mel jacobson on tue 20 mar 07
many will agree, and write you.
get your kiln in gentle reduction and leave
it there for the entire firing.
in and out does not work well.
many on this list that fire gas will
start about cone 08 and depending on the
glazes start a good reduction color and back
pressure at the spy/ports...about four inches.
it you get good heat rise just leave it alone.
i clear out at cone 10..open the damper and
ports for about ten minutes. then close it
up tight.
for some glazes i add wood on the way down...just small
bits.
i soak at 1900 F. and that duration depends on the glazes
i am working with.
mel
from: mel/minnetonka.mn.usa
website: http://www.visi.com/~melpots/
Clayart page link: http://www.visi.com/~melpots/clayart.html
Chris Trabka on wed 21 mar 07
The entire
>cooling took about 20 hrs though, which seemed excessive.
>
Lesley,
I've had 2 kilns both gas. A small updraft (12 cubic feet stacking) and a
larger MFT (32 cubic feet stacking). The small one took 48 hours to cool.
The large one is still above red heat after 12 hours of cooling (72 hours
of cooling before opening).
Chris
Lesley Anton on wed 21 mar 07
Mel,
Thanks for your post. I just have a couple of questions.
Do you add wood to your gas kiln? (sorry if that sounds like a dumb
question but it sounds like your kiln is a regular gas kiln)
Is your kiln brick? Mine is fiber and I have trouble getting matte
glazes to go matte - I have to fire down the kiln, otherwise it cools
in 8 hrs and the matte glazes are shiny - I have been going very
slowly lately, and they seem to be getting better, but I'm not sure
how slowly. I've tried cooling naturally till about 1800 then slow
cooling for about 4-5 hrs thru to 1500 but I didnt' get that total
matte, just a little. Then I tried slow cooling right when I reached
cone 10, (did some clearing out) then slowed down thru to 1500,
(about 7 hrs as I slept) and it worked great. Beautiful. The entire
cooling took about 20 hrs though, which seemed excessive. What do
you think?
Thanks
Lesley Anton
On Mar 20, 2007, at 7:48 AM, mel jacobson wrote:
> many will agree, and write you.
> get your kiln in gentle reduction and leave
> it there for the entire firing.
> in and out does not work well.
>
> many on this list that fire gas will
> start about cone 08 and depending on the
> glazes start a good reduction color and back
> pressure at the spy/ports...about four inches.
> it you get good heat rise just leave it alone.
>
> i clear out at cone 10..open the damper and
> ports for about ten minutes. then close it
> up tight.
> for some glazes i add wood on the way down...just small
> bits.
> i soak at 1900 F. and that duration depends on the glazes
> i am working with.
> mel
>
> from: mel/minnetonka.mn.usa
> website: http://www.visi.com/~melpots/
>
> Clayart page link: http://www.visi.com/~melpots/clayart.html
>
> ______________________________________________________________________
> ________
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your subscription
> settings from http://www.ceramics.org/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at
> melpots@pclink.com.
Vince Pitelka on thu 22 mar 07
Chris wrote:
> I've had 2 kilns both gas. A small updraft (12 cubic feet stacking) and a
> larger MFT (32 cubic feet stacking). The small one took 48 hours to cool.
> The large one is still above red heat after 12 hours of cooling (72 hours
> of cooling before opening).
I guess you can let your kiln cool that slowly if you want to, but there's
certainly no reason for it. You should be able to cool any studio kiln in
less than 24 hours, and if it takes longer, you need to let more air into
the kiln. It won't hurt anything as long as you don't shock the pots at
quartz inversion or below. When I was doing pots full-time in California I
had a 100-cubic foot natural-draft downdraft IFB gas kiln, and when I was in
a rush I would cycle a cone-10 glaze-firing every 20 hours - firing,
cooling, unloading, and reloading.
- Vince
Vince Pitelka
Appalachian Center for Craft, Tennessee Technological University
Smithville TN 37166, 615/597-6801 x111
vpitelka@dtccom.net, wpitelka@tntech.edu
http://iweb.tntech.edu/wpitelka/
http://www.tntech.edu/craftcenter/
Ron Roy on sun 25 mar 07
I would think most of us would prefer the glazes that came out of a slow
cooling kiln rather than a fast cooled kiln.
Does anyone have any first hand comparisions?
RR
>Chris wrote:
>> I've had 2 kilns both gas. A small updraft (12 cubic feet stacking) and a
>> larger MFT (32 cubic feet stacking). The small one took 48 hours to cool.
>> The large one is still above red heat after 12 hours of cooling (72 hours
>> of cooling before opening).
>
>I guess you can let your kiln cool that slowly if you want to, but there's
>certainly no reason for it. You should be able to cool any studio kiln in
>less than 24 hours, and if it takes longer, you need to let more air into
>the kiln. It won't hurt anything as long as you don't shock the pots at
>quartz inversion or below. When I was doing pots full-time in California I
>had a 100-cubic foot natural-draft downdraft IFB gas kiln, and when I was in
>a rush I would cycle a cone-10 glaze-firing every 20 hours - firing,
>cooling, unloading, and reloading.
>- Vince
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Hank Murrow on sun 25 mar 07
On Mar 25, 2007, at 11:11 AM, Ron Roy wrote:
> I would think most of us would prefer the glazes that came out of a
> slow
> cooling kiln rather than a fast cooled kiln.
>
> Does anyone have any first hand comparisions?
Dear Ron;
I think that many just prefer whatever their kiln gives them, and
become habituated to that.
As for myself, the faster cooling cycle can produce clear, shiny
surfaces resembling glass. I prefer the mat to semi-mat surfaces that
come from longer cooling in part because reflections kill form. In
addition, the clay/glaze interface is developed to a much richer
state with long cooling. The interplay between clay and glaze is what
I am after, so I design my cooling cycle so that crystalline growth
is maximized.
It comes down to personal preference, once all results are possible
in one's studio/kiln milieu. I fire to cone 10_11 in both Oxidation
and Reduction. I have six firing schedules, depending upon my
preferences.
Cheers, Hank
Hank Murrow
www.murrow.biz/hank
Lee Love on mon 26 mar 07
On 3/26/07, Ron Roy wrote:
> I would think most of us would prefer the glazes that came out of a slow
> cooling kiln rather than a fast cooled kiln.
>
> Does anyone have any first hand comparisions?
I crash cool to 1000*C. The red colors on my unglazed ware tend to
be brighter. The same with high alumiina shinos. Euan began doing
this because he uses a high silica clay body and it helps avoid
cristabolite crystal formation, therefore, making a stronger clay
body. It is a Mick Casson trick (our kiln design is influenced by
the first chamber of Casson's woodfired design.) Many kilns cannot
force cool as fast as ours, because our design has a high level of air
movement through it.
Here is a quote from a web page:
http://www.northwalespotters.co.uk/spring2001/petra.htm
"He said that one of the important firing techniques they learnt was
crash cooling the gas kiln from 1300 oC to 1000 oC in 1 - 1=BD hours.
This technique brightened colour and promoted good crystal formation
in the clay which made the body stronger and helped prevent dunting."
But my kiln is hardbrick with an insulation brick liner, so cooling
from there is 24 to 36 hours. Depending on how quick I need to get
things out of the kiln.
--
Lee in Mashiko, Japan
Minneapolis, Minnesota USA
http://potters.blogspot.com/
"To affect the quality of the day, that is the highest of arts." -
Henry David Thoreau
"Let the beauty we love be what we do." - Rumi
Patty Kaliher on mon 26 mar 07
The art center I attend has a new large front loading electric kiln and a
couple of round top loading kilns. Cone 6 glaze loads heat and cool in the
top loading kiln in 24 hours. The large front loading kiln requires a bit
under 72 hours. We label and fire test tiles in both. The slow cooling
kiln is so much better. Glazes develop real character. Neither kiln is
programmed to hold at temperature or fire down.
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of Ron Roy
Sent: Sunday, March 25, 2007 2:12 PM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Re: dan and laurel/reduction
I would think most of us would prefer the glazes that came out of a slow
cooling kiln rather than a fast cooled kiln.
Does anyone have any first hand comparisions?
RR
>Chris wrote:
>> I've had 2 kilns both gas. A small updraft (12 cubic feet stacking) and a
>> larger MFT (32 cubic feet stacking). The small one took 48 hours to cool.
>> The large one is still above red heat after 12 hours of cooling (72 hours
>> of cooling before opening).
>
>I guess you can let your kiln cool that slowly if you want to, but there's
>certainly no reason for it. You should be able to cool any studio kiln in
>less than 24 hours, and if it takes longer, you need to let more air into
>the kiln. It won't hurt anything as long as you don't shock the pots at
>quartz inversion or below. When I was doing pots full-time in California I
>had a 100-cubic foot natural-draft downdraft IFB gas kiln, and when I was
in
>a rush I would cycle a cone-10 glaze-firing every 20 hours - firing,
>cooling, unloading, and reloading.
>- Vince
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
____________________________________________________________________________
__
Send postings to clayart@lsv.ceramics.org
You may look at the archives for the list or change your subscription
settings from http://www.ceramics.org/clayart/
Moderator of the list is Mel Jacobson who may be reached at
melpots@pclink.com.
Maid O'Mud on mon 26 mar 07
Since I started firing down, I've been much happier with
my glazes. Overlaps develop lovely crystals too :-)
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
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of Ron Roy
Subject: Re: dan and laurel/reduction
I would think most of us would prefer the glazes that came out of a slow
cooling kiln rather than a fast cooled kiln.
Does anyone have any first hand comparisions?
RR
--
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Checked by AVG Free Edition.
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11:07 AM
Ron Roy on mon 26 mar 07
Hi Hank,
Makes sense to me - why not consider cooling rate because it has such a
dramatic effect on the way pots look.
RR.
>On Mar 25, 2007, at 11:11 AM, Ron Roy wrote:
>
>> I would think most of us would prefer the glazes that came out of a
>> slow
>> cooling kiln rather than a fast cooled kiln.
>>
>> Does anyone have any first hand comparisons?
>
>Dear Ron;
>
>I think that many just prefer whatever their kiln gives them, and
>become habituated to that.
>
>As for myself, the faster cooling cycle can produce clear, shiny
>surfaces resembling glass. I prefer the mat to semi-mat surfaces that
>come from longer cooling in part because reflections kill form. In
>addition, the clay/glaze interface is developed to a much richer
>state with long cooling. The interplay between clay and glaze is what
>I am after, so I design my cooling cycle so that crystalline growth
>is maximized.
>
>It comes down to personal preference, once all results are possible
>in one's studio/kiln milieu. I fire to cone 10_11 in both Oxidation
>and Reduction. I have six firing schedules, depending upon my
>preferences.
>
>Cheers, Hank
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Gail Dapogny on mon 26 mar 07
Is it the crash cooling that brightens the colors, and the later, =20
slow-cooling? Not challenging, just curious.
Gail
Gail Dapogny
Ann Arbor, Michigan
gdapogny@umich.edu
www.pottersguild.net
www.claygallery.org
On Mar 25, 2007, at 11:59 PM, Lee Love wrote:
>
> I crash cool to 1000*C. The red colors on my unglazed ware tend to
> be brighter. The same with high alumiina shinos. ...
> "He said that one of the important firing techniques they learnt was
> crash cooling the gas kiln from 1300 oC to 1000 oC in 1 - 1=BD hours.
> This technique brightened colour and promoted good crystal formation
> in the clay which made the body stronger and helped prevent dunting."
>
Colleen Riley on tue 27 mar 07
Donovan built a kiln for a client who previously was firing a small, leaky
kiln with a firing/cooling cycle of 24 hours. (^10 reduction)
His new kiln was larger and cooled in 36+ hours. After his first firing, he
called and said that the cones gave true ^10 readings but his glazes were
underfired. This happened with the next couple firings and finally, he sent
us samples of his old fired mugs and the new ones. Donovan took one look at
them and immediately knew what the 'problem' was. Told the client to leave
his damper open after firing for faster cooling...and lo, next firing the
glazes were back to what he was used to with his old kiln.
Dono and I both agreed that the slower cooled glazes were better... quieter,
richer surfaces with small crystals, compared to the runny, glassy 'whammy'
surfaces of the quick-cooled pots. But he sold a lot of the glassy pots so
that's what he wanted.
>RR.
>
>>On Mar 25, 2007, at 11:11 AM, Ron Roy wrote:
>>
>>> I would think most of us would prefer the glazes that came out of a
>>> slow
>>> cooling kiln rather than a fast cooled kiln.
>>>
>>> Does anyone have any first hand comparisons?
>>
Lee Love on tue 27 mar 07
On 3/27/07, Gail Dapogny wrote:
> Is it the crash cooling that brightens the colors, and the later,
> slow-cooling? Not challenging, just curious.
If I don't "crash cool" to 1000*C, the colors of the flashing on
shigaraki clay and high alumina shino red colors are not as intense.
They have traditionally had problems with cristabolite and dunting
in Mashiko.
Euan once told me about a town hall meeting in Ichikai where
the old guys were talking about it. Mashiko clay is found between
seams of yellow sand, and it is very sandy.
I could try to emulate an electric kiln and keep the stoke
doors open until just before quartz-inversion to see if that makes any
difference. Problem is, the work at the opening (where the air comes
in) to the firebox might cool too quickly.
I think the cooldown and hold is specifically to deal with the
shortcomings of electric kilns and the more finicky cone 6 glazes.
--
Lee in Mashiko, Japan
Minneapolis, Minnesota USA
http://potters.blogspot.com/
"To affect the quality of the day, that is the highest of arts." -
Henry David Thoreau
"Let the beauty we love be what we do." - Rumi
Ron Roy on thu 29 mar 07
I agree with this - if you can't modify the body and leave out the fine
silica that leads to cristobalite formation and/or increase the spar to eat
it up.
But - it does happen on the way up so you still have some - and the longer
the firing the more of it is produced.
One of the advantages of making a body up from different clays, feldspars
and fillers is - you can make adjustments to take care of such problems.
There is an excellent article by Peter Songhen in Studio Potter vol 28 #1
which I did the dilatometery for.
RR
>On 3/26/07, Ron Roy wrote:
>> I would think most of us would prefer the glazes that came out of a slow
>> cooling kiln rather than a fast cooled kiln.
>>
>> Does anyone have any first hand comparisions?
>
>I crash cool to 1000*C. The red colors on my unglazed ware tend to
>be brighter. The same with high alumiina shinos. Euan began doing
>this because he uses a high silica clay body and it helps avoid
>cristabolite crystal formation, therefore, making a stronger clay
>body. It is a Mick Casson trick (our kiln design is influenced by
>the first chamber of Casson's woodfired design.) Many kilns cannot
>force cool as fast as ours, because our design has a high level of air
>movement through it.
>
>Here is a quote from a web page:
>
>http://www.northwalespotters.co.uk/spring2001/petra.htm
>
>"He said that one of the important firing techniques they learnt was
>crash cooling the gas kiln from 1300 oC to 1000 oC in 1 - 1=BD hours.
>This technique brightened colour and promoted good crystal formation
>in the clay which made the body stronger and helped prevent dunting."
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
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