Luke Nealey on tue 4 jan 11
Marion(NC):
I have deleted original message that preceded this so started this new
string.
I have been struggling with your comment about pyrolysis products not likin=
g
to burn above 1100 or so (for at least 500 miles of drive to and from
beach). It doesn't seem to me that there is any thermodynamic reason why
these things wouldn't burn(react) readily throughout the kiln firing temp
range. Are there competing reactions at that point, is there a phase
transition somewhere that is using the energy rather than it rasing the
temperature in the kiln?
My epiphanic moment in figuring out firing and rebuilding my kiln is that
with modern insulative materials firing fuel kilns to whatever cone is a
mass transfer, not a heat transfer problem. I think Nils talking about
chimney stall or some other mass transfer explanation is much more likely
than the wood not burning as readily. But I am wrong on a pretty much dail=
y
basis.
Regards,
Luke Nealey, Rankin County MS
Lee on tue 4 jan 11
On Tue, Jan 4, 2011 at 7:08 AM, Luke Nealey wrote:
> beach). =3DA0It doesn't seem to me that there is any thermodynamic reason=
w=3D
hy
> these things wouldn't burn(react) readily throughout the kiln firing temp
> range.
Luke, when folks transition from gas firing to wood firing, they seem
to think more fuel means more heat. When actually, you need fuel
plus oxygen to get heat. Because it isn't recognized, folks tend to
overstoke when they stall and choke off the needed oxygen, when they
should be backing off on the stoking a little to have a better
oxygen/fuel ratio.
At about 1100*C, I have found stoking a little less smaller wood
helps keep the temperature rising. Once past this point, you can go
back to the way you were stoking before.
--
=3DA0Lee Love in Minneapolis
http://mingeisota.blogspot.com/
=3DA0"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
Neon-Cat on tue 4 jan 11
Oh Luke, 1100 miles struggling with a burning question? I wish you could
have called or emailed. Sometimes when I have one of these nagging question=
=3D
s
but no time or resources for an immediate answer I=3D92ll just assure mysel=
f
that it is something to explore later. The mind is most easily satisfied
given a time-table and distractions, like a good CD. Anyway, I had to go
back and look, here=3D92s what I wrote before:
=3D93After you=3D92re underway with firing, flaming combustion will occur e=
ntir=3D
ely
in the gas phase outside the wood itself. In general, self-sustaining
diffusion flames from wood typically burn around 1100=3DB0 C or somewhat hi=
gh=3D
er.
Before this, given the processes of thermal wood degradation (pyrolysis),
the various gases evolved may lack the oxygen necessary for combustion unti=
=3D
l
they have gone far enough through the kiln to mix with air in proportions
between the lower and upper limits of their respective flammabilities.=3D94
It might be easy for you to think in terms of a two-step process. First we
get the wood going. Whether you all are stoking big wood-fired kilns or som=
=3D
e
of us are burning lesser amounts of wood in pits or barrels, up to about 93=
=3D
2
F (500 C) the earliest common products (there may be others) from the
pyrolysis of wood are (in no special order):
Carbon dioxide, CO2
Carbon monoxide, CO
Acetic acid, CH3COOH
Formic acid, HCOOH
Methanol, CH30H
Water, H20
Glyoxal, C2H2O2
Formaldehyde, CH2O
Hydrogen, H2
Oils & tars
Charcoal or char
Next, with increased heat we get smaller molecules of gases that burn with =
=3D
a
lot of release of energy. These burning gases ignite other burning gases an=
=3D
d
it is not necessary to have the embers from the wood or an external pilot
light them =3D96 they ignite each other. It is then that these gases have b=
ec=3D
ome
capable of creating self-sustaining =3D91diffusion flames=3D92 (the technic=
al n=3D
ame).
So you want to think in terms of babying these gases once you begin to get
them =3D96 giving them some containment, the right amount of air so they ar=
e
happy to burst into flame, and giving them the time needed to be of use. Yo=
=3D
u
don=3D92t want them to whisk away out of the kiln before they get burned, y=
ou
don=3D92t want to starve them of air, you do want some mixing of gases and =
ai=3D
r,
etc. In my pit fire work done roughly between 1000 =3D96 1350 F (538-732 C)=
I
cannot get self-sustaining diffusion flames although I can, in my enclosure=
=3D
,
burn tars and oils that are ignited by wood embers and the burning of other
tars and oils. You, however, can get these glorious self-diffusion flames
around 2012 F (1100 C) and they will burn remote from the wood you are
stoking. At this point you could think in terms of all the techniques and
tricks of the trade used to fire natural gas or propane kilns, as far as
getting the most out of these gases.
Mel just gave us a nice post on wood firing and Lee and others have given
good tips and hints, too. I have read in a number of places that the best
wood to burn is 3/4=3D94 in diameter. Mel has his 1=3D94 wood and others th=
eir =3D
small
diameter =3D93party wood=3D94 =3D96 they release gases more quickly and eas=
ily.
Burning seasoned wood is always best =3D96 even then it may contain 15-20%
water. Unseasoned (green) wood or wet wood may have a water content of 25 t=
=3D
o
50% and it takes more time and energy to first evaporate this excess water
before it becomes useful. Even totally dry, wood always evolves water, just
as the burning of natural gas and propane evolves water =3D96 through combu=
st=3D
ion
reactions. Instead of 20% or so water as a product from burning dried wood,
you=3D92ll maybe get 25-28% or more water yield when burning green or damp =
wo=3D
od.
The additional water can, for us pit firing types, give a nice swirly
black-effects during carbonization of our work =3D96 but I am not intereste=
d =3D
in
sustaining a kiln to actually fire my work, I just want smoke and flame
effects.
Wood and plant fuels contain cellulose as one of their many constituents.
Cellulose evolve water in the first stage of thermal decomposition before
other changes occur:
(C6H10O5)n ---heat---> 6nC + 5nH2O
cellulose ----heat---> carbon + water
Other wood constituents also evolve water. So you will always have evolutio=
=3D
n
of water when wood-firing, even using dry wood.
I hope this has helped answer your questions. If not, ask and maybe more
folks will chime in =3D96 I always like to read about wood firing be it in =
bi=3D
g
kilns or in small pits, barrels, or bonfires.
Happy firing!
Marian
Neon-Cat Ceramics
www.neon-cat.com
Luke Nealey on tue 4 jan 11
As I stated before NC, I have a problem with your saying that at a certain
temperature things do not burn as well or are harder to burn. I think what
you were trying to say(that's presumptive I know) is that above 1100C its
easy to be burning your fuel in the chimney rather than the chamber. I
agree, but that is a mass transfer issue and not a combustion issue. The
"not burn as well" was what was bugging me. Liked your post on hematite.
Regards,
Luke Nealey
Rankin Co. MS
On Tue, Jan 4, 2011 at 2:10 PM, Neon-Cat wrote:
> Next, with increased heat we get smaller molecules of gases that burn wit=
=3D
h
> a lot of release of energy. These burning gases ignite other burning gase=
=3D
s
> and it is not necessary to have the embers from the wood or an external
> pilot light them =3D96 they ignite each other. It is then that these gase=
s =3D
have
> become capable of creating self-sustaining =3D91diffusion flames=3D92 (th=
e te=3D
chnical
> name). So you want to think in terms of babying these gases once you begi=
=3D
n
> to get them =3D96 giving them some containment, the right amount of air s=
o =3D
they
> are happy to burst into flame, and giving them the time needed to be of u=
=3D
se.
> You don=3D92t want them to whisk away out of the kiln before they get bur=
ne=3D
d,
> you don=3D92t want to starve them of air, you do want some mixing of gase=
s =3D
and
> air, etc. In my pit fire work done roughly between 1000 =3D96 1350 F (538=
-7=3D
32 C)
> I cannot get self-sustaining diffusion flames although I can, in my
> enclosure, burn tars and oils that are ignited by wood embers and the
> burning of other tars and oils. You, however, can get these glorious
> self-diffusion flames around 2012 F (1100 C) and they will burn remote fr=
=3D
om
> the wood you are stoking. At this point you could think in terms of all t=
=3D
he
> techniques and tricks of the trade used to fire natural gas or propane
> kilns, as far as getting the most out of these gases.
>
Neon-Cat on tue 4 jan 11
Luke, I've looked at saved sent mail and my saved original Word doc. drafts
of list posts and for the life of me I cannot find where I wrote that "at a
certain temperature things do not burn as well or are harder to burn".
Around 2012 F (1100 C) is the standard acceptable point in a vast amount of
literature across industry disciplines where it is taught that
self-sustaining diffusion flames from wood typically burn -- you can work
with the gases at and beyond this temperature or against them -- that was m=
=3D
y
point. Burning gases will ignite newly formed gases far from the original
wood source and/or near the source. There's much more energy to be had
burning the gases.
If by mass transfer you mean mass loss (of the wood being burned) this
occurs in the early stage of heating due to drying (moisture migration
through and out of the wood) and later through pyrolysis. If I was thinking
about building and firing a wood kiln I=3D92d still want to concentrate on
getting the most out of the volatile, flammable gases I do manage to produc=
=3D
e
with the wood fuel I=3D92m using. Calculating mass loss (and then the amoun=
t =3D
of
combustible gases one might theoretically obtain) is an extremely difficult
task due to multiple variables. After all that one would still need to make
good use of the gases produced.
But whatever, I give up.
You big boys can chat among yourselves...
Marian
Neon-Cat
On Tue, Jan 4, 2011 at 4:57 PM, Luke Nealey wrote:
> As I stated before NC, I have a problem with your saying that at a certai=
=3D
n
> temperature things do not burn as well or are harder to burn. I think wh=
=3D
at
> you were trying to say(that's presumptive I know) is that above 1100C its
> easy to be burning your fuel in the chimney rather than the chamber. I
> agree, but that is a mass transfer issue and not a combustion issue. The
> "not burn as well" was what was bugging me. Liked your post on hematite.
>
> Regards,
> Luke Nealey
> Rankin Co. MS
Craig Edwards on wed 5 jan 11
Hello Lee and Mel: I thank-you for your sage advise. I know how hard this
knowledge is to come by. Thank you for sharing it with everyone.
I hope that you can help me out here. What do I do when I'm at 1100C, and
cut back on wood, as advised, and I start to lose temp, not gain, or does
this always work?
Any advise would be greatly appreciated.
Make Good Pots
~Craig
New London MN
http://woodfiredpottery.blogspot.com/
On Tue, Jan 4, 2011 at 9:14 AM, Lee wrote:
> On Tue, Jan 4, 2011 at 7:08 AM, Luke Nealey wrote:
>
> > beach). It doesn't seem to me that there is any thermodynamic reason w=
=3D
hy
> > these things wouldn't burn(react) readily throughout the kiln firing te=
=3D
mp
> > range.
>
> Luke, when folks transition from gas firing to wood firing, they seem
> to think more fuel means more heat. When actually, you need fuel
> plus oxygen to get heat. Because it isn't recognized, folks tend to
> overstoke when they stall and choke off the needed oxygen, when they
> should be backing off on the stoking a little to have a better
> oxygen/fuel ratio.
>
> At about 1100*C, I have found stoking a little less smaller wood
> helps keep the temperature rising. Once past this point, you can go
> back to the way you were stoking before.
>
> --
> Lee Love in Minneapolis
> http://mingeisota.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
>
--
gary navarre on wed 5 jan 11
Hey Folks, Paul,=3D0A=3D0A I'm wondering if the stalling you are discussing=
is =3D
with a Bourry fire box or the updraft/crossdraft with/out grate of the glor=
=3D
y hole on a traditional Anagama? If I recall the earlier successful firings=
=3D
of the '86-'90 Hobagama correctly, when one stalled I fired off the coal p=
=3D
ile for a while with a little stoking. When it got to where cones were bend=
=3D
ing I loaded up the back side of the Bourry with big stuff to hold the high=
=3D
heat and stoked skinny sticks in a smaller hole just above the throat arch=
=3D
. Each time I stoked the small hole the pyrometer would rise and then fall =
=3D
back down to just a bit above where I stoked before. As soon as the needle =
=3D
stopped it meant the kiln was holding it's own on the big stuff and I could=
=3D
stoke more to get a rise. If the needle kept falling it would be time to a=
=3D
dd more big stuff to hold the gains. Eventually I side stoked about 2/3's t=
=3D
he way back along the chamber and got the tail hotter by adding that to the=
=3D
stoking
pattern already started. I don't recall the damper setting, half in maybe,=
=3D
but the chimney cap was about a quarter open in a 9"x9" chimney top exit.=
=3D
=3D0A=3D0A In this newer larger Hobagama, 65cu.ft. 9' long inside, my "stal=
ling=3D
" came after I got the front to ^13. Besides making changes in the Mousehol=
=3D
es to get more air to the ash piles and making more space on the back side =
=3D
of the Bourry box for bigger stuff up to 6"x36". I've also changed the way =
=3D
air will come into the Bourry closer to the combustion zone at the hobs. I'=
=3D
m also going to punch a couple more secondary stoke holes in the chamber wa=
=3D
ll so I can stoke skinny fuel between the stacks of shelves close to the to=
=3D
p inside. There will be much tighter stacking in the bottom front to push t=
=3D
he flame up into the crown and along the top instead of racing along the fl=
=3D
oor out the exit flue. The door stoke hole with soaps for inside grate bars=
=3D
worked pretty good but the fuel needed to be held higher up in the setting=
=3D
so it's heat can work along the top before falling to the floor. I'm also =
=3D
going to leave the active damper open after the front gets hot and keep
the chimney cap closed to 1/3rd. or 1/4 open. In the last firing I think I=
=3D
closed the damper to much so ^13 stayed up front (stalled) and secondary s=
=3D
toking in the wrong spots in the tail didn't help much. Interesting things =
=3D
happened with one of the passive damper holes but I'll get into that when I=
=3D
post the video for the end of the second firing.=3D0A=3D0A I start this ki=
ln w=3D
ith two coffee cans of charcoal, bank up the front firebox with big wood, v=
=3D
ary little air and let it cook. As it gets hotter I use skinnier sticks and=
=3D
more air to increase temperature and bigger stuff to hold the gains. That'=
=3D
s the plan anyway, thanks for reading along while I think out how I'm gonna=
=3D
pull this off in the next firing. Let us only hope we get some helpers fro=
=3D
m those students Tim Zablaki in Iron Mountain is encouraging to do clay and=
=3D
they can catch the bug and come help fire so until then stay in there and =
=3D
don't run out of fuel eh.=3D0A=3D0AGary Navarre=3D0ANavarre Pottery=3D0ANav=
arre Ent=3D
erprises=3D0ANorway, Michigan, USA=3D0Ahttp://www.NavarrePottery.etsy.com=
=3D0Ahtt=3D
p://www.youtube.com/GindaUP=3D0Ahttp://public.fotki.com/GindaUP/=3D0A=3D0A=
=3D0A--- =3D
On Wed, 1/5/11, Paul Herman wrote:=3D0A=3D0A> =
From=3D
: Paul Herman =3D0A> Subject: Re: [Clayart] Woo=
d =3D
Kiln Stalling=3D0A> To: Clayart@LSV.CERAMICS.ORG=3D0A> Date: Wednesday, Jan=
uary=3D
5, 2011, 10:56 AM=3D0A> Hi Craig and All,=3D0A> =3D0A> What is this stall =
at 110=3D
0C that you all are writing about?=3D0A> We do not=3D0A> experience any sta=
ll h=3D
ere, but have to continually hold the=3D0A> kiln back.=3D0A> The durn thing=
jus=3D
t wants to run away and get smokin' hot.=3D0A> We also use=3D0A> quite larg=
e wo=3D
od evidently. Someone wrote about 1 inch=3D0A> square wood,=3D0A> yikes! Fo=
r ou=3D
r kiln, logs 4"X5"X24" are just about right=3D0A> for the=3D0A> front, 2x2x=
24 a=3D
re good on the sides.=3D0A> =3D0A> One thing pretty much for sure is that a=
ll w=3D
ood kilns are=3D0A> different=3D0A> from each other to some degree. My firi=
ng t=3D
echniques would=3D0A> probably=3D0A> not travel well to other peoples kilns=
, an=3D
d there are no=3D0A> hard and fast=3D0A> rules to wood firing. You really h=
ave =3D
to get to know your=3D0A> particular=3D0A> kiln and develop a firing strate=
gy f=3D
or that situation.=3D0A> =3D0A> Vive la difference!=3D0A> =3D0A> Paul Herma=
n=3D0A> =3D
=3D0A> Great Basin Pottery=3D0A> Doyle, California US=3D0A> www.greatbasinp=
ottery=3D
.com/=3D0A> =3D0A> =3D0A> =3D0A> =3D0A> On Jan 5, 2011, at 5:51 AM, Craig E=
dwards wro=3D
te:=3D0A> =3D0A> > Hello Lee and Mel: I thank-you for your sage=3D0A> advis=
e.=3DA0 =3D
I know how=3D0A> > hard this=3D0A> > knowledge is to come by. Thank you for=
sha=3D
ring it with=3D0A> everyone.=3D0A> > I hope that you can help me out here. =
What=3D
do I do=3D0A> when I'm at=3D0A> > 1100C, and=3D0A> > cut back on wood, as =
advise=3D
d, and I start to lose=3D0A> temp, not gain, or=3D0A> > does=3D0A> > this a=
lways =3D
work?=3D0A> > Any advise would be greatly appreciated.=3D0A> >=3D0A> > Make=
Good =3D
Pots=3D0A> > ~Craig=3D0A> > New London MN=3D0A> > http://woodfiredpottery.b=
logspo=3D
t.com/=3D0A> =3D0A=3D0A=3D0A
Lee on wed 5 jan 11
On Wed, Jan 5, 2011 at 7:51 AM, Craig Edwards wro=
=3D
te:
> cut back on wood, as advised, and I start to lose temp, not gain, or does
> this always work?
> Any advise would be greatly=3DA0appreciated.
Craig, I doubt we know much you don't. :^) I think, for folks new
to wood firing, overstoking is the most frequent problem.
No, reducing wood or using smaller wood doesn't always work at
1100*C. If reducing the amount of wood stoked has no effect, it
might mean that isn't your problem. If you stall then and reducing
stoking doesn't help, you might have to change the air flow in the
kiln.
I think Mel mentioned opening the damper. Too many coals can be a
factor. The condition of the wood you are stoking. Air flow,
mouse holes. The last crew stoking. Barometric pressure. And
sometimes, kiln design.
It is always important to only change one thing, and then
see what happens. If you change too many things, you never know which
thing you did fixed things.
--
=3DA0Lee Love in Minneapolis
http://mingeisota.blogspot.com/
=3DA0"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
tony clennell on wed 5 jan 11
Craig: You sly fox you. Only a smart lawyer asks a question he already
knows the answer to. Your test of knowledge is legit. It is not simply
a case of less wood it is "less wood, more often". You don't simply
reduce the amount of calories going into the firebox but keep the
calories going in and burn them up faster. Do I pass?????
I have written before on clayart that this 2100F Cone 4 temp seems
like hitting the wall on many wood kilns. Time to burp or fart the
gases. Give her the same amount of food with a smaller spoon.
Sometimes it is necessary to use more thinly split wood so that it
combusts almost as soon as it enters the firebox. Once I get Cone 6
down it seems I can go back to heavier wood and a more steady climb
without too much fuss.
I would like to fire with you one of these days. I'm a fan of your
work and work ethic.
Cheers,
Tony
On Wed, Jan 5, 2011 at 8:51 AM, Craig Edwards wro=
=3D
te:
> Hello Lee and Mel: I thank-you for your sage advise. =3DA0I know how hard=
t=3D
his
> knowledge is to come by. Thank you for sharing it with everyone.
> I hope that you can help me out here. What do I do when I'm at 1100C, and
> cut back on wood, as advised, and I start to lose temp, not gain, or does
> this always work?
> Any advise would be greatly appreciated.
>
> Make Good Pots
> ~Craig
> New London MN
> http://woodfiredpottery.blogspot.com/
>
>
>
> On Tue, Jan 4, 2011 at 9:14 AM, Lee wrote:
>
>> On Tue, Jan 4, 2011 at 7:08 AM, Luke Nealey wrote=
=3D
:
>>
>> > beach). =3DA0It doesn't seem to me that there is any thermodynamic rea=
so=3D
n why
>> > these things wouldn't burn(react) readily throughout the kiln firing t=
=3D
emp
>> > range.
>>
>> Luke, when folks transition from gas firing to wood firing, they seem
>> to think more fuel means more heat. =3DA0 When actually, =3DA0you need f=
uel
>> plus oxygen to get heat. =3DA0Because it isn't recognized, folks tend to
>> overstoke when they stall and choke off the needed oxygen, when they
>> should be backing off on the stoking a little to have a better
>> oxygen/fuel ratio.
>>
>> =3DA0At about 1100*C, I have found stoking a little less smaller wood
>> helps keep the temperature rising. =3DA0 Once past this point, you can g=
o
>> back to the way you were stoking before.
>>
>> --
>> =3DA0Lee Love in Minneapolis
>> http://mingeisota.blogspot.com/
>>
>> =3DA0"Ta tIr na n-=3DF3g ar chul an tI=3D97tIr dlainn trina ch=3DE9ile"=
=3D97that i=3D
s, "The
>> land of eternal youth is behind the house, a beautiful land fluent
>> within itself." -- John O'Donohue
>>
>
>
>
> --
>
Lee on wed 5 jan 11
On Wed, Jan 5, 2011 at 8:39 AM, tony clennell wro=
=3D
te:
> Craig: You sly fox you. Only a smart lawyer asks a question he already
> knows the answer to. Your test of knowledge is legit. It is not simply
> a case of less wood it is "less wood, more often". You don't simply
> reduce the amount of calories going into the firebox but keep the
> calories going in and burn them up faster.
Tony, that isn't what is proposed. You can increase the
useable calories by adjusting the fuel/air ratio. Just because you
are chucking in mega calories of fuel, without oxygen, it is not
available.
I've fired many times with crews of beginners, and overstoking is
their primary mistake.
> combusts almost as soon as it enters the firebox. Once I get Cone 6
> down it seems I can go back to heavier wood and a more steady climb
> without too much fuss.
Also, past this point, you can add wet wood (or dunked wood like
Craig has) and/or water. It is counter-intuitive, that putting water
on your fire can increase heat energy, but if it is done at high temp,
not only can you get an increase in temp, you can even out the kiln
and cause "water reduction."
Another thing I've learned firing with large crews or
multiple crews: You need one captain of the ship and then only one
officer of the watch. If you don't have them, then stoking becomes a
crap shoot. On the other hand, it is always good to have another set
of eyes and another mind to bounce off of. At the end, when firing
turns into a marathon, it is easy to zone out.
--
=3DA0Lee Love in Minneapolis
http://mingeisota.blogspot.com/
=3DA0"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
Paul Herman on wed 5 jan 11
Hi Craig and All,
What is this stall at 1100C that you all are writing about? We do not
experience any stall here, but have to continually hold the kiln back.
The durn thing just wants to run away and get smokin' hot. We also use
quite large wood evidently. Someone wrote about 1 inch square wood,
yikes! For our kiln, logs 4"X5"X24" are just about right for the
front, 2x2x24 are good on the sides.
One thing pretty much for sure is that all wood kilns are different
from each other to some degree. My firing techniques would probably
not travel well to other peoples kilns, and there are no hard and fast
rules to wood firing. You really have to get to know your particular
kiln and develop a firing strategy for that situation.
Vive la difference!
Paul Herman
Great Basin Pottery
Doyle, California US
www.greatbasinpottery.com/
On Jan 5, 2011, at 5:51 AM, Craig Edwards wrote:
> Hello Lee and Mel: I thank-you for your sage advise. I know how
> hard this
> knowledge is to come by. Thank you for sharing it with everyone.
> I hope that you can help me out here. What do I do when I'm at
> 1100C, and
> cut back on wood, as advised, and I start to lose temp, not gain, or
> does
> this always work?
> Any advise would be greatly appreciated.
>
> Make Good Pots
> ~Craig
> New London MN
> http://woodfiredpottery.blogspot.com/
James Freeman on wed 5 jan 11
On Wed, Jan 5, 2011 at 11:56 AM, Paul Herman wr=
ote:
What is this stall at 1100C that you all are writing about? We do not
experience any stall here, but have to continually hold the kiln back.
The durn thing just wants to run away and get smokin' hot. We also use
quite large wood evidently. Someone wrote about 1 inch square wood,
yikes! For our kiln, logs 4"X5"X24" are just about right for the
front, 2x2x24 are good on the sides.
It seems intuitively obvious that both the optimal size of the pieces of
wood and the optimal charge will be proportional to the size and intensity
of the fire that one's firebox can accommodate.
If I build a small campfire, then dump a big armload of wood on it, I might
very well snuff out the fire, or at least greatly inhibit it. Conversely,
if I build a huge, roaring bonfire, I could likely dump a whole small tree
on it without setting the fire back in any material way.
We heat our wood in order to release from it our combustible fuel. Bigger
chunks of wood take relatively large amounts of heat to convert them to
combustible gas. A large fire can often easily afford to supply such heat,
whereas a small fire may not have the required horsepower. Hold a match to
a log, and nothing happens, as the match cannot supply enough heat to
release sufficient gas from the log. A match can, however, supply enough
heat to release fuel from dry tinder, and the burning tinder can supply
enough heat to release fuel from twigs, and the burning twigs can supply
enough heat to release fuel from sticks...
Big kiln, big firebox, big fire..., bigger charge of bigger wood is probabl=
y
fine. Small kiln, smaller firebox, smaller fire..., probably not so much
so. Perhaps we are talking apples and oranges here.
All the best.
...James
James Freeman
"...outsider artists, caught in the bog of their own consciousness, too
preciously idiosyncratic to be taken seriously."
"All I say is by way of discourse, and nothing by way of advice. I should
not speak so boldly if it were my due to be believed."
-Michel de Montaigne
http://www.jamesfreemanstudio.com
http://www.flickr.com/photos/jamesfreemanstudio/
http://www.jamesfreemanstudio.com/resources
<#>
<#>
<#> <#>
Stephani Stephenson on wed 5 jan 11
Hi Craig
I don't have anything new to add here, but What Lee and Tony say jives wi=
=3D
th
my experience as well.=3D20
smaller 'spoons'....smaller faster 'spoons', each combusting=3D20
thoroughly as soon as possible as it enters the firebox.
I also have, time and time again, seen that point where a kiln stalls .
Without fail, most people want to add more fuel, but they tend to do so =
=3D
in
heavier rather than lighter doses. The tendency is also to monkey with m=
=3D
ore
than one variable as one tries to counteract the stall. pretty soon it
becomes impossible to tell what the effect is of any single variable,
especially with the inevitable delay in kiln response....
I can't speak to the damper issue because IMHO, and I do mean IMHO, eac=
=3D
h
kiln is unique and each kiln has a sweet spot with regard to the best
combination of damper and draw and fuel and tempo: open enough to allow=3D2=
0=3D
=3D20
for thorough fuel combustion and circulation, and yet not so open as to c=
=3D
ool
things down...=3D20
and each kiln , as Tony alluded to , has a unique way of inhaling and
exhaling....
I have gotten to where i tossed in a rhythm of sticks, visualizing them
combusting before they hit any surface in the firebox ,to unstick a stal=
=3D
led
kiln.
so yeah, i would start with reviewing my fuel loads and stoking tempo=3D20=
=3D20=3D
would love to be near a wood kiln these past few evenings...brrrrr!.
Stephani Stephenson
Luke Nealey on thu 6 jan 11
As the first name on this thread and with a couple caveats from other
threads of this morning(IMHO and begging pardon) let me review a bit.
The question I asked was in reference to a post of Marian's that addressed
this 1100C stalling phenomenon. She mentioned that how the wood/fuel burnt
at that temperature changed and affected firing progress. I was not clear
on what she meant.
I am interested in why this stalling happens, apart from Nils talking about
chimney height and null points(Art of Firing, clayart), there seems to be n=
o
explanation. Marian's proposal that at that point the way wood combusts
may make sense, if at that point there is a sudden jump in oxygen demand
because you have increased/changed the actual fuel in the kiln. The solutio=
n
of feeding smaller spoonfuls may address this. I was asking why it happens
not if it does or what to do.
Regards,
Luke Nealey
Rankin Co. MS
>
>
>
>
Edouard Bastarache on thu 6 jan 11
Luke,
the same stalling occurs with our propane kiln
"Go figger"
Gis,
Edouard Bastarache
Spertesperantisto
Sorel-Tracy
Quebec
http://www.flickr.com/photos/30058682@N00/
http://edouardbastarache.blogspot.com/
http://www.facebook.com/edouard.bastarache
http://bastaracheblogsarts.blogspot.com/
----- Original Message -----
From: "Luke Nealey"
To:
Sent: Thursday, January 06, 2011 11:19 AM
Subject: Re: Wood Kiln Stalling
> As the first name on this thread and with a couple caveats from other
> threads of this morning(IMHO and begging pardon) let me review a bit.
>
> The question I asked was in reference to a post of Marian's that addresse=
d
> this 1100C stalling phenomenon. She mentioned that how the wood/fuel
> burnt
> at that temperature changed and affected firing progress. I was not clea=
r
> on what she meant.
>
> I am interested in why this stalling happens, apart from Nils talking
> about
> chimney height and null points(Art of Firing, clayart), there seems to be
> no
> explanation. Marian's proposal that at that point the way wood combusts
> may make sense, if at that point there is a sudden jump in oxygen demand
> because you have increased/changed the actual fuel in the kiln. The
> solution
> of feeding smaller spoonfuls may address this. I was asking why it happen=
s
> not if it does or what to do.
>
> Regards,
> Luke Nealey
> Rankin Co. MS
>
>
>
>>
>>
>>
>>
>
Lee on thu 6 jan 11
On Thu, Jan 6, 2011 at 6:13 PM, Steve Mills
wrote:
> As has become obvious over the years I am NOT a "scientific" type, but am=
=3D
ong other
>things I am a musician and I have a good "Ear".
> LISTEN to a Kiln!
The great thing about our craft is that it is a mix of science, art
and poetry. There is nothing like the sound of a fire breathing
dragon.
--
=3DA0Lee Love in Minneapolis
http://mingeisota.blogspot.com/
=3DA0"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
tony clennell on fri 7 jan 11
Lee: Actually I prefer "silence is golden". When our bourry firebox
train kiln is going full bore you could hear a sparrow fart in
Arkansas. Absolutely silent but deadly.
Cheers,
Tony
On Thu, Jan 6, 2011 at 10:03 PM, Lee wrote:
> On Thu, Jan 6, 2011 at 6:13 PM, Steve Mills
> wrote:
>> As has become obvious over the years I am NOT a "scientific" type, but a=
=3D
mong other
>>things I am a musician and I have a good "Ear".
>> LISTEN to a Kiln!
>
> The great thing about our craft is that it is a mix of science, art
> and poetry. =3DA0 There is nothing like the sound of a fire breathing
> dragon.
>
> --
> =3DA0Lee Love in Minneapolis
> http://mingeisota.blogspot.com/
>
> =3DA0"Ta tIr na n-=3DF3g ar chul an tI=3D97tIr dlainn trina ch=3DE9ile"=
=3D97that is=3D
, "The
> land of eternal youth is behind the house, a beautiful land fluent
> within itself." -- John O'Donohue
>
Lee on fri 7 jan 11
On Fri, Jan 7, 2011 at 7:24 AM, tony clennell wro=
=3D
te:
> Lee: Actually I prefer "silence is golden". When our bourry firebox
> train kiln is going full bore you could hear a sparrow fart in
> Arkansas. Absolutely silent but deadly.
Yeah, there are a lot of "old lady" aspects of Bourry boxes. ;^)
--
=3DA0Lee Love in Minneapolis
http://mingeisota.blogspot.com/
=3DA0"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
Dannon Rhudy on fri 7 jan 11
Steve Mills said:
..........among other things I am a musician and I have a good "Ear".
LISTEN to a Kiln!
As the heat grows inside a wood burning Kiln the sound of the burn changes
in tone.........
I strongly agree with Steve on this issue. Kiln sound/song changes
a great deal during a firing. (It also changes with high/low
atmospheric pressure, but that's another story). I learned to
fire kilns more or less on my own, since no one ever thought
to "teach" firing, in or out of school. Most students didn't
fire anyway until grad school. So, I learned by doing/seeing/
smelling/hearing. All the kilns were old, and pretty basic.
I learned at once that the sound it made told me more about
what was going on than just about anything else. I could tell
when I stepped out to the kiln patio whether the firing was going
properly or not. I've never been unhappy about learning to
fire by firing, firing for teachers who didn't want to be
bothered, or staying up until I figured out what was going
on. And, no matter how much technical assistance is available,
I still listen to the kiln to achieve the firing I want.
regards
Dannon Rhudy
Steve Mills on fri 7 jan 11
Are you talking about the kiln or the fart??
Steve M
Steve Mills
Bath
UK
Sent from my Itouch
On 7 Jan 2011, at 13:24, tony clennell wrote:
> Lee: Actually I prefer "silence is golden". When our bourry firebox
> train kiln is going full bore you could hear a sparrow fart in
> Arkansas. Absolutely silent but deadly.
> Cheers,
> Tony
>=3D20
> On Thu, Jan 6, 2011 at 10:03 PM, Lee wrote:
>> On Thu, Jan 6, 2011 at 6:13 PM, Steve Mills
>> wrote:
>>> As has become obvious over the years I am NOT a "scientific" type, but =
a=3D
mong other
>>> things I am a musician and I have a good "Ear".
>>> LISTEN to a Kiln!
>>=3D20
>> The great thing about our craft is that it is a mix of science, art
>> and poetry. There is nothing like the sound of a fire breathing
>> dragon.
>>=3D20
>> --
>> Lee Love in Minneapolis
>> http://mingeisota.blogspot.com/
>>=3D20
>> "Ta tIr na n-=3DC3=3DB3g ar chul an tI=3DE2=3D80=3D94tIr dlainn trina c=
h=3DC3=3DA9ile"=3D
=3DE2=3D80=3D94that is, "The
>> land of eternal youth is behind the house, a beautiful land fluent
>> within itself." -- John O'Donohue
>>=3D20
Vince Pitelka on fri 7 jan 11
Steve Mills wrote:
"..........among other things I am a musician and I have a good "Ear".
LISTEN to a Kiln! As the heat grows inside a wood burning Kiln the sound of
the burn changes in tone........."
Dannon Rhudy wrote:
"I strongly agree with Steve on this issue. Kiln sound/song changes a grea=
t
deal during a firing. (It also changes with high/low atmospheric pressure,
but that's another story). I learned to fire kilns more or less on my own,
since no one ever thought to "teach" firing, in or out of school. Most
students didn't fire anyway until grad school. So, I learned by
doing/seeing/smelling/hearing."
Steve, Dannon, and everyone -
It is interesting that this thread comes up so soon after the discussion on
"learning to see" - about how making and looking at art can enhance one's
powers of seeing. It is amazing how few people actually proactively
"listen." Instead, in our culture most people learn to "tune out" the sound=
s
around them, to avoid listening to anything except whatever is in the
foreground and seems most important. They often miss the sounds that are
truly important. Like Steve, I am a musician, and have been for over 50
years. Making art helps you to see, and making music helps you to hear.
But you don't need to be a musician to cultivate sensitive hearing. You
just have to listen carefully and proactively.
This isn't going to help much with a programmable electric kiln, other than
hearing the reassuring "click-click" of the relays. But with all gas and
wood kilns, listening is critically important. With multiple gas burners,
it is more important that they sound the same than that the settings are th=
e
same, because the settings aren't absolutely repeatable, whereas when you
listen carefully, the sound doesn't mislead you.
Too many people equate loud combustion noise with more power going into the
kiln, but in most cases, louder noise means too much oxygen and a heavily
oxidizing flame that is inefficient in terms of heatwork. There are burner=
s
that need to be loud, like liquefied propane burners, or high-pressure
venturis running on pounds of LPG, but I greatly prefer a gentle power
burner or a quiet low-pressure venturi, where the most efficient neutral
flame is almost silent.
I love the sound of a big wood kiln at its peak efficiency, where there is
no roar, no sound of rushing air, just a deep, faint rumble that can barely
be heard, and the muted crackle of the flames in the firebox.
- Vince
Vince Pitelka
Appalachian Center for Craft
Tennessee Tech University
vpitelka@dtccom.net; wpitelka@tntech.edu
http://iweb.tntech.edu/wpitelka
Steve Mills on fri 7 jan 11
As has become obvious over the years I am NOT a "scientific" type, but amon=
g=3D
other things I am a musician and I have a good "Ear".=3D20
LISTEN to a Kiln!=3D20
As the heat grows inside a wood burning Kiln the sound of the burn changes =
i=3D
n tone and character e.g. l love the sound when She picks up her skirts an=
d=3D
gets going, it turns from an uneasy spluttering rumble to a soft roar.=3D2=
0
Perhaps it is because as the firing progresses, the relationship between th=
e=3D
physical structure inside and the moving gasses changes.=3D20
I can hear when mine starts to stall, so act on it. The same happens with m=
y=3D
Gas Kiln, only much subtler.=3D20
Perhaps this is where we should look for clues???
Steve M
Steve Mills
Bath
UK
Sent from my Itouch
On 6 Jan 2011, at 16:19, Luke Nealey wrote:
> As the first name on this thread and with a couple caveats from other
> threads of this morning(IMHO and begging pardon) let me review a bit.
>=3D20
> The question I asked was in reference to a post of Marian's that addresse=
d=3D
> this 1100C stalling phenomenon. She mentioned that how the wood/fuel bur=
n=3D
t
> at that temperature changed and affected firing progress. I was not clea=
r=3D
> on what she meant.
>=3D20
> I am interested in why this stalling happens, apart from Nils talking abo=
u=3D
t
> chimney height and null points(Art of Firing, clayart), there seems to be=
n=3D
o
> explanation. Marian's proposal that at that point the way wood combusts
> may make sense, if at that point there is a sudden jump in oxygen demand
> because you have increased/changed the actual fuel in the kiln. The solut=
i=3D
on
> of feeding smaller spoonfuls may address this. I was asking why it happen=
s=3D
> not if it does or what to do.
>=3D20
> Regards,
> Luke Nealey
> Rankin Co. MS
>=3D20
>=3D20
>=3D20
>>=3D20
>>=3D20
>>=3D20
>>=3D20
Craig Edwards on mon 10 jan 11
> Hey Vince and all: I noticed also, how most potters can barely be heard
> when a big wood kiln is at its peak efficiency-- they tend to get quiet i=
n
> the presence such a force of nature and the seeming miracle of wood burni=
ng
> white hot.
Thanks to all for the response to the stall question. I personally learned
allot about how folks wood fire and their relationship to firing. Good
hearing from old friends.
Tony, I'll put firing together on the bucket list. Would be a great time.
Luke-- I think that mass transfer explains much of what happens inside a
kiln. I recently was awarded a Legacy grant, partly, to research just that.
~Cheers
Make Good Pots
~Craig
New London MN
http://woodfiredpottery.blogspot.com/
> I love the sound of a big wood kiln at its peak efficiency, where there i=
s
> no roar, no sound of rushing air, just a deep, faint rumble that can bare=
ly
> be heard, and the muted crackle of the flames in the firebox.
> - Vince
>
> Vince Pitelka
> Appalachian Center for Craft
> Tennessee Tech University
> vpitelka@dtccom.net; wpitelka@tntech.edu
> http://iweb.tntech.edu/wpitelka
>
--
jonathan byler on wed 12 jan 11
I am pretty sure this has much to do with difficulties when firing. a
system that is efficient at 500F is not likely to be efficient at
2000F and vice versa.
I would love to work with an actual combustion scientist/engineer
sometime to figure out how to make kilns more efficient and easy to
fire. as it is, I go on seat of the pants knowledge and many
centuries worth of collected observations. that is good, but by no
means scientific.
On Jan 6, 2011, at 6:13 PM, Steve Mills wrote:
> Perhaps it is because as the firing progresses, the relationship
> between the physical structure inside and the moving gasses changes.
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