cape1764@biddeford.com on thu 25 apr 96
HELP!!!!! Its 1:00 am and I think I've got a stalled kiln. This is the 1st time
I've fired it. It was modeled after another kiln but I used 4 Ransome venturi
burners B4a's instead of 2 front facing forced air ones. It's around 40cu.ft
total space with around 32cu ft loading area downdraft car kiln. My flue is 9"x
9" the after chamber is about 4" and the chimney is about 12". I preheated
Tue.. night and started firing @ 6:00am Wed. Body reduction at 3:30 @ ^09. Body
Reduction was heavy and I slightly eased it after 1 hour by adding a little air
and pulling the damper a little to about 2". Then the burners were set at
25Water column inches.( the highest I estimated I would need to go.) Cone 1 was
down in the middle at 8:00pm and by 9:00pm it had dropped top and bottom. At
10:00pm I turned up to 30" and still had slight reduction. (3-4" back pressure
flame out of the top peep.) At 11:30 NOTHING had happened. Cone 8 is standing
there like a soldier. Not even softening. So I pulled the damper to about 2
1/2" and gave the burners a little more air. The air opening is a little more
than 1/4" on each burner. I just checked it and still nothing. My top peep
back pressure is gone. It looks like a pretty oxidized atmosphere and I'm
tired. Am I being too impatient? Any suggestions would be wonderful. Weather
is crisp and dry. about 46 degrees. I have 2 500 gal tanks of propane
supplying the kiln. They aren't completely full but at least 3/4 each ( or they
were Wed.AM) I was hoping for a climbing reducing atmosphere but will have to
settle for a glaze reduction at the end instead(if I ever get there) TIA Tracy
the tired one.
art_selsor@vino.emcmt.edu on thu 25 apr 96
Dear Tracy,
What is your altitude? I fire with venturis, one 60 cu ft and one 48 cuft.
My students sometimes get stalled. I usually play with the damper by firing
in reduction with the damper 75-85% closed. I also cut back on the gas
and the air but (due to bureacracy of Univ) I have two monster venturis
with natural gas on each kiln. I fire most of the way up with hard flame
out the top peep hole and a gentle flame out the bottom. Try not to have
the hot part of your flame going up the chimney. Could be your after chamber
is too small. Do you have a draft if you light some newspaper and put it
in the flu? Venturis need a good draw. -Marcia in Montana
Marvin Bartel on thu 25 apr 96
>----------------------------Original message----------------------------
>HELP!!!!! Its 1:00 am and I think I've got a stalled kiln.
There are lots of ways kilns can require more fuel than we anticipate.
1. You don't say what brick or fiber you used or how much and what type of
insulation it has. Brick mass and heat loss are important factors.
2. Natural draft will likely require more generous flue, chimney height,
chimney size, etc. than forces draft to get the same amount of oxygen
through the kiln.
* * * * * * Marvin Bartel * * * * * *
Art Dept., Goshen College
Goshen IN 46526
marvinpb@goshen.edu
phone 219-535-7592
fax 219-535-7660
http://www.goshen.edu
* * * * * * * * * * * * * * * * * * *
See Goshen College Alumnus
Dick Lehman on Ceramics Monthly Cover
* * * * * * * * * April, 1996 * * * * * * * * * *
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