Jon Pacini on fri 8 apr 05
Greetings All--- Hi Craig---you wrote--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---
When you’re reducing a kiln the pragmatic question is, how do the clay and
glazes perform? As long as everything is working Ok, you’re firing fine.
There are some pretty bizarre firing practices out there and yet some very
fine ware results from them. I doubt there is an “all encompassing” perfect
firing cycle anyway.
From a technical standpoint, black coring from inappropriate reduction will
weaken the body. You can also induce other clay and glaze faults by reducing
at various inappropriate times or by reducing ‘heavily’.
When I was in school, the firings were pretty much as you described your
instruction. Body reduction followed by neutral/oxidation then reduction
during the last couple of cones and then a brief cleanup period at the very
end. We fired in a West Coast up draught and rarely had problems. Looking
back on it, I attribute a lot of the success to very open, Buff, fireclay
based bodies, which were very prevalent here on the west coast at the time.
I’ve pretty much dropped the early body reduction part and don’t recommend
it unless it’s a necessity for some special effect you’re trying to achieve.
Copper Reds take special care, as do some Iron effects.
My reason for dropping the ‘body reduction’ cycle was because if you go back
to neutral/oxidation there after, I felt you pretty much would re-oxidize
what you had just reduced. So what’s the point in reducing in the first
place?
Also with the advent of tighter bodies, inadvertent heavy reduction or long
periods of reduction early on, becomes much more problematic. Tight bodies
tend to trap carbonates and sulfates in the body during reduction and then
later when these materials expand as gasses, they will express their
additional volume as bloats. If they do escape the body later in the firing,
they will many times cause pin holing or blistering of glazes.
By reducing a kiln solely near the end of the firing, the glaze and clay
surface get reduced, but the interior of the ware remains clean.
Theoretically you should get rid of the organics in the bisque, but marginal
bisque firing practices seem to insure that this stuff still ends up in a
lot of glaze firings. That’s a whole other topic though.
So in the end, in my opinion --- since you asked for it--- is that what ever
works to achieve the results you’re looking for is cool. But if you want to
avoid as many problems as possible, reduce as little as possible to achieve
those desired results.
Best regards
Jon Pacini
Clay Manager
Laguna Clay Co.
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