Erin Hayes on fri 19 sep 97
Hello Vince, and Clayarters!
After requesting everyone's help with my failing Alpine, I made a list
of all the things recommended to me and started with the least expensive
and easiest. I had one last kilnload of summer student work, so one
chance to see what worked before waitng for fall quarter student work to
accumulate.
Both Nils Lou and Vince Pitelka recommended that I remove the kiln
shelf/baffle and radients which serve as the bag wall in Alpines. This
I did, and, crossing my fingers while I loaded, stacked the kiln with
work and lots of conepacks to test the heat distribution.
I will include conepack appearance and firing info at the end of this
post, so you can skip it if you want. Anyone wanting more nauseating
detail than this can write me directly.
(USUAL DISCLAIMERS APPLY FROM HERE ON)
It was a fine firing - more even than the kiln has ever been. The
bottom warmed up faster and stayed even throughout the firing. The top
shelf had only one cool spot - directly under the damper, and even that
was at temperature. The reduction was better too. Even our stubborn
clear glaze fluxed beautifully transparent.
I saw no ill effects in this first firing from removing the baffles.
The hottest zone was the middle of the kiln and the back of the bottom
shelf, which are the places it fired hottest originally, too.
All in all a dramatic change from Gadget's wildly uneven recent
firings. I will let you all know how it goes as I begin patching the
old girl. Those in a technical frome of mind can now proceed to the
firing info...
LOADING -
It was not an especially tight kilnload, but it was a full firing. Lots
of plates. I loaded the cones on the bottom shelf, about the middle of
the stack and at the top shelf. There was a single conepack at each
corner and in the middle of the shelf. The bottom front left pack was
in front of a peephole, as was the top right front. No guard cone was
used, unfortunately.
FIRING -
Started at 7am, down at 5:25. It was overfired because I expected the
bottom peep to show the most accurate cone reading. This was one of the
only two cool spots, so the top peep would have been more accurate. The
kiln was likely ready to be shut down at 5.
The pyrometers usually have read about 50 degrees lower than the cones
showed. In this firing, they were much more responsive, seeming to read
much more accurately, especially toward the end of the firing. The
pyrometer read 2375F at the bottom when the bottom peep showed Cone 10
bending. This turned out to be a little on the cool side compared to the
rest of the kiln, but it was better performance than before.
Body reduction was begun at 1:20 - at 1700F - with about 8" of flame at
the damper, and ended at 2:20. The kiln went into natural reduction
with about an 8 " flame about 3:25, so I let it go without adjustment
for Glaze Reduction. I neutralized the atmopsphere at 4:40.
CONE PACKS, BOTTOM SHELF -
Left Front pack has cone 10 bent to about 2 - 3 o'clock; cooler than
others (due to peep?)
Left Back has Cone 10 completely down with slightly rounded edges
Right Back has Cone 10 completely down with slightly rounded edges
Right Front has Cone 10 completely down with slightly rounded edges
Middle pack has Cone 10 completely bent with sharp edges
MIDDLE SHELF -
Left Front pack has Cone 10 flat with edges rounded but "10" still
easily readable
Left Back pack has Cone 10 flat with edges rounded but "10" still easily
readable
Right Back has Cone 20 flat with edges rounded and "10" nearly illegible
(hottest zone)
Right front pack has Cone 10 flat with edges rounded but "10" still
easily readable
Middle pack pack has Cone 10 flat with edges rounded but "10" still
easily readable
TOP SHELF -
Left front has Cone 10 completely down with slightly rounded edges
Left back has Cone 10 completely down with slightly rounded edges
Right Back has Cone 10 completely down with slightly rounded edges
Right Front has Cone 10 completely down with slightly rounded edges
Middle pack has Cone 10 bent to 2 0'clock (coolest zone)
The hottest zone was the middle shelf area, but all areas of the kiln
showed well-fluxed glazes and even reduction.
Erin.
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