Les & Beth Tepe on sun 24 sep 00
Our 13 cubic foot Aim Gas kiln runs three Orton-cones different from middle
to top. The top is cooler. Are any of you firing with Aim Kiln model #7407
who might be able to shed some light on our problem? If the model number
doesn't help, it is a top loader, flat roof with three ball valve burners
located in the floor of the kiln. If any one should want a description of
our firing schedule for a recent bisque run, we can supply the information.
Beth & Les Tepe, Newton IA
(Beth is the potter, Les is the fireman.)
Chris Clarke on sun 24 sep 00
Beth & Les
I just purchased that kiln and will be firing it soon. I'll tell you
what happens, I'm firing first to cone6 then to cone9. Did you set up the
bottom like they say?
----- Original Message -----
From: Les & Beth Tepe
Sent: Sunday, September 24, 2000 4:47 AM
Subject: Kiln Temperature Dif
> Our 13 cubic foot Aim Gas kiln runs three Orton-cones different from
> to top. The top is cooler. Are any of you firing with Aim Kiln model
> who might be able to shed some light on our problem? If the model number
> doesn't help, it is a top loader, flat roof with three ball valve burners
> located in the floor of the kiln. If any one should want a description of
> our firing schedule for a recent bisque run, we can supply the
> Beth & Les Tepe, Newton IA
> (Beth is the potter, Les is the fireman.)
> Send postings to firstname.lastname@example.org
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Bruce Girrell on mon 25 sep 00
Beth and/or Les Tepe wrote:
>Our 13 cubic foot Aim Gas kiln runs three Orton-cones different from middle
>to top. The top is cooler.
Our (roughly) 35 cu ft Stack O' Bricks (TM) bisque kiln exhibited the same
problem. The "hot air rises" argument doesn't cut it with me. After some
suggestions from Cameron Harman and others, I realized that the real problem
was that my kiln was choked.
There were two causes for this: 1) the kiln is an updraft with no flue at
all - just an exhaust port and 2) in an effort to provide more stacking
space, I had made the shelf just above the burner ports too large,
restricting the flow of gases within the kiln.
I did three things. First, I cut down the bottom support shelf so that there
was more room available for the combustion products to move up in the kiln.
Second, I rearranged the support shelf and its supporting bricks so that the
flame path became more constricted toward its end, thereby forcing the flame
further up the walls. Finally, I placed some flame diverter bricks (brick
fragments) in the flame path to force the flame further up the walls.
The result is that I now have at most about 1/2 cone between the bottom
shelf and the top shelf despite the four foot internal height of this kiln.
It probably would have been better if I could have solved the problem with
better draft (adding a flue), because I would have improved fuel efficiency
as well as evening out the temperature, but that wasn't really an option
for me. One way or another, though, if the top of your kiln is cooler than
the bottom, you are going to have to get the flame to move upward. Find
whatever may be restricting it in your kiln and give it room to breathe.
Force it up with diverters if necessary. Invite the flame upward by
providing better draft. If you already have a flue, remember that a flue can
sometimes resonate like an organ pipe, restricting flow. Usually changing
the height by just a little will kill the resonance and dramatically improve
Bruce and Lynne Girrell
in frosty northern Michigan having a ball with horsehair recently