Use a yardstick to check the clearance between the ware and the kiln lid.
Before Closing the Kiln Lid
Recent Q&As: The 05-1/2 pyrometric cone; length of firings in Cone-Fire mode; programming a rate in a fraction of one degree; annealing glass beads
BEFORE CLOSING THE KILN LID
With the kiln lid open, lay a yardstick across the top of the kiln. The stick will show you the clearance between the ware and the closed lid. Especially when under a tight deadline, it is easy to close a lid on ware that is too high for the kiln.
Have at least one element row between the top shelf and the kiln lid. Experiment with witness cones to know just how high you can place the top shelf. The cones will detect a cool area of the kiln.
Q. In a recent firing, the 07 and 06 witness cones were flat but the 05 only started to bend. The difference between cones 5 and 6 is no where near that large.
A. Pyrometric cone 06 is 39 degrees F hotter than cone 07. Cone 05 is 60 degrees F hotter than 06. Because there is such a wide temperature difference between 06 and 05, Orton eventually added the 05-1/2 cone.
Q. How does a controller fire to a pyrometric cone?
A. Cone-Fire mode fires to the temperature that will bend the witness cone. The speed varies during the firing, with a faster speed near the beginning and a slower speed at the end. During the last 1-1/2 hours, the firing rate is 108 degrees F per hour. We use this as a convenient rate, because the cone temperature is listed in the 108 degree F column on the Orton pyrometric cone chart. If the voltage is low, elements are worn out, or for some other reason the kiln cannot maintain the programmed firing rate, the controller will adjust the shut-off temperature so that the cone still bends to maturity. As long as the kiln can maintain the programmed rate, it will fire a given program in exactly the same length of time for every firing.
Q. I want to program a rate of 4.2 degrees per hour in the Sentry 12-key controller. Is it possible to program a fraction of a degree?
A. The Sentry controller rate is programmed as degrees per hour in whole numbers. There is a way to program in tenths of a whole degree, however.
First, we would need to configure your controller to program a rate in degrees per minute instead of degrees per hour. (At the factory, we can configure the Sentry 12-key controller rate as degrees per hour, which is the default; degrees per minute; or as elapsed time needed to reach a particular temperature.)
After the controller is configured as degrees per minute, you can then program a heating rate of 0.07 degrees per minute, which is the same as 4.2 degrees per hour.
Q. I anneal glass beads. I program segment 1 to 940F with a 4-hour hold. When my bead session is finished, I skip to segment 2. Can I program segment 2 with the same 940F target temperature as segment 1?
A. I assume this is because you want your beads to soak for a certain period, perhaps 30 minutes, at 940F after you skip to segment 2. Yes, you can program duplicate target temperatures in consecutive segments. Orton controllers made before 2006, however, have a problem with duplicate consecutive target temperatures. Changing one of the consecutive target temperatures by just 1 degree, however, will correct the problem.
“Many of our customers, in very stressful jobs, find release through clay. One, a doctor, found clay to be the road back from a mental breakdown.” --Stephen Mills
Today the smell of broccoli and cheese wafted through the office. We held a Thanksgiving potluck--a Paragon tradition.
I hope you have a chance to get away from your kiln and be with your family tomorrow. All of us at Paragon wish you a happy and safe Thanksgiving.
With best wishes,
Arnold Howard Paragon Industries, L.P. – Better Designed Kilns 2011 South Town East Blvd., Mesquite, Texas 75149-1122 Voice: 972-288-7557 & 800-876-4328 / Fax: 972-222-0646 / firstname.lastname@example.org / www.paragonweb.com
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