primalmommy on tue 2 apr 02
Electric kiln question: I fired a load in a big evenheat kiln, and
decided for a change (it was a cold night) to fire with all the
peepholes closed like the manual suggests. I figured it would help with
slow cooling. It took longer than usual for the kilnsitter to pop after
reaching full power (I set it to get to 100% in 8 hours.) Does lack of
air circulation cause an electric kiln to "stall" like fuel kilns?
When the kiln sitter shut it off (I was listening to the baby monitor
from the house) I went out turned it back on at 20% for an hour or so,
again trying to slow the cooling in a very unscientific way. SOme of the
glazes came out pretty nicely, a few seemed underfired.
Here's the mystery: I had a 6 and a 7 cone on each shelf, and they seem
to have bent to an equal degree: halfway for the top shelf, less for the
middle, maybe a quarter for the bottom. I knew that a ^6 kilnsitter shut
off would be cooler than ^6, but why the hell would me ^7 be the same
shape as ^6? They are identical. Shouldn't ^6 be touching before ^7
starts to bend?
Any opinions would be welcomed.
Yours, Kelly in Ohio
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Dannon Rhudy on wed 3 apr 02
>
..... mystery: I had a 6 and a 7 cone on each shelf, and they seem
>to have bent to an equal degree:...why the hell would me ^7 be the same
>shape as ^6? They are identical. Shouldn't ^6 be touching before ^7
>starts to bend?......
Well, Kelly - remember that heat work affects the cones. Not
just the temp, but also the time. I often have cones 8 and 9
bending in unison, with 10 and 11 not far behind. The degree
difference is small, and the rise per hour affects everything
too. For some interesting comparisons look at the cone charts
in the back of Susan Peterson's Craft and Art of Clay.
regards
Dannon Rhudy
Frederich, Tim on wed 3 apr 02
Kelly,
Cone 6 and cone 7 are very close together and at a very slow heating rate
cone 7 will tend to come down right after cone 6. They may look like they
came down together but you will find that there is probably more glass
formation in the cone 6. Under normal conditions, cone 7 should be starting
before cone 6 has touched the shelf. This is true of almost all of the
cones. The next higher cone will usually start to deform before the lower
cone has slumped to the shelf. I hope this answers your question.
Best regards,
Tim
-----Original Message-----
From: primalmommy [mailto:primalmommy@IVILLAGE.COM]
Sent: Wednesday, April 03, 2002 12:48 AM
To: CLAYART@LSV.CERAMICS.ORG
Subject: cone mystery
Electric kiln question: I fired a load in a big evenheat kiln, and
decided for a change (it was a cold night) to fire with all the
peepholes closed like the manual suggests. I figured it would help with
slow cooling. It took longer than usual for the kilnsitter to pop after
reaching full power (I set it to get to 100% in 8 hours.) Does lack of
air circulation cause an electric kiln to "stall" like fuel kilns?
When the kiln sitter shut it off (I was listening to the baby monitor
from the house) I went out turned it back on at 20% for an hour or so,
again trying to slow the cooling in a very unscientific way. SOme of the
glazes came out pretty nicely, a few seemed underfired.
Here's the mystery: I had a 6 and a 7 cone on each shelf, and they seem
to have bent to an equal degree: halfway for the top shelf, less for the
middle, maybe a quarter for the bottom. I knew that a ^6 kilnsitter shut
off would be cooler than ^6, but why the hell would me ^7 be the same
shape as ^6? They are identical. Shouldn't ^6 be touching before ^7
starts to bend?
Any opinions would be welcomed.
Yours, Kelly in Ohio
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