william schran on mon 21 may 01
I'd like to ditto what John said about the mechanical shut off device
for electric kilns. I have never trusted them, never will, to give
accurate readings. I use them as they should be used, a back-up
safety device. I always use witness cones, for both bisque & glaze
firings. To do otherwise is simply foolish. I feel the same about the
computer controllers - I'd still use witness cones.
Bill
Brad Sondahl on tue 22 may 01
Since comments are running against kilnsitters, and since I feel
otherwise, I'll speak for them. I've used them for 20 years, over 100
firings per year, only occasionally using backup cones. I occasionally
dink with the set screw if the shut off lever won't stay in place when
you're starting the kiln, or if I install a new rod. I fire crystalline
glazes with it, and learn the hotter and colder parts of the kiln. I
can tell the cone the kiln reaches on opening without witness cones,
since I know my glazes. Also I may substitute a lower or higher cone
for a while if I'm not getting the results I want. Many more problems
have resulted from burned out elements than anything related to the
kilnsitter, and those would still occur using witness cones, unless you
checked both top and bottom.
Several times in 20 years I've had severe overfires, wrecking pots and
sagging shelves. If I had set the timer more carefully those wouldn't
have happened. The time spent remaking those pots would be nothing
related to the time of babysitting 2000 kiln loads to a visual shutoff.
Since I live and work in the same place, I usually wait for slight
brightening of lights that signals the kiln is done before resting
easy. Otherwise I'm free to do other stuff.
If the Dawson kiln sitter didn't work as designed, the design would have
been changed or discarded. It's simple. It works.
Brad Sondahl
--
For original art, music, pottery, and literature, visit my homepage
http://pages.about.com/bsondahl
Pottery homepage http://sondahl.freeyellow.com
william schran on wed 23 may 01
Brad - You said it yourself, "several times over the years I've had
severe overfires". Every firing degrades elements, thermocouples,
sitter sensing rod and anything else exposed to the heat of the kiln.
Often this happens over a long period of time, we don't pay
attention, we get lazy, we forget. It's easy to throw that little
cone in the sitter and sit back and think all will be fine. Except
when it's not, like when a show is coming up, you're rushing to get
that last firing in that's full of the best "stuff" I've ever done.
That's when it will happen and ya start kicking your self.
Well, I was that way. One melt down was one too many for me. Now, I
track my firings, check the kiln often (just another part of the the
whole "pottery making" process), have never had an overfire in the
last 20 years and know when it's time to change the elements on each
of the five kilns.
It just comes down to - we each got our own way of doing stuff and
habits are hard to change.
PS - like your web site.
Bill
william schran on thu 24 may 01
Vince - Except if the timer also failed. I've seen it happen! I
always shake my head when folks tell me "the sitter will shut off the
kiln, I don't need to be there".
I do use the sitter on a couple of our school kilns to shut them off.
But I also have witness cones in each and every firing. I check the
kiln (look at cones) about when it should shut off and sometimes I
shut off the kiln prior to the sitter tripping if the cones are
melted properly.
Look forward to reading your book.
Bill
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