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How to Duplicate Glaze Results from a Test Kiln

Use witness cones to duplicate glaze results from one kiln to another.


How to Duplicate Glaze Results from a Test Kiln

Recent Q&As: Monitoring a kiln during long firings; undoing steps in kiln programming

Memorable Quote

News: Jennifer Quarles Wins Paragon Kiln



A potter told me she perfected a copper glaze in a small electric test kiln. Thrilled with the results, she made a large batch of glaze and fired it in a production kiln. But the pieces in the large kiln turned beige instead of copper.

To assure that a glaze in a production kiln turns out the same as in a test kiln, use the same firing schedule in both kilns. This is easy to program if the kilns are digital. Use witness cones.

Cool the glazes at the same rate in both kilns. The cooling rate is often more important than the firing rate in duplicating glaze results. Small kilns cool faster than large kilns. So as your large kiln cools, write down the display temperature every hour. Figure the cooling rate by subtracting the ending temperature from the beginning temperature of each hour. Then program the same cooling rate in the test kiln.

Even if you fire both kilns with the same firing and cooling profile, glaze results can still differ slightly. This is because glazes of different colors can affect adjacent pieces in a large kiln. Also, a downdraft kiln vent may slightly alter glaze color in the large kiln.



Q. Though I have read that one should never leave a kiln unattended, I have been firing glass while away from home or overnight. Should I avoid this?

A. We recommend that you monitor the kiln during operation. This does not mean giving it your constant attention. Check the kiln occasionally, especially toward the end of the firing. This advice applies even to digital kilns that shut off automatically. It is a good idea to check on glass before the kiln shuts off. This is to make sure it has fused to the exact degree that you had envisioned when you designed the pieces.

Q. I have a Paragon SC-2 with Sentry Xpress controller. While programming, is there a way to say oops, that's not what I wanted and then cancel everything I just did and start over at idle?

A. If you do not touch the keys of the controller for one minute during programming, the controller will go back to Idle and will retain the previous program.



“I used to feel jealous of jewelers. They could carry everything in a little bag. Now I’ve joined them with my clay beads and buttons. It is wonderful!” –heard from a potter at last week’s NCECA pottery convention in Philadelphia



Jennifer Quarles of Austin, Texas won a Paragon Digital FireFly kiln. “This is the first time I’ve ever won anything!” she said. Her name was drawn on Friday, April 2 at the NCECA pottery convention in Philadelphia, Pennsylvania. Congratulations, Jennifer!


I meet interesting people at trade shows. Last week a retired judge related terrible experiences from her courtroom days. Then she said, “Clay sculpture is so relaxing. I go where the clay takes me.” She finds clay to be more relaxing than even reading, because her mind wanders to the past while she reads but not while she is in clay.

At the same event, a retired heart surgeon told me about massaging hearts and bringing patients back to life. “It was very stressful,” he said. “It used to take me a week to unwind on vacation.” As with the judge, clay was his passion.

Thank you,

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 / /

PRIVACY NOTICE: Under no circumstance do we share or sell your email address.

Copyright 2010, by Paragon Industries, L.P.

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