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Help! Asbestos firebricks? - Forno Bravo Forum: The Wood-Fired Oven Community


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Help! Asbestos firebricks?

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  • Help! Asbestos firebricks?

    Can someone PLEASE give me some advice about the dangers and likelihood of asbestos being in firebricks?! I've just bought some second hand bricks (I'm in Australia) in a private sale and I'm mainly worried as they are very light to lift. I've read that firebricks used to contain asbestos, and as these are old I have no info about them. I'll attach a photo, but as I said it's the weight that has me scared.

    Are modern firebricks light weight?

    Advice is much appreciated.

  • #2
    Re: Help! Asbestos firebricks?

    If they are light, they are insulating firebrick, not suitable for wearing surfaces (like the floor), and not suitable for the oven mass (like the walls). They are normally used in kilns which want to maintain a high heat, but not store it like an oven.

    They are fine for any application in which they will not be exposed to abrasion, asbestos or not.


    • #3
      Re: Help! Asbestos firebricks?

      Hello R W,

      You may have insulating kiln brick and not firebrick. Look at the Firebrick Primer in the Pompeii section since it is a good reference. You want a brick that weighs over seven pounds with a dimension of roughly 4" x 2.5" x 9". Most weigh nearly eight pounds. You will find firebrick in various colors and sizes close to the dimensions I've described. Firebrick has thermal mass due to their density and weight. That is what holds the heat for our baking purpose. Light insulating brick does not hold heat and is used in kilns to hold heat in while an item such as a ceramic is baked, then the oven cools while the fire source is reduced or extinguished. If you can scrape material off the brick with your thumb nail and the brick has a very porous appearance like a sponge then you have insulating kiln brick. There are several types. Can you see cracks in the brick? Can you break one of the bricks by hand? That might confirm that you have insulating brick. If so, you might want to place them under your hearth with a layer of vermicrete or perlcrete in addition since their main purpose is insulating and not holding heat.

      Asbestos is most harmful when the particles become airborn and inhaled. Latent dust particles are still harmful even when mixed in soil because wind can lift them into the air. I recall seeing piles of mined asbestos stored near a mobile home in a mining town. As a child, I recall a student brought asbestos samples to school after a weekend camping trip with family. Search the internet for information about asbestos and its commercial uses. That should give you some idea of the composition and appearance of the bricks you are concerned about.


      Here is the link to my oven number 1 construction photos!

      Here is the link to my oven number 2 construction photos!


      • #4
        Re: Help! Asbestos firebricks?

        Yep, insulating firebricks are made of refractory clay and sawdust, fired to high temperature. They are fine as insulation, and about as effective as vermiculite concrete.

        Asbestos turned up in all sorts of things back in the day, but firebricks were not likely to be one of them. Asbestos does not naturally occur in clay deposits, and it would be unnecessarily expensive to be used as an additive. (clay in cheap, in industrial quantities)
        My geodesic oven project: part 1, part 2


        • #5
          Re: Help! Asbestos firebricks?

          Thanks a bunch guys. RW