Imbolchottie@AOL.COM on sun 16 nov 03
After two firings, almost back to back, I have some questions about a "False
Cone." I'm using a Keith gas updraft, about 50 cubic feet (shaky math skills
on that one). It has a total of 10 burners, 4 for the outer ring (corners)
and six for the inner ring. Why so many, I dunno.
I have come to ignore the bottom corner kiln pack since it is sitting almost
on top of a burner -- of course it is going to get hotter than the rest of the
kiln. I'm using a pyrometer (I think it's called) in the top peep hole until
2000, then I take it out and go by color and cone alone. My cone packs are
^5. ^6 and ^7 -- and as Ron suggested I have them spread out in the kiln to
check for uneven temperatures in firings.
From the firing on Tuesday you'd look at all the cone packs and say "He
overfired." (But he got some really great results, esp the Waterfall from MC6G)
All three of the cones were down. So today I sat on top of it like a mother
hen and I watched as the ^7 started falling AT THE SAME TIME as ^6, at one point
a little faster. I asked someone else in the studio and they said - "Oh,
false cone, ignore it." The cone lied to me, how dare it.
The vase project, first run came out with some great results - pin hole here
and there and an occasional dark spot, but I think that was a fragment that I
let slide in the screening of the glazes - I didn't want to add the ashes,
then screen them out - that would be silly. But the results gave me the gumption
to go ahead and glaze the other 40 vases. Cool down tonight and tomorrow,
Xmas on Monday afternoon.
Today while firing I did busy work - reclaiming old clay - and threw about 8
vases over a foot tall. Great thing about the vase project is that it got me
working on different shapes and now those shapes are coming out in larger
forms. Also started more mugs and working on handles and aiming for equal drying
times. Next on my shopping list is a styrofoam cool as a small damp box.
Also cast the first vase from my first mold (plaster and I have a long road ahead
of us I can tell and it ain't smooth sailing!) and that was fun - looks like
an instant archaeological find, but hey, first try, not bad.
False Cone, almost forgot why I wrote, is it an old cone? The box is lidless
but most of our cones are Orton so I am assuming this is also. I did make
sure they were stamped ^7 also. I doubled checked the cone packs and had
someone else check them just because I am a dunce at times, as well as dyslexic.
Man alive, in a few days you folks rack up the posts, I have some reading to
do. The jury has been out for a long time on Griffin Grip but I have enjoyed
the discussions.
Jonathan in Los Angeles
And I can't wait for the d -- m supermarket strike to be over with. I can
work around the food and the banking but the drugstore is gonna find me dipping
my finger in the Lithium carb before the month is out!
Snail Scott on sun 16 nov 03
At 12:20 AM 11/16/03 EST, you wrote:
>...the ^7 started falling AT THE SAME TIME as ^6, at one point
>a little faster...
With fast firings, the time factor needed to melt
the cones is a bit compressed, so tiny differences
like the angle of the cone in the pack can have a
larger relative effect.
Also, if the cones are close to the peephole, the
draft from frequent checking can hit one cone
more than its neighbors, cooling it and slowing
its drop.
Another effect is what's sometimes called 'cone
freeze' which doesn't happen as often as people
think, but is real. This seems to happen during
very long, slow firings, when the temperature
stalls out just below the cone temperature for
an extended time. (Probably not what's happening
in your case, though.)
Also, Orton has changed their formulations from
time to time, and if one of those cones is out
of an older batch, it may be calibrated a little
differently.
-Snail
Ron Roy on mon 17 nov 03
Hi Jonathan,
Hey - sounds like you are having too much fun down there - settle down and
suffer a bit like the rest of us.
The false cone advice is no good - if you can't trust your cones you are in
deep do do. And why do you take the pyrometer out at 2000 - they are very
handy for telling you how fast you are firing - which brings me to why the
cones went down together. Thats a sign - firing too fast - 100F for that
last 100F is still fast by me. When you see you target cone starting to
bend slow down to almost a stall - add more reduction if you have to - give
your kiln a chance to even out, the glazes a chance to smooth out and bond
with the clay. Those updrafts can be hard to control but slow is much
better than fast.
RR
>After two firings, almost back to back, I have some questions about a "False
>Cone." I'm using a Keith gas updraft, about 50 cubic feet (shaky math skills
>on that one). It has a total of 10 burners, 4 for the outer ring (corners)
>and six for the inner ring. Why so many, I dunno.
>
>I have come to ignore the bottom corner kiln pack since it is sitting almost
>on top of a burner -- of course it is going to get hotter than the rest of the
>kiln. I'm using a pyrometer (I think it's called) in the top peep hole until
>2000, then I take it out and go by color and cone alone. My cone packs are
>^5. ^6 and ^7 -- and as Ron suggested I have them spread out in the kiln to
>check for uneven temperatures in firings.
>
>From the firing on Tuesday you'd look at all the cone packs and say "He
>overfired." (But he got some really great results, esp the Waterfall from
>MC6G)
>All three of the cones were down. So today I sat on top of it like a mother
>hen and I watched as the ^7 started falling AT THE SAME TIME as ^6, at one
>point
>a little faster. I asked someone else in the studio and they said - "Oh,
>false cone, ignore it." The cone lied to me, how dare it.
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
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