The firing schedules programmed into Cone-Fire mode
are listed in Appendix B, pages 32 - 33. Should you ever
want to customize a Cone-Fire program, make the desired
changes to a firing schedule and program it in Ramp-Hold
(page 14).
During a cone firing, press
5
(Present Status) to see
which stage, or segment, of the firing the kiln has reached.
The number displayed will be a segment number from the
schedule listed in Appendix B that you are firing.
Note:
Pre-Heat shows in Present Status as
[PRHT]
. It is not given a separate segment
number.
CAUTION:
Cone numbers beginning with 0 are
lower in temperature than those without the 0.
When programing a Cone-Fire, be sure you know
the difference between an 05 and 5. See “Tempera-
ture Equivalents Chart for Orton Self-Supporting
Pyrometric Cones,” Appendix D, page 36.
Low Fire Cones 022 - 011
This range includes decals, over-decorations, lusters,
and golds. You can usually fire fast. Good venting is impor-
tant because of the oils and other organics. Do not close the
lid from the vented position until all odor has disappeared.
Middle Fire Cones 010 - 01
Glazes fired on bisque ware (ware that has already been
fired) can be fired faster than greenware.
High Fire Cones 1 -10
This is the firing range for porcelain and stoneware.
These bodies fire nearly to vitrification and can shrink up to
16%. Water, carbon and sulfur burn out during the early
stages and must be vented. The amount of oxygen in the
kiln affects the color of the fired clay. The high fire sched-
ules programmed into Cone-Fire slow down during the last
216°F/120°C (two hours) to produce better density in the
ware.
Cone-Fire Features
Speed [SPD]
When you select Medium speed in a Cone-Fire pro-
gram, the kiln uses the standard firing schedules listed on
pages 32 - 33. When you select Fast (1), the standard sched-
ules fire 20% faster. On Slow (3), they fire 20% slower.
You can alter the firing speed even more under Speed
(SPD) in Options. You can increase or decrease the firing
time of a standard schedule by up to 40%. For instance, if
you are on a tight deadline, you can reduce a 7 hour fast
cone firing to 5 ½ hours.
Note:
The final segment heating rate will not
change. It will always be 108°F/60°C per hour. SPD
option affects only the earlier ramp segments.
Pre-Heat [PRHT]
Moist greenware can explode during firing. This hap-
pens when the moisture in the clay rapidly turns to steam
and cannot escape from the clay fast enough. The Sentry
Pre-Heat feature dries the ware at low temperature before
the moisture can turn to steam.
Pre-Heat is sometimes necessary when firing thick
greenware. It may also be necessary in humid weather,
which inhibits drying. If possible, however, avoid using
Pre-Heat to dry greenware. If the greenware feels damp or
cool when you touch it to your cheek, dry it longer outside
the kiln before firing. Use a dehumidifier in humid
weather. Drying greenware in the kiln tends to rust the kiln.
Note:
During Pre-Heat, vent the lid or use the op-
tional Orton Vent Master. Otherwise the fire-
bricks will absorb moisture, leading to rust behind
the steel case. Moisture in the firebricks can also
slow down the firing.
CAUTION:
Venting the lid during Pre-Heat is so
important that some ceramists use the extended
vent position. If you do this, you must be near your
kiln at the end of Pre-Heat to lower the lid.
Pre-Heat raises the temperature 60°F/33°C per hour to
200°F/93°C. Then it holds at 200°F/93°C for the period of
time that you specify. Pre-Heat works in Cone-Fire only.
After Pre-Heat is finished, the kiln will automatically begin
firing to the cone you have selected.
Note:
Above an altitude of 6,000 feet / 9,656
kilometers, water boils at a lower temperature.
This may cause moisture in the ware to turn to
steam even during Pre-Heat.
Mirror Test
This test will help you
determine how much
Pre-Heat to use.
Occasionally during
Pre-Heat, hold a mirror
near the top peephole.
(Be careful to avoid
burns.) The mirror must
be at room temperature,
so hold it near the peep-
hole for only several sec-
onds at a time.
If the mirror fogs,
moisture is still escaping
from the ware. When the
mirror no longer fogs, you can exit Pre-Heat and begin the
firing.
To interrupt Pre-Heat and begin firing to the cone in
Cone-Fire, press
9
(Skip Segment).
[SKIP]
, alternating
with
[RA 2]
, will appear. Press
ENTER
. Segment 1 of the
main firing will now begin.
12
Cone-Fire / Ramp-Hold
Do not leave your kiln unattended during operation.
Vent the kiln until moisture no longer
fogs a mirror.
