Instruction manual

5
We suggest using the witness cone to trouble shoot prob
-
lems with the ware. If china paints appear faded and you
suspect it is due to over-firing, test fire with a witness cone.
Anotherexample:glazecrazingdue to under-fired bisque.
How to Interpret the Bending
of a Pyrometric Cone
The cones illustrated here are called self-supporting
cones. They are the easiest type of witness cone to use.
1. Correct Bend
When the self-supporting cone
bends so that the tip is approxi
-
mately even with the top of the
base, the cone has been exposed to
the correct amount of heat work
for thatconenumber. This iscalled
a 6 o’clock bend.
2. Under-Fired Cone
The cone in this photo has not
bent far enough. It indicates that
the kiln did not fire long enough or
hot enough.
3. Over-Fired Cone
When a cone collapses or pud-
dles, it indicates that the kiln
over-fired the ware rated to that
cone number.
Note: Do not beoverly concerned with achieving an ex
-
act 6 o’clock bend. The difference between a 3 o’clock
and a 6 o’clock bend is only a few degrees of
temperature.
HowtoCorrectforUnder-or
Over-Fired Cones
Before changing a firing because of an under- or
over-fired cone, make sure the correct cone was in the kiln.
For instance, if you fired to cone 05, make sure the cone in
the kiln was not a cone 5 instead. (Seethecone temperature
chart on page 17.)
Compensating for an Under-Fired Cone
I
Fire to the same cone number next time, but add hold
time. How much hold time to add is a matter of experi
-
mentation.Ageneral guidelinewould be 10-30 minutes.
An over-fired cone.
Two Firing Modes:
Cone-Fire and Ramp-Hold
To give you greater flexibility, your controller has two
firing modes: Cone-Fire and Ramp-Hold.
Cone-Fire Mode (see below)
Cone-Fire mode fires the ware to a pyrometric cone
number using the Orton cone tables on page 17. This mode
is for ceramics, pottery, stoneware, and glazes. Your sup
-
plier can tell you which cone number to program.
Ramp-Hold Mode (see page 7)
Use Ramp-Hold mode to create custom firings. Select
your own firing speed, temperature, and temperature hold
time in up to 8 steps, or segments.
The chart shows the recommended firing mode for sev
-
eral types of ware:
Type of Firing Suggested Firing Mode
China Painting Cone-Fire
Ceramic Decals Cone-Fire
Ceramic Glaze Cone-Fire
Ceramic Greenware Cone-Fire
Glass Bead Annealing Ramp-Hold
Glass Fusing Ramp-Hold
Glass Slumping Ramp-Hold
Lost Wax Ramp-Hold
Cone-Fire
Cone-Fire mode fires the wareto a pyrometric
cone.Cone-Fire is notdesigned forheat treat-
ing, glass fusing and enameling. For these fir-
ings, use Ramp-Hold mode (page 7). You can
also use Ramp-Hold to fire ceramic pieces
that require a custom firing schedule.
Pyrometric Witness Cones
It is important to understand pyrometric witness cones,
because clay and glazes are rated to cone numbers. Pyro
-
metric cones are small pyramids of clay that bend when ex
-
posed to the correct amount of heat work. Cones are rated
by number. See page 17 for a list of cone numbers and their
temperatures.
When a witness cone bends during firing, the clay and
glaze in that firing, rated to that cone number, have re
-
ceived the correct amount of heat.
Place the pyrometric witness cone on the kiln shelf near
the ware you are firing. Use the cone to check for firing ac
-
curacy. The cone is the most accurate measurement of heat
work in a ceramic firing. This is because the cone measures
the combined effects of time, kiln atmosphere, and temper
-
ature.
A cone fired to maturity.
An under-fired cone.