Berry Silverman on sat 24 jan 98
Well, I need sage advice, so I'm risking the embarassment of a stupid
question.
Are there ways to cool down the kiln, without damage to the ware, in
order to get more firings? I am firing to ^06 glaze in a Skutt 1227 (10
cubic feet.) I use a slow firing speed since I am doing tableware --
platters and large bowls -- and want to avoid warping. So it takes
about 12 hours for a ^06 firing. It then takes another 24 hours before
the temp is about 150 degrees or lower, which is when I feel comfortable
unloading (without hearing the crackle, crackle if I open the lid).
Do the downdraft venting systems safely speed the firing and/or cooling?
I am concerned about crazing or shivering from temp changes which are
too rapid. Is there anything I can do other than add more kilns?
I patiently await your replies as I patiently wait for the the kilns to
cool.
Berry in Tucson, Arizona, where there is nothing extreme happening right
now.
Cindy on sun 25 jan 98
Berry,
There are all sorts of ways to cool a kiln. A downdraft vent will do it all
right. So will notching the lid up a bit, opening the peeps, and so on. I
don't know about ^06 glazes, but a few of my ^6 glazes lose their splendor
if cooled quickly. And, of course, the shock is pretty hard for the
elements to take. A gradual cooling, using a downdraft vent, would, I
suppose, be easier on the elements than encouraging air currents by opening
peeps and cracking the lid. Or, you could situate your kiln in an unheated
building at below zero temps like mine is. That speeds things up a bit,
too. (Tho not as much as you might think, and entirely dependent on Jack
Frost.)
One idea to consider may be obtaining a smaller kiln for those rush jobs.
Smaller kilns naturally cool a lot faster.
Just a few thoughts,
Cindy in Custer, SD
Laura Conley on mon 26 jan 98
I don't understand why a slow firing is necessary to prevent warping. Isn't
warping due to the clay being so mature that it doesn't hold its shape?
Therefore wouldn't it be the cone you fire to, for this particular clay
body, that is important, not the rate? If this is true, could you simply
speed up the firing, assuming that it doesn't negatively affect your glazes?
Also, perhaps someone could respond to the question of opening a cooling
glaze firing while the ware is still quite hot - I have heard it causes more
crazing, but have never seen this convincingly myself.
Laura Conley
Boulder, CO
Berry Silverman wrote:
> ----------------------------Original message----------------------------
> Well, I need sage advice, so I'm risking the embarassment of a stupid
> question.
>
> Are there ways to cool down the kiln, without damage to the ware, in
> order to get more firings? I am firing to ^06 glaze in a Skutt 1227 (10
> cubic feet.) I use a slow firing speed since I am doing tableware --
> platters and large bowls -- and want to avoid warping. So it takes
> about 12 hours for a ^06 firing. It then takes another 24 hours before
> the temp is about 150 degrees or lower, which is when I feel comfortable
> unloading (without hearing the crackle, crackle if I open the lid).
>
> Do the downdraft venting systems safely speed the firing and/or cooling?
> I am concerned about crazing or shivering from temp changes which are
> too rapid. Is there anything I can do other than add more kilns?
>
> I patiently await your replies as I patiently wait for the the kilns to
> cool.
>
> Berry in Tucson, Arizona, where there is nothing extreme happening right
> now.
Tony Hansen on tue 27 jan 98
>Are there ways to cool down the kiln, without damage to the ware, in
>order to get more firings?... It then takes another 24 hours before
>the temp is about 150 degrees or lower, which is when I feel comfortable
>unloading (without hearing the crackle, crackle if I open the lid).
>I am concerned about crazing or shivering from temp changes which are
>too rapid. Is there anything I can do other than add more kilns?
If your glazes shiver or craze I wonder if the firing is the problem?
If cooling a kiln slowly prevents crazing then I suspect that time
will bring out what the kiln did not. Actually quick cooling ware
is an excellent way to check the glaze fit. While low fire ware can't
take a lot of thermal shock it should not be sensitive enough to
craze on a firing considerably faster than yours.
--
-------
T o n y H a n s e n thansen@digitalfire.com
Get INSIGHT, Magic of Fire at http://digitalfire.com
Lesley Alexander on wed 28 jan 98
Tony, could you elaborate on how fast one can cool a kiln? I've
heard that for a 8-14 cu foot kiln, one should take about 36 hours after a
Cone 10 firing. Are you suggesting that a perfectly fitting glaze could be
done much more rapidly, or were your comments directed to low fire?
Tracy Wilson on fri 30 jan 98
I have a 40 cu. ft. downdraft sprung arch car kiln. The first 4 courses are
hard brick. The rest is soft brick I fire to ^10 taking about 16 to 18
hours. If I shut it off at 10pm the first night, I'll pull the damper,
burner port covers and peep bricks the following night(2nd day) around 10
pm and the next morning (third day) I can crack the door. I check to be
sure with a long single sheet of newspaper. If I stick it in the top peep
and it catches on fire (451 degrees F.)then I'll wait a little longer. But
usually I can open it around 6 or 7am that morning. No pinging or anything!
It's lucky I'm only 100 feet from the studio. I'm a VERY impatient potter.
------------------------------------
Tracy Wilson
Saltbox Pottery
4 Shaw Rd.
Woolwich, ME 04579
phone: 207-443-5586
fax: 207-442-8922
email: saltbox@ime.net
web: http://www.ime.net/~dwilson/
-------------------------------------
Vince Pitelka on sat 31 jan 98
> Tony, could you elaborate on how fast one can cool a kiln? I've
>heard that for a 8-14 cu foot kiln, one should take about 36 hours after a
>Cone 10 firing. Are you suggesting that a perfectly fitting glaze could be
>done much more rapidly, or were your comments directed to low fire?
I have always operated on the premise that you can cool a kiln as fast as
you fire it to maturity. In 30 years in ceramics this has always served me
well. If I fire a stoneware load in ten hours, I know I can cool it in ten
hours with absolutely no problems. I always do a reasonable soak and
oxidation cleanup at the end of a firing, but then I leave the damper and
ports open. If I shut the kiln off in the afternoon or evening, I can
unload it the next morning with no problem. In production many years ago I
succumbed to the temptation to fire and cool very quickly. I repeatedly
cycled my 100 cu.ft. car kiln in fifteen hours - thats loading, firing,
cooling, and unloading. My beautiful 14x28 silcar kilnselves really
suffered, but the wares did not seem to suffer a bit.
This was mentioned by someone else, but I'd like to re-emphasize it. If you
have glazes which craze if you cool the kiln too abruptly in the final
stages, then they are going to craze anyway in regular use. It is a bit
dishonest to cool the kiln excessively slowly to minimize crazing which is
going to happen anyway after the customer purchases your wares.
- Vince
Vince Pitelka - vpitelka@DeKalb.net
Home 615/597-5376, work 615/597-6801, fax 615/597-6803
Appalachian Center for Crafts
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
Talbott on sun 1 feb 98
On a cone 10 firing in our 50 cubic foot kiln I allow about 60 hrs for a
cool down period. ....Marshall
101 CLAYART MUGS (Summer 1998)
2ND ANNUAL CLAYARTERS' GALLERY - NAPLES, MAINE (Summer 1998)
E-MAIL ME FOR APPLICATIONS
http://fmc.utm.edu/~dmcbeth/cag/naples.htm
Celia & Marshall Talbott, Pottery By Celia, Route 114, P O Box 4116,
Naples, Maine 04055-4116,(207)693-6100 voice and fax,(call first)
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