Brad Sondahl on wed 20 jun 12
Here's a link to how my one year old kiln looked when I opened it this
morning... http://sondahl.com/blog/June2012%20001.jpg
I tried to fit in one more firing before leaving on vacation, and it
was the perfect storm---the contacts in the porcelain block arced and
welded together, so even the timer wouldn't shut it off.. Finally
most the elements burned out, and fortunately all the burning was
inside the kiln so my studio was safe... I've had a few overfirings
before, but this one was the worst... Yes, I've learned not to fire
when I'm not around as a failsafe...
I'm curious to know if others have been having trouble with newer
porcelain contact blocks in kiln sitters--I already replaced one under
warranty when it ceased working after about 6 months, and this one was
getting touchy already again when it fried.
Later in the day my old kiln also had burned out one of the load wires
leading into the porcelain block. I was able to fix that one...
Obviously the Achilles heel of electric kilns are the places where the
full load has to be switched. I've used kilnsitters for 35 years, but
I'm wondering if the digital controllers are any better for
durability, to justify the $400 or more price difference to upgrade...
Brad Sondahl, sondahl.com
Neil Estrick on thu 21 jun 12
The level of corrosion will vary depending on your environment. Moist are=
=3D
as=3D20
will cause faster corrosion, like in my studio that is not air conditione=
=3D
d. The=3D20
contacts on the porcelain blocks will corrode just like any other connect=
=3D
ion in=3D20
the kiln. But unlike the other connections that are always together, on a=
=3D
sitter=3D20
the parts that actually connect (the faces of the plates) are exposed, an=
=3D
d will=3D20
corrode and make for bad contact. It's hard to see that connection, so if=
=3D
you=3D20
notice that your other connections are corroding, it's a good idea to tak=
=3D
e apart=3D20
the sitter and clean it up.
Computer controlled kilns are very difficult to over-fire like that. If t=
=3D
he=3D20
computer or thermocouples freak out that badly they should shut down. The=
=3D
=3D20
computers have a lot of fail-safes built in. The only time I have seen a=3D=
20=3D
computerized kiln over-fire was when a relay stuck on a small 18" tall ki=
=3D
ln. A=3D20
kiln that size only has 2 relays, so half the kiln was stuck on. That sai=
=3D
d, it only=3D20
over-fired low-fire work. It did not ruin the kiln. To ruin a kiln, all o=
=3D
f the=3D20
relays would have to stick on, and the odds of that happening are very sl=
=3D
im. I=3D20
have never seen more than one relay stick at a time.
Neil Estrick
Neil Estrick Gallery, LLC
Kiln Repair Tech
L&L Distributor
Paula Rutledge on thu 21 jun 12
On 21 Jun 2012, at 19:18:18 -0700 Brad Sondahl wrote ab=
=3D
out=3D20
Subject: Cooked kiln blues <=3D
ed when I opened it this
morning... http://sondahl.com/blog/June2012%20001.jpg>>
Brad,
I am so sorry to hear about your kiln meltdowns...literally. It hurt to =
=3D
look at the photo. I'm impressed. I have never seen anyone have kiln shel=
=3D
ves fail like that before. We have glued some pots permanently to kiln she=
=3D
lves before ...but never had them end up like yours did.=3D20
I have been firing with digital controllers for the past five years. Fo=
=3D
r the first two years, they were very old, very well used (at college) and=
=3D
they never went crazy and refused to shut off. The only part that is loc=
=3D
ated inside the kiln from the controller is the cone holder and if you h=
=3D
it it, it breaks the electric circuit and everything shuts down. In order =
=3D
for it to stick "on" something would have to somehow wedge in it exactly =
=3D
without knocking any of the little control rods out of alignment. On ours, =
=3D
if you get any one of the three out of where it should be, the whole thing =
=3D
drops apart and stops. Somehow you would have something fall and land exac=
=3D
tly at the base of the cone UNDER the cone without jarring any of the par=
=3D
ts. And then the software program to stop at cone 6 (or whatever you choo=
=3D
se) would have to fail to not shut off . Both of those would have to happe=
=3D
n before you could melt the kiln. When we were blessed to get three brand=
=3D
new kilns for the college ceramic studio, I had the privilege of helping d=
=3D
o the run-in firings on the new kilns & kiln setters [ their first firings=
=3D
to check calibrations and toughen up the bricks and shelves.] [It was gre=
=3D
at getting to know the new kilns and how they worked!] Digital controllers=
=3D
make it really easy to special ramps ups, holds, cool downs...whatever a p=
=3D
otter's heart could desire. I highly recommend digital controllers. Digit=
=3D
al controllers don't take away from firing. Firing is still "hands on". Y=
=3D
ou still have to pay attention to what you are doing. It is good tool; it =
=3D
can allow you to vary your ramps without having to be sitting on top of it =
=3D
every second it fires. And it is also one more safety tool. =3D20
You should think of yourself as blessed that the firing was contained in t=
=3D
he kiln and did not burn down a building or worse. Hopefully, this will be=
=3D
the worst thing that happens to you this year.
Paula Rutledge (a Clay Art reader)
p.s. =3D20
Next time you use "Cooked Kiln Blues"... make it the name of a blue gra=
=3D
ss band or a title of a short story...just don't make it describe anymore=
=3D
firing accidents.
Steve Mills on thu 21 jun 12
Brad,
Here in the UK we've had some Kiln Sitters weld themselves shut as a result=
o=3D
f arcing at switch-on, causing over-firing, so we always advised our custom=
e=3D
rs to set and activate the sitter before turning on the main switch.=3D20
All normal household power switches use the over-centre principle so that a=
s=3D
the surface lever is depressed, the contacts come together very quickly in=
d=3D
eed, faster than you or I can move, minimising arcing.=3D20
The sitter is switched off by the falling weight at great speed, but to tur=
n=3D
it on while it's live causes a lot of arcing which we can't see till we ta=
k=3D
e it apart and see the damage!
Steve Mills
Bath
UK
www.mudslinger.me.uk
Sent from my iPod
On 21 Jun 2012, at 03:18, Brad Sondahl wrote:
> Here's a link to how my one year old kiln looked when I opened it this
> morning... http://sondahl.com/blog/June2012%20001.jpg
> I tried to fit in one more firing before leaving on vacation, and it
> was the perfect storm---the contacts in the porcelain block arced and
> welded together, so even the timer wouldn't shut it off.. Finally
> most the elements burned out, and fortunately all the burning was
> inside the kiln so my studio was safe... I've had a few overfirings
> before, but this one was the worst... Yes, I've learned not to fire
> when I'm not around as a failsafe...
> I'm curious to know if others have been having trouble with newer
> porcelain contact blocks in kiln sitters--I already replaced one under
> warranty when it ceased working after about 6 months, and this one was
> getting touchy already again when it fried.
> Later in the day my old kiln also had burned out one of the load wires
> leading into the porcelain block. I was able to fix that one...
> Obviously the Achilles heel of electric kilns are the places where the
> full load has to be switched. I've used kilnsitters for 35 years, but
> I'm wondering if the digital controllers are any better for
> durability, to justify the $400 or more price difference to upgrade...
>=3D20
> Brad Sondahl, sondahl.com
Ben Morrison on thu 21 jun 12
-Ben
________________________________
Fr=3D
Sad news buddy.=3D0A=3D0A-Ben=3D0A=3D0A=3D0A=3D0A__________________________=
______=3D0A Fr=3D
om: Brad Sondahl =3D0ATo: Clayart@LSV.CERAMICS.ORG =3D0AS=
ent:=3D
Wednesday, June 20, 2012 7:18 PM=3D0ASubject: Cooked kiln blues=3D0A =3D0A=
Here's=3D
a link to how my one year old kiln looked when I opened it this=3D0Amornin=
g.=3D
.. http://sondahl.com/blog/June2012%20001.jpg=3D0AI tried to fit in one mor=
e =3D
firing before leaving on vacation, and it=3D0Awas the perfect storm---the c=
on=3D
tacts in the porcelain block arced and=3D0Awelded together, so even the tim=
er=3D
wouldn't shut it off..=3DA0 Finally=3D0Amost the elements burned out, and=
for=3D
tunately all the burning was=3D0Ainside the kiln so my studio was safe...=
=3DA0 =3D
I've had a few overfirings=3D0Abefore, but this one was the worst...=3DA0 Y=
es, =3D
I've learned not to fire=3D0Awhen I'm not around as a failsafe...=3D0AI'm c=
urio=3D
us to know if others have been having trouble with newer=3D0Aporcelain cont=
ac=3D
t blocks in kiln sitters--I already replaced one under=3D0Awarranty when it=
c=3D
eased working after about 6 months, and this one was=3D0Agetting touchy alr=
ea=3D
dy again when it fried.=3D0ALater in the day my old kiln also had burned ou=
t =3D
one of the load wires=3D0Aleading into the porcelain block.=3DA0 I was able=
to =3D
fix that one...=3D0AObviously the Achilles heel of electric kilns are the p=
la=3D
ces where the=3D0Afull load has to be switched.=3DA0 I've used kilnsitters =
for =3D
35 years, but=3D0AI'm wondering if the digital controllers are any better f=
or=3D
=3D0Adurability, to justify the $400 or more price difference to upgrade...=
=3D
=3D0A=3D0ABrad Sondahl, sondahl.com
Brad Sondahl on fri 22 jun 12
I did hear from one other person who had a kiln drastically overfire
with a kilnsitter in its first year... I do wonder if there are some
bad contacts or springs going into their manufacture... The
manufacturer's kiln tech is baffled still also...
I ordered replacements for both kilns today--the old one was on its
last legs and is exhibiting the same symptoms that led to the massive
failure of the other one. I decided to change to the electronically
controlled model so as to avoid this issue in the future. I'm saving
quite a lot by not replacing the top and bottom lids, which I'd never
thought of doing previously. In the past I have saved the lids, and
especially the bottom ones are usually in quite good condition, since
they are shielded from some of the heat by the bottom shelf, and never
get the stress of opening and closing that the upper lid does. Having
gone through a few kilns, I've had enough lids that I've added them
under the new kiln (3 of them under one of my kilns, 2, soon to be 3
under the other) as additional insulation... When the "new" kiln
massively overfired, it shriveled 1/4 inch or more of the insulating
kiln bricks in the upper lid, but interestingly left the cement
between the bricks sticking out like untamped mortar on housing
bricks... So I intend to flip that lid to the bottom, and use the
bottom (in excellent shape) for the top...
I'm looking forward to having two mostly shiny new kilns...
Brad Sondahl sondahl.com
John Britt on fri 22 jun 12
Forgot to mention the "Witness Cones". They should be in every load and t=
=3D
hat is=3D20
how the kiln is shut off. When you see it go down, you know to make sure =
=3D
it is=3D20
shut off.
Life is much less interesting but ....
John Britt Potter
John Britt on fri 22 jun 12
Hate to say it but kilns overfire all the time, digital and manual. Digit=
=3D
al's can jump=3D20
ramps, have relays stick, or for some unknown reason just over fire.That =
=3D
is why=3D20
they say shut off at they say shut off at the breaker. Just ask the kiln =
=3D
boys and=3D20
girls. Plenty of examples. They are actually countless.
Manuals are just as bad or worse. The cones can stick or not bend for man=
=3D
y=3D20
reasons, like firing in reduction (meaning filling a bisque with earthenw=
=3D
are pots=3D20
which give off sulfur gas and cause the cone 05 to bubble and stick) or h=
=3D
aving a=3D20
pot or shelf too close to the kiln sitter (then it expands and touches th=
=3D
e rod), and=3D20
electrical storm which shuts off power temporarily and then it comes back=
=3D
on and=3D20
you "forget" about it (the cone has not "frozen " and wedged into the hol=
=3D
der) and=3D20
the timer you turned to 20 hours doesn't help, etc.=3D20
The the maximum, "Never fire unattended" is necessary. As soon as you sa=
=3D
y, you=3D20
have never had a kiln over fire- watch out!
John Britt Pottery
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