Brad Sondahl on mon 10 sep 01
A while back I blithely supported the Dawson Kilnsitter as generally
reliable, as it generally has been. Simple device, works simply.
Then I bought a new kiln this summer and in the 2 months I've had it,
have toasted several bisques, once to the point of needing new shelves.
That worst time, the cone was blobs on the supports like the bit of
marshmallow left on the stick after you've pulled the main part off.
Still the little lip hadn't moved up enough to shut the kiln off. But
on cooling, it moved freely.
Yes the kilnsitter was calibrated. Yes I use a backup timer, but
obviously with too much time on it. No, I don't use witness cones in
every firing, as I am too busy firing up to two kilns a day to monitor
them closely.
There is no mystery to how the kiln sitter works-- a little rod pivots
to allow the shut off gadget to drop and disconnect the kiln. I decided
the pivot might be sticking.
My wife convinced me to replace the porcelain tube assembly--which I've
just done. It's fired twice successfully since then. This was
considerably cheaper than losing another load of pots. I'll try to
monitor and keep fingers crossed.
Anyone with similar experiences?
Brad Sondahl
Incidentally I guess the sky didn't fall on my webpages, for which I'm
very happy.
--
For original art, music, pottery, and literature, visit my homepage
http://pages.about.com/bsondahl
Pottery homepage http://sondahl.freeyellow.com
New music site at mp3.com http://www.mp3.com/sondahl
Gesine Rodger on tue 11 sep 01
Hi. Someone told me a long time ago to put kiln wash on those two little
prongs that stick out from the porcelain tube. I had trouble with my bisque
kiln shutting off as well. My husband is in the business of calibration
and he checked it and everything was okay. Since I have used kiln wash, I
have never had that problem again. Gesine
Gesine's Pottery
gesine@vaxxine.com
From: "Brad Sondahl"
To:
Sent: Tuesday, September 11, 2001 12:56 AM
Subject: Kiln sitter failures
> A while back I blithely supported the Dawson Kilnsitter as generally
> reliable, as it generally has been. Simple device, works simply.
> Then I bought a new kiln this summer and in the 2 months I've had it,
> have toasted several bisques, once to the point of needing new shelves.
> That worst time, the cone was blobs on the supports like the bit of
> marshmallow left on the stick after you've pulled the main part off.
> Still the little lip hadn't moved up enough to shut the kiln off. But
> on cooling, it moved freely.
> Yes the kilnsitter was calibrated. Yes I use a backup timer, but
> obviously with too much time on it. No, I don't use witness cones in
> every firing, as I am too busy firing up to two kilns a day to monitor
> them closely.
> There is no mystery to how the kiln sitter works-- a little rod pivots
> to allow the shut off gadget to drop and disconnect the kiln. I decided
> the pivot might be sticking.
> My wife convinced me to replace the porcelain tube assembly--which I've
> just done. It's fired twice successfully since then. This was
> considerably cheaper than losing another load of pots. I'll try to
> monitor and keep fingers crossed.
> Anyone with similar experiences?
> Brad Sondahl
> Incidentally I guess the sky didn't fall on my webpages, for which I'm
> very happy.
> --
> For original art, music, pottery, and literature, visit my homepage
> http://pages.about.com/bsondahl
> Pottery homepage http://sondahl.freeyellow.com
> New music site at mp3.com http://www.mp3.com/sondahl
>
>
____________________________________________________________________________
__
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your subscription
> settings from http://www.ceramics.org/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at
melpots@pclink.com.
>
Arnold Howard on tue 11 sep 01
I've heard of the type of Kiln Sitter failure Brad describes: the
rod fails to move downward during firing, but when cool, it moves
freely. The best solution seems to be replacing the tube assembly.
Arnold Howard
Paragon
--- Brad Sondahl wrote:
> A while back I blithely supported the Dawson Kilnsitter as
> generally
> reliable, as it generally has been. Simple device, works simply.
> Then I bought a new kiln this summer and in the 2 months I've had
> it,
> have toasted several bisques, once to the point of needing new
> shelves.
> That worst time, the cone was blobs on the supports like the bit
> of
> marshmallow left on the stick after you've pulled the main part
> off.
> Still the little lip hadn't moved up enough to shut the kiln off.
> But
> on cooling, it moved freely.
> Yes the kilnsitter was calibrated. Yes I use a backup timer, but
> obviously with too much time on it. No, I don't use witness
> cones in
> every firing, as I am too busy firing up to two kilns a day to
> monitor
> them closely.
> There is no mystery to how the kiln sitter works-- a little rod
> pivots
> to allow the shut off gadget to drop and disconnect the kiln. I
> decided
> the pivot might be sticking.
> My wife convinced me to replace the porcelain tube
> assembly--which I've
> just done. It's fired twice successfully since then. This was
> considerably cheaper than losing another load of pots. I'll try
> to
> monitor and keep fingers crossed.
> Anyone with similar experiences?
> Brad Sondahl
> Incidentally I guess the sky didn't fall on my webpages, for
> which I'm
> very happy.
> --
> For original art, music, pottery, and literature, visit my
> homepage
> http://pages.about.com/bsondahl
> Pottery homepage http://sondahl.freeyellow.com
> New music site at mp3.com http://www.mp3.com/sondahl
>
>
______________________________________________________________________________
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your
> subscription
> settings from http://www.ceramics.org/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at
melpots@pclink.com.
__________________________________________________
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Tom Wirt/Betsy Price on tue 11 sep 01
Brad...
I've always heard that the kiln sitter is for when you die during a
firing. But we still do it like everyone else.
Some time ago I ran into a sticking sitter...found out that the rod
can bend under full heat and hang up. This rod apparently comes in
rolls which are straightened out and the cut for use as rods. Near
the end of the roll, where the radius is tighter, this wire can
apparently have a "memory" and, under heat, rebend. Doesn't happen
often, but it can.
Also, you can replace just the wire part about as easily as replacing
the whole tube. A tube can easily last through a dozen wires. Only
touchy part is to get the slip washer retainer back in the same place
on the new wire.
And finally, the tips of the cone support rods should be painted with
a bit of kiln wash or, preferably, ITC 100. The cones can hang up and
prevent a shut off.
Tom Wirt
Craig Martell on tue 11 sep 01
Hello Brad:
Sorry that you've had some loss due to sitter failure.
You've already received some sound advice on sitter maintainance and I'd
bet you know that stuff anyway. My feeling has been that any automatic
shutoff device is a luxury and not a sure thing. The way I handle any
firing, gas or electric is by being there and monitoring the kilns. My
bisques have large senior cones in the kiln that I watch, digital
pyrometers, and sitter cones. I've never overfired a bisque or a
glaze. Same deal with the gas kiln except for sitter cones.
I hope I'm not coming off as self righteous here but even if we are busy
with other tasks, monitoring kilns is important unless we can afford to
lose loads. I can't! I know the firing profiles of my kilns pretty well
so I can factor in the times that I need to be there to check things. The
pyros help too because they inform me of important temp points I need to be
aware of.
regards, Craig Martell in Oregon
william schran on wed 12 sep 01
Brad - I've said this before, and I'll say it again - the kilnsitter
is a mechanical device, and ANY mechanical device can fail at
anytime. Have sitters in three of our five kilns at school, but use
witness cones in every single firing (bisque & glaze). Used to fire
with kilnsitter, had one failure. One time was enough to convince me.
Loss of a entire load of ware is more expensive than a few minutes of
my time to check the cones.
Bill
Arnold Howard on wed 12 sep 01
Bill's message about Kiln Sitters applies to electronic
controllers. I received a message just this morning from someone
who over-fired an electronic kiln.
Arnold Howard
Paragon
--- william schran wrote:
> Brad - I've said this before, and I'll say it again - the
> kilnsitter
> is a mechanical device, and ANY mechanical device can fail at
> anytime. Have sitters in three of our five kilns at school, but
> use
> witness cones in every single firing (bisque & glaze). Used to
> fire
> with kilnsitter, had one failure. One time was enough to convince
> me.
> Loss of a entire load of ware is more expensive than a few
> minutes of
> my time to check the cones.
> Bill
>
>
______________________________________________________________________________
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your
> subscription
> settings from http://www.ceramics.org/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at
melpots@pclink.com.
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John Baymore on wed 12 sep 01
Anyone with similar experiences?
Brad,
When I did that little survey about "kiln accidents" a while back, the
number of electric kiln fires , meltdowns, and other such so-called
disasters outweighed gas kiln problems heavily. A huge percentage of
those electric kiln incidents seemed to point directly to kiln sitter and=
electronic controller failure..... accompanied / contributed to, through
"casual attention" of the potter to the firing kiln...believing that the
electronic controls were "failsafe".
It was not truly a "scientific study" and the overall sample was not
huge..... but it gave some indication. It was good enough info that I us=
ed
the stats in a "confrontational" case between a gas kiln owner and the
landlord of the building the kiln was in. BTW...... we "won" handliy,
armed for "bear" .
So.... yes..... it happens more frequently than most think. You're not
alone.
Best,
..............................john
John Baymore
River Bend Pottery
22 Riverbend Way
Wilton, NH 03086 USA
603-654-2752 (s)
800-900-1110 (s)
JohnBaymore.com
JBaymore@compuserve.com
John.Baymore@GSD-CO.com
"Earth, Water, and Fire Noborigama Woodfiring Workshop 2002 Dates TBA"=
FireRight on wed 12 sep 01
Let us be careful about conclusions drawn from collections of
anecdotal recollections.
The KilnSitter has, over the years, been our chief competitor. As an
engineer, I can validate this product as a high quality device, both in
terms of design and manufacture. As a competitor, I openly acknowledge that
the low price of this product has also made it a perennial "best value"
choice.
It could very well be that the low cost of this control has often
made it a realistic option for those who would otherwise have had to rely
totally on manual operation. One can only wonder how many firings were saved
that might otherwise, having slipped the mind of harried merchants,
distracted teachers and sleeping school janitors, have become disasters.
Our controls, although always more expensive than the KilnSitter,
provide the same basic functions ... convenience and some assurance against
"human error". Our "Model 09" ... probably the first practical electronic
control for electric kilns ... first shipped in 1977. In spite of our
exuberance as a new start up with a hot new product, it's intended purpose
and limitations were prominently explained in the handbook that shipped with
it, along with bold-face warnings in red print about leaving the kiln
unattended beyond the expected firing time. In my experience, these comments
have rarely been misunderstood. But we are all human ... after months or
years of reliable performance, users sometimes become complacent. By
Murphy's Law, "controller reliability varies inversely with operator
complacency", so at that point problems become possible.
As for statistics, at the time our company began, hobby ceramics was
extremely "hot", and thousands of KilnSitters were being installed each year
as standard equipment on new kilns, and by all kiln manufacturers. Today
hobby ceramics is mostly a memory and we both have more competition, yet the
KilnSitter remains the default for those who don't have a "computer" budget.
A large number of failures involving this control probably reflects nothing
more than its ubiquity in the field.
It probably needn't be said, but if the anecdotal "horror stories"
involve more electric kilns with automatic controls than gas kilns, the
correct conclusion might well be that electric kilns far outnumber gas
kilns, and electrics are far more likely to have some sort of automatic
control, simply because automatic control is much more difficult and costly
to implement on a gas kiln.
Gene Warner
FireRight
> A huge percentage of those electric kiln incidents seemed to point
> directly to kiln sitter and electronic controller failure..... accompanied
> / contributed to, through "casual attention" of the potter to the firing
> kiln...believing that the electronic controls were "failsafe".
>
> It was not truly a "scientific study" and the overall sample was not
> huge..... but it gave some indication.
Sandra Talarico on wed 12 sep 01
I have a Skutt electric kiln. With a kiln sitter
AND and electronic controller. While I thoroughly
enjoy not having to be around every few hours to turn
up the kiln (the electronic controller), I'm ALWAYS
there to watch the kiln within the last 45 minutes
of the firing. I always have cone packs that I can
see through the peepholes to be sure that the kiln
shuts off at the appropriate time.
The only foolproof evidence of firing temperature
in your kiln are the witness cones. Even the manufacturer
of the kiln strongly advises that the kiln-firer be present
for the kiln shutoff time.
Sandy Talarico
Jeremy Hellman on wed 12 sep 01
Hello all,
One thought about kiln sitter failures and computerized controller failures
is that it is possible to have BOTH devices on the same electric kiln.
If you buy your kiln with the controller as an integral part of the kiln,
you do not get a sitter.
However if you buy or already have an electric kiln with a sitter, you can
buy a controller which can be mounted on the wall near the kiln, or on a
separate stand, and you get to use BOTH. It costs about $100 US additional
to get both, compared to having only the controller.
My 7 cu ft electric kiln has both. When I'm firing, I put a small cone at
exactly the number I wish to reach in the sitter. If the controller doesn't
turn off the firing, then the controller does. (If the sitter and cone shut
down the firing, I cannot cool down using the controller, but that's a price
I'm willing to pay for not over firing my kiln.)
You could also have a limit timer on the kiln.
For the truly cautious (or paranoid ) you could also put witness cones
near the peep holes.
Most engineers build back-up systems for daily use. For me, the controller
and the sitter provide a back-up.
One further caution-- a newby mistake I made in an early bisque firing. I
placed my shelf too close to the sitter (and this was a kiln with only a
sitter). When the cone melted, the upper bar in the sitter was caught by the
badly placed shelf, and the kiln never shut off. After a few extra hours of
firing I manually shut down the kiln, to find a fully vitrified kiln of
unglazed pots.
Now I've exceedingly cautious about how my shelves are placed in the kiln,
relative to the kiln sitter.
Bonne
Bonnie Hellman still in SW CO for a few more days of vacation thinking about
the terrorist activities and thinking about the temperatures in the World
Trade Center reaching higher than my bisque firings.
Coolpots@AOL.COM on sun 16 sep 01
Brad,
Just last week my Skutt failed to reach temperature. Having fired over 200
times, I just knew it was the elements. I quickly called Skutt and ordered
all new elements. In the meantime I called around to find a kiln repairman in
my area. Not an easy thing to find, but got lucky. When he came out he turned
it on and noticed that just the top two elements weren't heating up. After
taking off the cover we discovered that the plug between the rings had burned
out. Since he didn't have a plug with him and after making several calls and
couldn't find one, he wired it direct to the middle ring. Now I can't take
the rings apart to move it, which I probably won't do anyway. He suggested we
wire the other plug direct too.
I told him in the past I had been having trouble with the kiln sitter. He
pulled out the rod and showed me it was bent. He replaced it with a thicker
one and mentioned I should turn it once or twice a year as they tend to bend
in the heat. I have learned in the past not to trust my sitter. It is not
perfect. I log all my firings and know when it should shut off. If it shuts
off early, I know the cone has broken in the sitter and need to fire longer.
I ALWAYS use a witness cone. It has saved my bacon many times. I don't know
much about working on kilns and I'm glad I know a guy that can help me next
time. He said my elements look good and do not need to be replaced, so I will
just keep them until a later time. It is extremely frustrating to under fire
or over fire. Too much work goes into what we do to have it ruined by the
kiln. The only answer I know is to time everything to assure it reaches the
temp it should. Oh, how nice things are when fired right. Fills my heart with
joy. By the way, I had this underfired load that I worried about. I put
everything back in the kiln the same way I had removed it and couldn't
believe my eyes after refiring. All but one came out just gorgeous. Some of
the glazes were cracking and even peeling, but when they reached the right
temp. they were great. So Brad, good luck to you in your future firings. By
the way, I don't leave more than 30 min. extra on my timer just in case.
Vicki in Cool, CA
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