moisture can build up inside the Kiln Sitter tube
as the kiln cools.
If the Kiln Sitter weight is still in the upper position af-
ter the kiln shuts off, the Limit Timer turned off the kiln.
Let the kiln cool to room temperature and examine the
small cone in the Kiln Sitter. Find out why the cone did
not shut off the kiln. You may have loaded the wrong cone,
or the actuating rod may be out of adjustment. You may
need to add more time to the Limit Timer the next time
you fire so that the falling weight shuts off the kiln.
Selecting Cones for the
Kiln Sitter
Only the small Orton pyrometric cone or the Bell bar
may be used in the Kiln Sitter. The pyrometric bar will
fire a little hotter than the small pyrometric cone.
The small cone or the bar may not react to heat in ex-
actly the same way as a large pyrometric cone placed up-
right on the shelf. This is because of the difference in
size, weight, and positioning in the kiln.
A rule of thumb is to fire one cone hotter in the Kiln
Sitter than on the shelf. For the first few firings, place
three large pyrometric witness cones on a shelf a few
inches from the Kiln Sitter cone. One of these large cones
should be the same number as the small cone or bar in
the Kiln Sitter. The other two large cones should be one
cone hotter and one cone cooler.
Examine the cones after your first testing firing. If the
witness cone of the correct
number is still straight, and
the Kiln Sitter shut off prop-
erly, fire a hotter cone in the
Kiln Sitter the next time. If the
witness cone bends too far or
“puddles,” fire a cooler cone in
the Kiln Sitter.
For instance, if you have a
small cone 05 in the Kiln Sit-
ter, the large cones on the shelf
should be 04, 05, and 06. When
the Kiln Sitter shuts off and
the kiln cools completely, in-
spect the cones. If the large
cone 05 on the shelf bent to six
o'clock, the small Kiln Sitter
cone and the large witness
cone should be of the same
cone number during future
firings. If the large cone 04
bent to six o'clock, use a cone
rated one cone cooler in the
Kiln Sitter than on the shelf. If
the large cone 06 bent to six
o'clock, use a cone rated one
cone hotter in the Kiln Sitter
than on the shelf. (See the
cone temperature charts in “Paragon Ceramic Kiln In-
struction & Service Manual” to understand how cones
are rated.)
Since the witness cones are on the shelf where the
ware is placed, the witness cones measure the maturity of
the ware more accurately than the small cone in the Kiln
Sitter. To get like firings, you must place the cone in the
Kiln Sitter exactly the same way each time. You MUST
always center the cone so that at least 3/16" of the thick
end of the cone extends past the cone support. Do not try
to get a hotter firing except by using a hotter cone, and
vice versa.
If your Kiln Sitter is
properly adjusted and
the small cone is cor-
rectly inserted, the cone in the Kiln Sitter will bend into a
U" shape at the end of the firing.
Loading Around the
Refractory Tube
Loading too close to the Kiln Sitter refractory tube
could cause an overfire.
Keep ceramic
shelves at least 1/2
inch above or be-
low the Kiln Sitter
tube. If jarred, a
shelf that is even
with the tube
could stop the ac-
tuating rod from
dropping all the
way, causing an
overfire.
Do not position poorly
stilted ware near the
end of the refractory
tube. If someone
bumps the kiln, an un-
stable stilted piece
could fall against the
actuating rod, causing
an overfire.
Never load moist
greenware in your kiln.
It could explode, and a
piece of clay could lodge beneath the actuating rod
or inside the porcelain tube.
9
An overfired witness cone.
An underfired witness cone.
Witness cone fired to matu-
rity.
