Elizabeth Priddy on tue 23 feb 10
You know how you are never supposed to test with a load that matters?
I am trying it this time, so I hope it works out.
I usually fire to cone 06, so it won't be far off. I was just actually try=
ing to find out if there is some particular temp that has a test for "done"=
for bisque the same way that there are tests for vitrification.
I should know this! (but I really don't.)
- ePriddy
Elizabeth Priddy
Beaufort, NC - USA
Elizabeth Priddy on tue 23 feb 10
Anybody bisque to cone 07? Is it a clean bisque?
- ePriddy
Elizabeth Priddy
Beaufort, NC - USA
http://www.elizabethpriddy.com
Vince Pitelka on wed 24 feb 10
DJ Brewer wrote:
"At the school, we always bisque to 08. I've noticed a lot of crazing on
some glazes -- especially celadon -- but that may be due to misfitting
glaze and claybody. We use mostly shop clay that is a mixture of the
class "slop buckets" and the ingredients by the clay mixer. It's a
sturdy, groggy mix that does well at both cone 6 and cone 10.
Would bisquing to 08 factor in on glazes crazing? Somehow, my intuition
tells me "no" (but then, my intuition does not know beans about it!)"
DJ -
If you are talking about making utilitarian pots, then there is no such
thing as a claybody that "does well at both cone 6 and cone 10." If it is
dense and vitrified at cone 10 with no serious warping or slumping, then it
is going to be pretty seriously underfired at cone 6 and most glazes are
going to craze, since the claybody is not shrinking as much as it is
supposed to when fired to maturity.
- Vince
Vince Pitelka
Appalachian Center for Craft
Tennessee Tech University
vpitelka@dtccom.net; wpitelka@tntech.edu
http://iweb.tntech.edu/wpitelka
Lee Love on wed 24 feb 10
On Wed, Feb 24, 2010 at 5:23 PM, Elizabeth Priddy wr=
=3D
ote:
> They all look fine. =3DA0I used paper clay to repair a backing hanger and=
w=3D
hen I touched it, it disintegrated, but the pieces look fine at ^07.
>
> Thanks for the heads up. =3DA0I will let you know how the glaze firing go=
es=3D
re the pinholing.
Sponging helps prevent pinholing that appears right after you glaze.
--
Lee, a Mashiko potter in Minneapolis
http://mashikopots.blogspot.com/
=3D93Observe the wonders as they occur around you. Don't claim them. Feel
the artistry moving through and be silent.=3D94 --Rumi
Larry Kruzan on wed 24 feb 10
Hi E,
I bisque to 05. I would think that 07 might not achieve a complete burnout
of the organics and might lead to pinholes in the glazes firing.
That said - in school we bisque fired to 09. Shows I no expert, but 05 work=
s
for me.
Larry Kruzan
Lost Creek Pottery
www.lostcreekpottery.com
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Larry Kruzan on wed 24 feb 10
<<<<<<<<<<<<<>>>>>>>
But a final point--most of the pinhole problems Ron and I see are caused by
inadequate bisque firing. So if you lower your bisque temperature examine
the final glaze fired pots carefully for pinholes.
Regards,
John
<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>
Thanks John,
That's where I was going, test, test, TEST, TEST - and if it works for you
great! Each of us work differently so there is no iron clad rule except tha=
t
the ware needs to be bisqued hot enough for the way you work. If you are
having pinholes - this MIGHT be the place to look for a solution.
(you said it so much eloquently than I ever could)
Larry Kruzan
Lost Creek Pottery
www.lostcreekpottery.com
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Snail Scott on wed 24 feb 10
On Feb 23, 2010, at 3:20 PM, Elizabeth Priddy wrote:
> Anybody bisque to cone 07? Is it a clean bisque?
What cone is room temperature? maybe ^030? ^032?
I've got limited patience for glazes that can't be used
for single-firing. No prima-donna chemistry for me!
Seriously, I do often bisque to ^08, and it does fine for
me. I am not fussy about glaze application or response,
though, and my glazes (the few I use) are not fussy
either, but my stuff ain't yours. I expect that the right
bisque for your clay and glazes will only be determined
experimentally.
-Snail
Vince Pitelka on wed 24 feb 10
Larry Kruzan wrote:
"I bisque to 05. I would think that 07 might not achieve a complete burnout
of the organics and might lead to pinholes in the glazes firing."
Larry -
The "water-smoking period," when volatiles are outgassing
(chemically-combined water, carbon dioxide, sulfur dioxide, carbon smoke
from coal and waxes) from the clay during bisque-firing (or single-firing),
lasts from about 800F to 1400F. As long as you do not fire too fast throug=
h
this range, and as long as there is ample oxygen in the kiln to encourage
oxidation of the sulfur and carbon, all volatiles will be gone by 1400F
(cone 017).
In general terms, it is important to remember that minimal sintering begins
at early red heat around 900F, and as the clay is heated beyond that point,
a glassy phase progressively strengthens the sintered bonds between
refractory particles. The lower you bisque, the more the bisqued clay is
porous and weak. The higher you bisque, the more the bisqued clay is dense
and strong. Obviously this has major implications regarding glazing.
- Vince
Vince Pitelka
Appalachian Center for Craft
Tennessee Tech University
vpitelka@dtccom.net; wpitelka@tntech.edu
http://iweb.tntech.edu/wpitelka
Lee Love on wed 24 feb 10
I met Mashiko potter Toshi Okuma at NCC in 1990. He bisqued at 012.
Said nobody bisque over that temp in Mashiko.
Toshi was "thrifty" too, but when I finally got to Mashiko, I found
that what he said was true. Bisque was not done by cones or
pyrometer, but to red heat. Red heat is below 012 (dull red is about
020.)
I find that shinos like the lower bisque. I have
screwed up loads, because I fired higher, to cone 06 because I put
class work in the bisque.
I used to thing maybe it was earthenware or cone 6 that was
fussier than traditional stoneware and porcelain firing. But I have
been testing terracotta in single firing, and it is working pretty
well. I started with terra sigged work and single fire worked fine.
So I tried my clear glazes and majolica. Everything works well. I
justt need to add some cmc to the majolica. It is a little flaky.
Of course, you have to adjust the glaze to get the right coat on
leather hard.
You have to test to see if this works on your glaze and clay body.
--
Lee, a Mashiko potter in Minneapolis
http://mashikopots.blogspot.com/
=3D93Observe the wonders as they occur around you. Don't claim them. Feel
the artistry moving through and be silent.=3D94 --Rumi
John Hesselberth on wed 24 feb 10
On Feb 24, 2010, at 2:25 AM, Elizabeth Priddy wrote:
> I usually fire to cone 06, so it won't be far off. I was just =3D
actually trying to find out if there is some particular temp that has a =3D
test for "done" for bisque the same way that there are tests for =3D
vitrification.
>=3D20
> I should know this! (but I really don't.)
Needed bisque temperature is dependent on the clay body itself (how much =
=3D
junk is there to burn out) as well as how you stack and how fast you =3D
fire. What is needed is to get every piece of pottery hot enough with =3D
enough access to oxygen that the volatiles can burn off. Jack Troy =3D
bisques to 010 and claims never to have a problem. I don't know how =3D
tightly he stacks his bisque kiln or how fast he fires. Guessing from =3D
the pieces of his I am familiar with, I would bet he is stacking fairly =3D
loosely--I haven't seen him make a lot of stackable pieces like open =3D
bowls. =3D20
In MC6Gs we recommend 04 because we know lots of potters are prone to =3D
stack several bowls inside each other and don't do a soak at the end to =3D
even things out. So that is a conservative way to assure success.
Strength of the bisqueware and handling through glazing is another =3D
consideration as is appropriate absorbency for your glazes. If you are =3D
breaking pots as you handle them in glazing consider bisque firing =3D
higher. If your pots are not absorbing glaze fast enough, consider =3D
bisque firing lower.
But a final point--most of the pinhole problems Ron and I see are caused =
=3D
by inadequate bisque firing. So if you lower your bisque temperature =3D
examine the final glaze fired pots carefully for pinholes.
Regards,
John
DJBrewer88 on wed 24 feb 10
at the school, we always bisque to 08. I've noticed a lot of crazing on
some glazes -- especially celadon -- but that may be due to misfitting
glaze and claybody. We use mostly shop clay that is a mixture of the
class "slop buckets" and the ingredients by the clay mixer. It's a
sturdy, groggy mix that does well at both cone 6 and cone 10.
Would bisquing to 08 factor in on glazes crazing? Somehow, my intuition
tells me "no" (but then, my intuition does not know beans about it!)
DJ
On 2/24/2010 12:20 AM, Larry Kruzan wrote:
Hi E,
I bisque to 05. I would think that 07 might not achieve a complete burnout
of the organics and might lead to pinholes in the glazes firing.
That said - in school we bisque fired to 09. Shows I no expert, but 05
works
for me.
Larry Kruzan
Lost Creek Pottery
www.lostcreekpottery.com
Rikki Gill on wed 24 feb 10
Hi Larry,
I bisque porcelain to cone 07. I fire to cone 10 -11. Works for me.
No pinholing, just the right amount of glaze.
Rikki Gill
----- Original Message -----
From: "Larry Kruzan"
To:
Sent: Tuesday, February 23, 2010 10:20 PM
Subject: Re: bisque at 07?
> Hi E,
> I bisque to 05. I would think that 07 might not achieve a complete burnou=
t
> of the organics and might lead to pinholes in the glazes firing.
>
> That said - in school we bisque fired to 09. Shows I no expert, but 05
> works
> for me.
>
> Larry Kruzan
> Lost Creek Pottery
> www.lostcreekpottery.com
>
>
>
>
>
>
>
> E-mail message checked by Spyware Doctor (7.0.0.514)
> Database version: 6.14410
> http://www.pctools.com/en/spyware-doctor-antivirus/
Steve Irvine on wed 24 feb 10
Elizabeth,
I regularly bisque to cone 09 without problems. A bisque at 07 should be =
=3D
fine.
Steve Irvine
www.steveirvine.com
Lee Love on wed 24 feb 10
On Wed, Feb 24, 2010 at 8:36 AM, John Hesselberth
wrote:
> On Feb 24, 2010, at 2:25 AM, Elizabeth Priddy wrote:
> But a final point--most of the pinhole problems Ron and I see are caused =
=3D
by inadequate >bisque firing. So if you lower your bisque temperature exami=
=3D
ne the final glaze fired pots >carefully for pinholes.
Pinholes are created in low bisque because there is a lot of air in
the bisque clay. People who low bisque used a sponge to wipe the
bisque (no control in dunking your bisque or pouring water over it.)
What is so nice about this traditional approach is that you can
vary the absorbency according to the glaze by the amount of sponging
you do. You can also vary the sponging according to the thickness of
the clay.
I was the sponger during my apprenticeship. It takes
practice, but I became very good.
Also, this isn't a problem with single fire at leather hard,
because the clay is less absorbent than hard bisque. This is also
proof that organics in the clay do not create these pinholes that you
see immediately after glazing.
--
Lee, a Mashiko potter in Minneapolis
http://mashikopots.blogspot.com/
=3D93Observe the wonders as they occur around you. Don't claim them. Feel
the artistry moving through and be silent.=3D94 --Rumi
Elizabeth Priddy on wed 24 feb 10
They all look fine. I used paper clay to repair a backing hanger and when =
I touched it, it disintegrated, but the pieces look fine at ^07.
Thanks for the heads up. I will let you know how the glaze firing goes re =
the pinholing.
- ePriddy
Elizabeth Priddy
Beaufort, NC - USA
http://www.elizabethpriddy.com
Hank Murrow on wed 24 feb 10
On Feb 24, 2010, at 10:09 AM, Lee Love wrote:
>
> Pinholes are created in low bisque because there is a lot of air in
> the bisque clay. People who low bisque used a sponge to wipe the
> bisque (no control in dunking your bisque or pouring water over it.)
It is useful to remind ourselves that the lovely pinholing of
traditional shino wares is due to the extraordinary openness of the
Mogusa clay that was used in its making. Such a clay vitrifies around
Cone 18! Tea practitioners called the spots nest holes(suana) or
citron skin(yuzuhada). My own western attempt at mogusa-like clay
does these wonderfully despite bisquing @ C07, and orangey pits are
often produced from the reduction atmosphere in the kiln. The effect
can be seen here:
http://www.flickr.com/photos/claycraft/3865811478/
Cheers, Hank in Eugene,
Glazing some wares like these for the 25th anniversary firing of the
East Creek anagama next week.
Ron Roy on thu 25 feb 10
Hi Vince,
My information is - the organics don't really start burning out till
after 700C (1300F) - certainly that is supported by the amount of
smoke coming out of a bisque kiln.
I recommend cone 04 - have always fired bisque to that temperature -
and that recommendation has cured many a pinholing problem.
The type of clay used and how much carbon and sulphur etc is present
matters a lot - especially when there is iron present in the clay.
There is another huge advantage to an 04 bisque - the glazes can be
kept thicker in the bucket which means they stay floated for longer
periods.
As you have noted - the amount of new oxygen supplied is essential for
combustion - so I would add - if you do want to bisque lower, make
sure there is adequate O2 - a vent running and working properly, an
open spy and or a lid a bit open - and enough time for any burning to
take place - especially with thicker or nested pieces.
RR
Quoting Vince Pitelka :
> Larry Kruzan wrote:
> "I bisque to 05. I would think that 07 might not achieve a complete burno=
ut
> of the organics and might lead to pinholes in the glazes firing."
>
> Larry -
> The "water-smoking period," when volatiles are outgassing
> (chemically-combined water, carbon dioxide, sulfur dioxide, carbon smoke
> from coal and waxes) from the clay during bisque-firing (or single-firing=
),
> lasts from about 800F to 1400F. As long as you do not fire too fast thro=
ugh
> this range, and as long as there is ample oxygen in the kiln to encourage
> oxidation of the sulfur and carbon, all volatiles will be gone by 1400F
> (cone 017).
>
> In general terms, it is important to remember that minimal sintering begi=
ns
> at early red heat around 900F, and as the clay is heated beyond that poin=
t,
> a glassy phase progressively strengthens the sintered bonds between
> refractory particles. The lower you bisque, the more the bisqued clay is
> porous and weak. The higher you bisque, the more the bisqued clay is den=
se
> and strong. Obviously this has major implications regarding glazing.
> - Vince
>
> Vince Pitelka
> Appalachian Center for Craft
> Tennessee Tech University
> vpitelka@dtccom.net; wpitelka@tntech.edu
> http://iweb.tntech.edu/wpitelka
>
Elizabeth Priddy on thu 25 feb 10
The tiles bisqued at ^07 glazed fine, maybe better than the o5-06 from bef=
=3D
ore. I have some old bique ready to include in this firing and so I will l=
=3D
ook for pinholing.=3D0A=3D0AWill know more tomorrow.=3D0A=3D0A=3D0A- ePridd=
y=3D0A=3D0AEli=3D
zabeth Priddy=3D0ABeaufort, NC - USA=3D0A=3D0Ahttp://www.elizabethpriddy.co=
m=3D0A=3D
=3D0A=3D0A--- On Wed, 2/24/10, John Hesselberth w=
rote=3D
:=3D0A=3D0A> From: John Hesselberth =3D0A> Subject=
: Re: =3D
bisque at 07?=3D0A> To: Clayart@LSV.CERAMICS.ORG=3D0A> Date: Wednesday, Feb=
ruar=3D
y 24, 2010, 9:36 AM=3D0A> On Feb 24, 2010, at 2:25 AM,=3D0A> Elizabeth Prid=
dy w=3D
rote:=3D0A> =3D0A> > I usually fire to cone 06, so it won't be far=3D0A> of=
f.=3DA0 =3D
I was just actually trying to find out if there=3D0A> is some particular te=
mp=3D
that has a test for "done" for=3D0A> bisque the same way that there are te=
st=3D
s for vitrification.=3D0A> > =3D0A> > I should know this!=3DA0 (but I reall=
y don'=3D
t.)=3D0A> =3D0A> Needed bisque temperature is dependent on the clay body=3D=
0A> it=3D
self (how much junk is there to burn out) as well as how=3D0A> you stack an=
d =3D
how fast you fire. What is needed is to get=3D0A> every piece of pottery ho=
t =3D
enough with enough access to=3D0A> oxygen that the volatiles can burn off.=
=3DA0=3D
Jack Troy=3D0A> bisques to 010 and claims never to have a problem. I don't=
=3D
=3D0A> know how tightly he stacks his bisque kiln or how fast he=3D0A> fire=
s. G=3D
uessing from the pieces of his I am familiar with, I=3D0A> would bet he is =
st=3D
acking fairly loosely--I haven't seen him=3D0A> make a lot of stackable pie=
ce=3D
s like open bowls.=3DA0 =3D0A> =3D0A> In MC6Gs we recommend 04 because we k=
now lo=3D
ts of potters=3D0A> are prone to stack several bowls inside each other and =
do=3D
n't=3D0A> do a soak at the end to even things out. So that is a=3D0A> conse=
rvat=3D
ive way to assure success.=3D0A> =3D0A> Strength of the bisqueware and hand=
ling=3D
through glazing is=3D0A> another consideration as is appropriate absorbenc=
y =3D
for your=3D0A> glazes. If you are breaking pots as you handle them in=3D0A>=
gla=3D
zing consider bisque firing higher. If your pots are not=3D0A> absorbing gl=
az=3D
e fast enough, consider bisque firing lower.=3D0A> =3D0A> But a final point=
--mo=3D
st of the pinhole problems Ron and I=3D0A> see are caused by inadequate bis=
qu=3D
e firing. So if you lower=3D0A> your bisque temperature examine the final g=
la=3D
ze fired pots=3D0A> carefully for pinholes.=3D0A> =3D0A> Regards,=3D0A> =3D=
0A> John=3D
=3D0A> =3D0A=3D0A=3D0A
David McBeth on thu 25 feb 10
I use to bisque to Cone 010 consistently. After 10 plus years of firing
that way, last semester we started having serious bloating problems in the
Cone 10 glaze firing with our stoneware. I have slowed down the bisque and
now bisque the stoneware to 07-08 over a longer firing. I am still happy t=
o
bisque the porcelain to around 010I use to bisque to Cone 010 consistently.
After 10 plus years of firing that way, last semester we started having
serious bloating problems in the Cone 10 glaze firing with our stoneware. =
I
have slowed down the bisque and now bisque the stoneware to 07-08 over a
longer firing. I am still happy to bisque the porcelain to around 010
On 2/24/10, Vince Pitelka wrote:
>
> Larry Kruzan wrote:
> "I bisque to 05. I would think that 07 might not achieve a complete burno=
ut
> of the organics and might lead to pinholes in the glazes firing."
>
>
> Larry -
> The "water-smoking period," when volatiles are outgassing
> (chemically-combined water, carbon dioxide, sulfur dioxide, carbon smoke
> from coal and waxes) from the clay during bisque-firing (or single-firing=
),
> lasts from about 800F to 1400F. As long as you do not fire too fast
> through
> this range, and as long as there is ample oxygen in the kiln to encourage
> oxidation of the sulfur and carbon, all volatiles will be gone by 1400F
> (cone 017).
>
> In general terms, it is important to remember that minimal sintering begi=
ns
> at early red heat around 900F, and as the clay is heated beyond that poin=
t,
> a glassy phase progressively strengthens the sintered bonds between
> refractory particles. The lower you bisque, the more the bisqued clay is
> porous and weak. The higher you bisque, the more the bisqued clay is den=
se
> and strong. Obviously this has major implications regarding glazing.
>
> - Vince
>
> Vince Pitelka
> Appalachian Center for Craft
> Tennessee Tech University
> vpitelka@dtccom.net; wpitelka@tntech.edu
> http://iweb.tntech.edu/wpitelka
>
--
David McBeth
Professor of Art
Department of Visual and Theatre Arts
University of Tennessee - Martin
731-881-7416
KATHI LESUEUR on thu 25 feb 10
In this discussion about bisque temperature one thing becomes clear.
There is no one answer. I, also, used to bisque with no problems to
cone 010. But, it seems that over the years clays have gotten
increasingly dirty. As a result my bisque temp is now cone 06 and
done over a longer time. I know people that take it to 05. Over and
over we tell people that they have to test and come up with their own
answers. What happens with my clay isn't necessarily what will happen
with someone else. There is no cheap way to find out what your clay
needs. You must test it.
KATHI LESUEUR
http://www.lesueurclaywork.com
Hank Murrow on thu 25 feb 10
On Feb 25, 2010, at 10:48 AM, KATHI LESUEUR wrote:
> In this discussion about bisque temperature one thing becomes clear.
> There is no one answer. I, also, used to bisque with no problems to
> cone 010. But, it seems that over the years clays have gotten
> increasingly dirty. As a result my bisque temp is now cone 06 and
> done over a longer time.
The problem seems to have arisen because folks use the thin-wall
electric kilns without a soak, or a ramp down to clear the
combustibles. It is possible to bisque at 012 or lower if one allows
an adequate soak. Of course, how one glazes is a related, but not
binding issue.
Cheers, Hank
Lee Love on thu 25 feb 10
On Thu, Feb 25, 2010 at 10:29 AM, David McBeth wrote:
> =3DA0After 10 plus years of firing that way, last semester we started hav=
in=3D
g
> serious bloating problems in the Cone 10 glaze firing with our stoneware.=
=3D
=3DA0I
> have slowed down the bisque and now bisque the stoneware to 07-08 over a
> longer firing. =3DA0I am still happy to bisque the porcelain to around 01=
0
You have to listen to you clay. I have found that a high iron clay
with an iron saturated glaze is more prone to bloating. Unglazed
porcelain/light natural clay is the lest likely to bloat.
--
Lee, a Mashiko potter in Minneapolis
http://mashikopots.blogspot.com/
=3D93Observe the wonders as they occur around you. Don't claim them. Feel
the artistry moving through and be silent.=3D94 --Rumi
Lee Love on thu 25 feb 10
I should add: high iron clay with iron saturated clay in REDUCTION.
The lest likely is unglazed porcelain in oxidation.
On Thu, Feb 25, 2010 at 3:29 PM, Lee Love wrote:
> You have to listen to you clay. =3DA0 =3DA0I have found that a high iron =
clay
> with an iron saturated glaze is more prone to bloating. =3DA0 =3DA0Unglaz=
ed
> porcelain/light natural clay is the lest likely to bloat.
--
Lee, a Mashiko potter in Minneapolis
http://mashikopots.blogspot.com/
=3D93Observe the wonders as they occur around you. Don't claim them. Feel
the artistry moving through and be silent.=3D94 --Rumi
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