Snail Scott on fri 23 aug 02
At 02:37 PM 8/23/02 -0000, you wrote:
>...When I finally opened the kiln
>this morning I found the cone 05 melted (as expected) but that the
>cone 04 had barely started to bend when the kiln shut off.=20
You mean that the witness cone 04 had just started to=20
bend, when the ^04 in the sitter shut off the kiln?
That's closer than most kilns, actually. A matter of=20
maybe 10=BAF at most. If you want it closer, you can=20
recalibrate your kiln sitter by moving the slider on=20
the deadfall flap so that the sitter cone has to bend=20
further before triggering the sitter to turn off.
I wouldn't bother, though. That's pretty dang close=20
already, and you scarcely need better accuracy than=20
that for a bisque.=20
For a glaze firing, you can put a higher cone in the=20
sitter to act just as a fail-safe. The witness cones=20
wil tell you when to turn the kiln off manually, and=20
the sitter will only shut it off if you aren't there=20
to do it yourself, to prevent overfiring.=20
With my kiln, and my (pretty thick) sculpture, a ^6=20
witness cone is about equal to a ^7 in the sitter. I=20
could tinker with it, but why bother? I know that a=20
^7 will get me the result I want. If it's a glaze that=20
prefers a slow cool, I put a ^8 in the sitter, to make=20
sure it doesn't trigger too soon, and I turn it down=20
manually when the witness cones say "^6".
>...Also, as the kiln was cooling
>down I could hear sounds coming from the kiln, but my pieces are not
>craked.
Everything makes little sounds in cooling; don't sweat=20
it.
=20
=20
-Snail
dreampotter2000 on fri 23 aug 02
Hi everyone:
I am fairly new to this message board and am posting for the first
time, even though I have been reading and learning a lot from all
your suggestions. I am a beginner, self taught potter. I have a
used Gare kiln (about 9 years old). This kiln has switches to start
each set of elements separately. The kiln also has a kiln sitter
with a backup timer. I have been using witness cones to verify that
it is firing to the correct temperature. Yesterday I tried bisquing
some pieces to cone 04 and the kiln shut off in 3 hours and 45
minutes. I had started the kiln with the first and second elements
on, then an hour later turned on the 3rd and 4th elements, and an
hour later turned on the 5th. (The kiln has a 6th switch to turn on
the top elements but in my tests the 6th elements are not turning on
so I had decided not to use them. As it is, my top shelf is lower
than that area in the kiln and I thought I would not need them. I
did not wait for the moisture to come out of the kiln since I was re-
firing some pieces already bisqued). When I finally opened the kiln
this morning I found the cone 05 melted (as expected) but that the
cone 04 had barely started to bend when the kiln shut off. Any
suggestions as to what I should do? Also, as the kiln was cooling
down I could hear sounds coming from the kiln, but my pieces are not
craked. Do elements make sounds as they cool down? Thank you in
advance for any suggestions you send my way.
Stephani Stephenson on fri 23 aug 02
Dreampotter wrote
"When I finally opened the kiln
this morning I found the cone 05 melted (as expected) but that the
cone 04 had barely started to bend when the kiln shut off. Any
suggestions as to what I should do? "
Dreampotter
you mentioned that you use witness cones as well as a cone in the
kilnsitter.
Which cone was in the kilnsitter, the cone 04 you refer to above? Or was
the cone 04 a witness cone
alongside the 05 cone which melted????
you can adjust the kilnsitter so that the shutoff is triggered by
either a slightly bent junior cone or a bar , or only triggered after
the junior cone or bar in the kilnsitter is 'bent ' significantly. The
adjustment occurs on the outside of the kilnsitter. A small screw ,
when loosened, will allow you to move a bar up or down. this bar is
hooks up with the rod mechanism... (sorry, my terms may be vague here)
and determines how much a cone will bend before tripping the shutoff of
the kiln.
one way to fire is to adjust the kilnsitter so that only a slight cone
bend releases the shutoff. For a cone 04 firing you would insert an 03
cone , knowing that the kiln would shutoff as soon as the 03 started
to bend, and ensuring that you have truly gone through the 04 range.
this is preferable to adjusting the kilnsetter so that the 04 bends
significantly (very deep 'u' or 'v' shape) before the shutoff occurs.
the reasoning behind this, is that more shutoff problems happen in the
latter case. the cone 04 is likely to melt and interfere with the rod
dropping which allows the kiln to shut off. This can cause overfiring.
so a soft 03 is less problematic over time, and ensures you are getting
'through' the cone 04 temps not just 'to ' them.
when you do find just the right 'position' for this bar. Scratch a line
in it to mark the spot, so that if you ever have to readjust it the
future you will know where to set it.
if you had a cone 04 in the sitter and a cone 05 and 04 witness cones
sitting together side by side, this would explain why 05 might have
dropped and 04 didn't.
also with a quick firing and a quick shutoff, the kiln would not be
soaking or 'working' at the 04 temp very long, and thus not as likely
to drop that particular cone.
as for the sounds coming from the kiln on cooling....is this a well
insulated kiln? how long is the cooling? are the sounds like 'pinging'
sounds? if kiln cools quickly this is likely the sound of the pots, not
the elements. that's a whole other topic, but read up on
silica/cristobalite/cooling!
best wishes
Stephani Stephenson
Carlsbad/Encinitas CA
steph@alchemiestudio.com
Arnold Howard on mon 26 aug 02
It is normal for the kiln to make faint popping noises as it cools.
The firebricks expand so much that the kiln is actually taller when
it fires. The noises are from the kiln contracting in size as it
cools.
Have you checked the element lead wires and switch for the top
element? Often, a kiln repair is simple and fairly inexpensive.
Arnold Howard
Paragon
--- dreampotter2000 wrote:
I have a
> used Gare kiln (about 9 years old). This kiln has switches to
> start
> each set of elements separately. I had started the kiln with the
first and second
> elements
> on, then an hour later turned on the 3rd and 4th elements, and an
> hour later turned on the 5th. (The kiln has a 6th switch to turn
> on
> the top elements but in my tests the 6th elements are not turning
> on
> so I had decided not to use them. As it is, my top shelf is
> lower
> than that area in the kiln and I thought I would not need them.
Also, as the kiln was
> cooling
> down I could hear sounds coming from the kiln, but my pieces are
> not
> craked. Do elements make sounds as they cool down? Thank you in
> advance for any suggestions you send my way.
>
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