Doug Trott on mon 14 dec 09
I tried out my new wood kiln yesterday, in spite of my belief that my
chimney is too short, and sure enough, I could go no higher than 1900 deg
F. Got there in 7 hours, but tried one thing after another for more than 3
hours before giving up. So I guess I'll just have to wait until I can
complete the chimney (somewhat weather-dependent here in west-central
Minnesota).
Meanwhile, is it worth re-firing to cone 10 in my electric kiln? I have
multiple stoneware bodies, all from Continental clay, with varying amounts
of iron. My concern is that I would loose reduction effects, and my shinos
would turn out white, etc.
Any advice? Thanks!
Doug
Lee Love on mon 14 dec 09
Are you firing with a pyrometer ? A typical reason for not
reaching temperature is overstoking.
--
Lee, a Mashiko potter in Minneapolis
http://mashikopots.blogspot.com/
"Ta tIr na n-=3DF3g ar chul an tI=3D97tIr dlainn trina ch=3DE9ile"=3D97tha=
t is, "T=3D
he
land of eternal youth is behind the house, a beautiful land fluent
within itself." -- John O'Donohue
Hank Murrow on mon 14 dec 09
On Dec 14, 2009, at 12:33 PM, Doug Trott wrote:
> I tried out my new wood kiln yesterday, in spite of my belief that my
> chimney is too short, and sure enough, I could go no higher than
> 1900 deg
> F. Got there in 7 hours, but tried one thing after another for
> more than 3
> hours before giving up. So I guess I'll just have to wait until I can
> complete the chimney (somewhat weather-dependent here in west-central
> Minnesota).
>
> Meanwhile, is it worth re-firing to cone 10 in my electric kiln? I
> have
> multiple stoneware bodies, all from Continental clay, with varying
> amounts
> of iron. My concern is that I would loose reduction effects, and
> my shinos
> would turn out white, etc.
Dear Doug;
Chances are that you have reduced the snot out of those shinos trying
to get temperature; so try a cone 10 firing in your electric and see
what happens...... just a few pots at first.
Cheers, Hank
Doug Trott on mon 14 dec 09
I definitely did reduce the heck out of everything during that firing. My
limited understanding is that clay and glaze can "re-oxidize," at least on
the surface, if reduction isn't maintained - so I'm apt to lose all that
good reduction. But perhaps, as you say, I'll just try a couple pieces in
the electric. I can always fire them again in the wood kiln later if they
don't turn out. Thanks!
Doug
On Mon, Dec 14, 2009 at 6:32 PM, Hank Murrow wrote:
>
>
> Dear Doug;
>
> Chances are that you have reduced the snot out of those shinos trying to
> get temperature; so try a cone 10 firing in your electric and see what
> happens...... just a few pots at first.
>
> Cheers, Hank
>
Paul Herman on mon 14 dec 09
Doug,
I've always kind of frowned on refires. My advice, chuck that stuff
out on the shard pile (good and hard) and make some new ones. Fire
them after you add on to the chimney.
Best wishes,
Paul Herman
Great Basin Pottery
Doyle, California US
www.greatbasinpottery.com/
On Dec 14, 2009, at 12:33 PM, Doug Trott wrote:
> I tried out my new wood kiln yesterday, in spite of my belief that my
> chimney is too short, and sure enough, I could go no higher than
> 1900 deg
> F. Got there in 7 hours, but tried one thing after another for more
> than 3
> hours before giving up. So I guess I'll just have to wait until I can
> complete the chimney (somewhat weather-dependent here in west-central
> Minnesota).
>
> Meanwhile, is it worth re-firing to cone 10 in my electric kiln? I
> have
> multiple stoneware bodies, all from Continental clay, with varying
> amounts
> of iron. My concern is that I would loose reduction effects, and my
> shinos
> would turn out white, etc.
>
> Any advice? Thanks!
>
> Doug
Lee Love on tue 15 dec 09
I have never been satisfied with electric kiln woodfire refires. I
frequently refire in a wood kiln, to good result. This "Mars
Teabowl" was fired in the woodkiln three times:
http://picasaweb.google.com/lh/photo/9bqpXOZM7eIqOmra_URPQg?feat=3D3Ddirect=
li=3D
nk
or
http://tinyurl.com/mars-chawan
--
Lee, a Mashiko potter in Minneapolis
http://mashikopots.blogspot.com/
"Ta tIr na n-=3DF3g ar chul an tI=3D97tIr dlainn trina ch=3DE9ile"=3D97tha=
t is, "T=3D
he
land of eternal youth is behind the house, a beautiful land fluent
within itself." -- John O'Donohue
Doug Trott on tue 15 dec 09
Well folks, I opened the wood kiln this afternoon and was a little
surprised. Not as much apparent reduction as I was expecting, and the
shinos were mostly gray-white. But, glazes melted more than expected, and =
I
had a lot of good flashing. Also a good bit of ash. So I grabbed a variet=
y
of pieces, and they're currently in the electric kiln on the fast glaze
cycle. I didn't think to schedule a down-fire, but I did schedule a 30 min
hold at cone 10, just to be sure the ash melts. So perhaps by this time
tomorrow I can share how it all turned out! I'm hoping I'll be able to tel=
l
which pieces are worth pulling out of the wood kiln to fire electric, and
which to keep in. I appreciate all the ideas and info.
Doug
On Tue, Dec 15, 2009 at 11:55 AM, jonathan byler wrote=
:
> ...
>
> I have not done wood firings, but I am pretty sure that most of the
> effect comes from ash getting on the pots, and NOT from super heavy
> reduction. super heavy reduction is a waste of fuel... black smoke
> is wasted fuel and heat it gets you nothing that you can't get with
> mere flames coming from the spyhole. it is supposed to be quite
> normal for a wood kiln to alternate between reducing and oxidizing
> atmospheres the whole way through the firing as you stoke the kiln and
> it burns up a load of wood and then you stoke it again.
>
> go ahead and fire them up in your electric kiln - the pots that didn't
> get to temp. It won't hurt them, and they may come out gorgeous. you
> may have some weird color issues, but it is better than throwing away
> the whole lot of them. do a fast glaze schedule with moderately slow
> cooling, perhaps even fire down between about 2150 and 1800F to keep
> it from cooling too fast.
>
> -jon
>
>
gary navarre on tue 15 dec 09
Hay Folks, Doug,=3D0A=3D0A Since you already reduced the hell out of the bo=
dy i=3D
t would be a good idea to break a piece or two to see how bad the carbon co=
=3D
ring is and look at the vitrification. If vitrification has started and it =
=3D
is dark gray or black I don't know if you could re-cook the carbon out enou=
=3D
gh to alleviate the brittleness caused by carbon interfering with the cohes=
=3D
iveness of the glass melt in the body. If the carbon doesn't go into the su=
=3D
rface too much there is a better chance of the body re-firing into a well b=
=3D
onded glass phase. Then re-fire the shards from the first test, even take p=
=3D
ictures cause I'd like to see what it looks like too, and see if there is a=
=3D
ny positive change. If the carbon stays trapped in the body the pots won't =
=3D
last a long time in use. The decorative effect of over reduction can be int=
=3D
eresting but the soundness of the wear is more important to good work. =3D0=
A=3D
=3D0AGary Navarre=3D0ANavarre Pottery=3D0ANavarre Enterprises=3D0ANorway, M=
ichigan,=3D
USA=3D0Ahttp://www.youtube.com/GindaUP=3D0Ahttp://public.fotki.com/GindaUP=
/=3D0A=3D
=3D0A=3D0A--- On Mon, 12/14/09, Doug Trott wrote:=3D0A=
=3D0A> Fr=3D
om: Doug Trott =3D0A> Subject: Re: [Clayart] Re-fire woo=
d =3D
in electric?=3D0A> To: Clayart@LSV.CERAMICS.ORG=3D0A> Date: Monday, Decembe=
r 14=3D
, 2009, 8:04 PM=3D0A> I definitely did reduce the heck out=3D0A> of everyth=
ing =3D
during that firing.=3DA0 My=3D0A> limited understanding is that clay and gl=
aze =3D
can=3D0A> "re-oxidize," at least on=3D0A> the surface, if reduction isn't m=
aint=3D
ained - so I'm apt to=3D0A> lose all that=3D0A> good reduction.=3DA0 But pe=
rhaps,=3D
as you say, I'll just=3D0A> try a couple pieces in=3D0A> the electric.=3DA=
0 I ca=3D
n always fire them again in the=3D0A> wood kiln later if they=3D0A> don't t=
urn =3D
out.=3DA0 Thanks!=3D0A> =3D0A> Doug=3D0A> =3D0A> On Mon, Dec 14, 2009 at 6:=
32 PM, Han=3D
k Murrow =3D0A> wrote:=3D0A> =3D0A> >=3D0A> >=3D0A> > Dear=
Doug;=3D0A>=3D
>=3D0A> > Chances are that you have reduced the snot out of=3D0A> those sh=
inos=3D
trying to=3D0A> > get temperature; so try a cone 10 firing in your=3D0A> e=
lect=3D
ric and see what=3D0A> > happens...... just a few pots at first.=3D0A> >=3D=
0A> > =3D
Cheers, Hank=3D0A> >=3D0A> =3D0A=3D0A=3D0A
jonathan byler on tue 15 dec 09
doug,
you will always have oxidation conditions on cooling, (unless you fire
down) and this is a good thing. too much reduction in any kiln is a
waste of fuel and time and energy (your own). if you have too much
reduction atmosphere, you end up either not getting to temperature,
taking too long to get to temperature, and worst of all, you can get
bubbling on the surface of the glaze.
I was firing our raku kiln here once, and one of the way I tell if a
glaze is ready is to watch and see if there are bubbles forming on the
surface of the pots. I had this time let the flames from the burner
get reducing and the bubbles never stopped... and the quick cool down
didn't help heal those over either. a period of having an oxidizing
atmosphere towards the end of the firing is going to change your
glazes as far as I can tell... the majority of reduction affects are
supposed to happen well earlier in the firing at around cone 012 - 08
or so before the glazes fully melt.
I have not done wood firings, but I am pretty sure that most of the
effect comes from ash getting on the pots, and NOT from super heavy
reduction. super heavy reduction is a waste of fuel... black smoke
is wasted fuel and heat it gets you nothing that you can't get with
mere flames coming from the spyhole. it is supposed to be quite
normal for a wood kiln to alternate between reducing and oxidizing
atmospheres the whole way through the firing as you stoke the kiln and
it burns up a load of wood and then you stoke it again.
go ahead and fire them up in your electric kiln - the pots that didn't
get to temp. It won't hurt them, and they may come out gorgeous. you
may have some weird color issues, but it is better than throwing away
the whole lot of them. do a fast glaze schedule with moderately slow
cooling, perhaps even fire down between about 2150 and 1800F to keep
it from cooling too fast.
-jon
On Dec 14, 2009, at 6:57 PM, Paul Herman wrote:
> Doug,
>
> I've always kind of frowned on refires. My advice, chuck that stuff
> out on the shard pile (good and hard) and make some new ones. Fire
> them after you add on to the chimney.
>
> Best wishes,
>
> Paul Herman
>
> Great Basin Pottery
> Doyle, California US
> www.greatbasinpottery.com/
>
>
>
>
> On Dec 14, 2009, at 12:33 PM, Doug Trott wrote:
>
>> I tried out my new wood kiln yesterday, in spite of my belief that my
>> chimney is too short, and sure enough, I could go no higher than
>> 1900 deg
>> F. Got there in 7 hours, but tried one thing after another for more
>> than 3
>> hours before giving up. So I guess I'll just have to wait until I
>> can
>> complete the chimney (somewhat weather-dependent here in west-central
>> Minnesota).
>>
>> Meanwhile, is it worth re-firing to cone 10 in my electric kiln? I
>> have
>> multiple stoneware bodies, all from Continental clay, with varying
>> amounts
>> of iron. My concern is that I would loose reduction effects, and my
>> shinos
>> would turn out white, etc.
>>
>> Any advice? Thanks!
>>
>> Doug
Doug Trott on tue 15 dec 09
Thanks Sam - that's encouraging! I don't have a good rutile blue yet - jus=
t
have shino (glaze and flashing slip) and Ranch Butter (from John Britt's
book). This kiln should throw a lot of ash (and it looks like it did) so I
have a lot of unglazed pieces too.
On Mon, Dec 14, 2009 at 10:47 PM, Maid O'Mud wrote:
> Hi Doug
>
> I've had the same problem and refired in my electric. Most
> pieces come out great. Had big blistering problems with my
> rutile blue glaze, tho.
>
>
> Sam Cuttell
> Maid O'Mud Pottery
> RR 1
> Melbourne, Ontario
> N0L 1T0
> CANADA
>
> "First, the clay told me what to do.
> Then, I told the clay what to do.
> Now, we co-operate."
> sam 1994
>
> http://www.ody.ca/~scuttell/
> scuttell@ody.ca
>
>
Chaeli Sullivan on tue 15 dec 09
Hey Doug
Often try and fire stuff in my gas kiln for reduction.=3DA0 Often, it doesn=
't=3D
reach the desired temps.=3DA0 The first time this happened, took a chance =
an=3D
d refired them in the electric kiln.=3DA0 They turned out beautifully.=3DA0=
=3D20
Now, it is often "standard procedure" for me:=3DA0 if they don't fire "righ=
t"=3D
in the gas kiln, to refire them in the electric for the reduction effects =
=3D
have already been achieved in the first firing.
Hope this helps
Chae
On Dec 14, 2009, at 12:33 PM, Doug Trott wrote:
> I tried out my new wood kiln yesterday, in spite of my belief that my
> chimney is too short, and sure enough, I could go no higher than
> 1900 deg
> F.=3DA0 Got there in 7 hours, but tried one thing after another for more
> than 3
> hours before giving up.=3DA0 So I guess I'll just have to wait until I ca=
n
> complete the chimney (somewhat weather-dependent here in west-central
> Minnesota).
>
> Meanwhile, is it worth re-firing to cone 10 in my electric kiln?=3DA0 I
> have
> multiple stoneware bodies, all from Continental clay, with varying
> amounts
> of iron.=3DA0 My concern is that I would loose reduction effects, and my
> shinos
> would turn out white, etc.
>
> Any advice?=3DA0 Thanks!
>
> Doug
=3D0A=3D0A=3D0A
Lee Love on tue 15 dec 09
On Mon, Dec 14, 2009 at 8:04 PM, Doug Trott wrote:
> I definitely did reduce the heck out of everything during that firing. =
=3D
=3DA0My
> limited understanding is that clay and glaze can "re-oxidize," at least o=
=3D
n
> the surface, if reduction isn't maintained - so I'm apt to lose all that
> good reduction. =3DA0But perhaps, as you say, I'll just try a couple piec=
es=3D
in
> the electric. =3DA0I can always fire them again in the wood kiln later if=
t=3D
hey
> don't turn out. =3DA0Thanks!
Doug,
Did you use a pyrometer? A digital one is important when you
are first learning to stoke. When we are new to wood firing, we
usually overstoke, and a pyrometer can help you avoid this.
Traditional wood kilns never fired in constant reduction.
The noborigama fire primarily in oxidation. The kilns only spent a
little time in what we think of as reduction. That is one reason they
look different compared to gas or oil fired pots. Much of the
richness comes from the cycling between reduction/neutral/oxidation.
Usually, temperature climb does not come in the
reduction of the firing. When you first stoke, the temperature always
drops.
Heat comes from oxygen plus fuel. If you put too
much fuel in, it is like stopping off the air to the engine.
Woodfirers who don't glaze all the pots in the firing often
have pots they have to refire. Save those pots for the next wood
firing, and put some in the kiln with your new work.
--
Lee, a Mashiko potter in Minneapolis
http://mashikopots.blogspot.com/
"Ta tIr na n-=3DF3g ar chul an tI=3D97tIr dlainn trina ch=3DE9ile"=3D97tha=
t is, "T=3D
he
land of eternal youth is behind the house, a beautiful land fluent
within itself." -- John O'Donohue
Doug Trott on tue 15 dec 09
Lee - thanks for your thoughts! Yes, I do use a pyrometer, though I went
with analog - I am distrustful of the granularity a digital pyrometer
provides! I had my first pause around 600 - 700 degrees, and wasn't sure i=
=3D
f
it was because I didn't have enough draft (my damper was half closed) or
because the heat was going up the chimney. I tried different damper
settings and determined it was the former, and then shot up the rest of the
way to 1900. I know what you mean about over-stoking - I remember the NCC
kiln is very sensitive to that, and so I varied my stoking, generally
decrease the amount while increasing the frequency. I did longer pauses
occasionally, to let the grate clear more, but found I lost temperature. I
also purposefully tried overstoking, both leaving the door closed and open
(for secondary air), and it did cause me to drop 100 - 150 degrees.
I was also raking out coals, which I remember is usually needed for the NCC
kiln to get the last 200 degrees. My temporary grate bars deformed earlier
than I though they might, so I know that's my secondary problem - not havin=
=3D
g
enough air between the coals and grate.
I do agree with your general observations! I think people tend to focus to=
=3D
o
much on fuel, and not enough on draft.
Thanks!
Doug
On Tue, Dec 15, 2009 at 9:15 AM, Lee Love wrote:
>
> Doug,
>
> Did you use a pyrometer? A digital one is important when you
> are first learning to stoke. When we are new to wood firing, we
> usually overstoke, and a pyrometer can help you avoid this.
> ...
> Woodfirers who don't glaze all the pots in the firing often
> have pots they have to refire. Save those pots for the next wood
> firing, and put some in the kiln with your new work.
>
> --
> Lee, a Mashiko potter in Minneapolis
> http://mashikopots.blogspot.com/
>
> "Ta tIr na n-=3DF3g ar chul an tI=3D97tIr dlainn trina ch=3DE9ile"=3D97t=
hat is, =3D
"The
> land of eternal youth is behind the house, a beautiful land fluent
> within itself." -- John O'Donohue
>
Ric Swenson on tue 15 dec 09
my advice....re-fire...what do you have to lose? Some may work...maybe not=
reproducibile... but why waste?
could br interesting result... keep trying!
ric
"...then fiery expedition be my wing, ..."
-Wm. Shakespeare, RICHARD III, Act IV Scene III
Richard H. ("Ric") Swenson, Teacher,
Office of International Cooperation and Exchange of Jingdezhen Ceramic Inst=
itute,
TaoYang Road, Eastern Suburb, Jingdezhen City.
JiangXi Province, P.R. of China.
Postal code 333001.
Mobile/cellular phone : 86 13767818872
< RicSwenson0823@hotmail.com>
http://www.jci.jx.cn
> Date: Mon, 14 Dec 2009 16:57:55 -0800
> From: potterpaul@FRONTIERNET.NET
> Subject: Re: Re-fire wood in electric?
> To: Clayart@LSV.CERAMICS.ORG
>
> Doug,
>
> I've always kind of frowned on refires. My advice, chuck that stuff
> out on the shard pile (good and hard) and make some new ones. Fire
> them after you add on to the chimney.
>
> Best wishes,
>
> Paul Herman
>
> Great Basin Pottery
> Doyle, California US
> www.greatbasinpottery.com/
>
>
>
>
> On Dec 14, 2009, at 12:33 PM, Doug Trott wrote:
>
> > I tried out my new wood kiln yesterday, in spite of my belief that my
> > chimney is too short, and sure enough, I could go no higher than
> > 1900 deg
> > F. Got there in 7 hours, but tried one thing after another for more
> > than 3
> > hours before giving up. So I guess I'll just have to wait until I can
> > complete the chimney (somewhat weather-dependent here in west-central
> > Minnesota).
> >
> > Meanwhile, is it worth re-firing to cone 10 in my electric kiln? I
> > have
> > multiple stoneware bodies, all from Continental clay, with varying
> > amounts
> > of iron. My concern is that I would loose reduction effects, and my
> > shinos
> > would turn out white, etc.
> >
> > Any advice? Thanks!
> >
> > Doug
_________________________________________________________________
Windows Live: Friends get your Flickr, Yelp, and Digg updates when they e-m=
ail you.
http://www.microsoft.com/middleeast/windows/windowslive/see-it-in-action/so=
cial-network-basics.aspx?ocid=3DPID23461::T:WLMTAGL:ON:WL:en-xm:SI_SB_3:092=
010
David on wed 16 dec 09
I have never really had success in re-firing. Yes the glaze melts but even =
=3D
if I keep on the low side of the melting temperature melting range a lot is=
=3D
lost. I agree with the person that said to send it all to the scrap pile a=
=3D
lthough I know how hard that can be to do.
When I read your original post I was surprised at how quickly you decided t=
=3D
he beast wouldn't reach temperature. In my noborigama I sometimes "stall" f=
=3D
or 10 hours or so if I make a couple of mistakes in the stoking.
A note not directly related to this post.
=3DA0Someone seems to be=3DA0 under the impression noborigama fire primaril=
y in=3D
oxidation I suggest they go to Kyoto and look at the nobori there. The Kyo=
=3D
to type nobori are dragons that probably can't be fired in oxidation.=3DA0 =
Ky=3D
ushu type are primarily designed for oxidation but can be fired in heavy re=
=3D
duction. My nobori is a Kyushu type.=3D20
Dave
Togei's blog
=3D20
Lee Love on wed 16 dec 09
On Wed, Dec 16, 2009 at 1:57 PM, David wrote:
> I have never really had success in re-firing. Yes the glaze melts but eve=
=3D
n
> if I keep on the low side of the melting temperature melting range a lot =
=3D
is
>lost.
If you have to glaze all your wood fired work, you probably aren't
going to have good luck refiring. But if your work is unglaze, and
depend on the kiln for fly ash and flashing, it works pretty well.
You can see some here (these were all fired 3 times):
http://picasaweb.google.com/togeika/55TeaBowls#5332937287724402930
http://picasaweb.google.com/togeika/55TeaBowls#5332937411953040658
These were fired twice, once in the ware chamber and once in the ash pit:
http://picasaweb.google.com/togeika/55TeaBowls#5332937653217334434
http://picasaweb.google.com/togeika/55TeaBowls#5332937642159274338
The climbing kilnns we are most familiar with in the west did
not fire in the kind of reduction we get in the gas or oil kiln (we
are hardly influenced by the Kyoto kilns.)
Often, pots had to be fired in saggers to get proper reduction,
so they were protected from the oxidizing cycle. The copper reds,
for example, were fired in saggers. Most of the Mino kiln was fired
in oxidation, with spots of reduction. In this situation, our
western shinos will not go red. You have to have higher alumina
content to get the red color.
--
Lee, a Mashiko potter in Minneapolis
http://mashikopots.blogspot.com/
"Ta tIr na n-=3DF3g ar chul an tI=3D97tIr dlainn trina ch=3DE9ile"=3D97tha=
t is, "T=3D
he
land of eternal youth is behind the house, a beautiful land fluent
within itself." -- John O'Donohue
Doug Trott on thu 17 dec 09
I refired a few pieces in the electric kiln, and if my digital camera worke=
=3D
d
I would post some photos somewhere. The shino did not turn out well - I ha=
=3D
d
a some good ash, but they were otherwise grayish-white. They looked ok
where I had just used the shino as a liner glaze. The unglazed pieces, and
those with just flashing slips, turned out pretty well. A little lighter
than I'm guessing they would have been if they had reached temperature in
the wood kiln, but they flashed well and also had good ash.
It was asked why I gave up so "soon." It's a fast-fire design, and ought t=
=3D
o
climb fairly rapidly, which it had done. I was almost 4 hours at 1900, and
it didn't budge, except to go down when I fiddled with the damper or
over-stoked. It got to 1900 in 7 hours, and would have done it quicker if =
=3D
I
had not been experimenting with damper positions. If I had been climbing
slowly I would have proceeded, but I couldn't see wasting wood. I couldn't
think of any reason why the kiln would start climbing again.
Thanks all!
Doug
On Wed, Dec 16, 2009 at 3:57 PM, Lee Love wrote:
> On Wed, Dec 16, 2009 at 1:57 PM, David wrote:
>
> >... But if your work is unglaze, and
> depend on the kiln for fly ash and flashing, it works pretty well.
> ...
>
> --
> Lee, a Mashiko potter in Minneapolis
> http://mashikopots.blogspot.com/
>
> "Ta tIr na n-=3DF3g ar chul an tI=3D97tIr dlainn trina ch=3DE9ile"=3D97t=
hat is, =3D
"The
> land of eternal youth is behind the house, a beautiful land fluent
> within itself." -- John O'Donohue
>
Paul Haigh on thu 17 dec 09
Good flashing, melted ash, bland shinos- sounds like you got hot enough but=
reduced too late or not enough. I don't think the electric will help you a=
t all as it's oxidation.
I refire a lot of stuff in wood fire- it seems less able to flash as well t=
he second time around, but it definitely can add some life. Electric or gas=
refire is nice for softening crusty ash, but that is about the limit of my=
knowledge on these firing methods (never fired either myself).
-pH
http://wileyhill.com
>Date: Tue, 15 Dec 2009 23:14:03 -0600
>From: Doug Trott
>Subject: Re: Re-fire wood in electric?
>Well folks, I opened the wood kiln this afternoon and was a little
surprised. Not as much apparent reduction as I was expecting, and the
shinos were mostly gray-white. But, glazes melted more than expected, and I
had a lot of good flashing. Also a good bit of ash. So I grabbed a variety
of pieces, and they're currently in the electric kiln on the fast glaze
cycle. I didn't think to schedule a down-fire, but I did schedule a 30 min
hold at cone 10, just to be sure the ash melts. So perhaps by this time
tomorrow I can share how it all turned out! I'm hoping I'll be able to tell
which pieces are worth pulling out of the wood kiln to fire electric, and
which to keep in. I appreciate all the ideas and info.
Lee Love on thu 17 dec 09
On Thu, Dec 17, 2009 at 8:43 AM, Doug Trott wrote:
> I refired a few pieces in the electric kiln, and if my digital camera wor=
=3D
ked
> I would post some photos somewhere. =3DA0The shino did not turn out well =
- =3D
I
Part of my last slide lecture included shino an oribe pots. I saw a
spectacular show at the Idemitsu in Tokyo. Mostly, in the West, we
are only inspired by the tea bowls, which sometimes have red color.
But that only occured in special parts of the kiln and the tea bowls
were put there. The large majority of the pots turned out whitish to
grey. That is where e-shino, or "picture shino" came from: the
potters trying to make the oxidized grey pots interesting by
decorating them with gosu and iron slip. That, in turn, help create
oribe, in the new climbing kilns that were so efficent, they had not
reduction areas.
> It was asked why I gave up so "soon." =3DA0It's a fast-fire design, and o=
ug=3D
ht to
> climb fairly rapidly, which it had done. =3DA0I was almost 4 hours at 190=
0,=3D
and
> it didn't budge, except to go down when I fiddled with the damper or
> over-stoked.
Wood kilns often stall at this temp. About 1100*C.
Folks that are unexperienced, want to stoke heavier, when actually,
the changes in the kiln require lighter stoking to get any heat rise.
In my kiln in Mashiko, I stoked about 2kgs of wood until
1900*F. When the kiln stalled, I started stoking 1.5kgs of wood per
stoke, and the kiln started to rise in temperature again. At the
end, I could stoke heavier again. It took about 400kgs of wood to
glaze fire. I could reach 2300*F in 5 hours, but I tried to slow
down and fire between 19 and 28 hours.
You might not need a taller chimney. Just a proper stoking cycle.
--
Lee, a Mashiko potter in Minneapolis
http://mashikopots.blogspot.com/
"Ta tIr na n-=3DF3g ar chul an tI=3D97tIr dlainn trina ch=3DE9ile"=3D97tha=
t is, "T=3D
he
land of eternal youth is behind the house, a beautiful land fluent
within itself." -- John O'Donohue
Doug Trott on thu 17 dec 09
Lee -
My wood is of fireplace length, but split smaller than what's usually done
for a fireplace (half as thick). I started stoking five pieces at a time,
then later went to three. I set aside a bunch of pieces that were on the
small side, with no bark, for final stoking. I went into that pile at the
end of my attempts, and went to one piece at a time, but of course with
shorter pauses in between. Did that for at least a half hour, with no
change. When I tried things that caused me to lose temperature, I could
regain it quickly - but just go no further.
Part of the problem was my grate bending from the heat, and decreasing
primary air flow. I am picking up stainless steel bars tomorrow, so that
part should be solved. My chimney is only about five feet taller than the
kiln - ridiculously short, so I'mpretty sure that's the major part of the
puzzle. But I will pay close attention to stoking next go-around.
Thanks!
Doug
On Thu, Dec 17, 2009 at 11:19 AM, Lee Love wrote:
> ...
>
> You might not need a taller chimney. Just a proper stoking cycle.
>
>
> --
> Lee, a Mashiko potter in Minneapolis
> http://mashikopots.blogspot.com/
>
> "Ta tIr na n-=3DF3g ar chul an tI=3D97tIr dlainn trina ch=3DE9ile"=3D97t=
hat is, =3D
"The
> land of eternal youth is behind the house, a beautiful land fluent
> within itself." -- John O'Donohue
>
gsomdahl on thu 17 dec 09
I've seen this stall in three different kilns. The stall would occur
between 1900F and 2100F. The atmosphere temperature would not change,
except for the small cycle do to stoking, but everything in the kiln
would show a gradual color change against a color chart. When the colors
got to the range that corresponded to the pyrometer the measured
temperature would start to rise again. This has been so consistent, that
a couple of people that I've fired with, just schedule in a soak with
lighter stoking at their stall point until the furniture and hard bricks
can catch up.
Gene Somdahl
Lee Love wrote:
> Wood kilns often stall at this temp. About 1100*C.
> Folks that are unexperienced, want to stoke heavier, when actually,
> the changes in the kiln require lighter stoking to get any heat rise.
>
--
This is a post only account. Send replies to "gene" at my ".com" domain nam=
ed "somdahl".
gary navarre on thu 17 dec 09
Hay Folks,
Now that I've thought about it I had some interesting wood re-fires in sal=
t, especially with rutile in those ash slips I like. Some Dragon Pots with=
no glaze took more than a few years for me to appreciate, other folks seem=
ed to like them, so I decided to keep them for my retirement fund. You migh=
t want to set some aside until a salt kiln comes by, you might have a decen=
t change in some pieces. However, most of the time I've also just set them =
back in the wood kiln for the next firing and they turned out different. I =
have one pot from the '70's that has been in a bunch of firings and is not =
done yet. I've also wondered what would happen if I re-fired one of those s=
alted pots in this kiln... like if any volatiles from the salt would still =
be around, probably not eh.
The other solution would be modify your kiln for better combustion like ad=
ding a few feet of stack to increase the draft but like you said the weathe=
r makes working outside uncomfortable. There's folks here who have made tho=
se fast fires work but after the hassles we had at Western Michigan I chose=
to continue with the Hobagama. The main problem we had was over stoking an=
d clogging the firebox with coals. The metal culvert stack wasn't much help=
either, nothing holds a draft like a double walled 11'+ tapered hard brick=
stack!
Too bad your camera is not working, what is wrong with it? Maybe you could=
do some drawings in Paint or something with measurements and we could do s=
ome math.
Gary Navarre
Navarre Pottery
Navarre Enterprises
Norway, Michigan, USA
http://www.youtube.com/GindaUP
http://public.fotki.com/GindaUP/
--- On Thu, 12/17/09, Paul Haigh wrote:
> From: Paul Haigh
> Subject: Re: [Clayart] Re-fire wood in electric?
> To: Clayart@LSV.CERAMICS.ORG
> Date: Thursday, December 17, 2009, 8:53 AM
> Good flashing, melted ash, bland
> shinos- sounds like you got hot enough but reduced too late
> or not enough. I don't think the electric will help you at
> all as it's oxidation.
>
> I refire a lot of stuff in wood fire- it seems less able to
> flash as well the second time around, but it definitely can
> add some life. Electric or gas refire is nice for softening
> crusty ash, but that is about the limit of my knowledge on
> these firing methods (never fired either myself).
>
> -pH
> http://wileyhill.com
>
> >Date: Tue, 15 Dec 2009 23:14:03 -0600
> >From: Doug Trott
> >Subject: Re: Re-fire wood in electric?
>
> >Well folks, I opened the wood kiln this afternoon and
> was a little
> surprised. Not as much apparent reduction as I was
> expecting, and the
> shinos were mostly gray-white. But, glazes melted more than
> expected, and I
> had a lot of good flashing. Also a good bit of ash. So I
> grabbed a variety
> of pieces, and they're currently in the electric kiln on
> the fast glaze
> cycle. I didn't think to schedule a down-fire, but I did
> schedule a 30 min
> hold at cone 10, just to be sure the ash melts. So perhaps
> by this time
> tomorrow I can share how it all turned out! I'm hoping I'll
> be able to tell
> which pieces are worth pulling out of the wood kiln to fire
> electric, and
> which to keep in. I appreciate all the ideas and info.
>
Craig Edwards on sat 19 dec 09
Hello Doug and All: I hope that this makes it to the list, the last few
haven't.
I'm really glad to hear that you got your kiln burning-- lining up the wood
and the hundred other things to get a woody going is quite the chore.
Congratulations!! The first firings are always a challenge.
Sounds like you fired in the cold. When the cold snap hit here, I hung up
my spurs for the season, time to cut wood and fire in the spring. My frien=
=3D
d
Mike Hill (Vermillion, SD) just did a winter firing, when you have wind
chills at -10F etc that's tough stuff.
Here is how I solved the short chimney issue. During a firing there was a
strong wind from the Northwest and it was causing back pressure and a
stall. It became apparent that the chimney was to short on the kiln. The
solution that seemed to work for me, was to make it taller. I climbed up on
the roof in between stokes and added bricks to the chimney. I put an extra =
=3D
4
feet on the chimney and then it started to work well. Although it seemed it
a lot of work at the time, there was the realization that it had to be done
sooner or later. I opted to increase the chimney right then, that way I
would come out with pots that reached temp and a taller chimney. Adding
chimney or firing extra hours/days seem to be just part of the rodeo.
--=3D20
Good Fires Make Good Pots
~Craig
New London MN
http://woodfiredpottery.blogspot.com/
On Thu, Dec 17, 2009 at 1:43 PM, Doug Trott wrote:
> Lee -
>
> My wood is of fireplace length, but split smaller than what's usually don=
=3D
e
> for a fireplace (half as thick). I started stoking five pieces at a time=
=3D
,
> then later went to three. I set aside a bunch of pieces that were on the
> small side, with no bark, for final stoking. I went into that pile at th=
=3D
e
> end of my attempts, and went to one piece at a time, but of course with
> shorter pauses in between. Did that for at least a half hour, with no
> change. When I tried things that caused me to lose temperature, I could
> regain it quickly - but just go no further.
>
> Part of the problem was my grate bending from the heat, and decreasing
> primary air flow. I am picking up stainless steel bars tomorrow, so that
> part should be solved. My chimney is only about five feet taller than th=
=3D
e
> kiln - ridiculously short, so I'mpretty sure that's the major part of the
> puzzle. But I will pay close attention to stoking next go-around.
>
> Thanks!
>
> Doug
>
> On Thu, Dec 17, 2009 at 11:19 AM, Lee Love wrote=
=3D
:
>
> > ...
> >
> > You might not need a taller chimney. Just a proper stoking cycl=
=3D
e.
> >
> >
> > --
> > Lee, a Mashiko potter in Minneapolis
> > http://mashikopots.blogspot.com/
> >
> > "Ta tIr na n-=3DF3g ar chul an tI=3D97tIr dlainn trina ch=3DE9ile"=3D9=
7that is=3D
, "The
> > land of eternal youth is behind the house, a beautiful land fluent
> > within itself." -- John O'Donohue
> >
>
Doug Trott on sat 19 dec 09
Gene - I've been part of three firings of the NCC kiln, and every time
people wonder about the grate, what it's made out of, etc. It's very nice
the way the bars stick out of the front - good place to rest a mug (at leas=
t
for a while!). I'm surprised to hear they're hollow.
Interesting idea about u-beams. In my case, my grate runs sideways, becaus=
e
my firebox doesn't run crossways but goes into the kiln three feet (it's tw=
o
feet wide by two feet deep). My theory is that a more narrow firebox will
allow more even reduction; we'll see.
I did pick up low-carbon bars yesterday. Interesting, I thought stainless
steel was the best, but I was shown that the low carbon had a higher meltin=
g
point than stainless (something like 2700 vs 2550). Also a little cheaper.
But that will definitely help the air flow - I might not even need to rake
out coals. I designed the firebox with slots on the sides for bars - I
figured I'd need to replace them at some point, plus I access the chamber
via the firebox, and it's easier with the bars removed.
Doug
On Fri, Dec 18, 2009 at 7:49 AM, gsomdahl wrote:
> I was on the crew that built the NCC wood kiln. The grating bars on that
> kiln were hollow square iron tubes. I suggested that they should be U-bea=
ms
> with the open side down. Since they penetrated the walls of the firebox t=
hey
> would act as a secondary air source that would not get blocked by ash bui=
ld
> up. I don't think NCC ever used my idea but it's something you could try.
> Gene Somdahl
>
> ...
>
>
>
> --
> This is a post only account. Send replies to "gene" at my ".com" domain n=
amed "somdahl".
>
>
gary navarre on sat 19 dec 09
Hay Folks,=3D0A=3D0A As I recall now I did just about the same thing on tha=
t la=3D
st kiln and lagged it in as I went. I think I also added brick while the ki=
=3D
ln was just starting to fire when it was cold out and the stack was kept wa=
=3D
rm enough for the lag to dry and then bisque itself in place. When you clam=
=3D
up at the end and cover the chimney the heat will seep into wall and fire =
=3D
it solid enough to last. This time around I lagged in at least the first 11=
=3D
' and loose stacked a bit of red brick and a checker pattern of air holes w=
=3D
ith plugs out of soaps to about 12=3DBD'. I'm thinking the holes will add a=
ir=3D
and burn off any heavy smoke during blast stoking. Also if it rains I can =
=3D
put on a chimney cap and still have enough openings to maintain draft. If I=
=3D
need more stack I guess I'll need a taller scaffold or another ladder but =
=3D
I see pretty good draft in my tests so I think I'm good to go... if I can e=
=3D
ver get the wench full. I think I got the front floor setting figured out s=
=3D
o back to
more clay punching. Stay in there eh!=3D0A=3D0AGary Navarre=3D0ANavarre Po=
ttery=3D
=3D0ANavarre Enterprises=3D0ANorway, Michigan, USA=3D0Ahttp://www.youtube.c=
om/Gin=3D
daUP=3D0Ahttp://public.fotki.com/GindaUP/=3D0A=3D0A=3D0A--- On Sat, 12/19/0=
9, Craig=3D
Edwards wrote:=3D0A=3D0A> From: Craig Edwards oodf=3D
iredpots@GMAIL.COM>=3D0A> Subject: Re: [Clayart] Re-fire wood in electric?=
=3D0A=3D
> To: Clayart@LSV.CERAMICS.ORG=3D0A> Date: Saturday, December 19, 2009, 12:=
53=3D
PM=3D0A> Hello Doug and All:=3D0A=3D0A=3DA0 It became apparent that the ch=
imney wa=3D
s to=3D0A> short on the kiln. The=3D0A> solution that seemed to work for me=
, wa=3D
s to make it taller.=3D0A> I climbed up on=3D0A> the roof in between stokes=
and=3D
added bricks to the chimney.=3D0A> I put an extra 4=3D0A> feet on the chim=
ney =3D
and then it started to work well.=3D0A> Although it seemed it=3D0A> a lot o=
f wo=3D
rk at the time, there was the realization that=3D0A> it had to be done=3D0A=
> so=3D
oner or later. I opted to increase the chimney right=3D0A> then, that way I=
=3D
=3D0A> would come out with pots that reached temp and a taller=3D0A> chimne=
y. A=3D
dding=3D0A> chimney or firing=3DA0 extra hours/days seem to be just=3D0A> p=
art of=3D
the rodeo.=3D0A> =3D0A> =3D0A> =3D0A> =3D0A> -- =3D0A> Good Fires Make Goo=
d Pots=3D0A> ~=3D
Craig=3D0A> New London MN=3D0A> http://woodfiredpottery.blogspot.com/=3D0A=
=3D0A=3D0A =3D
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