Lee Love on thu 23 dec 10
On Thu, Dec 23, 2010 at 8:47 PM, Mike wrote:
> Why is 1100C a typical stall point, I wonder?
I don't know. But, for some reason, woodkilns seem to need less
fuel for optimal heat energy. Once you get past it, fuel can be
increase.
Did you have to do much coal raking?
> I opened the kiln a couple days back. Much was undercooked, but the resul=
=3D
ts
> were terribly enlightening. Much of it will get re-fired. I have a much
> better feel now for what needs to go where in the stacks, and I may play
> with the exit flues of the first chamber a bit.
Refires helps you fill the kiln faster. Good luck! I am excited
to see results!
--
=3DA0Lee, a Mashiko potter in Minneapolis
http://mingeisota.blogspot.com/
=3D93Observe the wonders as they occur around you. Don't claim them. Feel
the artistry moving through and be silent.=3D94 --Rumi
mel jacobson on thu 23 dec 10
it cannot be stressed enough that cones are
a potters best friend.
but, you must learn to match cones with your work.
it is up to you.
it is just a tool, and like all tools you have
to master them.
like testing a clay or glaze, where the cone
has bent, how far over, what cone to step up to...they
all count.
so many young (new) potters think that when a
glaze recipe says...CONE6, that means the word of god.
no it does not.
it may be one thing at 5, something else at 6 and the
very best `may` be cone 7 or 8. the person that built
that glaze may have used a very different clay body
than you have. time of firing is very important. fast, slow,
medium or soak. it all changes.
so, how do you know what a glaze will do until you
try it with different conditions. different clay, different time.
like:
my new wonder blue...it comes from colleen riley palmquist.
it is a cone 6, very runny glaze. i fire it to cone 11.
she uses it in her salt kiln.. (she was testing a cone 6-7
salt firing.) nice.
my god does it move and go hare's fur.
don't use it on the outside of mugs...it will be a new
gift for your kiln shelf. a big gift.
but, inside platters, inside bowls...wonderful.
and, that glaze makes crystals like mad.
so the glaze police would say...`naughty mel, using that glaze
at cone 11.`
screw the glaze police.
my carpenter buddy just left my studio with 8 big bowls.
his two favorites are bright copper red with wonder blue inside.
cash. his Christmas shopping is done....15 minutes.
(he is going to keep the red and blue ones. oatmeal
for presents...safe that way.
now i will convert that cash into a gang of my grandkids, daughter, wife
and a couple of friends...`TRUE GRIT` the new cohen brothers movie
and a fun lunch. (in spite of really bad weather, i have had a great
sale this month.)
nice.
the cohen brothers grew up just a few miles from me...sorta just
down the block. different high school. but, their sort of values,
ideas are a part of the minnesota culture... `FARGO` was
a perfect example.
mel
and, a very merry Christmas to all that still believe in Christmas.
i sure do. and, i will have our neighbors that are African Muslim
over for Christmas cheer...they would not miss it. the value
of loving friends never change.
one of my favorite photos is of sharlene, is sitting at a table with
6 very pretty women from Senegal at my neighbors holiday party.
she looks very `white`. of course those gals all speak french, english
some spanish and two african languages. french is native.
we are blessed. it is such a compliment when we realize we are the
only white people at that party.
from: minnetonka, mn
website: http://www.visi.com/~melpots/
clayart link: http://www.visi.com/~melpots/clayart.html
new book: http://www.21stcenturykilns.com
alternate: melpots7575@gmail.com
Lee Love on thu 23 dec 10
On Thu, Dec 23, 2010 at 6:06 PM, Mike wrote:
>
>
> To make a long story short, the kiln stalled at around 1100C.
Mike,
Wood kilns typically stall at 1100*C. Sometimes,
reducing the amount of wood you are stoking helps get the rise back.
My kiln in Mashiko stalled at 1100*C. I would switch from 2kg/stoke
to 1.5kg/stoke and start gaining temp again.
Also, pyrometers seem to be less reliable after that temp.
They can tell you what direction you are going, but not the exact
temperature.
Did you use any pull tiles or rings? When will you open it?
--
=3DA0Lee, a Mashiko potter in Minneapolis
http://mingeisota.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 fri 24 dec 10
On Fri, Dec 24, 2010 at 4:52 PM, Mike wrote:
> needs to be more refractory, if anything. Traditionally, Karatsu is
> mostly cone 5-8,
Mike, Traditional Mashiko clay is only good to cone 8. The Mashiko
Co-op adds shigaraki nami to their "Mashiko" clay to allower it to
fire to cone 9/10
Clay I got from when the sewer pipe was going into Hamada's
compound was between bands of sand, about 2 meters down. Fukuyan
said to add keibushi fireclay to it to make a useable clay.
> much like Oribe and Shino.
Not what you mean about Shino. Do you mean Mogusa clay?
It is very refractory. I've fired it to cone 13/14 3 times and it is
still porous. My next experiment will be using Shino on Yellowbanks.
--
=3DA0Lee, a Mashiko potter in Minneapolis
http://mingeisota.blogspot.com/
=3D93Observe the wonders as they occur around you. Don't claim them. Feel
the artistry moving through and be silent.=3D94 --Rumi
Craig Edwards on fri 24 dec 10
Hey Mike: Maybe I can jump in here. I normally don't post to clayart becaus=
e
there is already more than enough advise on wood firing.
I've noticed that 1100C is the temp that wood will burn at in a natural sor=
t
of way. Getting to that temp is relatively easy. The damper can be off
somewhat, you can over/under stoke, or have erratic stoking etc.... Beyond
that the wood is going to temps that it would rather not, and you must be a
bit more clever. Some kilns are more forgiving than others.
On the kiln I fire most often now, the air settings and the stokes need to
be spot on. To much or to little wood/ air and the kiln will stall forever=
.
Something simple like the size of the pieces of wood has stalled me. Now th=
e
wood is separated for different stages of the fire. The wood that we stoke
at the end is split finer, and very dry... we call it the "party wood".
An easy way around 1100C is wooden door(rifling) stoking, that will get you
around 1100C, but if you don't know the proper settings for air and wood
amounts beyond that, it will do just that.
I think that you will find that there is a lot more than just making temp
with wood firing.
Clay is important... the right clay in the right part of the kiln. I used t=
o
use clay that was too refractory and needed to fire much hotter to
get satisfactory results. First there is the clay, then the kiln, then the
potter.... a mantra if ever there was one.
Also, I haven't noticed that much difference in cones. Cone 10 pretty much
looks like cone 10, maybe slight difference, but not two or three cones.
Different things happen in different kilns.
Cheers,
--
Make Good Pots
~Craig
New London MN
http://woodfiredpottery.blogspot.com/
Mike on fri 24 dec 10
(2010/12/24 1:59), mel jacobson wrote:
> it cannot be stressed enough that cones are
> a potters best friend.
Truer words have never been spoken. Fired my wood kiln for the first
time last week, never having fired a wood kiln before, had no idea how
to proceed or what to expect. It was my good fortune that my mentor
Tsuruta san was on hand to assist.
To make a long story short, the kiln stalled at around 1100C. We stoked
from dusk until dawn and further, and the temp readings never stopped
fluctuating between 1080C and 1130C. I was getting very frustrated,
desperate even. Suddenly, like a light going on, I remembered all of the
cone packs I'd set.
"Tsuruta san, there are cones! I forgot about them, let's take a look."
Could have sworn I detected a faint smile at some points in the firing,
and this was one of them. Looked at the cones, and 12 was halfway down.
Shows how accurate the thermocouples were for judging the state of the
ware. Suddenly, things didn't seem so hopeless.
I have a sneaking suspicion that Tsuruta san hadn't forgotten about
those cones and was waiting for me to remember. I've never really placed
much importance on the thermocouple readings and don't know why I let
them trip me up this time. Too easy to get hypnotized by those numbers.
Cones are definitely my best friend.
Mike
in Taku, Japan
http://karatsupots.com
http://karatsupots.blogspot.com
Workshop in Taku, Spring 2012: To Be Announced
Mike on fri 24 dec 10
Hi Lee,
Nope, no pull tiles this time around. The entire load was a test. Maybe
20+ glaze and clay combinations that I spread all over the place, to
compare what I got in different parts of the kiln, and they reflected
exactly what the cones told me. I think I will pull some trials from the
next run, just to see what particular glazes look like in different
phases of the melt.
Why is 1100C a typical stall point, I wonder?
I opened the kiln a couple days back. Much was undercooked, but the
results were terribly enlightening. Much of it will get re-fired. I have
a much better feel now for what needs to go where in the stacks, and I
may play with the exit flues of the first chamber a bit.
Mike
in Taku, Japan
http://karatsupots.com
http://karatsupots.blogspot.com
Workshop in Taku, Spring 2012: To Be Announced
(2010/12/24 10:09), Lee Love wrote:
> On Thu, Dec 23, 2010 at 6:06 PM, Mike wrote:
>>
>> To make a long story short, the kiln stalled at around 1100C.
> Mike,
>
> Wood kilns typically stall at 1100*C. Sometimes,
> reducing the amount of wood you are stoking helps get the rise back.
> My kiln in Mashiko stalled at 1100*C. I would switch from 2kg/stoke
> to 1.5kg/stoke and start gaining temp again.
>
> Also, pyrometers seem to be less reliable after that temp.
> They can tell you what direction you are going, but not the exact
> temperature.
>
> Did you use any pull tiles or rings? When will you open it?
>
> --
> Lee, a Mashiko potter in Minneapolis
> http://mingeisota.blogspot.com/
>
> =E2EURoeObserve the wonders as they occur around you. Don't claim them. F=
eel
> the artistry moving through and be silent.=E2EUR=9D --Rumi
>
Neon-Cat on sat 25 dec 10
Mike and Lee -- After you=3D92re underway with firing, flaming combustion
will occur entirely in the gas phase outside the wood itself. In
general, self-sustaining diffusion flames from wood typically burn
around 1100=3DB0 C or somewhat higher. Before this, given the processes of
thermal wood degradation (pyrolysis), the various gases evolved may
lack the oxygen necessary for combustion until they have gone far
enough through the kiln to mix with air in proportions between the
lower and upper limits of their respective flammabilities.
Flaming is responsible for about one-half to two-thirds of all the
heat liberated during firing with the rest contributed by the glowing
combustion of the wood charcoal. So, the goal is to encourage these
diffusion flames by kiln design, air-fuel ratios, size and shape of
wood burned, and all the other things you guys and gals work so hard
to do.
It must be grand to have a wood firing kiln! I'd love to see photos.
Marian
Neon-Cat Ceramics
http://www.neon-cat.com/ceramic_art_purchase__enjoy
On Thu, Dec 23, 2010 at 9:47 PM, Lee Love wrote:
> On Thu, Dec 23, 2010 at 8:47 PM, Mike wrote:
>
>> Why is 1100C a typical stall point, I wonder?
Mike on sat 25 dec 10
Hi Craig,
This is all very interesting. Aside from stacking a bit tighter, one of
the first things I will do for the next firing is to re-think how open
the primary air needs to be at the various stages. In retrospect,
perhaps is was too open for the kind of pull that chimney has. Also
perhaps the exit flues from the first chamber need a bit of tweaking,
but I think I'll just try changing one thing at a time. Maybe some
bricks standing next to the exit flues that can be knocked over during
the firing to change the amount of air being sucked through. Easy to do
that.
The reason I bring these two things up is that during the firing, when
the temp got high enough, we started getting that lovely rumbling roar
following the stokes. When we stoked the front, we could hear it in the
first chamber, and maybe the second. When we moved to stoke the rear of
the first chamber, we'd get that roar, but we were hearing it in the
flues behind the second chamber, between the second chamber and the
chimney. And when we looked at the flame, it was moving pretty
horizontally from that stoke point, not going up at all (the stacks of
ware were too open at the bottom too, probably) Later, we really clammed
up the front of the kiln, used fiber between the primary air covers, so
the only air going in the front was from the spaces created by
expansion. Stoking the second chamber, it went up like clockwork, up
down up down, gaining about 10 degrees with every stoke, and the roar
didn't come from the rear flue collection box. Oh, and we were stoking
the "party wood".
Completely separate here is the issue of clay. I will have to completely
re-think clay for this kiln, but so many kinds went in the first firing
that there are many clues for the second. Mostly, the clay at the front
needs to be more refractory, if anything. Traditionally, Karatsu is
mostly cone 5-8, much like Oribe and Shino. Getting hammered right there
in the firebox is not the norm for this stuff. BTW, the clay we took out
of the hole when we dug the kiln is really nice stuff. Probably best at
around cone 6-8, but could go as high as 9 or 10, depending on the shape
and size, without bloating too badly.
Mike
in Taku, Japan
http://karatsupots.com
http://karatsupots.blogspot.com
Workshop in Taku, Spring 2012: To Be Announced
(2010/12/24 22:39), Craig Edwards wrote:
> Hey Mike: Maybe I can jump in here. I normally don't post to clayart beca=
use
> there is already more than enough advise on wood firing.
> I've noticed that 1100C is the temp that wood will burn at in a natural s=
ort
> of way. Getting to that temp is relatively easy. The damper can be off
> somewhat, you can over/under stoke, or have erratic stoking etc.... Beyon=
d
> that the wood is going to temps that it would rather not, and you must be=
a
> bit more clever. Some kilns are more forgiving than others.
> On the kiln I fire most often now, the air settings and the stokes need t=
o
> be spot on. To much or to little wood/ air and the kiln will stall forev=
er.
> Something simple like the size of the pieces of wood has stalled me. Now =
the
> wood is separated for different stages of the fire. The wood that we stok=
e
> at the end is split finer, and very dry... we call it the "party wood".
> An easy way around 1100C is wooden door(rifling) stoking, that will get y=
ou
> around 1100C, but if you don't know the proper settings for air and wood
> amounts beyond that, it will do just that.
> I think that you will find that there is a lot more than just making temp
> with wood firing.
> Clay is important... the right clay in the right part of the kiln. I used=
to
> use clay that was too refractory and needed to fire much hotter to
> get satisfactory results. First there is the clay, then the kiln, then th=
e
> potter.... a mantra if ever there was one.
> Also, I haven't noticed that much difference in cones. Cone 10 pretty muc=
h
> looks like cone 10, maybe slight difference, but not two or three cones.
> Different things happen in different kilns.
> Cheers,
>
>
> --
> Make Good Pots
> ~Craig
> New London MN
> http://woodfiredpottery.blogspot.com/
>
Mike on sun 26 dec 10
Hi Lee,
Sure, Mogusa is pretty refractory, but they didn't fire it higher than
cone 8 or so. That's all I meant, sorry for the mixup.
Mike
in Taku, Japan
http://karatsupots.com
http://karatsupots.blogspot.com
Workshop in Taku, Spring 2012: To Be Announced
> Not what you mean about Shino. Do you mean Mogusa clay?
> It is very refractory. I've fired it to cone 13/14 3 times and it is
> still porous. My next experiment will be using Shino on Yellowbanks.
>
| |
|
