Tammy Young on tue 8 oct 02
I have had my manual kiln for 1 month now and keep experiencing inconsistent
firings. I use Orton self-supporting cones. My small cones (used to trigger the
kiln-sitter) seem to be bending before my test cones causing my kiln to
prematurely shut off. Yesterday I fired small beads to cone 6 and used two test
cones also 6 in bottom and top of kiln - my kiln shut off and the test cones
were still straight as if they'd just come out of the box. My firing schedule
is usually as follows: low 2 hrs, med 3 hrs and high 3 hrs. Yesterday my kiln
never reached the full 8 hrs as the small cone bent within 6 hrs shutting my
kiln off. I understand that small cones require more heat to bend than the
larger cones. If this is the case why then have my large cones not bent before
my small cone?
On some days my firings are fine and the very next day using the same # cone
the above will happen. Do you think I need to change my firing schedule? Or is
it just my new kiln being broken in? Or perhaps when I am firing to cone 6 I
should use a small cone 7 in the kiln-sitter so my large cones have a chance to
reach temperature. I always fire the same amount of ware and all about the same
size.
Thanks in advance for any comments.
Tammy Young
Lily Krakowski on wed 9 oct 02
A quick laundry list, because I do not know the specifics really, despite
description so clear and lucid it would make an artist's statement!!
1. New kilns ( this I believe from Emmanuel Cooper) often fire differently
from what they will once they are settled in (my term). so it may simply be
that.
2. In my experience with the old style cone (not self-supporting) I needed
a higher cone number in the sitter. I do not know about the self-supporting
ones but have no reason to think it is other.
3. I have been using bars instead of baby (junior) cones in my sitter
because the way the little cone sits in the sitter affects its deformation.
Closer to the tip, cooler. Closer to the end, hotter. This is great when
it is what you want..... but if it ain't...
4. Shelves and kiln furniture affect the firing. I seem to recall that 1/2
the heat is aborbed by the shelves and such. Therefore the more shelves the
longer it will take, but also, in my observation when a kiln is densely
packed with lots of shelves it cools more slowly, affecting glaze results.
5. The circulation of air does affect kiln firings. I keep my lowest shelf
a good 1-2 inches off the floor, leave about an inch from walls, and between
half shelves--which I try to stagger. Not recommendation, but works for me.
Tammy Young writes:
> I have had my manual kiln for 1 month now and keep experiencing inconsistent
> firings. I use Orton self-supporting cones. My small cones (used to trigger the
> kiln-sitter) seem to be bending before my test cones causing my kiln to
> prematurely shut off. Yesterday I fired small beads to cone 6 and used two test
> cones also 6 in bottom and top of kiln - my kiln shut off and the test cones
> were still straight as if they'd just come out of the box. My firing schedule
> is usually as follows: low 2 hrs, med 3 hrs and high 3 hrs. Yesterday my kiln
> never reached the full 8 hrs as the small cone bent within 6 hrs shutting my
> kiln off. I understand that small cones require more heat to bend than the
> larger cones. If this is the case why then have my large cones not bent before
> my small cone?
> On some days my firings are fine and the very next day using the same # cone
> the above will happen. Do you think I need to change my firing schedule? Or is
> it just my new kiln being broken in? Or perhaps when I am firing to cone 6 I
> should use a small cone 7 in the kiln-sitter so my large cones have a chance to
> reach temperature. I always fire the same amount of ware and all about the same
> size.
> Thanks in advance for any comments.
> Tammy Young
>
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Lili Krakowski
P.O. Box #1
Constableville, N.Y.
(315) 942-5916/ 397-2389
Be of good courage....
Arnold Howard on wed 9 oct 02
Tammy, to make the witness cones bend all the way, use a hotter
cone in the Kiln Sitter than you use on the shelf. The Kiln Sitter
cone often does not match the cones on the shelf. It varies from
one kiln to the next.
I understand that you are also getting inconsistent firing results
with the Kiln Sitter.
Do you place the small cone on the cone supports the same way every
time?
Do you use a thin layer of kiln wash on the cone supports and
actuating rod?
Are you careful not to place the cone right up against the
porcelain tube? Doing so can affect the bending of the cone,
because the cone can stick to the tube.
Have you adjusted the Kiln Sitter with the firing gauge?
Does the actuating rod move freely inside the porcelain tube?
With best wishes,
Arnold Howard
Paragon Industries, Inc.
--- Tammy Young wrote:
> I have had my manual kiln for 1 month now and keep experiencing
> inconsistent
> firings. I use Orton self-supporting cones. My small cones (used
> to trigger the
> kiln-sitter) seem to be bending before my test cones causing my
> kiln to
> prematurely shut off. Yesterday I fired small beads to cone 6 and
> used two test
> cones also 6 in bottom and top of kiln - my kiln shut off and the
> test cones
> were still straight as if they'd just come out of the box. My
> firing schedule
> is usually as follows: low 2 hrs, med 3 hrs and high 3 hrs.
> Yesterday my kiln
> never reached the full 8 hrs as the small cone bent within 6 hrs
> shutting my
> kiln off. I understand that small cones require more heat to bend
> than the
> larger cones. If this is the case why then have my large cones
> not bent before
> my small cone?
> On some days my firings are fine and the very next day using the
> same # cone
> the above will happen. Do you think I need to change my firing
> schedule? Or is
> it just my new kiln being broken in? Or perhaps when I am firing
> to cone 6 I
> should use a small cone 7 in the kiln-sitter so my large cones
> have a chance to
> reach temperature. I always fire the same amount of ware and all
> about the same
> size.
> Thanks in advance for any comments.
> Tammy Young
>
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Brad Sondahl on wed 9 oct 02
You can trust the standing cones over the kiln sitter. It may need a
slight adjustment to read accurately. This can be done with the little
metal gadget that came with the sitter, or by just slightly extending
the metal tip on the part that flips down, since you are underfiring.
If you can see the cones through the peepholes, and you see that they
are still standing when the kiln has shut off, you can restart your
kiln by lifting the part that flips down slightly, and pushing the
button in again. This will help you get to your desired cone, with
frequent vigilance. When you judge the kiln done, just push down on the
flipper to shut it off.
Another option is using minibars instead of small cones. They melt at a
slightly higher temperature in the setter than equivalent cones. It
also may work using a cone 7, but you would want to monitor through the
peeps towards the end. The length of firing isn't critical-- a new kiln
can easily reach cone 6 in less than 8 hours, and shouldn't affect
quality of glazes significantly.
Brad Sondahl
--
For original art, music, pottery, and literature, visit my homepage
http://home.earthlink.net/~bsondahl/
Pottery sales page http://sondahl.freeyellow.com
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Snail Scott on wed 9 oct 02
At 03:42 PM 10/8/02 +0000, you wrote:
>...My small cones (used to trigger the
>kiln-sitter) seem to be bending before my test cones causing my kiln to
>prematurely shut off.I understand that small cones require more heat to
bend than the
>larger cones. If this is the case why then have my large cones not bent
before
>my small cone?
Not true. You may just need to recalibrate your
sitter. Also, if your witness cones are close to
center of the shelf or surrounded by work, they
will not heat as quickly as the sitter cone. I
take it for granted that there will always be a
discrepance between the sitter cone and the
witness cones, so it the temperature needs to be
precise, I shut down manually when the witness
cone it right, and use the sitter as a failsafe
only. For bare stoneware, I generally put a ^7
in the sitter to give me a ^6 on the witness
cone, and let the sitter shut it off. For glazes,
I put a ^8 in the sitter, and set it to soak
manually when the witness cones tell me to. The
^8 ensures that the sitter won't trigger at all
unless I wasn't there to do my job.
These settings happen to work well for my work
in my kiln. (Your mileage may differ.) ;)
I could probably recalibrate, but why bother? I
know what to expect, and how to make my kiln do
what I want. I don't really care if the sitter
matches the witness cones, as long as it matches
my expectations!
If it bothers you, though, just reset your sitter.
Slide the flap in the deadfall up a smidge, to
delay the shutoff until the temperature is higher;
you may need to fine-tune it a few times. Even
then, though, there's a bit of variance with each
firing, mainly depending on how the kiln is loaded.
Witness cones are your best indicator, so if it's
really critical, rely on them over the sitter.
-Snail
Reno, NV
william schran on thu 10 oct 02
Tammy - You have answered your question - use a small cone 7 (or 8)
in the kiln sitter for your cone 6 firings. Be sure to monitor your
firings towards the end so you can shut off the kiln at the
appropriate time - when the witness cones bend.
Bill
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