Someone asked recently if opening the lid of a hot kiln would damage the firebricks. The answer is usually no.
Kiln manufacturers recommend that you wait until you can unload pieces bare-handed before opening the lid of the kiln. This is to prevent damage to the ware rather than to the kiln. For instance, if you remove glass too soon, it may break as it cools.
Most electric kilns are made with K-23 firebricks, which have a low alumina content. (K-25 bricks have a higher alumina content.) Low-alumina firebricks can withstand dramatic temperature change without cracking. That's one of the reasons we use K-23 bricks in electric kilns.
It's better to wait until the kiln has cooled to room temperature before opening it. Nevertheless you can open a hot electric kiln to remove raku pieces without undue damage to the bricks. Glass fusers can open the lids of their hot kilns to rake or emboss the surface of softened glass.
It is also okay to open ceramic fiber kilns at higher temperatures. You can open the SC-2 at 1600 degrees F, for instance, to remove silver clay.
Rapid firing should not harm your kiln, either. The K-23 bricks and ceramic fiber are less susceptible to cracking from rapid firing than any clay you will ever place inside the kiln. The bricks and fiber are soft and fragile yet also surprisingly durable.
Kate Schatz of Richardson, Texas wrote, "Thanks for your story about finding the ancient pot when you were young. I tell my students about the history of clay and that their fingerprint will be there forever in their clay piece."
With best wishes,
Arnold Howard Paragon Industries, L.P. - Better Designed Kilns 2011 South Town East Blvd. Mesquite, TX 75149-1122 Voice: 972-288-7557 & 800-876-4328 / Fax: 972-222-0646 firstname.lastname@example.org / www.paragonweb.com
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