Craig Dunn Clark on mon 26 apr 04
Keep things nice and even
Joe, I used to fire a 60 cubic foot updraft loaded with busts from the
life modeling class at a school that I attended. I took the advice that I
had heard from Don Reitz at a workshop. He basically said that the way to
successfully fire really big pieces is over about four days. He said to just
put a small piece in with the load and sell it and that would pay for the
firing costs. I thought then and maintain that is easy for him to say.
Regardless, his point about taking it slow and easy was made and followed by
me.
Additionally, it is important to really know your kiln well before
firing large pieces. I am convinced that the successful firing of a large
gas kiln filled with big pots is an ongoing dialogue between the potter, the
pots and the kiln. I not just making this up. It is a dance. If one of the
partners misses a few steps the rythum may be lost. Things become mechanical
and awkward. THink about what a flame looks like, how it moves, how it
feels. Pay attentiion to things like eddies and currents. Feel what is going
on. Connect yourself to kiln. It is living and breathing.
After a few four day firings I gradually cut things back to a little
more than a two day firing cycle. I would "candle" the kiln over night with
all ports and the door slightly ajar for about 12 hours. By this I mean I
ran it up on pilots alone at this stage. This brought the kiln temp up to a
bit over 150F with a nice dry atmoshpere. At that point I would close the
peep holes, the door and let it candle for another six to eight hours. The
firing would then have been on going for a little better than 20 hours. The
temp would climbd another few hundred degrees. I would then turn on the
burners just slightly. THe flame was luminous and just enough to get a nice
draft going. I would let this go over night.
The next morning, I would turn it up a little bit more. Still just
running on natural draft. Let it cruise that way until temp hit red heat. At
that point I started to increase the temp a bit more robustly. It was
important to pay attention to the color of the atmoshpere and the cones in
the top and bottom of the kiln. Since some of the pieces were upwards of
30inches tall an even temperature was important. What seemed to be
"instinctual" in this part of just came from having fired that old kiln what
seemed like a thousand times (not really, probably only several hundred
before leaving.)
A number of the poor-starving-artist students, including yours truly at
the time, would take sand from the foundry and wedge it into the clay body
that we were using. The department chair, who was an accomplished figure
modeler, just used a standard terra cotta clay body that he mixed up with
about 15% AP Green 38mesh grog (if memory serves me correctly. That was a
good fifteen years ago and data access is becoming increasingly difficult
for me.)
Hope this helps
Craig Dunn Clark
619 East 11 1/2 st
Houston, Texas 77008
(713)861-2083
mudman@hal-pc.org
----- Original Message -----
From: "Joseph Coniglio"
To:
Sent: Monday, April 26, 2004 10:09 AM
Subject: Bisquing Large / Large Coil Pots
> Scenerio:
>
> Pot's way too large for the Skut 1027.
>
> Will have to --bisque-- with a Propane updraft.
>
> --This is a large terra cotta garden pot. Coiled with 1 in diameter coils
> with a wicked 2 in rim. Pot stands over waist high.
>
> Can't even tell if it's dry enough to bisque. This is way out of what I
> figured were the normal conventions.
>
> Worked on a slow dry. Let's say it's dry.
>
> 1) Fear the pots gonna blow up. How do I slow this bisque down
> especially since the gas comes up to temperature rather quickly??
>
> 2) Would it pay to over grog the terra cotta body??
>
>
> Thank you.
> Joe
>
>
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