Frederich, Tim on mon 1 apr 02
Good morning all,
I would like to thank Mel for jumping in. I do not look at Clayart on the
weekends since this is the only time that I get to work in the studio or
work on the house.
Small cones were developed by Orton around 1930- 1932, long before the
development of the kilnsitter or other kiln watching devices. Small cones
were also used as witness cones even though they are harder to see in the
kiln chamber. The reason that the equivalent temperature is different from
a large cone of the same number is the size of the cone and the heating
rate. Gravity allows the large cone to fall at a faster pace at a specific
heating rate. Small cones and large cones of the same number are made from
the same composition.
The weight of the kiln sitter rod will not make the cone bend earlier. The
cone still has to achieve a certain amount of temperature over a period of
time (heatwork) in order for deformation of the material to begin. The
weight of the rod used in the kilnsitter is a minor amount and is not
putting any major force on the cone itself if the kilnsitter is adjusted
correctly.
As other people on the list have said, please use witness cones to control
the firing. They are still the most accurate form of heatwork measurement
that we have.
Mel, tell Kerry that if cone 11 is melted then you have a cone11 firing and
not a cone 10 firing. I agree with you that cone 11 should be just starting
in order to have a cone 10 firing.
Best regards,
Tim
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