Skutt KilnMaster Kilns Manufactured between 2000 and 2006 - Manual (Page 14)

12
General Ceramic
Information
P YROMETRIC C ONES
Ceramic firing to the accuracy we know
today would be impossible without pyro-
metric cones. These long tetrahedrons of
controlled composition measure the com-
bined effects of time and temperature
accomplished during a firing. Please refer
to Appendix 2 which further describes the
theory of heat work. The KilnMaster
Controller uses the patented Orton
process of time and temperature when in
the Cone Fire mode. Even though you are
operating a fully automatic kiln, you still
need to verify the temperature on the shelf
using Self-Supporting Cones.
Senior Cones are designed to be placed
standing in angled holders or Commercial
cone plaques or Self Supporting Orton
Cones. We recommend using the Self-
Supporting Cones that have a precise 8˚
angle built into the base allowing the cone
to bend properly. When the cones soften
and bend to the top of the base (90˚ is per-
fect), the correct firing time and tempera-
ture have been reached. It is important
that the cone is standing at the proper
angle (as precut at the base) for it to bend
at its standard temperature.
Obviously, if you wish to monitor firing
progress, Cones must be visible through a
peephole.
The traditional and still the most accu-
rate method of monitoring a firing is to
use three Self-Supporting Cones: the one
called the guide cone should be one num-
ber cooler than your desired firing; the fir-
ing cone should be the desired heat, and
the guard cone should be one number
hotter as shown below in a typical exam-
ple.
As your firing nears maturity, the guide
cone will bend or “drop”. This alerts you
to watch the firing cone. If the guard cone
is not straight, the best heat work has been
exceeded.
If you discover that your automatic kiln
is underfiring ware, check the load in your
kiln to ensure that it is evenly distributed
from top to bottom. It is easy to program a
5 to 10 minute hold at the end of your
Cone Fire. The hold can be prepro-
grammed or added at the end of a firing
schedule. See Cone Fire mode for detailed
instructions.
Cones are sensitive to moisture when
stored and to drafts when firing. Keep
them dry or invisible cracks may develop,
causing early bending. If you have a cone
problem, try fresh ones from another
source. Place cones at least 3” back from
peepholes to avoid a false response to cool
air.
At high temperatures cones can be hard
to see. Viewing through dark glasses can
help. Try to keep ware back from cones as
far as possible to avoid a cone melting into
the ware.