Janet H Walker on wed 16 oct 96
I have a box of cones that I suspect of having somehow "gone bad".
They are Orton large cone 6. When I surround them on either side
with Orton large cone 5 and 7, I get peculiar results. The 5 drops
OK and then the 7 bends and the 6 stays stiff upright or sometimes
twists a little to one side. According to the pyrometer, the temp
is going to around 1200C (with 60c/hr rise for the last 3 hr). I've
tried some self-supporting ^6 cones elsewhere in the kiln and they
seem to indicate that I'm getting at least part way to ^6. (Not all
the way down.) The literature from Orton does not mention any
requirements for storage conditions. In particular, it says that
the humidity is NOT important. Anyhow, here I am with this box of
cones, stored exactly with the others and acting very peculiar. Is
this anomaly something that others know about? or was I just lucky?
Any explanations?
While I'm asking about cones, could someone recommend a good
treatise on heat-work? I'm trying to understand how long to soak.
If I'm trying to reach ^6 but I soak for 45 minutes is that going to
be enough to turn it into ^7? Is there some kind of formula for
determining how much more time is equivalent to how much more
temperature? I assume there is some kind of limit somewhere (after
all, leaving a piece of wood at 100 degres for a very long time never
causes it to spontaneously combust...)
Many thanks for help, advice, etc with either issue.
Jan Walker
Fun & Functional Arts
Cambridge MA USA
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