Snail Scott on mon 4 nov 02
At 08:10 PM 11/4/02 -0600, Vince wrote:
>...If we are checking cones, I am assuming we are talking about
>a gas kiln. Unless a kiln is being fired in oxidation, then air will not
>enter the spyholes when you remove the plugs...
This is very true, to the extent that gas kilns being
fired in reduction will tend to have a bit of back-
pressure against the peepholes. (I should have been
more specific.) Still, I don't see what checking
cones has to do with gas versus electric firing. I
use cones in an electric kiln, too, same as in a
gas kiln. How else would I know when to soak, slow-
cool or shut down, or whether it's firing evenly?
I'll let the kiln-sitter shut it off with bisque,
but not with any firing where the temperature really
matters.
-Snail
vince pitelka on mon 4 nov 02
> It's not good to subject your cones to repeated
> blasts of cold air from an open peephole; it
> distorts their accuracy, later.
Snail -
Your advice on Clayart is generally so impeccably correct, but the above is
questionable. If we are checking cones, I am assuming we are talking about
a gas kiln. Unless a kiln is being fired in oxidation, then air will not
enter the spyholes when you remove the plugs. So the only time the above is
true is when someone is firing in oxidation. As you know, most people who
have gas kilns fire reduction, with a slight partial reduction atmosphere
from body reduction through the rest of the firing, except for perhaps a
brief oxidation cleanup after the cones are down. So, during most of the
period when we would be checking the cones, there is back pressure within
the kiln, and when the spyhole plugs are removed, gases/flames come out.
Best wishes -
- Vince
Vince Pitelka
Appalachian Center for Crafts
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
Home - vpitelka@dtccom.net
615/597-5376
Work - wpitelka@tntech.edu
615/597-6801 ext. 111, fax 615/597-6803
http://www.craftcenter.tntech.edu/
Ned Ludd on tue 5 nov 02
Hi Vince and Snail
Whenever, around peak temperature, I check the cones, my gas kiln
_needs_ to be in oxidation or at least neutral. Or I can barely see
them. Reduction and cone ten temperature are a combo that makes my
cones practically invisible. So I stop reduction momentarily just to
get a good view of the cones.
Therefore there is no or almost no back pressure at that point, and
perhaps indrawn cold air could affect the cones, as Snail suggests.
best
Ned
>At 08:10 PM 11/4/02 -0600, Vince wrote:
>>...If we are checking cones, I am assuming we are talking about
>>a gas kiln. Unless a kiln is being fired in oxidation, then air will not
>>enter the spyholes when you remove the plugs...
>
>Snail replies:
>This is very true, to the extent that gas kilns being
>fired in reduction will tend to have a bit of back-
>pressure against the peepholes. (I should have been
>more specific.) Still, I don't see what checking
>cones has to do with gas versus electric firing. I
>use cones in an electric kiln, too, same as in a
>gas kiln. How else would I know when to soak, slow-
>cool or shut down, or whether it's firing evenly?
>I'll let the kiln-sitter shut it off with bisque,
>but not with any firing where the temperature really
>matters.
>
> -Snail
>
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