As previously mentioned in the introduction, the insulation comprising the lining of the kiln is composed of a micro-fiber alumina silicate refractory material. Under a microscope, these fibers resemble quartz crystals and, when heated to the temperatures the kiln operates at, a portion of these fibers fuse together. When the fibers fuse together, some of the voids between the fibers are filled with the newly fused fibers and the insulation shrinks approximately 2% to 5%. This has no effect on the insulating properties of the insulation, however small cracks may form in the insulation. The following procedure helps to stabilize the kiln lining once the initial shrinkage of the insulation is complete.
As described in Step 3, light the kiln and maintain the kiln in the idle mode (1700° to 1800° F.) for 30 minutes. After 30 minutes, slowly raise the temperature of the kiln to 2100° F. and let the kiln remain at that temperature for an additional 15 minutes. When the 15 minutes have expired, you will need to tighten the stainless steel jacket, to hold the newly tempered insulation in place and to minimize any cracking of the insulation.
Starting at the bottom of the kiln and using a 5/16 nut driver; tighten the bottom clamp until the clamp is snug. Do not over-tighten the clamp; all it needs to be is snug. Work your way up the kiln, clamp after clamp, applying the same amount of torque to all of the clamps, until you reach the top of the kiln. While tightening the clamps, in order to hold the lid and body in place, put your gloved hand on the outside edge of the kiln lid and hold enough down pressure on the kiln to keep the body and lid in place while tensioning the clamps. The lid will be hot, but if you hold down on the outside edge of the lid and keep your gloved hand out of the center of the lid, it’s manageable.
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This procedure is simpler than the description of how to perform it and takes less time to complete than it does to read this portion of the instructions. As you use your kiln, it doesn’t hurt to check the clamps tension once in a while. However, the kiln must be up to temperature for the procedure to be effective.
After the stainless steel jacket has been re-tensioned, turn the burner back down to the idle mode and allow the kiln to cool down to 1700° to 1800° F. When the kiln has cooled to the idle mode temperature, close the needle valve and turn the burner off. Leave the lid and burner in place and allow the kiln to cool down to room temperature. Always re-stack your kiln and leave the lid and burner in place when you shut the kiln down after using it. This minimizes rapid thermal shock from affecting the kilns insulation.
Once your kiln has cooled to room temperature, remove the burner and the lid and body of the kiln and inspect the condition of the kiln insulation. Small cracks in the insulation are of no concern and have no effect on the kiln’s performance. However, if there are any larger cracks that you feel need attention, you can fill them later with Liner Restore and then apply Armor Coat to the interior of the kiln. As you use the kiln, the insulation will ‘temper’ from the heat and will stabilize and no longer shrink, however the lining may become somewhat brittle. That is just the nature of the beast, so to speak. So, just be aware of this fact and treat it with care.