting
the vitrification of the clay? I would like not to have to use it but do not
know the proper way to substitute something else for it. Any advice? Thanks,
Paul B
Paul Herman on wed 2 jul 03
Hello Paul B,
I believe the Redart is a relatively fusible clay at ^10. So it will act
as a flux and a colorant.
Iron does strange things in reduction firing. It's a powerful body flux,
but won't dissolve Cristobolite (a form of silica). If you use a lot of
Iron in the body, then you have to use less Feldspar, a body flux which
WILL dissolve Cristobolite. Too much Cristobolite will cause fit and
heat shock problems. Too much flux and it bloats and sags.
I'm leaning towards lighter bodies, and when I want color, use an Iron
bearing fireclay like Lincoln.
If you want to read up on it, there's an article published by Studio
Potter magazine, "Body Building for Potters" by Jim Robinson. It
explained some things in a very understandable way. And of course
Hamers' "Potter's Dictionary".
Happy mixing, from Doyle, where the mosquitos are out, and there's no
Moon at all.
Paul Herman
Great Basin Pottery
423-725 Scott Road
Doyle, California 96109 US
potter@psln.com
----------
>From: Paul
>To: CLAYART@LSV.CERAMICS.ORG
>Subject: REDART IN STONEWARE BODIES
>Date: Wed, Jul 2, 2003, 6:53 PM
>
> Hello,
> I am testing some cone 10 stoneware formulas and hope to be making all of my
> own clay soon, after using a manufactured clay for several years. So i am no
> expert on stoneware formulas, and have a question about the use of Redart
> clay in them. Some of the recipes i am looking into call for 10 percent
> redart, and i was wondering what the function of this low-fire clay would be
> in a high-fire body. Is it generally for color or does it act as a body flux
> in some way? Is there a way to eliminate it from the body without affecting
> the vitrification of the clay? I would like not to have to use it but do not
> know the proper way to substitute something else for it. Any advice? Thanks,
> Paul B
Craig Dunn Clark on thu 3 jul 03
Try swapping it out for GoldArt. Worked well for me in the past. The
stoneware body that I made for years, mixed in a handy-dandy Soldner mixer
and de-aired in Venco, was 100lb Hawthorn Bond, 50lb ball clay, 50 lb
either goldart or redart, about 10% custar spar and grog to taste. We would
use the goldart and redart interchangeably depending upon the color of the
clay body that we were after.
Hope this helps
Craig Dunn Clark
619 East 11 1/2 st
Houston, Texas 77008
(713)861-2083
mudman@hal-pc.org
----- Original Message -----
From: "Snail Scott"
To:
Sent: Thursday, July 03, 2003 9:43 AM
Subject: Re: REDART IN STONEWARE BODIES
> At 09:53 PM 7/2/03 -0400, you wrote:
> >i was wondering what the function of [redart] would be
> >in a high-fire body. Is it generally for color or does it act as a body
flux
> >in some way? Is there a way to eliminate it...
>
>
> Both. In reduction, the fluxing properties
> of iron become relevant. In oxidation, it
> mainly acts as a colorant.
>
> Redart is also a fairly coarse clay, and
> is thus useful for its texture, too. Though
> often called a low-fire clay, it's not all
> that low-fire, really.
>
> Do you want a red body, or not? Iron will
> act as a flux in reduction whether added as
> red clay or as an oxide; the clay is just
> easier to deal with. To remove Redart from
> a reduction body and make it white, but still
> fire at the same temperature, you may need
> to add a flux, like feldspar.
>
> If you work in oxidation, you can probably
> just remove Redart from the recipe with
> little change aside from color.
>
> -Snail
>
>
____________________________________________________________________________
__
> 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 thu 3 jul 03
At 09:53 PM 7/2/03 -0400, you wrote:
>i was wondering what the function of [redart] would be
>in a high-fire body. Is it generally for color or does it act as a body flux
>in some way? Is there a way to eliminate it...
Both. In reduction, the fluxing properties
of iron become relevant. In oxidation, it
mainly acts as a colorant.
Redart is also a fairly coarse clay, and
is thus useful for its texture, too. Though
often called a low-fire clay, it's not all
that low-fire, really.
Do you want a red body, or not? Iron will
act as a flux in reduction whether added as
red clay or as an oxide; the clay is just
easier to deal with. To remove Redart from
a reduction body and make it white, but still
fire at the same temperature, you may need
to add a flux, like feldspar.
If you work in oxidation, you can probably
just remove Redart from the recipe with
little change aside from color.
-Snail
clayart@DIGITALFIRE.AB.CA on thu 3 jul 03
You can find more information about redart here:
http://digitalfire.ab.ca/cermat/ceramicmaterials/material.php?goto=redart
I\'ve found that low fire red clays are not a great idea as
fluxes in high fire, you end up with yucky brown colors
instead of reds.
I just made an awesome throwing terra cotta body using
redart, its recipe is on the page above.
Work on this body has led us down the
path of investigating mica. There are a couple of suppliers
in North America and you can add small amounts to low fire
bodies to give them sparkle.
-------8<--------
Hello Paul B,
I believe the Redart is a relatively fusible clay at ^10. So it will act
as a flux and a colorant.
Iron does strange things in reduction firing. It\'s a powerful body flux,
but won\'t dissolve Cristobolite (a form of silica). If you use a lot of
Iron in the body, then you have to use less Feldspar, a body flux which
WILL dissolve Cristobolite. Too much Cristobolite will cause fit and
heat shock problems. Too much flux and it bloats and sags.
I\'m leaning towards lighter bodies, and when I want color, use an Iron
bearing fireclay like Lincoln.
If you want to read up on it, there\'s an article published by Studio
Potter magazine, \"Body Building for Potters\" by Jim Robinson. It
explained some things in a very understandable way. And of course
Hamers\' \"Potter\'s Dictionary\".
Happy mixing, from Doyle, where the mosquitos are out, and there\'s no
Moon at all.
Paul Herman
Great Basin Pottery
423-725 Scott Road
Doyle, California 96109 US
potter@psln.com
----------
>From: Paul
>To: CLAYART@LSV.CERAMICS.ORG
>Subject: REDART IN STONEWARE BODIES
>Date: Wed, Jul 2, 2003, 6:53 PM
>
> Hello,
> I am testing some cone 10 stoneware formulas and hope to be making all of my
> own clay soon, after using a manufactured clay for several years. So i am no
> expert on stoneware formulas, and have a question about the use of Redart
> clay in them. Some of the recipes i am looking into call for 10 percent
> redart, and i was wondering what the function of this low-fire clay would be
> in a high-fire body. Is it generally for color or does it act as a body flux
> in some way? Is there a way to eliminate it from the body without affecting
> the vitrification of the clay? I would like not to have to use it but do not
> know the proper way to substitute something else for it. Any advice? Thanks,
> Paul B
______________________________________________________________________________
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.
--------
Tony Hansen, Digitalfire Corp.
David Beumee on thu 3 jul 03
Just to add to what Paul has said:
In a reducing atmosphere, most of any red iron oxide present,
such as is contained in Redart clay, is converted to
black iron oxide, and fluid liquids form quickly and team up
with feldspathic melts, which can dissolve benificial
mullite and quartz crystals. As iron - rich liquids cool into
glass, the glass has a brittle character, meaning that your
teapot may shatter with hot water. It's much better to leave
out iron entirely from the body and use iron bearing slips
as a coating to give color.
Another lesson from Jim Robinson.
David Beumee
7/2/03 11:39:08 PM, Paul Herman wrote:
>Hello Paul B,
>
>I believe the Redart is a relatively fusible clay at ^10. So it will act
>as a flux and a colorant.
>
>Iron does strange things in reduction firing. It's a powerful body flux,
>but won't dissolve Cristobolite (a form of silica). If you use a lot of
>Iron in the body, then you have to use less Feldspar, a body flux which
>WILL dissolve Cristobolite. Too much Cristobolite will cause fit and
>heat shock problems. Too much flux and it bloats and sags.
>
>I'm leaning towards lighter bodies, and when I want color, use an Iron
>bearing fireclay like Lincoln.
>
>If you want to read up on it, there's an article published by Studio
>Potter magazine, "Body Building for Potters" by Jim Robinson. It
>explained some things in a very understandable way. And of course
>Hamers' "Potter's Dictionary".
>
>Happy mixing, from Doyle, where the mosquitos are out, and there's no
>Moon at all.
>
>Paul Herman
>Great Basin Pottery
>423-725 Scott Road
>Doyle, California 96109 US
>potter@psln.com
>
>----------
>>From: Paul
>>To: CLAYART@LSV.CERAMICS.ORG
>>Subject: REDART IN STONEWARE BODIES
>>Date: Wed, Jul 2, 2003, 6:53 PM
>>
>
>> Hello,
>> I am testing some cone 10 stoneware formulas and hope to be making all of my
>> own clay soon, after using a manufactured clay for several years. So i am no
>> expert on stoneware formulas, and have a question about the use of Redart
>> clay in them. Some of the recipes i am looking into call for 10 percent
>> redart, and i was wondering what the function of this low-fire clay would be
>> in a high-fire body. Is it generally for color or does it act as a body flux
>> in some way? Is there a way to eliminate it from the body without affecting
>> the vitrification of the clay? I would like not to have to use it but do not
>> know the proper way to substitute something else for it. Any advice? Thanks,
>> Paul B
>
>______________________________________________________________________________
>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.
>
clayart@DIGITALFIRE.AB.CA on thu 3 jul 03
Redart is 200 mesh airfloated, it is very fine.
It is very much a low fire clay, it has stoneware
properties by cone 1.
-------8<--------
Redart is also a fairly coarse clay, and
is thus useful for its texture, too. Though
often called a low-fire clay, it\'s not all
that low-fire, really.
--------
Tony Hansen, Digitalfire Corp.
Ron Roy on fri 4 jul 03
Hi Paul,
Yes - Redart is a strong melter at cone 10 - even more so in reduction.
It's not the right thing to use in cone 10 reduction bodies - promotes
cristobalite procuction big time.
It's usually in a body to get some kind of toasty colour - better to do
that other ways.
Take out the red art and replace it with a pot spar - like G200. When you
test the clay for absorbancy you will know if you have to take some out or
add more. What you want to have is about 2% absorbancy for a stoneware
body.
Just do 5 LB. tests till you get close - wait for at least a week before
testing for workability
If you want to know how to test clay let me know and I'll sent instructions.
RR
>Hello,
>I am testing some cone 10 stoneware formulas and hope to be making all of my
>own clay soon, after using a manufactured clay for several years. So i am no
>expert on stoneware formulas, and have a question about the use of Redart
>clay in them. Some of the recipes i am looking into call for 10 percent
>redart, and i was wondering what the function of this low-fire clay would be
>in a high-fire body. Is it generally for color or does it act as a body flux
>in some way? Is there a way to eliminate it from the body without affecting
>the vitrification of the clay? I would like not to have to use it but do not
>know the proper way to substitute something else for it. Any advice? Thanks,
>Paul B
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Donn Buchfinck on fri 4 jul 03
there are several reasons you use redart in a clay body,
to begin with it kills two birds with one stone.
redart is an ultra plastic clay, so you can use some of it instead of some
ball clay.
and then there is the fluxing action,
and on top of that it imparts a nice warm tone to the clay body that makes
all the glazes that react with iron look great.
DO NOT SKIMP ON MATERIALS
you get what you pay for.
cheap materials = bad looking pots
Donn Buchfinck
San Francisco, CA
march5_potterywebpage
clayart@DIGITALFIRE.AB.CA on fri 4 jul 03
Strange that this would work since goldart is a
plastic stoneware and redart is a non-plastic
earthenware. Didn\'t the plasticity and maturity
of the body change drastically?
-------8<--------
Try swapping it out for GoldArt. Worked well for me in the past. The
stoneware body that I made for years, mixed in a handy-dandy Soldner mixer
and de-aired in Venco, was 100lb Hawthorn Bond, 50lb ball clay, 50 lb
either goldart or redart, about 10% custar spar and grog to taste. We would
use the goldart and redart interchangeably depending upon the color of the
clay body that we were after.
Hope this helps
Craig Dunn Clark
619 East 11 1/2 st
Houston, Texas 77008
(713)861-2083
mudman@hal-pc.org
----- Original Message -----
From: \"Snail Scott\"
To:
Sent: Thursday, July 03, 2003 9:43 AM
Subject: Re: REDART IN STONEWARE BODIES
> At 09:53 PM 7/2/03 -0400, you wrote:
> >i was wondering what the function of [redart] would be
> >in a high-fire body. Is it generally for color or does it act as a body
flux
> >in some way? Is there a way to eliminate it...
>
>
> Both. In reduction, the fluxing properties
> of iron become relevant. In oxidation, it
> mainly acts as a colorant.
>
> Redart is also a fairly coarse clay, and
> is thus useful for its texture, too. Though
> often called a low-fire clay, it\'s not all
> that low-fire, really.
>
> Do you want a red body, or not? Iron will
> act as a flux in reduction whether added as
> red clay or as an oxide; the clay is just
> easier to deal with. To remove Redart from
> a reduction body and make it white, but still
> fire at the same temperature, you may need
> to add a flux, like feldspar.
>
> If you work in oxidation, you can probably
> just remove Redart from the recipe with
> little change aside from color.
>
> -Snail
>
--------
Tony Hansen, Digitalfire Corp.
clayart@DIGITALFIRE.AB.CA on sat 5 jul 03
Sounds good, but Redart is an ultra non-plastic clay.
Mix it with water and try to throw something.
-------8<--------
there are several reasons you use redart in a clay body,
to begin with it kills two birds with one stone.
redart is an ultra plastic clay, so you can use some of it instead of some
ball clay.
and then there is the fluxing action,
and on top of that it imparts a nice warm tone to the clay body that makes
all the glazes that react with iron look great.
DO NOT SKIMP ON MATERIALS
you get what you pay for.
cheap materials = bad looking pots
Donn Buchfinck
San Francisco, CA
--------
Tony Hansen, Digitalfire Corp.
Craig Martell on sat 5 jul 03
Hi:
I have to agree with Ron Roy about stoneware bodies with red clay additions
being problematic. This is more of a problem in reduction than oxidation.
The fluxes in the red clays don't nullify cristobalite in the way that
feldspar does. If you add enough red clay to a stoneware body at the
expense of some feldspar, there's a more than good chance of ware failure
from cristobalite. I've seen this happen several times. A friend of mine
decided to flux his stoneware body with red clay instead of spar so the
claybody would have a higher content of plastic materials. What he had was
a body that caused most of his glazes to shiver and many pots came out of
the kiln in more than one piece.
regards, Craig Martell Hopewell, Oregon
Ron Roy on sun 6 jul 03
There is a very good reason not to use Red Art in a cone 10 reduction
stoneware body. I was hoping I would not have to write this all out again
so I did not include it in my first post on the subject.
RedArt starts melting fairly early - about cone 6 - this means you cannot
use as much KNaO in a body that is fluxed with it. KNaO is a great
controller to help minimize cristobalite in such bodies.
It would be a much better strategy to use red iron and a kaolin instead of
Red Art simply because you could get more KNaO into the body.
Cristobalite is a form of silica that goes through it's inversion at about
200C - clearly not something you want in a clay body that needs to go
through ovenware temperatures. It is also a royal pain when glazes have
lower expansion rates. Cracking mugs and teapots are the result in that
scenario.
There is a wonderful article on this subject in the Studio Potter (vol 28
#1) article by Peter Sohngen.
Anyone working with cone 10 reduction bodies should read this article - he
also makes the case for not using silica (the micro fine stuff we usually
get now) because it also aids cristobalite production.
Been all through this with stoneware bodies over the last 40 years - and
because I have a dilatometer I know where of I speak.
RR
>there are several reasons you use redart in a clay body,
>to begin with it kills two birds with one stone.
>redart is an ultra plastic clay, so you can use some of it instead of some
>ball clay.
>and then there is the fluxing action,
>and on top of that it imparts a nice warm tone to the clay body that makes
>all the glazes that react with iron look great.
>
>DO NOT SKIMP ON MATERIALS
>
>you get what you pay for.
>cheap materials = bad looking pots
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Ron Roy on sun 6 jul 03
I agree with Paul here and I have the dilatometer charts to prove it.
The more recent article is by Peter Sohngen (wol 28 #1) - I did the
dilatometer work for it.
Read it to see why the kind of silica you use is even a worse offender.
RR
>I believe the Redart is a relatively fusible clay at ^10. So it will act
>as a flux and a colorant.
>
>Iron does strange things in reduction firing. It's a powerful body flux,
>but won't dissolve Cristobolite (a form of silica). If you use a lot of
>Iron in the body, then you have to use less Feldspar, a body flux which
>WILL dissolve Cristobolite. Too much Cristobolite will cause fit and
>heat shock problems. Too much flux and it bloats and sags.
>
>I'm leaning towards lighter bodies, and when I want color, use an Iron
>bearing fireclay like Lincoln.
>
>If you want to read up on it, there's an article published by Studio
>Potter magazine, "Body Building for Potters" by Jim Robinson. It
>explained some things in a very understandable way. And of course
>Hamers' "Potter's Dictionary".
>
>Happy mixing, from Doyle, where the mosquitos are out, and there's no
>Moon at all.
>
>Paul Herman
>Great Basin Pottery
>423-725 Scott Road
>Doyle, California 96109 US
>potter@psln.com
>
>----------
>>From: Paul
>>To: CLAYART@LSV.CERAMICS.ORG
>>Subject: REDART IN STONEWARE BODIES
>>Date: Wed, Jul 2, 2003, 6:53 PM
>>
>
>> Hello,
>> I am testing some cone 10 stoneware formulas and hope to be making all of my
>> own clay soon, after using a manufactured clay for several years. So i am no
>> expert on stoneware formulas, and have a question about the use of Redart
>> clay in them. Some of the recipes i am looking into call for 10 percent
>> redart, and i was wondering what the function of this low-fire clay would be
>> in a high-fire body. Is it generally for color or does it act as a body flux
>> in some way? Is there a way to eliminate it from the body without affecting
>> the vitrification of the clay? I would like not to have to use it but do not
>> know the proper way to substitute something else for it. Any advice? Thanks,
>> Paul B
>
>______________________________________________________________________________
>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.
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
| |
|
