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bisque firing /gas kiln synopsis (long)

updated sat 3 jul 99


Joyce Lee on fri 2 jul 99

Many posts were repetitions of same information. However, I learn by
repetition, as do many others, and there's usually an extra twist or
attitude that makes the post valuable. I also relish the little bits
that reveal something of the poster's personality/character ... not to
make anybody self-conscious, but we are basically a diverse and
rewarding group of people with which to associate! Lots of posts simply
stated that the potter does bisque in a gas kiln, giving size of kiln.
As promised for those interested:

1)In Olympic up-draft, I always bisque to ^05 to ensure that gases have
escaped. Upper shelf may go to ^03 but would not want to go higher.

2) Warm kiln on pilot overnight.

3) An unusually large number of you of varying ages (informally gathered
stat) attended the University of Montana. Reports indicate that their
gas bisque firings were successful over an impressive number of years.

4) Problem on large gas kilns especially ... getting a small enough
flame initially. Difficulty in turning some gas burners down low enough
to dry without blowing the ware up. Big gas kiln with a "manifold on it
with a pilot light for each burner" helped.

5) Keep pilot light on overnight to dry slowly and warm kiln.

6) Mushrooms grew inside of truck in northwest this past winter ... not
pertinent here, but can you believe that??? Respecting the poster, I
know it's true.

7)Large kilns - start slowly, hold to 100 C for about three hours, then
proceed at 50 C per hour up to 600 or so. After that, as fast as the
kiln will go ... 125 degrees C or so per hour. This schedule works for
once-firing also. Big terra cotta pots --- very big. Bisque slipcast
stoneware very fast ... about 8 hours to 800 degrees C.

8) Several pointed out that firing in electric kilns is a fairly recent

9) Patience was emphasized many times.

10) "If it explodes, you're hitting the boiling point too fast, and if
it cracks you're getting to the quartz inversion too fast."

11) Pack kiln full, candle overnight with just pilots, damper wide open
and spyholes open. In this instance pilot lights gave a "blue tongue of
flame about 2 or 3 inches long." Then start up slowly until hitting ^06.
If the "slow" part isn't followed, often can wind up with a pile of
shards. (I personally have plenty of those.)

12)Do NOT leave spy holes and door open in the inital stages. Seal all
but the exit flue. "every pot in the kiln (as well as the furniture) is
being heated rather than just those close to the burners."

13) When candling without pilot burners, if you have four burners, light
only two and at very low pressure. Light burners while candling on
opposing corners for evenness. For a six burner kiln, still candle on 2.

14) Once red heat is achieved, GO FOR IT! "as long as you keep the
atmosphere oxidised and the flame is clean and not impinging directly on
the ware."

15) Allow plenty of space for the flame to burn readily . very
important. Edges of bowls etc in the flame path can become distorted or
flashed; the flashing makes them difficult to glaze.

16) Soak for about 20 minutes by turning the gas pressure back to about
two thirds of its reading for the last 20 degrees C. (some said half


In the Mojave thinkin' her fingers have just had a pretty good workout
... enough "fitness" for today in this heat ... I've vowed to myself not
to mention that it's been 111 F in the shade of our front door.