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vermiculite insulation - 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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vermiculite insulation

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  • vermiculite insulation

    i am in the process of building an alan scott design oven. i just poured the concrete over the dome this past weekend. my intentions are to eventually clad it with grapefruit size granite stones as a finished coat. my question is regarding the vermiculite insulation. is it best to pour the vermiculite dry first and then cover it with a vermiculite/portland mixture or just use a damp vermiculite/portland mixture with venting right off the bat? thank you in advance.

    need real bread,
    bernie

  • #2
    Re: vermiculite insulation

    General consensus around here is that it's best to mix the vermiculite and portland thouroughly while dry, add water, then apply the damp oatmeal-consistency mixture. Check out some of the other threads, and look at the photo section on insulation for some good illustrations.
    -jamie

    My oven build is finally complete!

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    • #3
      Re: vermiculite insulation

      Gee,
      how much thermal mass do you want in your oven?
      The bricks in your barrel vault are probably 4 1/2" thick, with a layer of concrete over that to increase the mass, you now need at least 4 to 5" vermiculite cement to insulate the vault AND then a cement layer to hold your rock in place. If you don't do this, you will need all day and a truck load of wood to get it hot and it will drain the heat out and cool down quicker than it took to get hot without being well insulated.
      I would not have put the cement layer on, but a thermal superwool or similar insulating blanket or 4" vermiculite insulation straight onto your vault bricks and then your final finish to accommodate your rocks.

      Rastys
      If you don't succeed the first time, try again and again until you get it right!

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      • #4
        Re: vermiculite insulation

        The Alan Scott design is more of a bread oven, I think. They generally have more thermal mass that a pizza oven.

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        • #5
          Re: vermiculite insulation

          thanks for your helpful replies. i was concerned about loosing insulating value when wetting the vermiculite. as for the thermal mass, i did not even think of the outer stonework adding thermal mass. i considered it cosmetic being on the outside of the insulation. up here in manitoba, canada it may be a blessing. soon, i should have some bread.

          thanks again,
          bernie

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          • #6
            Re: vermiculite insulation

            Bernie,
            if you don't insulate well your vault, then your decorative stone outer surface will add to your thermal mass, absorb your oven heat and release it to the atmosphere.
            By all means do your rock finish layer but I would put at least 4" vermiculite cement under it to provide your insulation.
            Mix your vermiculite 6 pts to Portland cement 1 pt to a porride/oatmeal consistency.
            I mixed mine in a wheelbarrow with a flat bladed fork and then carefully added the water till it held together in a ball when squeezed, a bit like a snowball. Little if any water should be squeezed out of it when squeezed. It is quite unusual to mix as the added water washes the portland off the vermiculite but be careful not to put too much water into the mix and that it well mixed before applying it to your vault.

            Rastys
            If you don't succeed the first time, try again and again until you get it right!

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