Linda Arbuckle on thu 2 jan 97
In response to some of the recent posts about cones behaving badly...
I'd second the advice to call Orton about the electric kiln problems.
In gas reduction firing, if you reduce your iron-bearing cones (usually the
lower temperature cones that look reddish), it effects the iron in surface
of the cones so that the cones will no longer read accurately. Have you
ever noticed when you kiln is a bit uneven, and you go into reduction at
(usually at 010 or so), the remaining cones seem to stay up for a long time,
then just vanish? They melt inside instead of bending gradually, and the
liquified cones "go" suddenly. Orton does sell low or no-iron cones for
reduction, I think, but I've never been anyplace that had them. Since the
hi-temp cones used to judge glaze done-ness don't have iron, they remain
accurate.
Perhaps one of the better chemists on the list can explain what the
phenomenon is with the reduced iron in the cones that makes the outside
"skin" over and not bend, but melt from inside? I'm out of my depth.
I assume that if you had localized reduction in an electric kiln (thru
burning out combustables in clay or wax, or armatures, etc. and/or lack of
enough oxygen) you might similarly affect cones in an electric kiln.
May the kiln gods/goddesses smile in '97.
Linda
Linda Arbuckle
Associate Professor, Graduate Coordinator
University of Florida, Box 115801
Gainesville, FL 32611-5801
e-mail: arbuck@nervm.nerdc.ufl.edu
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