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Vermiculite Concrete hearth insulation - Forno Bravo Forum: The Wood-Fired Oven Community



I'm Peter Reinhart! Ask Me Anything! Monday, February 15, 2016 7:00-8:00 pm EST

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.

Ask Me Anything New Forum Feature

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.
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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 Concrete hearth insulation

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  • Vermiculite Concrete hearth insulation

    Iím going to pour my vermiculite concrete layer this weekend. I poured test sample of the vermiculite and noticed areas of small air pockets. Should I be concerned with moisture or air pocket in the bottom insulation layer that may expand later when heat is applied? Perhaps it is assumed that hot air and steam slowly works its way out thru the brick floor and is not a problem.

  • #2
    Re: Vermiculite Concrete hearth insulation

    Air pockets are the point of vermiculite concrete. It's the air trapped in the layer that insulates. You're good to go.
    My geodesic oven project: part 1, part 2


    • #3
      Re: Vermiculite Concrete hearth insulation

      Exactly...the air pockets are your friend. However, I would pat the wet mixture down lightly when you pour it and level it...tiny airpockets is the idea, big caves of air probably not so great.
      Check out my oven progress here: http://www.fornobravo.com/forum/phot...dex.php?u=4147

      See ALL of my pictures here:


      • #4
        Re: Vermiculite Concrete hearth insulation

        Something I noticed when I was stuccoing my oven- in the front, where my vermicrete had slumped a little and was a tad thick, I took a brick and "sanded" it a little to get it flat. I noticed that the newly exposed inside was much softer and crumblier than the outside. Sort of like when you make a sand castle and it dries on the outside, and when you mess with it, it all slides out. When I applied the vermicrete to the exterior of the landing and vent, I patted it into position. Did this bring the portland to the surface more, sort of making a shell around the vermiculite?

        I just covered the spot up with stucco as I had intended, but if I hadn't meant to do that, I would have had a problem, since it was a vertical surface. If it had been a horizontal one, I don't think it would have mattered. I have the same vermicrete under the oven and the insulating board, and it's never shifted or compacted in any way. But I didn't apply it the same way, either. It was mixed and dumped into the form, screeded flat, and left alone.

        Just wondering if the way you apply the vermicrete changes the insulating value and/or the structural integrity. Obviously, the layer around the oven doesn't need the same strength as the layer under it.



        • #5
          Re: Vermiculite Concrete hearth insulation

          Thanks for the input. I will pour my vermiculite with confidence and my pizza will taste great.
          I have posted a picture of my test pour (broken to see the inside). It is a very interesting medium to work with. Also, I found that mixing the dry vermiculite & cement, (5:1 ratio, each part being 2.5 quarts) in a 5 gallon bucket with lid works well. Tumble for a few minutes then I am then transferring it into other buckets until I have enough to mix with water and fill my form.
          PhotoPlog - Hearth and Stand