Joyce Lee, Jim Lee on fri 7 nov 97
If somebody could explain in simple terms the difference in oxidation
and neutral when firing in a reduction kiln, I would be most
appreciative. My firing instructions tend to switch terminology from
one to the other as if they were the same step, but there must be a
difference, right? Thank you as always.
Joyce
In the Mojave
WardBurner on sat 8 nov 97
Joyce asked;
<<<and neutral when firing in a reduction kiln, I would be most
appreciative. >>>>>
A neutral atmosphere is pretty much next to impossible to obtain in a gas
fired kiln. Neutral means nothing is changing in the atmosphere of the kiln.
This is far from what is happening. Combustion is a violent process at the
molecular level and releases quite a bit of energy (heat) and by products
(water vapor, carbon dioxide, carbon monmoxide, nitrous oxide, ect.) An
oxidation atmosphere, on the other hand, is one where there is an excess of
oxygen (one of the main components of combustion). Here's the shock for most
people;
You can not oxidize in an electric kiln. Oxidation firing in an electric kiln
is a misconception. What everyone wrongly refers to as oxidation is really a
neutral atmosphere. Nothing's really going on except the atmosphere just gets
hotter along with the ware.
An electric kiln will give you a neutral firing.
A gas kiln will give you a reduction firing, a stoichiometric firing, or an
oxidation firing. A stoichiometric ratio is achieved when there is perfect
combustion....no excess oxygen (oxidation) or a deficit of oxygen (reduction).
Some people mistakenly refer to a stoichiometric atmosphere as a neutral
atmosphere.
For new folks on the list, we've been through this before....so there's no
reason to start an argument over this. If that much loved (and maybe famous)
teacher of your's called an electric firing "oxidation", they were wrong and
didn't know it.
Marc Ward
Ward Burner Systems
PO Box 333
Dandridge, TN 37725
USA
423.397.2914 voice
423.397.1253 fax
wardburner@aol.com
Vince Pitelka on sun 9 nov 97
>A neutral atmosphere is pretty much next to impossible to obtain in a gas
>fired kiln. Neutral means nothing is changing in the atmosphere of the kiln.
>A gas kiln will give you a reduction firing, a stoichiometric firing, or an
>oxidation firing. A stoichiometric ratio is achieved when there is perfect
>combustion....no excess oxygen (oxidation) or a deficit of oxygen (reduction).
>Some people mistakenly refer to a stoichiometric atmosphere as a neutral
>atmosphere.
>For new folks on the list, we've been through this before....so there's no
>reason to start an argument over this. If that much loved (and maybe famous)
>teacher of your's called an electric firing "oxidation", they were wrong and
>didn't know it.
Marc -
I certainly respect your expertise, and as everyone on this list knows, I
feel strongly about people using correct terminology. But when certain
terminology is used for a long enough period of time and is accepted into
standard usage, it is not worth it trying to change it. Such is obviously
the case with several terms which have been extensively discussed on this
list.
In this situation, no one is going to stop using the term "neutral" and
switch to "stoichiometric." Potters and teachers I have known over the last
few decades have always used the term "neutral" to refer to that
middleground between clearly oxidizing and clearly reducing. The atmosphere
may not be truly neutral, in a scientific sense, since it is chemically
violent and constantly changing, as you point out, but "neutral" still seems
the best term for the situation. Similarly, the term "oxidation" has been
widely used for all firings which are not specifically reducing. A closed
electric kiln firing is not really an oxidation firing, but what about a
firing in a kiln equipped with an exhaust system which keeps a small but
steady flow of fresh air coming through the kiln. Wouldn't that be a true
oxidation firing??
In the end, a true oxidation firing in a gas kiln and almost any firing in
an electric kiln both result in clean bright colors characteristic of
oxidation firings. So it seems to me that there is little point in being
too strict about scientific definitions in this situation.
But I am always thirsty for new information on kilns and firing, and I
appreciate your generosity in sharing your expertise.
- Vince
Vince Pitelka - vpitelka@DeKalb.net
Home 615/597-5376, work 615/597-6801, fax 615/597-6803
Appalachian Center for Crafts
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
Michael W Greenfield on tue 11 nov 97
Here's a question then. In an electric kiln equipped with one of the new
"hoodless" ventilation systems that actually draw fresh room air into the
kiln (i.e. Skutts Enviro-vent). Wouldn't that remove the neutral
environment and replace it with an one rich in oxygen?
mike
On Sat, 8 Nov 1997 17:29:14 EST WardBurner writes:
>----------------------------Original
>message----------------------------
>Joyce asked;
>
><<<>oxidation
>and neutral when firing in a reduction kiln, I would be most
>appreciative. >>>>>
>
>A neutral atmosphere is pretty much next to impossible to obtain in a
>gas
>fired kiln. Neutral means nothing is changing in the atmosphere of the
>kiln.
>This is far from what is happening. Combustion is a violent process at
>the
>molecular level and releases quite a bit of energy (heat) and by
>products
>(water vapor, carbon dioxide, carbon monmoxide, nitrous oxide, ect.)
>An
>oxidation atmosphere, on the other hand, is one where there is an
>excess of
>oxygen (one of the main components of combustion). Here's the shock
>for most
>people;
>
>You can not oxidize in an electric kiln. Oxidation firing in an
>electric kiln
>is a misconception. What everyone wrongly refers to as oxidation is
>really a
>neutral atmosphere. Nothing's really going on except the atmosphere
>just gets
>hotter along with the ware.
>
>An electric kiln will give you a neutral firing.
>
>A gas kiln will give you a reduction firing, a stoichiometric firing,
>or an
>oxidation firing. A stoichiometric ratio is achieved when there is
>perfect
>combustion....no excess oxygen (oxidation) or a deficit of oxygen
>(reduction).
>Some people mistakenly refer to a stoichiometric atmosphere as a
>neutral
>atmosphere.
>
>For new folks on the list, we've been through this before....so
>there's no
>reason to start an argument over this. If that much loved (and maybe
>famous)
>teacher of your's called an electric firing "oxidation", they were
>wrong and
>didn't know it.
>
>Marc Ward
>Ward Burner Systems
>PO Box 333
>Dandridge, TN 37725
>USA
>423.397.2914 voice
>423.397.1253 fax
>wardburner@aol.com
>
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