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Patching Firebricks

Patching a broken firebrick is not difficult. It just requires patience and a little practice. Here is a technique that you can use to repair broken firebricks in the lid, walls, and floor of a kiln. Do not breathe the brick dust. Wear a mask.


First, you will need to make a firebrick sanding block. Use very coarse sandpaper such as 28 grit. Use the self-adhesive type that has a peel-away backing so that you can stick the sandpaper to the sanding block.

For sanding small firebrick sections, you may need a sanding block as small as 1/2” x 1”. Banding steel, which is used to reinforce shipping crates, makes a good miniature sanding block. Take a 6” piece of banding steel and bend it 90 degrees at one end. The length of the bend should be whatever size you need, such as 1”. Then cut the sandpaper to the correct size, peel off the sandpaper backing, and press the sandpaper onto the outer side of the bent end of the banding steel.

You could also make sanding blocks out of sheet metal, wood, etc.


Practice patching firebrick scraps before working on your kiln.

1) Use a hacksaw blade to cut an outline around the broken brick section. Cut a small rectangle or square.

2) Use the hacksaw to remove most of the brick within that outline. Then sand the brick to smoothen the bottom of the recess. If the repair section is small, you will need a miniature sanding block.

3) After the recess is smooth, make a firebrick plug to fit into the recess. The plug should be a little smaller in width and depth so that the brick seam is 1/16” on all sides. Spend time to make the plug fit precisely. The seam should be only 1/16" on the sides and bottom of the plug. A thicker seam will likely break later due to the difference in expansion between the firebrick and cement.

4) Use a vacuum cleaner to remove the dust.

5) Spray a little water onto all mating brick surfaces.

6) Working rapidly before the water dries out, wipe a generous amount of firebrick repair cement onto mating surfaces.

7) Press the plug tightly into place. Do not move it once the mating surfaces make contact. Hold the brick piece for one minute.

8) Allow to dry for 24 hours. Then sand the surface smooth.


We are holding a Basic Kiln Maintenance Seminar June 2 – 3, 2006. The seminar fee is $95. You are most welcome to attend.

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 /

Feel free to email this Kiln Pointer to friends. To read back issues Click here or go to, select “Support,” and then “Kiln Pointers” from the drop menu.

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Copyright 2006, by Paragon Industries, L.P.

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