don hunt on sat 13 apr 02
Fellow Kilnheads
Maybe I don't have as much a problem as a lack of understanding of the
process.
>From dead cold to about 800 I have just 2 burners on as low as they go.
I slowly (4 or 5 hours) close the door. I single fire part of the
load. I haven't really figured out a ideal speed for this part, but I
do have control here. Up to 1600 where I start reduction, I'm turning
on burners, increasing gas pressure, bringing in the damper, all the
stuff that I expect will increase temp at my desired rate. After 2000
though, increasing gas pressure brings the temp on my digital meter
down. At this point, I have good reduction, a 4-6 inch flame at the top
spyhole, no flame at the bottom and some flame at the top of the maybe
too short stack. Decreasing gas pressure brings decrease in reduction
but a rise in temp, this is what I'm calling a stall. Maybe its really
not. just typical of this kiln. Total firing time 15 hours. 7 hours to
1000, 4 hours from 2000 to cone 10. I'm not really complaining, firing
is very restful, I keep very close watch on the kiln and the time seems
to flow right by. I'm just tweaking. And I want to understand the
process.
Kathy,
The kiln cost about 5k to build.
Thanks,
Don
Dave Finkelnburg on sun 14 apr 02
Don,
If you increase gas and temperature drops, your kiln is simply starved
for air. You don't say whether your damper is wide open at this point. If
it is, you do need to do something with the stack or make another
modification to get air.
If damper is part way in and you add gas and see a temperature drop, you
need to add air at the same time you add gas. Open the damper a bit along
with the gas. You should be able to maintain about the same amount of
reduction and see a temperature rise.
I hope this helps. It would be useful to know more about the kiln
dimensions, wall thickness, damper arrangement, flue size--the specifics
that determine capacity.
Good firing!
Dave Finkelnburg
-----Original Message-----
From: don hunt
Subject: fiber down draft firing schedule
After 2000
>though, increasing gas pressure brings the temp on my digital meter
>down. At this point, I have good reduction, a 4-6 inch flame at the top
>spyhole, no flame at the bottom and some flame at the top of the maybe
>too short stack. Decreasing gas pressure brings decrease in reduction
>but a rise in temp, this is what I'm calling a stall.
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