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materials - Forno Bravo Forum: The Wood-Fired Oven Community

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New Forno Bravo Forum Feature

Forno Bravo Forum Community,

You will notice a new forum at the top of the main page called, "Ask Me Anything". This forum will be used for live one hour "Ask Me Anything" (AMA) sessions hosted by people who are knowledgeable in different areas pertaining to wood fired ovens. How it works:
- Each AMA will have a "sticky" thread where the community can post questions they would like answered during the live session. This will allow everyone to participate even if you can't be online for the live session. These questions will not be answered by the host until the live AMA; if you need an answer quickly, you should post it in the appropriate Forum area for the community to respond.
- Another thread will be posted for the live AMA. Registered users who are logged in during the live session can interact with the host by asking questions and receiving responses.
- The live thread will remain in the AMA forum to view after the session.

To kick off our AMA feature, we have invited author, chef and master bread maker and host of Pizza Quest, Peter Reinhart, to be our first host! Peter will be in the Forum on Monday, February 15th, from 7:00 - 8:00 pm EST. If you are unable to be online during the live session, you can post your questions in the sticky post. Peter will answer those questions during the live session on February 15th. You can view Peter's answers to your questions as well as what happened during the live session in the session thread.

We hope you enjoy this new feature! Please let us know if there is a topic that you'd like to have as an AMA and we'll look for a host!

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  • materials

    A few questions about materials:

    1. Vermiculite versus Perlite: is one better than the other?
    2. If using Vermiculite, what granule size is best for (1) lightweight concrete, (2) mortar and (3) loose insulation between the dome and outside structure?
    3. If using self mix mortar does it matter what type of sand is used?
    4. Most fire bricks I've seen advertised are 42% alumina: is this OK for floor and dome?
    5. If using regular clay bricks rather than fir bricks for dome, what mortar mix should be used?

    Thanks, in advance, for any replies.

    Chris Bowman (in the UK)

  • #2
    Re: materials

    Do a search on the forums, its all been done before.
    Here is the first question search results I came up with so no doubt the rest have been answered before too.

    http://www.fornobravo.com/forum/f6/v...lend-5932.html
    The English language was invented by people who couldnt spell.

    My Build.

    Books.

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    • #3
      Re: materials

      1. Vermiculite versus Perlite: is one better than the other?
      No.
      2. If using Vermiculite, what granule size is best for (1) lightweight concrete,...and (3) loose insulation between the dome and outside structure?
      Unlike some categories of human endeavor, size doesn't matter.
      (2) mortar
      Vermiculite/perlite isn't used in mortar.
      4. Most fire bricks I've seen advertised are 42% alumina: is this OK for floor and dome?
      At the temperatures that we run at, the alumina content isn't particularly important. Don't pay more for high alumina bricks.
      5. If using regular clay bricks rather than fir bricks for dome, what mortar mix should be used?
      For the best/cheapest mortar for dome construction, search for "homebrew mortar"
      Don't use plain clay bricks if you can at all avoid it. It's a ton of work to build a brick oven, and saving a few pennies may be short sighted.
      My geodesic oven project: part 1, part 2

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      • #4
        Re: materials

        Vermiculite versus Perlite: is one better than the other?

        I think there is some variation in the two materials depending where it comes from. I weighed a 100 L bag of vermiculite and it was 9.0 Kg and the same size bag of perlite was 7.5 Kg This is a significant difference. This perlite contains more air and therefore a better insulator.The perlite is a little dearer here and for preference I like to use vermiculite because it is a bit easier to mix and doesn't create irritating dust like perlite.
        Check the thermal conductivity of the two materials.
        Kindled with zeal and fired with passion.

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        • #5
          Re: materials

          As a general rule, the bigger the joint, the bigger the grain of sand needed. Since smaller joints are desirable in an oven, this requires a smaller grain. For one who has a small inside joint with a large outside (ie: a triangular-jointed soldier joint) it has been recommended to employ two kinds of mortar. Tscarborough, in one of his FB posts here, describes building the optimum mortar using multiple grain sizes in a single mortar akin to filling a jar with golf balls, then marbles, then ball bearings.
          Last edited by GianniFocaccia; 02-19-2011, 04:39 PM.

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