Jim Tabor on fri 2 apr 04
bruce freund wrote on the L&L controller thread:
"I think the chances of an over fire with a controller are fairly rare.."=
Heatwork from ramp and soak settings to a specific cone temp degree can c=
ause overfiring the ware and flattened cone(s). To reach the desired bend=
of the cone may require a lower peak temp setting than the cone value if=
the firing is slow (lower temp/hr rise and extended soak periods going u=
p and/or at the maturing temp). Fast firing may not give enough heatwork =
for desired results in the ware at the cone temp.
John H. also had some revealing images in his presentation at NCECA on th=
e effects of firing down (controlled cooling rates). He also said to prog=
ram your controller for better results than the automatic settings set by=
the factory for firing to a specific cone. When your equipment is in goo=
d condition, the cone will bend as expected in the automatic cone fire pr=
ogram (or at least mine does). However, I agree with John that it is not =
the best way to fire when you have a controller.=20
There are more reasons to program your firings than I want to go into now=
but others on the list may feel compelled to relate their experience. My=
basic take for multiple soak cycles involves burn out from dirty clays i=
n bisque, to even out the kilns temp (especially with dense heat sinking =
loads or uneven distribution of ware to space), and to reduce gassing tha=
t would create excess glaze bubbles or dimples in glazes.=20
Nail down a schedule that works best for your body/glaze system but don't=
pitch all the works that fail your expectations. Refiring has been menti=
oned in recent posts but understand that the fired glaze is a different m=
aterial than it was when fired the first time. Some glazes have a wider r=
ange of workability than others but many can be very disappointing when r=
efired at a lower, higher, or even the required temp. And then there are =
glazes that are greatly enhanced by refiring. Refire pots you would other=
wise put to the hammer to see how they change. You might discover somethi=
ng good from your experiment. At the risk of sounding a little crazy and =
unrelated to controllers, I fired a raku pot more than 30 times over a 15=
year period without ever getting a body crack and although it was differ=
ent from each post reduction, it looked good after ever firing. I wonder =
what would happen if I started another ritual piece in my regular firings=
?
Open up to the potential of heatwork using a combination of cones, firing=
schedules, and a collection of tests (notes too) from each firing. You m=
ay discover your good published ^6 glazes work even better at a real cone=
^7 or 8 with the new and improved slower ramp and hold firing programed =
at a ^5 temp setting. A dirty body will gas out better for fewer blemishe=
s and I imagine there will also be a better interface of body and glaze f=
rom the slower melt. I believe some good things happen from early soaks i=
n addition to soaks both at bisque and glaze firings.=20
Jim Tabor
Tulsa
=20
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