Snail Scott on sun 5 nov 06
At 11:55 AM 11/4/2006 -0500, Sandi wrote:
>...the diagram in the book
>shows that the target cone should be draped over but not touching the shelf,
>so does this mean I overfired again? Unfortunately, I didn't have an 03 or
>05 cone in there.
The difference between almost touching and
actually touching is almost nil in terms of
temperature. I doubt you overfired enough to
make any detectable difference at all. As for
what's correct: that depends on your results.
We so often talk about firing to ^6 or some
other cone as though we were landing the space
shuttle, where if it's not spot-on then it's
WRONG!!!
In fact, though we identify clays or glazes as
^6, or ^04 or whatever, it's more like saying
"My dog is 4 years old". Their birthday might
have been four months ago, but saying "4" is
close enough - it just means "closer to that
than to any other whole number."
So, your particular materials may actually
need a 'hard ^04' or a 'soft ^04' - a little
hotter or cooler than the theoretical 'perfect
^04'. Learn what the materials like, then
shut down (or start your soak or cool-down or
whatever) at whatever point they like best.
Point-just-touching-the-shelf is the official
manufacturer's recommendation for hitting the
exact rated cone number. (This is based on the
assumption that your cone pack doesn't have
your cone on top of 1/2" of clay, of course.)
This is the 'exact reading', but if your clay
does best a little cooler, then shut it down
when it's at '9:00', or when just starts to
tip, or when ther next higher cone starts to
tip if you want it hotter. (Don't try to get
an acurate reading after it touches the shelf -
it quits bending evenly at that point.)
>...I really need to do a glaze firing tomorrow, so I'm
>thinking if I want a ^6 firing, I should set the control for a ^5.5. The
>vent slot on the Vent Sure is 90% open now.Will my ^6 clays still mature
>properly? I do have witness cones 5,6&7.
Can you start your firings at a time when you
can be there for the finish? It's not possible
to overfire if you are there, and then you can
really see what's going on.
-Snail
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