Gail Dapogny on wed 11 oct 00
Hi,
I was the one who originally put forth a question about bisquing: how fast,
soaking, etc. , questions related to trying to burn out more impurities,
since we have enough problems with pitting and pinholing to drive me nuts
and annoy others. I 'm grateful to Cindy, Karen, and Scott -- also Tim
from Ortons -- who responded. The first three all pointed me toward firing
bisque at 100 degrees f per hour.
I'm going to quote a section of my original post below, because I would
like to have more responses since I need a hefty batch of answers to take
back to the group (guild) that I'm part of. If you have the time to send
me your words of wisdom, I would really appreciate any responses, detailed
or general.
>>"In our potters' guild, we fire our bisque in a down draft gas kiln to 06,
and soak at about 1450f.... I realized, after doing some reading, that we
had at some point in the past arrived at 1450 for our soak because it is
close to the top temp
for carbons to burn out. However, now I realize that sulfur continues
burning out well past 2000f, so clearly we are missing the boat here.
>>Currently we use 07 and 06 cones, and turn off when 06 is half over--a
little under 1900f; so we're rising about 175 degrees per hour. After an
overnight warmup, we start our main burners at around 800f and fire for
about 6 and a half hours. I did check with a stick and we're NOT reducing
the bisque so far as I can tell.
>>Now...keep in mind this is a GUILD, skeptical and slow to change. The
doubts are going to be:
>>1. How do we soak at the end without over-firing and making the ware brittle?
2. At what point should we begin the soak (earlier than top temperature so
as not to overfire?)
3. Should we continue to go slowly in the 1400s? How slow?
4. How long should the entire firing take after the warmup period?"
Again....thanks for responding if you can.
-----Gail
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