Malone & Dean McRaine on tue 4 may 99
Aloha ClayArteers: Over the years I have heard a few stories about fast
firing but generally the politically correct and romantically ideal firing
is long and slow. This is especially true of the image fostered by anagama
and climbing chambered kilns. These firings are generally recounted as
long, arduous, sleep deprived epics of dedication and community cooperation.
I haven't had the opportunity to participate in one of these initiations
into wood fired enlightenment but I AM a romantic and I would jump at the
chance.
Now let's get real. That ideal of long slow, ash filled firing is rarely
the norm in the clay world of today. Most of us, amateurs and journeymen
(and journeywomen) fire, as I do, with gas or electricity, not wood. Our
lives are busy and we're more interested in seeing our work finished than in
creating a community event. And since these processes only affect our work
via oxidation or reduction, fast firing is desireable. I mean, this is
America, we need speed. Actually, I lean more toward the pastoral ideals of
the 19th century but I'd have more time to enjoy them if I didn't have to
spend all day firing...
Until now I haven't had a kiln that could fire really fast. Now I can see
the possibility of going from 300F to 2250F in about four hours. Since I've
never fired this fast I'm wondering if it's wise to risk a kiln load of pots
to find out if it can be done.
Obviously, the first thing is to dry pots completely before going above
212F. I do the usual thing and candle the kiln overnight. I proceed slowly
to about 700F, moderaterly to 1200F, and then full bore to 2250F. This
usually takes about 8 hours. I'm single firing white clay. My biggest pots
are 18" and most are on the thin side, 3/8" or less. I figure some clays
might require longer for carbon burn-out. And there might be other dangers
associated with firing thicker pieces. Bisqueing might be a factor, too. In
'The Kiln Book' Fred Olsen describes fast firing his wood kiln from
400-2300F in 4 hours but he's probably firing bisque. His kiln is a
downdraft and mine is an updraft so there may be differences in air
circulation. There's a fast firing schedule, probably also for bisque, in
'The Energy-Efficient Potter' that goes from 200-2300F in three hours.
Brodie, the author, is using a high velocity burner system for maximum air
circulation in the kiln.
How fast can you go? How fast do you go? I'd like to hear from anybody that
has explored high speed firing. What are the dangers? What are the
parameters?
Dean in Beautiful, Expensive Kauai
nikom chimnok on fri 7 may 99
Hello Dean,
I figured Clayart would explode with responses to your queries, so I
didn't bother to respond the first day. But nobody answered, so I'll tell
you what I know.
First, how fast you can fire has most to do with your claybody. You
can design a clay which will fire fast, but you might be stuck with one
which will only fire slow. Several materials are the friends of the fast
firer: talc, wollastonite, grog, and kaolin. The enemies are ball clay and
very plastic red clays. Small particles sizes promote plasticity, and at the
same time allow water to migrate out of the pot slowly. Large particle size
and inert ingredients allow fast water migration and fast firing. I've seen
the clay formula for a local company that fires tiles in a continuous kiln,
from room temperature to 1200 degrees C to cool in one hour. The tiles are
pressed and contain very little clay.
The first danger of fast firing is explosion. If the water in the
clay boils and the steam can't escape, the pot will explode. Grog is the
best insurance against explosion. The second danger is cracking. Here's
where talc and wollastonite help.
The clay mix is extremely important. Our local clay is normally
once-fired for two days and cooled for two, and still explodes and cracks
50% and more. But with 60% local clay plus additions of ingredients
mentioned above, I can once-fire it with 100% success in 6 hours--that's
from the time of lighting the fire to cone 04. No candling.
Thickness is also important. The thicker it gets, the longer you
have to fire. This is easy to understand--it's the same problem of the
turkey being burnt on the outside but raw inside. With clay the result is
not inedibility, but explosions and cracking.
As to Fred Olsen's fast firing, I think he is not generally talking
about bisque. It's a pretty unusual claybody you can bisque in 4 hours. The
only time I've fired an Olsen kiln was in college, where we bisqued in an
electric kiln for about 12 hours, then glazed with wood in 6. It's much
easier to do a fast glaze firing than a fast bisque firing, because you
don't have the water to contend with. I'm not commenting here on the quality
of the glaze, only the possibility of breaking the pot.
At present we once-fire glazed pots about the size you're talking
about to 1230 C in around 16 hours. The clay contains 20% grog, and never
explodes. We start it slow, proceed at 50 degrees C per hour to 650, then
put the pedal to the metal and finish as fast as the kiln will go. Above
650, a rise of 300 degees per hour doesn't hurt a thing. We do get the odd
crack, but it is considered cheaper to put up with this than to buy the
ingredients to stop it.
I hope this discussion is helpful to you.
Regards,
Nikom, in Thailand, where the mangoes are now so plentiful they're
practically giving them away.
****************************************************************************
******
At 14:06 4/5/99 EDT, you wrote:
>----------------------------Original message----------------------------
(snip)
>Until now I haven't had a kiln that could fire really fast. Now I can see
>the possibility of going from 300F to 2250F in about four hours. Since I've
>never fired this fast I'm wondering if it's wise to risk a kiln load of pots
>to find out if it can be done.
(snip)
Bisqueing might be a factor, too. In
>'The Kiln Book' Fred Olsen describes fast firing his wood kiln from
>400-2300F in 4 hours but he's probably firing bisque..
(snip)
>How fast can you go? How fast do you go? I'd like to hear from anybody that
>has explored high speed firing. What are the dangers? What are the
>parameters?
>
>Dean in Beautiful, Expensive Kauai
>
>
David Hendley on sat 8 may 99
Dean,
I, too, thought you'd get lots of rersponses about this, and
was surprised at the lack of interest.
I agree with nikom chimnok that the problems with fast firing
are in the begining stages. With bisque-ware you can crank up
from 0 to red heat in an hour or two.
I can also tell you that tile factories fire AND cool to cone 1 or
so in about half an hour. The tiles are dry pressed and, I assume,
contain little and not very plastic clay, compared to throwing
claybodies.
Then we come to aesthetics.
Firing time does affect how glazes look, especially if you are
firing in reduction. A certain amount of time is required for that
rich, mellow, and deep glaze. You will just have to fire a quick
load and see how the pots look to you.
My kiln, a variation of the Olsen fast fire design, will fire bisque-
ware to cone 10 in less than 5 hours. But the glazes don't have
much life to them. I'll gladly slow it down to 8 hours for the
better pots that result.
What's an extra 3 hours for a whole load of a hundred pots?
David Hendley
Maydelle, Texas
hendley@tyler.net
http://www.farmpots.com
At 02:06 PM 5/4/99 EDT, you wrote:
>----------------------------Original message----------------------------
>Aloha ClayArteers: Over the years I have heard a few stories about fast
>firing but generally the politically correct and romantically ideal firing
>is long and slow. This is especially true of the image fostered by anagama
>and climbing chambered kilns. These firings are generally recounted as
>long, arduous, sleep deprived epics of dedication and community cooperation.
>I haven't had the opportunity to participate in one of these initiations
>into wood fired enlightenment but I AM a romantic and I would jump at the
>chance.
>
>Now let's get real. That ideal of long slow, ash filled firing is rarely
>the norm in the clay world of today. Most of us, amateurs and journeymen
>(and journeywomen) fire, as I do, with gas or electricity, not wood. Our
>lives are busy and we're more interested in seeing our work finished than in
>creating a community event. And since these processes only affect our work
>via oxidation or reduction, fast firing is desireable. I mean, this is
>America, we need speed. Actually, I lean more toward the pastoral ideals of
>the 19th century but I'd have more time to enjoy them if I didn't have to
>spend all day firing...
>
>Until now I haven't had a kiln that could fire really fast. Now I can see
>the possibility of going from 300F to 2250F in about four hours. Since I've
>never fired this fast I'm wondering if it's wise to risk a kiln load of pots
>to find out if it can be done.
>
> Obviously, the first thing is to dry pots completely before going above
>212F. I do the usual thing and candle the kiln overnight. I proceed slowly
>to about 700F, moderaterly to 1200F, and then full bore to 2250F. This
>usually takes about 8 hours. I'm single firing white clay. My biggest pots
>are 18" and most are on the thin side, 3/8" or less. I figure some clays
>might require longer for carbon burn-out. And there might be other dangers
>associated with firing thicker pieces. Bisqueing might be a factor, too. In
>'The Kiln Book' Fred Olsen describes fast firing his wood kiln from
>400-2300F in 4 hours but he's probably firing bisque. His kiln is a
>downdraft and mine is an updraft so there may be differences in air
>circulation. There's a fast firing schedule, probably also for bisque, in
>'The Energy-Efficient Potter' that goes from 200-2300F in three hours.
>Brodie, the author, is using a high velocity burner system for maximum air
>circulation in the kiln.
>
>How fast can you go? How fast do you go? I'd like to hear from anybody that
>has explored high speed firing. What are the dangers? What are the
>parameters?
>
>Dean in Beautiful, Expensive Kauai
>
clennell on sun 9 may 99
I think the reason that there were few responses to this question is people
take time to make nice pots with nice details why speed up the last detail.
Speed is nice to know is there. It's like having a V-8 engine when you
want to pass.
We just had our first firing in our new wood kiln. Didn't think to look at
the cones for an hour. The beast had gone from 06 to Cone 11. Held it
there for 6 hours. there goes that theory about hard bricks only being
good for landfill, retaining walls and patio stones. Believe only half of
what you read.
Now that we know we have the passing power, we will use cruise control and
keep the same speed for 6 hours, 12 hours or two days, as we feel like.
The knowlege that there is power under the hood is a comforting one.
Long live the muscle kilns.
tony
Tony and Sheila Clennell
4545 King Street
Beamsville, On. L0R 1B1
905-563-9382
Nils Lou on mon 10 may 99
Hey, Tony,
I bet I could make a patio with that new kiln of yours. Nils
On Sun, 9 May 1999, clennell wrote:
> ----------------------------Original message----------------------------
> I think the reason that there were few responses to this question is people
> take time to make nice pots with nice details why speed up the last detail.
> Speed is nice to know is there. It's like having a V-8 engine when you
> want to pass.
> We just had our first firing in our new wood kiln. Didn't think to look at
> the cones for an hour. The beast had gone from 06 to Cone 11. Held it
> there for 6 hours. there goes that theory about hard bricks only being
> good for landfill, retaining walls and patio stones. Believe only half of
> what you read.
> Now that we know we have the passing power, we will use cruise control and
> keep the same speed for 6 hours, 12 hours or two days, as we feel like.
> The knowlege that there is power under the hood is a comforting one.
> Long live the muscle kilns.
> tony
>
> Tony and Sheila Clennell
> 4545 King Street
> Beamsville, On. L0R 1B1
> 905-563-9382
>
gemopal@iniaccess.net.au on mon 10 may 99
wrote:
Original Article: http://www.egroups.com/list/clayart/?start=44406
> ----------------------------Original message----------------------------
> I think the reason that there were few responses to this question is people
> take time to make nice pots with nice details why speed up the last detail.
> Speed is nice to know is there. It's like having a V-8 engine when you
> want to pass.
> We just had our first firing in our new wood kiln. Didn't think to look at
> the cones for an hour. The beast had gone from 06 to Cone 11. Held it
> there for 6 hours. there goes that theory about hard bricks only being
> good for landfill, retaining walls and patio stones. Believe only half of
> what you read.
> Now that we know we have the passing power, we will use cruise control and
> keep the same speed for 6 hours, 12 hours or two days, as we feel like.
> The knowlege that there is power under the hood is a comforting one.
> Long live the muscle kilns.
> tony
>
> Tony and Sheila Clennell
> 4545 King Street
> Beamsville, On. L0R 1B1
> 905-563-9382
> Re fast firing - is this fast enough? Bisc 100 goblets in 20 minutes! Glaze
Graeme Anderson. Gemopal Pottery. Lightning Ridge. Australia.
http://www.iniaccess.net.au/~gemopal/
>
gemopal@iniaccess.net.au on tue 11 may 99
wrote:
Original Article: http://www.egroups.com/list/clayart/?start=44468
> ----------------------------Original message----------------------------
> wrote:
> Original Article: http://www.egroups.com/list/clayart/?start=44406
Sorry. Apparently cyber-space chewed up a lot of my previous message and neglec
Bisc 100 goblets to 1000 C in 20 minutes. Glaze to cone 10 in 1 hour.
An article in New Zealand Potter 20/2 1978 describes the kiln (60cm x 60 x 15)
- almost entirely fibre. Only one honeycomb shelf of fibre paper, made into cel
The magazine recently ceased publication, but it may be possible to buy photocop
Editor Howard S. Williams. New Zealand Potter Publications.
P.O. Box 881. Auckland. New Zealand.
Happy Potting. Graeme Anderson - from the home of the fabulous black opal.
http://www.iniaccess.net.au/~gemopal/
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