kiln sitter cones

updated tue 26 oct 04

Fonda Hancock on sat 24 jul 04

I am recently having trouble with the accuracy of the kiln sitter cones.
Historically I have had what I would consider normal temperature
variations among the witness cones on the various levels of the kiln and
the kiln sitter cone. The cone sitter cone is melting way early as
compared to the witness cones on the shelves. I use a kiln vent, but I
have recently had to shutdown the vent fan in order to reach cone 6 temp
(resistance readings indicate that the elements are close to needing
replacemtn). My kiln has been fired ~60 times with a balance of bisque
and glaze firings. I fire bisque to 04 and glaze to 6. In my most recent
firing I put a cone 7 in the cone sitter, the cone 6 witness cones did not
show sign of bending. I have double checked the setup of the kiln sitter.

My kiln and cones live in the basement of my home. I keep a dehumidifier
running in the basement. I have thought that basement conditions may be
having a negative effect on the kiln sitter cones. I realize that the
witness cones are more accurate than the kiln sitter. However, I would
expect the kiln sitter to be more accurate than this. Any ideas???

Gary Harvey on sat 24 jul 04

Just an observation from my own kiln. The kiln sitter cone always bends
first, then the witness cone. I then reset the kiln and fire about 30
minutes more for soaking. I think this is normal for my kiln. Gary Harvey,
Palestine TX
----- Original Message -----
From: "Fonda Hancock"
To:
Sent: Saturday, July 24, 2004 8:03 AM
Subject: Kiln Sitter Cones


> I am recently having trouble with the accuracy of the kiln sitter cones.
> Historically I have had what I would consider normal temperature
> variations among the witness cones on the various levels of the kiln and
> the kiln sitter cone. The cone sitter cone is melting way early as
> compared to the witness cones on the shelves. I use a kiln vent, but I
> have recently had to shutdown the vent fan in order to reach cone 6 temp
> (resistance readings indicate that the elements are close to needing
> replacemtn). My kiln has been fired ~60 times with a balance of bisque
> and glaze firings. I fire bisque to 04 and glaze to 6. In my most recent
> firing I put a cone 7 in the cone sitter, the cone 6 witness cones did not
> show sign of bending. I have double checked the setup of the kiln sitter.
>
> My kiln and cones live in the basement of my home. I keep a dehumidifier
> running in the basement. I have thought that basement conditions may be
> having a negative effect on the kiln sitter cones. I realize that the
> witness cones are more accurate than the kiln sitter. However, I would
> expect the kiln sitter to be more accurate than this. Any ideas???
>
>
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william schran on sat 24 jul 04

Fonda wrote: >I am recently having trouble with the accuracy of the
kiln sitter cones.
I would expect the kiln sitter to be more accurate than this. Any ideas???<

First thought would not be the cones, but adjustment of the kiln
sitter with the metal gauge that came with it.
Bill

Maurice Weitman on sat 24 jul 04

At 9:03 -0400 on 7/24/04, Fonda Hancock wrote:
>[...] However, I would expect the kiln sitter to be more accurate
>than this. Any ideas???

Hello, Fonda,

I found the same issues as you with a new kiln (vented, 10 cubic
feet, 3.5" brick + insulation) in a dry garage. I have a theory to
explain why my cone 7cone or bar in the kiln sitter bends to 90
degrees before the cone 6 witness cones budge.

I think in my kiln the rod that leans on top of the kiln sitter's
cone is too heavy, thus providing too much encouragement for the cone
to bend.

There is a small, disc-shaped counterweight (I believe mine is
color-coded red) on the inside of the kiln sitter that is supposed to
compensate for the weight of the rod. A longer rod needed on a
thicker-walled kiln will need a heavier counterweight.

I have used bars and small cones in the kiln sitter with little
difference in result. One may encourage the sitter to trip sooner or
later by placing the cone under the rod on a small cone's thinner or
thicker side, respectively.

Your situation may be different from mine since you had better
results at one time. And the fact that your elements have aged such
that they are close to needing replacement might point to a
different, perhaps more subtle explanation for your problem.

I'm surprised that your elements would be needing replacement after
only 30 or so cone-6 firings. Do you fire very quickly? If so, that
may have some bearing on element life and may explain the disparity
in kiln sitter cone bending time over the life of the elements.

If you run your kiln with the vent off, there's less cool air passing
over the kiln sitter cone, thus making it trip earlier. I'm also
surprised that your vent would inhibit your kiln from reaching cone
6. The vents I've used are adjusted so that there's the slightest
amount of negative pressure in the kiln, thus barely effecting the
kiln's temperature. Perhaps this bears investigation and adjustment.

Good luck.

Regards,
Maurice - happy to be home after a marathon "vacation" on the right
(hot and humid) coast where we visited friends and family in a dozen
homes in five states, slept in seven beds in a bit over two weeks,
spent time with four grandchildren, two "kids" and loads of siblings,
parents, cousins, aunts, and one day museum hopping. As I said,
we're happy to be home. Anything happen here while I was away?

Earl Brunner on sat 24 jul 04

Accuracy w/relation to witness cones should be consistent, if not accurate.
As long as they are consistent, you should be able to get good results.
Either by adjusting the kiln sitter or simply ignoring the discrepancy
between witness cones and the sitter cones, just put what ever cone you need
to make the witness cone drop when it should.
There are several factors working here. One the sitter may need
adjustment, but you also have to take into account that small cones or bars
actually don't melt at the same temperature as the big cones anyway. You
can go to the Orton website to see the charts.

Earl Brunner
Las Vegas, NV
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of william schran
Sent: Saturday, July 24, 2004 3:35 PM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Re: Kiln Sitter Cones

Fonda wrote: >I am recently having trouble with the accuracy of the
kiln sitter cones.
I would expect the kiln sitter to be more accurate than this. Any ideas???<

Bobbruch1@AOL.COM on sun 25 jul 04

Fonda Hancock writes
<<<<the accuracy of the kiln sitter cones.
Historically I have had what I would=20
consider normal temperature
variations among the witness cones=20
on the various levels of the kiln and
the kiln sitter cone.=A0 The cone sitter=20
cone is melting way early as
compared to the witness cones on the=20
shelves.=A0I use a kiln vent, but I have=20
recently had to shutdown the vent fan=20
in order to reach cone 6 temp
(resistance readings indicate that=20
the elements are close to needing
replacemtn).=A0 My kiln has been fired ~
60 times with a balance of bisque
and glaze firings.=A0 I fire bisque to 04=20
and glaze to 6.=A0 In my most recent
firing I put a cone 7 in the cone sitter,=20
the cone 6 witness cones did not
show sign of bending.=A0>>>>>>

I do the same, using a cone 7 in the
sitter for a cone 6 glaze, and find that
the sitter cones melt prior to the standing
cones bending at cone 6. I have always=20
looked at the sitter cones as a safety=20
mechanism and assume that they are not
meant for accuracy. I think you would want=20
to have the sitter shut down at 50 degrees=20
prior to reaching tempurature rather than at
50 degrees after - in case you were distracted
and didn't notice when your kiln was approaching
temperature. You then have to watch the=20
standing cones carefully to determine how much=20
you want them to bend before shutting off the kiln,
or beginning the soaking process.

Bob Bruch