mariko cruse on sun 24 jun 01
Dear Snail,
Thank you for your response. I am afraid I did not make myself clear as =
to what I wanted to know. Being a neophyte, suppose I want to emulate a =
particular bisque cone based on the discussions we had yesterday. =
Suppose I chose Cone 04. In my kiln Cone 05 bends all the way down =
shortly before the kiln sitter 04 trips. But a regular Cone 04 to bend =
down to 3 o'clock position, it will probably take at least 30 min. after =
the kiln sitter trips. Suppose I choose the kiln sitter, am I in =
accordance with the Cone 04 as was advised? I realize that the ultimate =
decision rests on me, but when numbers are used to represent and discuss =
the differences, I would like to be able to assume certain =
universalities in the interpretation of the numbers.. Where did I go =
wrong? I appreciate your comment and thank you. Mariko=20
william schran on mon 25 jun 01
Mariko - Go by the large witness cone on the kiln shelf.
Bill
John Hesselberth on mon 25 jun 01
on 6/24/01 11:20 PM, mariko cruse at marikocruse@MEDIAONE.NET wrote:
Suppose I=20
> chose Cone 04. In my kiln Cone 05 bends all the way down shortly before =
the
> kiln sitter 04 trips. But a regular Cone 04 to bend down to 3 o'clock
> position, it will probably take at least 30 min. after the kiln sitter tr=
ips.
> Suppose I choose the kiln sitter, am I in accordance with the Cone 04 as =
was
> advised? I realize that the ultimate decision rests on me, but when numb=
ers
> are used to represent and discuss the differences, I would like to be ab=
le to
> assume certain universalities in the interpretation of the numbers.. Wh=
ere
> did I go wrong? I appreciate your comment and thank you. Mariko
>=20
Hi Mariko,
The accepted reference point for any cone is when a large cone of that
number bends to somewhere between about 4 o'clock and tip touching. Kiln
Sitters=AE are well known to give something different readings in most cases.
Part of that depends on how you have calibrated the sitter, part depends on
whether you are using a small cone or a bar and part just depends! You hav=
e
to either cross calibrate your Kiln Sitter with large cones (e.g. you might
find that cone 02 in your sitter equals large cone 04) or (like many of us
do) just use the Kiln Sitter as a safety backup device and shut your kiln
off by watching cones.
Kiln Sitter calibration also drifts with time and you will have to regularl=
y
recalibrate it. As long-time members of Clayart know, I believe sitters ar=
e
an acceptable way to shut off a bisque kiln, but I would never trust one fo=
r
a glaze firing. For a glaze firing I put large cones in front of every
peephole and monitor the firing very closely. Most any kiln can also be at
different temperatures by 1-2 cones on different shelves. Learning how you=
r
kiln behaves and learning to fire it the way you want is part of learning
the craft of pottery. It takes quite a while, but you will be repaid many
times over by doing it well.
Regards, John
Web site: http://www.frogpondpottery.com Email: john@frogpondpottery.com
"The life so short, the craft so long to learn." Chaucer's translation of
Hippocrates, 5th cent. B.C.
Snail Scott on mon 25 jun 01
At 11:20 PM 6/24/01 -0400, you wrote:
..In my kiln Cone 05 bends all the way down shortly before the kiln sitter
04 trips. But a regular Cone 04 to bend down to 3 o'clock position, it will
probably take at least 30 min. after the kiln sitter trips. Suppose I
choose the kiln sitter, am I in accordance with the Cone 04 as was
advised?... Mariko
The simple answer is: The witness cone is nearly
always more accurate than the sitter cone.
For a bisque, the 1/2-cone difference you describe
is very minor, and I wouldn't worry much about the
discrepancy. "Close enough for jazz."
For a glaze firing, it may be more important,
depending on the glazes you use, and it may be
worth your trouble to recalibrate your sitter
to coincide more closely. Or not. If you prefer
to fire by witness cones, and use your sitter
mainly as a failsafe, just put a higher cone in
the sitter, so it doesn't trigger first.
There was a sitter-calibration thread recently,
so I won't go into detail, but templates are
available from most suppliers.
-Snail
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