Linda Kiepke on mon 28 feb 11
>=3D20
> Dear Clayart,
>=3D20
> I made an error in my description of the location of the ports in =3D
question on our Alpine kiln. They are located low on the sides of the =3D
kiln, towards the rear; not on the rear/back of the kiln.
>=3D20
> -Linda Kiepke
>=3D20
Vince Pitelka on tue 1 mar 11
Linda -
You asked about the side-port on Alpines. I fired huge amounts of cone-6
reduction in three Alpines while I was studio tech at UMass-Amherst in the
late 80s and early 90s. We always left the side ports open, and they were
very important in gauging the firing. There is nothing about leaving them
open that could harm the kiln.
Below I am reprinting the entirety of my short handout on the firing
schedule for those kilns. This includes only the schedules for cone-04
oxidation glaze-firing, and cone-6 reduction glaze firing, because that is
about all we did in those kilns. It has been a lot of years since I was
there, and I have fired so many other fuel kilns since then, but if you hav=
e
any specific questions I may be able to remember. I do know that the blowe=
r
rheostats were marked from 1-10, so keep that in mind in reference to the
numbers given below. I hope this helps.
- Vince
Vince Pitelka
Appalachian Center for Craft
Tennessee Tech University
vpitelka@dtccom.net; wpitelka@tntech.edu
http://iweb.tntech.edu/wpitelka
FIRING THE ALPINE GAS KILN
FIRING SCHEDULE - CONE 04 LO-FIRE GLAZE
For glaze firing in most kilns it is not necessary to fire overnight on low=
,
but the large Alpine updrafts are difficult to fire evenly, and this slow
overnight start seems to help equalize the temperatures.
10:00 p.m. - Light pilots. Open damper to 1/2". Turn blower rheostats to
the lowest setting. Turn main burner gas valves on until burners just
barely light.
8:00 a.m. - Turn blower rheostats to 30. Turn on main burner gas to 1"
pressure reading on gauge. Open damper to 1".
8:30 a.m. - Kiln approx. 500 degrees F. Turn air to 70 and gas to 2".
Leave damper at 1".
10:00 a.m. - Turn air on full and gas to 3". Put in spy-hole plugs. Open
damper to 1 1/2".
11:00 a.m. or as soon as bright red heat is visible through top spy-hole
plug - Close damper a little at a time until small blue flame shows at
damper and firebox side-ports.
2:00 p.m. approx. - Cone 04 down. Shut off main switch or valve, turn off
burner valves and rheostats, and close damper all the way.
In the later stages of the firing it is essential that you look for that
small blue flame at the firebox side-ports. This flame insures that you an
even atmosphere from top to bottom and will help to achieve even temperatur=
e
as well.
Most low-fire glaze-firings are conducted without any period of reduction
for the same reasons as in the bisque. Also, many low-fire glazes are
damaged by the reduction atmosphere. If you are firing un-glazed wares and
want to bring out the iron oxides in the clay or stains, a 15-minute period
of reduction will accomplish this: after the firing cone (cone 04) is down,
turn the air down to 50, leave the gas on 3", and close the damper until a
yellow-orange flame shows at the damper and side-ports.
Bubbles in the glaze always occur during firing as a result of
volatilization of materials in the clay and glazes, but they normally smoot=
h
out at the maturing temperature. If you have trouble with bubbles in the
glaze in low-fired wares it is most likely a result of the kiln cooling too
abruptly. A short soaking at maturing temperature should eliminate this by
allowing the volatilization to complete. To soak the kiln simply turn the
air back to 30, the gas to 1", and the damper to 1/2". Allow kiln to soak
for a half hour or so, and then shut off as instructed above.
ALPINE GAS KILN - CONE-6 REDUCTION FIRING
For glaze firing in most kilns it is not necessary to fire overnight on low=
,
but the Alpine updrafts are very difficult to fire evenly, and this slow
overnight start seems to help.
10:00 p.m. - Light pilots. Open damper to 1/2". Turn blower rheostats to
the lowest setting. Turn main burner gas valves on until burners just
barely light.
8:00 a.m. - Turn blower rheostats to 30. Turn on main burner gas to 1"
pressure reading on gauge. Open damper to 1".
8:30 a.m. - Kiln approx. 500 degrees F. Turn air to 70 and gas to 2".
Leave damper at 1".
10:00 a.m. - Turn air on full and gas to 3". Put in spy-hole plugs. Open
damper to 1 1/2".
11:00 a.m. or as soon as bright red heat is visible through top spy-hole
plug - Close damper a little at a time until small blue flame shows at
damper and firebox side-ports.
1:00 p.m. approx. - Kiln approx. 1800 degrees. Cone 07 down.
BODY REDUCTION - Turn air down to 50 (low-medium) and close damper until
orange flame shows at damper and firebox side-ports. Flames should not bac=
k
up out of burner ports.
After 30 minutes body-reduction open damper to 2", turn air on full and gas
back to 3", wait several minutes, and then close damper until small
blue-orange flame shows at side-ports in order to initiate
partial-reduction.
As temperature increases, flame at side-port will turn yellow-orange and
then yellow.
5:00 p.m. approx. - Kiln approx. 2200 degrees. Cone 6 down
Oxidation cleanup - turn gas down until all flames disappear from damper,
side-ports, and spy-holes. After fifteen minutes of oxidation cleanup, shu=
t
down kiln. . Shut off main switch or valve, shut off burner valves and air
rheostat, and close damper all the way. After two hours, open the damper
several inches to cool the kiln faster. Do not leave the damper open right
away.
From bright red heat onwards it is essential to maintain the small blue
flame (or blue-orange or yellow-orange flame in reduction) at the firebox
side-ports. This flame insures that you an even atmosphere from top to
bottom, and will greatly help to achieve even temperature as well.
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