mel jacobson on mon 6 nov 06
i have recommended often that
the best stacks are at least 10 inches wide.
and for a gas kiln with blowers...it should
not have to be more than 12 feet tall.
(a proper blower kiln does not need a stack. it needs
venting..not a stack.)
has to clear the roof line...so every application
is different.
corbeling in...adding caps and covers
are never advised for kilns.
so, a pinched in stack will, in most cases, stall.
a 70 sq inch flue in my mind, is just too big.
if you are concerned about the blowers sending
too much air and gas into the kiln...drop that number
to 45 sq inches.
we who build flat tops would think that 38 would be fine.
i love the spiral pipe stack lined with kaowool liners.
totally perfect. 10 inch liners work just great.
i itc them...and when you compare that stack to
building a brick stack...half the price...unless you
already have the hard brick. but, if you use brick,
make sure you mortar it tight.
no air leaks.
the smaller flue, and a tight straight stack will
always allow the potter to control the firing.
not so many chances for wind and weather to
control you.
my kiln in minnetonka has a 12 foot stack.
10 inches...spiral pipe.
it fires to cone 13 for the iron saga project...full.
45 cubic feet...about 10 hours. it never stalls.
and we have natural gas, 1.5" water column.
old denver burners, no blowers.
we use about 2/3 less gas than most people.
i know i could fire that kiln to cone 15 without
any stall.
the farm kiln...minnesota flat top, double venturi,
35 sq. inch flue....6 foot, 10 inch stack.
20 cubic feet.
propane...two natural air burners.
fires to cone 13 in four and half hours. no stall...ever.
both nils and donovan palmquist use this formula all the time.
the big difference in the kilns is based on donovan,s love
for arch kilns. he always adds an arch...and, he builds
absolutely perfect arches. but, both the nils design
and the palmquist design are almost identical. how the kiln
works is perfect. the arch is frosting...on a very nice cake.
from: mel/minnetonka.mn.usa
website: http://www.visi.com/~melpots/
Clayart page link: http://www.visi.com/~melpots/clayart.html
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