jonathan byler on mon 9 apr 12
I think we have fired straight lizella clay to ^10. seems to do best
a little cooler, though, closer to ^6 or so. I don't remember if it
is full vitreous at ^10 or not, but the color is not as nice at that
point so we haven't bothered. you could add some fireclay...
On Apr 9, 2012, at 7:44 PM, Vince Pitelka wrote:
> Scott Steder wrote:
> I've been tampering with a few cone 10 iron clay bodies, with hopes of
> making a self glazing clay. One that will react nicely in a wood
> kiln, my
> two formulas have included 10 percent of redart in one and 12
> percent in the
> other. There is 10 percent Neph sy, and 10 percent silica as well.
> To try
> and keep the clay body from slumping/bloating/melting I added
> kyanite to the
> batch, about 20 percent. Understanding that it is a very refractory
> material
> (aluminum silicate) figured it would help, I just havent found much
> liturature on it being added to earthenware bodies. I've done cone 6
> electric tests and they are not fully matured, although im still
> weary about
> the reaction it will have in reduction atmosphere. Any advice/
> experience
> with high fire earthenware clay bodies would be most appriciated.
>
> Hi Scott -
> What you are working towards is a brown stoneware. In my experience
> the
> wood-firers I have known don't much care for high-iron claybodies
> because
> they tend to come out REALLY dark in a long slow firing. It is
> curious that
> in such firings, a lot of porcelain and porcelaineous stoneware
> bodies are
> for all practical purposes self-glazing on the outside and often
> develop a
> very nice gloss where they are hit by the fine fly-ash. So I am not
> sure
> that loading up the clay with iron is the right solution if your
> primary
> concern is the "glaze" effect of the wood firing on the raw clay
> surface. I
> am also concerned that where the ash hits the clay and sits there
> for a
> while, the overload of iron will tend to cause the ash to run even
> more
> severely. But if you don't mind the very dark color you will get from
> high-iron clay, then this is certainly an area ripe for
> experimentation.
>
> Please forgive me for being such a stickler for terminology, but
> there is no
> such thing as high-fired earthenware. Earthenware claybodies by
> definition
> cannot survive to high-fire temperatures. They would bloat and slump
> long
> before reaching cone-10.
>
> It is not uncommon to add Kyanite or Mullite to stoneware bodies to
> make
> them more refractory and to add working structure. I do not think
> that 10%
> or 12% Redart would be enough to cause a stoneware body to bloat or
> slump,
> but if you are concerned, a good strategy might be to replace the
> neph sy
> with potash feldspar. That is more commonly used in high-fire
> claybodies,
> while neph sy is seen more often in cone-6 bodies.
> - Vince
>
> Vince Pitelka
> Appalachian Center for Craft
> Tennessee Tech University
> vpitelka@dtccom.net
> http://iweb.tntech.edu/wpitelka/
Scott Steder on mon 9 apr 12
Hi ALL, =3D0A=3DA0=3D0ABeen enjoying all the posts =3D0Athis is my first :)=
=3D0A=3DA0=3D
=3D0AI've been tampering with a few cone 10 iron clay bodies, with hopes of=
m=3D
aking a self glazing clay. One that will react nicely in a wood kiln, my tw=
=3D
o formulas have included 10 percent of redart in one and 12 percent in the =
=3D
other. There is 10 percent=3DA0Neph sy, and 10 percent=3DA0silica as well. =
=3DA0T=3D
o try and keep the clay body from slumping/bloating/melting I added kyanite=
=3D
to the batch, about 20 percent. Understanding that it is a very refractory=
=3D
material (aluminum silicate) figured it would help,=3DA0I just havent foun=
d =3D
much liturature on it being added to earthenware bodies. =3D0A=3DA0=3D0AI'v=
e done=3D
cone 6 electric tests and they are not=3DA0fully matured,=3DA0although im =
stil=3D
l weary about the reaction it will have in reduction atmosphere.=3DA0=3D0A=
=3DA0=3D
=3D0AAny advice/experience with high fire earthenware clay bodies would be =
mo=3D
st appriciated. =3D0A=3DA0=3D0A=3DA0=3D0AThanks ! =3D0AScott Steder
Vince Pitelka on mon 9 apr 12
Scott Steder wrote:
I've been tampering with a few cone 10 iron clay bodies, with hopes of
making a self glazing clay. One that will react nicely in a wood kiln, =3D
my
two formulas have included 10 percent of redart in one and 12 percent in =
=3D
the
other. There is 10 percent=3DA0Neph sy, and 10 percent=3DA0silica as well. =
=3D
=3DA0To try
and keep the clay body from slumping/bloating/melting I added kyanite to =
=3D
the
batch, about 20 percent. Understanding that it is a very refractory =3D
material
(aluminum silicate) figured it would help,=3DA0I just havent found much
liturature on it being added to earthenware bodies. I've done cone 6
electric tests and they are not=3DA0fully matured,=3DA0although im still =
=3D
weary about
the reaction it will have in reduction atmosphere.=3DA0Any =3D
advice/experience
with high fire earthenware clay bodies would be most appriciated.=3D20
Hi Scott -=3D20
What you are working towards is a brown stoneware. In my experience the
wood-firers I have known don't much care for high-iron claybodies =3D
because
they tend to come out REALLY dark in a long slow firing. It is curious =3D
that
in such firings, a lot of porcelain and porcelaineous stoneware bodies =3D
are
for all practical purposes self-glazing on the outside and often develop =
=3D
a
very nice gloss where they are hit by the fine fly-ash. So I am not =3D
sure
that loading up the clay with iron is the right solution if your primary
concern is the "glaze" effect of the wood firing on the raw clay =3D
surface. I
am also concerned that where the ash hits the clay and sits there for a
while, the overload of iron will tend to cause the ash to run even more
severely. But if you don't mind the very dark color you will get from
high-iron clay, then this is certainly an area ripe for experimentation.
Please forgive me for being such a stickler for terminology, but there =3D
is no
such thing as high-fired earthenware. Earthenware claybodies by =3D
definition
cannot survive to high-fire temperatures. They would bloat and slump =3D
long
before reaching cone-10. =3D20
It is not uncommon to add Kyanite or Mullite to stoneware bodies to make
them more refractory and to add working structure. I do not think that =3D
10%
or 12% Redart would be enough to cause a stoneware body to bloat or =3D
slump,
but if you are concerned, a good strategy might be to replace the neph =3D
sy
with potash feldspar. That is more commonly used in high-fire =3D
claybodies,
while neph sy is seen more often in cone-6 bodies.=3D20
- Vince
Vince Pitelka
Appalachian Center for Craft
Tennessee Tech University
vpitelka@dtccom.net
http://iweb.tntech.edu/wpitelka/
Rimas VisGirda on tue 10 apr 12
Straight Redart with some sand can sustain cone 10, I've fired 2x6x1/4 inch=
bars just to see... In an electric kiln it comes out looking like dark cho=
colate; in reduction it comes out looking like a brownie... -Rimas
Rimas VisGirda on tue 10 apr 12
When I was teaching we did a commercial underglaze section with AMACO Velve=
=3D
ts on Redart with about 10-20 % sand.=3DA0 We would overfire the work to c/=
3 =3D
and the Velvets got a really nice "hard" color and the Redart was a really =
=3D
pretty toasty orange. Some of the Velvets started to fuse past c/3. AMACO k=
=3D
eeps reformulating their stuff and now I find that some of the Velvets star=
=3D
t to get a shine as low as c/03... but that's a whole other bag... -Rimas=
=3D
=3D0A=3D0A=3D0A=3D0A=3D0A=3D0A________________________________=3D0AFrom: Su=
chman ceramics=3D
=3D0ATo: Rimas VisGirda =3D0ASen=
t: T=3D
uesday, April 10, 2012 10:29 AM=3D0ASubject: Re: cone 10 earthenware=3D0A=
=3D0A=3D0A=3D
I use it as the bulk of my ^1 body=3D0A=3D0A=3D0AOn Tue, Apr 10, 2012 at 4:=
51 AM,=3D
Rimas VisGirda wrote:=3D0A=3D0AStraight Redart with so=
me s=3D
and can sustain cone 10, I've fired 2x6x1/4 inch bars just to see... In an =
=3D
electric kiln it comes out looking like dark chocolate; in reduction it com=
=3D
es out looking like a brownie... -Rimas=3D0A>=3D0A=3D0A=3D0A-- =3D0A-e-in-o=
'side-=3D0Ap=3D
agan by nature=3D0A>http://www.flickr.com/photos/42169721@N04/=3D0A>http://=
www.=3D
etsy.com/shop/SalamanderStudios?ref=3D3Dsi_shop
Scott Steder on tue 10 apr 12
Rimas, Ben, and Vince
Thanks for the insight, I really am fond of darker clay bodies that ive see=
=3D
n as of late. I'm most likely going to fire only a few tea bowls in the woo=
=3D
d kiln, other (larger sculptures) I will do in the gas kiln and a small saw=
=3D
dust kiln here at Northren Illinois.=3DA0
The proper lingo (correction) is quite alright =3DA0I did realize the term =
hi=3D
gh fire earthenware was a bit incorrect but thats what intrigued me to do s=
=3D
ome experimentation, couldn't find any=3D0A information on the subject. The=
u=3D
se of N.S. was to introduce some extra Na2O3 but a different feldspar would=
=3D
make more sense.
I just did another test today with the same recipe, although I added 2% mas=
=3D
on stain 6000 (pink), 2% granular iron and illuminite combo, plus 2% dark r=
=3D
utile.~Very excited=3DA0
Will adding these courser iron particles/stains effect the clay body at all=
=3D
? I've used black silica sand and granular rutile before, noting that they =
=3D
streak underneath some glazes.
Has anyone experimented with putting rutile in clay bodies? I find myself p=
=3D
utting it in everything these days.=3DA0
Thanks again everyone!=3DA0
Those clay formulas will be a nice test for the next batch, thanks ben. Ill=
=3D
let you know the results.
From: Ben Morrison
To: Scott Steder =3D20
Sent: Monday, April 9, 2012 11:57 PM
Subject: Re: Cone 10 earthenware
=3D20
=3D0AScott,
I've=3D0A loaded about 10% earthenware into a body containing a high quanti=
ty=3D
of =3D0Afireclay. That body was a mixture of recycle and added dry clay. W=
e =3D
=3D0Awould mix up a batch of the stuff as the recycle would pile up. Adding=
=3D
=3D0Ain about 6 - 10% redart created a nice red stoneware. We'd also add =
=3D0Al=3D
incoln fireclay and feldspar mix for a nice buff white stoneware. =3D0AYou'=
re=3D
no where close to a self glazing clay body in this case though.=3D0A
=3D0A =3D0AI'm sure you'd have a difficult time formulating a high fire se=
lf g=3D
lazing clay body that would stand up. At any rate here are a couple recipes=
=3D
I've pulled from the Electric Kiln Ceramics 3rd Ed. book written by Richar=
=3D
d Zakin. I have not tried these myself, but they should serve as a jumping =
=3D
off point for your research.
=3D0A =3D0A
=3D0A =3D0ABd Body 2.9 Low Clay Content Body, Cone 3=3D0ASoda Spar=3DA0=3D=
A0=3DA0 =3DA0=3D
=3DA0=3DA0 =3DA0=3DA0=3DA0 28=3D0ATalc=3DA0=3DA0=3DA0 =3DA0=3DA0=3DA0 =3DA0=
=3DA0=3DA0 =3DA0=3DA0=3DA0 =3DA0=3DA0=3DA0=3D
=3DA0 24=3D0ABall Clay=3DA0=3DA0=3DA0 =3DA0=3DA0 =3DA0=3DA0=3DA0 =3DA0=3DA0=
=3DA0 30=3D0AKaolin=3DA0=3DA0=3DA0=3D
=3DA0=3DA0=3DA0 =3DA0=3DA0 =3DA0=3DA0=3DA0 =3DA0=3DA0 18=3D0A
=3D0A =3D0ABd Body 2.9a, Cone 3=3D0ASoda Spar=3DA0=3DA0=3DA0 =3DA0=3DA0=3D=
A0 =3DA0=3DA0=3DA0 28=3D0A=3D
Talc=3DA0=3DA0=3DA0 =3DA0=3DA0=3DA0 =3DA0=3DA0=3DA0 =3DA0=3DA0=3DA0 =3DA0=
=3DA0 =3DA0 24=3D0ABall Clay=3DA0=3DA0=3D
=3DA0 =3DA0=3DA0 =3DA0=3DA0=3DA0 =3DA0=3DA0=3DA0 20=3D0AStoneware Clay=3DA0=
=3DA0=3DA0=3DA0 10=3D0A
=3D0A=3D0ABoth of these bodies are said =3D0Ato be self glazing at cone 3 a=
nd tak=3D
e stains well. They are said to slump or =3D0Adistort easily if not handled=
w=3D
ith care.=3D0A
=3D0A=3D0ABest of Luck,=3D0A
=3D0A=3D0ABen
=3D0A =3D0A
=3D0A
From: Scott Steder
To: Clayart@LSV.CERAMICS.ORG=3D20
Sent: Monday, April 9, 2012 3:08 PM
Subject: Cone 10 earthenware
=3D20
=3D0AHi ALL,=3D20
=3DA0
Been enjoying all the posts=3D20
this is my first :)
=3DA0
I've been tampering with a few cone 10 iron clay bodies, with hopes of maki=
=3D
ng a self glazing clay. One that will react nicely in a wood kiln, my two f=
=3D
ormulas have included 10 percent of redart in one and 12 percent in the oth=
=3D
er. There is 10 percent=3DA0Neph sy, and 10 percent=3DA0silica as well. =3D=
A0To t=3D
ry and keep the clay body from slumping/bloating/melting I added kyanite to=
=3D
the batch, about 20 percent. Understanding that it is a very refractory ma=
=3D
terial (aluminum silicate) figured it would help,=3DA0I just havent found m=
uc=3D
h liturature on it being added to earthenware bodies.=3D20
=3DA0
I've done cone 6 electric tests and they are not=3DA0fully matured,=3DA0alt=
houg=3D
h im still weary about the reaction it will have in reduction atmosphere.=
=3D
=3DA0
=3DA0
Any advice/experience with high fire earthenware clay bodies would be most =
=3D
appriciated.=3D0A=3D20
=3DA0
=3DA0
Thanks !=3D20
Scott Steder
=3D20
Vince Pitelka on tue 10 apr 12
Jonathan Byler wrote:
"I think we have fired straight lizella clay to ^10. seems to do best a
little cooler, though, closer to ^6 or so. I don't remember if it is full
vitreous at ^10 or not, but the color is not as nice at that point so we
haven't bothered. you could add some fireclay..."
Hi Jonathan -
Lizella is not an earthenware clay. It's red stoneware like Okmulgee,
Carbondale, Newman Red, etc. They started out as earthenware clays, but as
is the case with buff stonewares and fireclays, were buried underground and
over geologic time some of the fluxes were leached away by acidic
groundwater and steam, rendering them more refractory.
One of the confusions here is between a clay identified as "earthenware,"
"stoneware," or "porcelain," and a fired product called "earthenware,"
"stoneware," or "porcelain." The only raw clays that can be called
earthenware are by definition the ones that cannot be fired to highfire
temperatures or they will bloat and slump. Traditionally the term
earthenware has referred to the high-iron surface clays we associate with
terracottas, but now of course we have low-fire talc and frit whiteware
bodies that cannot be fired above lowfire temperatures. And any claybody
fired to lowfire temperatures to form a porous, non-vitreous finished
product is earthenware once it's fired. That's one of the more confusing
things that messes people up in deciding what to call their work. If you
are using a stoneware or porcelain claybody and you only fire it to cone-04=
,
the product, by clear-cut definition, is not stoneware or porcelain. It is
earthenware.
- Vince
Vince Pitelka
Appalachian Center for Craft
Tennessee Tech University
vpitelka@dtccom.net
http://iweb.tntech.edu/wpitelka/
Edouard Bastarache on tue 10 apr 12
Hi Vince & all,
Eartenware "goofily" fired at cone 9=BD
http://www.flickr.com/photos/poussi/2512187811/in/photostream
Plejkore,
Edouard Bastarache
Spertesperantisto
Sorel-Tracy
Quebec
http://www.flickr.com/photos/30058682@N00/
http://edouardbastarache.blogspot.com/
http://smart2000.pagesperso-orange.fr/bloggs_edouard.htm
http://www.facebook.com/edouard.bastarache
----- Original Message -----
From: "Vince Pitelka"
To:
Sent: Tuesday, April 10, 2012 3:42 PM
Subject: Re: Cone 10 earthenware
> Jonathan Byler wrote:
> "I think we have fired straight lizella clay to ^10. seems to do best a
> little cooler, though, closer to ^6 or so. I don't remember if it is ful=
l
> vitreous at ^10 or not, but the color is not as nice at that point so we
> haven't bothered. you could add some fireclay..."
>
> Hi Jonathan -
> Lizella is not an earthenware clay. It's red stoneware like Okmulgee,
> Carbondale, Newman Red, etc. They started out as earthenware clays, but
> as
> is the case with buff stonewares and fireclays, were buried underground
> and
> over geologic time some of the fluxes were leached away by acidic
> groundwater and steam, rendering them more refractory.
>
> One of the confusions here is between a clay identified as "earthenware,"
> "stoneware," or "porcelain," and a fired product called "earthenware,"
> "stoneware," or "porcelain." The only raw clays that can be called
> earthenware are by definition the ones that cannot be fired to highfire
> temperatures or they will bloat and slump. Traditionally the term
> earthenware has referred to the high-iron surface clays we associate with
> terracottas, but now of course we have low-fire talc and frit whiteware
> bodies that cannot be fired above lowfire temperatures. And any claybody
> fired to lowfire temperatures to form a porous, non-vitreous finished
> product is earthenware once it's fired. That's one of the more confusing
> things that messes people up in deciding what to call their work. If you
> are using a stoneware or porcelain claybody and you only fire it to
> cone-04,
> the product, by clear-cut definition, is not stoneware or porcelain. It
> is
> earthenware.
> - Vince
>
> Vince Pitelka
> Appalachian Center for Craft
> Tennessee Tech University
> vpitelka@dtccom.net
> http://iweb.tntech.edu/wpitelka/
>
ronroy@CA.INTER.NET on tue 10 apr 12
HI Jonathan,
Just back on the list after traveling.
The big problem with high fire brown bodies is cristobalite formation
- you need about 10% spar to stop that but - because iron is a strong
flux in reduction bodies it's hard to get enough spar in to control
the cristobalite. Earthenware clay contains so much other melters that
it promotes cristobalite.
Best to not use silica - take a look at the article by Peter Sohngen
at the Studio Potter web site.
http://studiopotter.org/pdfs/Sohng%20pps84-89.pdf
One of the better clays for making such bodies is Newman because it is
refractory and has a lot of iron - like 7.7% - thats more than Redart.
I have a dilatometer if you need to know if you have any cristobalite
- best to avoid it - especially if you are doing any ovenware.
RR
Quoting jonathan byler :
> I think we have fired straight lizella clay to ^10. seems to do best
> a little cooler, though, closer to ^6 or so. I don't remember if it
> is full vitreous at ^10 or not, but the color is not as nice at that
> point so we haven't bothered. you could add some fireclay...
>
>
> On Apr 9, 2012, at 7:44 PM, Vince Pitelka wrote:
>
>> Scott Steder wrote:
>> I've been tampering with a few cone 10 iron clay bodies, with hopes of
>> making a self glazing clay. One that will react nicely in a wood
>> kiln, my
>> two formulas have included 10 percent of redart in one and 12
>> percent in the
>> other. There is 10 percent Neph sy, and 10 percent silica as well.
>> To try
>> and keep the clay body from slumping/bloating/melting I added
>> kyanite to the
>> batch, about 20 percent. Understanding that it is a very refractory
>> material
>> (aluminum silicate) figured it would help, I just havent found much
>> liturature on it being added to earthenware bodies. I've done cone 6
>> electric tests and they are not fully matured, although im still
>> weary about
>> the reaction it will have in reduction atmosphere. Any advice/
>> experience
>> with high fire earthenware clay bodies would be most appriciated.
>>
>> Hi Scott -
>> What you are working towards is a brown stoneware. In my experience
>> the
>> wood-firers I have known don't much care for high-iron claybodies
>> because
>> they tend to come out REALLY dark in a long slow firing. It is
>> curious that
>> in such firings, a lot of porcelain and porcelaineous stoneware
>> bodies are
>> for all practical purposes self-glazing on the outside and often
>> develop a
>> very nice gloss where they are hit by the fine fly-ash. So I am not
>> sure
>> that loading up the clay with iron is the right solution if your
>> primary
>> concern is the "glaze" effect of the wood firing on the raw clay
>> surface. I
>> am also concerned that where the ash hits the clay and sits there
>> for a
>> while, the overload of iron will tend to cause the ash to run even
>> more
>> severely. But if you don't mind the very dark color you will get from
>> high-iron clay, then this is certainly an area ripe for
>> experimentation.
>>
>> Please forgive me for being such a stickler for terminology, but
>> there is no
>> such thing as high-fired earthenware. Earthenware claybodies by
>> definition
>> cannot survive to high-fire temperatures. They would bloat and slump
>> long
>> before reaching cone-10.
>>
>> It is not uncommon to add Kyanite or Mullite to stoneware bodies to
>> make
>> them more refractory and to add working structure. I do not think
>> that 10%
>> or 12% Redart would be enough to cause a stoneware body to bloat or
>> slump,
>> but if you are concerned, a good strategy might be to replace the
>> neph sy
>> with potash feldspar. That is more commonly used in high-fire
>> claybodies,
>> while neph sy is seen more often in cone-6 bodies.
>> - Vince
>>
>> Vince Pitelka
>> Appalachian Center for Craft
>> Tennessee Tech University
>> vpitelka@dtccom.net
>> http://iweb.tntech.edu/wpitelka/
>
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