Cracks in the Kiln’s Firebrick Bottom
Someone recently sent me a photo of a cracked firebrick kiln bottom and wondered how to repair it. The photo shows two perpendicular cracks running across the entire bottom and several smaller cracks.
Cracking in the firebrick bottom is usually nothing to be concerned about. No repairs are needed in most cases. As the bricks expand with heat, the cracks come together tightly.
Examine the galvanized sheet metal base plate under the brick bottom. You can check it with a mirror and a flashlight. As long as the base plate is sound, the brick bottom cracks are nothing to worry about. If the steel base plate is falling apart with rust, you can replace it. Or, slide a piece of galvanized sheet metal under the kiln. It would fit between the kiln bottom and the kiln stand.
Though this isn’t essential, you could also place a kiln shelf in the bottom of the kiln. Some people place the shelf directly against the brick bottom. Others raise the shelf with 1 1/2” long, 1 1/2” wide posts.
If you use silica sand on the kiln shelves, be careful not to allow the sand to seep onto the firebrick bottom. The sand will get into the cracks and widen them. This is why we do not recommend that you use sand on the firebrick bottom.
Arnold Howard Paragon Industries, L.P. 2011 South Town East Blvd. Mesquite, TX 75149-1122 972-288-7557 800-876-4328 Fax: 972-222-0646 firstname.lastname@example.org