WardBurner@aol.com on wed 15 may 96
Hi,
I received this question from someone who had posted to the list and didn't
get an answer from any of us, so I thought I'd repost the Q along with my A.
the question: Is is possible (or practical) to do oxidation firings in a
gas kiln? Or am I limited to reduction glazes and clays. Sorry to sound so
dumb, but I'm self-taught and there are gaps in my base of knowledge. I
have a small electric kiln and may be needing a larger kiln, so I need to
decide if I should go with natural gas or a larger electric.
my answer to them: We just unloaded a cone 6 oxidation firing from our gas
kiln. That answers that... To be technical, you can't do an oxidation firing
in an electric kiln. Oxidation is a state that exists when you have more
oxygen available than is needed for complete combustion. Reduction is the
opposite, not enough oxygen for complete combustion. So when folks say they
fire oxidation in regards to electric, they are misinformed. They fire
electric. Nobody that I know of oxidizes a turkey for Thanksgiving. An
electric kiln heats a neutral atmosphere. There's nothing much going on in
there except radiational heating.
You might find that some of your glazes don't travel well from electric to
gas. But, all of them may be fine. You most likely will see no difference in
you clay.
Marc Ward
Ward Burner Systems
PO Box 333
Dandridge, TN 37725
423.397.2914 voice
423.397.1253 fax
wardburner@aol.com
Vince Pitelka on thu 16 may 96
Marc -
WHOA! An electric kiln is a neutral atmosphere, neither oxidizing nor
reducing??? I respect your level of knowledge, and appreciate all that you
post to the list, but I stumbled on this one. An electric kiln is not
hermetically sealed, so oxygen is always entering the kiln, and whenever an
atmosphere contains abundant free oxygen, it will oxidize any compound
chemically able to accept more oxygen atoms. And of course, heat greatly
accelerates the process. How about all this?
- Vince
Vince Pitelka - wkp0067@tntech.edu
Appalachian Center for Crafts - Tennessee Technological University
Smithville, TN
Bob Kavanagh on thu 16 may 96
I agree that due to the fact that there is oxygen just about everywhere we
might want to say that electric firings are oxidizing, but I think that is
not all there is to it. There is the common lanuage which we all use which
when we describe electric firings and I think we usually say electric is
oxidizing and so it's natural to continue to use this language because the
tradition is strong.
On the other hand, in a context in which one of our major points of
reference in firing is the reducing atmosphere, the words oxidation and
reduction get another set of meanings, related to the fact that we think of
them as opposites and in a context of burning something. A reducing
atmosphere occurs when we reduce the amount of oxygen normally used for
what we call (complete) combustion. In this context, an oxidizing fire
will always have a combustion component and is the state we usually think
of altering, if we want a reducing fire. In general we don't think of
electric firings as combustion firings in any conventional sense, so it
seems reasonable to say they are neither oxidizing nor reducing.
I wager that we'll continue to use both ways of talking even though they
appear to be contradictory.
Nils Lou on thu 16 may 96
Actually, I believe the electric firing of raw clay is slightly reducing
in the early stages of burning off organics when bisque firing. Any
firing of already bisqued work is probably neutral. Nils Lou
On Thu, 16 May 1996, Vince Pitelka wrote:
> ----------------------------Original message----------------------------
> Marc -
>
> WHOA! An electric kiln is a neutral atmosphere, neither oxidizing nor
> reducing??? I respect your level of knowledge, and appreciate all that you
> post to the list, but I stumbled on this one. An electric kiln is not
> hermetically sealed, so oxygen is always entering the kiln, and whenever an
> atmosphere contains abundant free oxygen, it will oxidize any compound
> chemically able to accept more oxygen atoms. And of course, heat greatly
> accelerates the process. How about all this?
> - Vince
> Vince Pitelka - wkp0067@tntech.edu
> Appalachian Center for Crafts - Tennessee Technological University
> Smithville, TN
>
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