MIchael Baxley on sat 8 jan 05
I have just purchased a cone art oval kiln, (Model 4227), and was wondering
what would be a good single-fire schedule for firing to cone six? The last
kiln I fired was a 70 cubic foot gas and it was about a 24 hour firing.
This kiln is much smaller, so I am uncertain how fast to fire it. Any feed
back would be wonderful!
Thank you,
Michael Baxley
Dave Finkelnburg on sun 9 jan 05
Michael,
In general your ware, not the kiln, should set your firing schedule. If the kiln is capable, fire as fast as the ware can stand, because that uses the least energy and takes you the least time. As you know, you need to fire to around cone 07 to 04 at a bisque rate...relatively slowly...and from there a glaze-fire rate...relatively fast. When I single-fired functional stoneware pots up to 10-mm (3/8-inch) thick I used a very conservative 65-degrees C (150F) per hour heating rate to cone 04, then a 150C (300F) heating rate to C6.
Whether your electric is vented, and how well, and how tight you stack it, may be a consideration for how fast you fire. You don't want to burn out organics so fast that you get into reduction in the early part of the firing. Electric kilns can be problematic for going into reduction when they are tight and tightly stacked. :-(
Good firing!
Dave Finkelnburg
MIchael Baxley wrote:I have just purchased a cone art oval kiln, (Model 4227), and was wondering
what would be a good single-fire schedule for firing to cone six?
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baxleypottery@netzero.net on mon 10 jan 05
Dear Dave,
Thank you for the feed back. I was looking for a good rule of thumb for speed, and I think you answered my question. I used to fire very slow in the gas, and was not sure exactly how fast I could go. It sounds like 150 per an hour is as fast as I would ever want to go.
Thanks,
MIchael
Snail Scott on mon 10 jan 05
At 02:49 PM 1/8/2005 -0500, you wrote:
>I have just purchased a cone art oval kiln, (Model 4227), and was wondering
>what would be a good single-fire schedule for firing to cone six?
The main thing to consider is how thick your clay is,=20
and how open the body is. This part is just like=20
firing a gas kiln. If it's thick or tight, give it=20
extra time on 'low'. I find that 3 hours on 'low' is=20
enough for, say, 3/4"-thick clay if it's coarse.=20
Thrown pottery with 'normal' wall thicknesses made=20
with a typically smooth throwing clay may only need=20
an hour on low. (I only bother with full-hour=20
increments; too easy to forget otherwise, and makes=20
for easier record-keeping.)=20
For pottery or slip-cast work, I'd candle for an hour,=20
('low' with the lid cracked), 'low' for another hour
with the lid shut, then an hour on, then 'med' for an=20
hour before turning to 'high'. There's no standard=20
electric kiln capable of firing too fast, IMHO. For 1"
thick handbuilt work, I might even candle overnight=20
for extra surety, and add an hour to the 'low' and=20
'med' phases, and then go to high.
(If this is a computerized kiln, treat candling as=20
equivalent to '200=BAF' when programming. Take it=20
slow (150=BAF per hour) to 900=BAF, then as fast as the=20
equipment will go to your intended cone. Very thin
work can go faster, but the kiln may not.)=20
For one-shot firing, as I'm sure you know, the only=20
difference is to treat the early phases like a bisque=20
and the later phases like a glaze firing. Candling=20
and the lowest temperature ranges are critical, but=20
once you've got red heat, you may as well go as fast=20
as the equipment will allow (which isn't very fast).
Soaking or slow-cooling may be necessary to develop=20
your preferred surfaces, since most electrics cool=20
much faster than most gas kilns.
-Snail
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