Craig Clark on fri 8 apr 05
please
This is a question that I have had for a number of years. Haven't
had the opportunity to fire a large reduction kiln for quite a while but
I did so for the better part of a decade. The question that was raised
from time to time was what exactly was too much reduction.
The overarching commandment of any fireing was that it be even. If 6
or 10 was bent at the top of the kiln then it had better be pretty close
to the same at the bottom. I reached a point where I was pretty good at
doing that....could almost do it by just looking and smelling.
We tended to fire with a nuetral atmosphere through the early stages
of the firing (water burning, quartz inversion.) When at bisque temp I
would go into a moderated body reduction as I had been taught. I'd hold
this reduced atmoshpere for about thirty minutes before going back to a
nuetral one. There was no billowing smoke but I could "smell" the
reduction and I would adjust it so that I could see evidence of a
luminous flame.
I would then go back to a more nuetral atmoshpere and continue in
this manner until getting toward a cone 5 or a cone 9 depending upon
whether the firing was to be a cone 6 or cone 10. We did both to satisfy
the different desires of the faculty and students.
As the witness cone before the final cone in the firing was
beginning to bend I would put the kiln into what I thought was a nice
"heavy reduction." There would be a nice bright spikey yellowish flame
comeing out the top of the kiln as well as a flame licking through both
the upper and lower peep holes on the doors. There was a distinct smell
of carbon in the atmosphere. I could see the black smoke coming off the
flame at the top of the kiln. But it was not "billowing."
Like I said before this is how I was taught and was able to fire the
kiln consistently and evenly using the method. I must have fired the
thing several hundred times before I left. We fired to get the results
we were after.
Since then I have been told that this probably was a case of "over
reduction." That is my question. If the glazes seem to be doing well
(admittedly we did not subject them to the types of tests that Ron and
John advocate and I now practice) and the results are as desired what is
it exactly that constitues a case of too much reduction.
Thanx for any and all comments
Craig Dunn Clark
619 East 11 1/2 st
Houston, Texas 77008
(713)861-2083
mudman@hal-pc.org
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