Matt MacIntire on mon 21 may 01
You are wise to consider that calibration is important with a kiln sitter.
Similarly, the selection and placement of the cone you use is very important
too.
I started to write out instructions for you, but then I realized they were
probably online. The proper method to adjust your kiln sitter can be found
here:
http://www.cdvkiln.com/menuman9.htm
This page is the manual for Kiln Sitters(r). Scroll down to find the
section on adjusting the sitter. These are excellent instructions, with
pictures. There is also a section of useful diagrams to determine AFTER a
firing if you sitter is adjusted correctly.
Note that in these instructions they show trigonal pyramid (regular)
pyrometric cones. With regular cones, you have to be VERY careful how you
position the cone. If you place the sensing bar over a thinner section of
the cone, naturally this will effect the endpoint when the sitter shuts off.
Use bar cones instead! Then the positioning of the cone itself matters much
less.
BTW... I disagree with John H.. I think kiln sitters are very dependable.
Like any tool, you have to know how to use them properly. To say they are a
bad tool because you don't put in a cone 6 to fire to cone 6 seems silly to
me. Who cares what cone you put in, if they yield consistent results, that
is what matters. Using the appropriate bar cone in a properly adjusted
sitter has yielded very reliable and predictable results. I still use
witness cones, but I often find that the kiln sitter shuts the kiln off at
the appropriate time, even if I forget to check.
It does take a firing or two to find the cone that works best for you. Use
regular witness cones for the first couple firings. Using a bar cone,
putting a cone 7 in the sitter gets me an almost perfect cone 6, maybe just
a teeny bit shy. What matters is that it is consistent. Probably the
sitter is MORE consistent than I am, since I get distracted.
It is still important to set the limit timer appropriately in case something
does go wrong with the sitter. Sometimes those sensing rods bend and get
stuck. I have seen bent ones as schools, but I have never seen one bend. I
know it can happen, it just never happened to me.
Good luck...
Matt
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