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Alumina Content - Forno Bravo Forum: The Wood-Fired Oven Community



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Alumina Content

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  • Alumina Content

    Hi. I was wondering if anyone could help me understand the pros and cons of Alumina content in casting refractory. I have read FB page on firebrick and how they recommend medium grade firebrick with 30% Al. I have also read the higher content can cause the oven to get too hot for bread. If I am just making pizza would the higher content be better? I also see that in the FB precast they use 80% Al precast. Is Al in precast differ from Al in firebrick? Is there any issue with the 80% Al in the precast and using firebrick with 30% on the floors? Maybe I am reading too deep now just let me know to stop over thinking.

  • #2
    Re: Alumina Content

    If you were building the first oven ever built, it would be wise thinking. In reality, the margin of error is so large that it is almost impossible to botch it such that your oven will not work for it's intended use. Use what you can find locally, build as accurately as you efficiently can, and cook some pizza.

    Or, just buy the kit or premade and cook that much faster. Either way, good luck.


    • #3
      Re: Alumina Content

      There are literally thousands of refractory products. Happily, they are made by companies that keep applications engineers on staff to answer questions just like these. Give the company in question a call, and tell them you have a technical question. And let us know what you find out.
      My geodesic oven project: part 1, part 2


      • #4
        Re: Alumina Content

        One quick note. Our castable recipe for the FB ovens is 80%+ Alumina and Silica (not just alumina). The make-up of the dome is basically the same as the firebrick floor -- with very little non-refractory impurities. We use large Medium duty firebrick tiles for the FB oven cooking floors (38% alumina).

        Check our Firebrick page for more info. The ultra high duty firebricks are for blast furnaces, and we are baking pizza, not melting metals. :-)

        Brick Oven Design | Choose the Right Brick Oven Brick

        Pizza Ovens
        Outdoor Fireplaces


        • #5
          Re: Alumina Content

          Dmun, it is true that they have technical people on staff, but I would caution you that unless you can articulate a specific question, and understand the answer as given, that you will not get much help as an individual from the manufacturer. It is usually better to ask your questions of the distributor, again with clear, specific questions. If they do not know your answer, they are in a better position to work with the manufacturer to figure out what you are trying to achieve and how best to do so.


          • #6
            Re: Alumina Content

            The question of alumina content is not a question of temperature. The bricks will (if they are heated to saturation) reach the same temperature regardless of their specification (assuming that you have a well insulated oven where the insulation will control the heat loss). The important issue is the bricks resistance to erosion (weare and tear) during repeated heating (hardness) and their specific weight (which will determine their heat capacity).