Anne K. Wellings on mon 6 may 02
Tim at Orton helped me with my question about a self-supporting witness
cone which did not melt properly, resulting in overfiring the bottom of
the kiln. The top part of the cone did not appear vitrified and had not
arched as usual, while the bottom part looked normal, and the cone had
bent at the base only.
Tim gave me much useful advice about firing my electric kiln. But it
sounds like the most significant factor in this instance was probably
that I placed the cone too close to the peephole, causing a draft which
kept the outside of the top part of the cone too cool to allow the proper
heatwork to take place. Blowing on the cones through the peephole could
have the same effect, he said.
This had never happened before in 2 years of firing this kiln. But I
guess I had placed the cone a little closer than usual to allow space for
one more pot on that shelf. Something to be aware of!
Anne
Orchard Valley Ceramics Arts Guild on tue 7 may 02
Anne,
Funny you should mention this!
I was having a heck of a time calibrating the electronic controller on
my new kiln. The bottom shelf was consistently a cone behind the
other shelves, no matter how I adjusted the thermocouple offsets.
Turns out the cones were too close to the peepholes. The bottom
peephole draws a lot of cool air from outside the kiln, while the others
tend to exhaust hot air --- this is why the cones on the bottom shelf
wouldn't go down.
Moving the cones to the center of the kiln showed that it had been
firing perfectly all along.
By the way - I assume that work placed to close to the bottom
peephole would suffer from the same effect. I now leave a "safe
zone" around the peephole, and I placed a shelf support in front
of it to break up the airflow.
>Tim at Orton helped me with my question about a self-supporting witness
>cone which did not melt properly, resulting in overfiring the bottom of
>the kiln. The top part of the cone did not appear vitrified and had not
>arched as usual, while the bottom part looked normal, and the cone had
>bent at the base only.
>
>Tim gave me much useful advice about firing my electric kiln. But it
>sounds like the most significant factor in this instance was probably
>that I placed the cone too close to the peephole, causing a draft which
>kept the outside of the top part of the cone too cool to allow the proper
>heatwork to take place. Blowing on the cones through the peephole could
>have the same effect, he said.
>
>This had never happened before in 2 years of firing this kiln. But I
>guess I had placed the cone a little closer than usual to allow space for
>one more pot on that shelf. Something to be aware of!
>
>Anne
Arnold Howard on tue 7 may 02
Witness cones are also very difficult to see when placed close to
the peepholes. For easier viewing, the ideal distance between cones
and the peepholes is about 12".
Arnold Howard
Paragon Ind. Inc.
--- Orchard Valley Ceramics Arts Guild
wrote:
> Anne,
>
> Funny you should mention this!
>
> I was having a heck of a time calibrating the electronic
> controller on
> my new kiln. The bottom shelf was consistently a cone behind the
> other shelves, no matter how I adjusted the thermocouple offsets.
>
> Turns out the cones were too close to the peepholes. The bottom
> peephole draws a lot of cool air from outside the kiln, while
> the others
> tend to exhaust hot air --- this is why the cones on the bottom
> shelf
> wouldn't go down.
>
> Moving the cones to the center of the kiln showed that it had
> been
> firing perfectly all along.
>
> By the way - I assume that work placed to close to the bottom
> peephole would suffer from the same effect. I now leave a "safe
> zone" around the peephole, and I placed a shelf support in front
> of it to break up the airflow.
>
> >Tim at Orton helped me with my question about a self-supporting
> witness
> >cone which did not melt properly, resulting in overfiring the
> bottom of
> >the kiln. The top part of the cone did not appear vitrified and
> had not
> >arched as usual, while the bottom part looked normal, and the
> cone had
> >bent at the base only.
> >
> >Tim gave me much useful advice about firing my electric kiln.
> But it
> >sounds like the most significant factor in this instance was
> probably
> >that I placed the cone too close to the peephole, causing a
> draft which
> >kept the outside of the top part of the cone too cool to allow
> the proper
> >heatwork to take place. Blowing on the cones through the
> peephole could
> >have the same effect, he said.
> >
> >This had never happened before in 2 years of firing this kiln.
> But I
> >guess I had placed the cone a little closer than usual to allow
> space for
> >one more pot on that shelf. Something to be aware of!
> >
> >Anne
>
>
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