Sentry Industries Sentry 2.0 Cone-Fire, Pyrometric Witness Cones, Firing Schedules

Use self-supporting witness cones on the shelf. They stand upright without cone holders.

Chapter 3

Cone-Fire

■The element that silhouettes the cones should be level with the lower part of the cone. If the element is in line with the upper part of the cone, you won’t be able to see the cone when it bends.

Cone-Fire mode is based on pyrometric cones. It is not designed for heat treating, glass fusing and enameling. For these firings, see “Ramp-Hold,” page 12. Use Ramp-Hold to fire ceramic pieces that require a custom firing schedule, such as some types of stone- ware sculpture or crystalline glaze.

Pyrometric Witness Cones

■If you use the three cone system, always have the higher tem- perature cone on the same side in every fir- ing. Otherwise you can lose track of which cone is which.

■Wear firing safety glasses when viewing the cones through the peephole.

Silhouette the lower part of the cone against an element. Keep the cone 8” - 12” away from the peephole.

The Sentry shuts off automatically without cones. Never- theless, every ceramic firing should include at least one wit- ness cone (also called the shelf cone). The witness cone is the most accurate measurement of heat work in a ceramic firing.

If you fire the same size load and type of ware regularly, the witness cones let you compare one firing to the next and alert you when something is wrong. For example, if the wit- ness cone bends less and less with each consecutive firing, this may indicate thermocouple temperature drift.

Note: If the bending of the witness cone does not match the Cone-Fire shut-off, you may want to ad- just Cone Offset or Thermocouple Offset. See pages 17 - 19. If the witness cones bend inconsis- tently from one firing to another, see “Sentry Trou- bleshooter,” a separate publication.

How to Position Cones on the Shelf

Position the witness cones

so that you can see them through a peephole during fir- ing. If the kiln takes longer than usual to fire, you may wonder if something has gone wrong and the kiln is overfiring. But by seeing the cones, you will know how the firing is progressing.

If you follow these guide- lines, you should be able to see the cones even at cone 10:

■Place the cones 8” - 12” away from a peephole. Posi- tioning them closer makes them difficult to see.

■Have enough space around the cones to keep them from touching a piece of ware when they bend.

■Position cones so that when viewed from the peephole, they are silhouetted by an element on the opposite kiln wall. (Keep cones at least 2” from an element.)

See your dealer if in

doubt about which cone number to use with each clay and glaze.

Firing Schedules

Cone-Fire uses three firing schedules:

■Low fire cones 022 - 011

■Medium fire cones 010 - 01

■High fire cones 1 - 10

Should you ever want to customize a Cone-Fire program, transfer the firing schedule to Ramp-Hold. See Appendix B, pages 26 - 27.

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 one of these firing schedules.

Note: Pre-Heat shows in Present Status as PRHT . It is not given a separate segment number.

Firing time in each segment is approximate and depends on the age of elements, voltage, size of load, and the firing speed you have chosen.

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 30.

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