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Vermiculite Questions - Forno Bravo Forum: The Wood-Fired Oven Community



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 Questions

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  • Vermiculite Questions

    I finally located vermiculite in the garden section of Lowe's. Is this the same product as what is used in the oven construction? I read somewhere that the correct ratio is 5:1 but nothing more. I assume this is 5 parts vermiculite to one part portland cement by volume. Is this correct?

  • #2
    Re: Vermiculite Questions

    Correct. I have seen builds here on the FB site that utilized ratios from 5:1 to 12:1. Understand that the higher the percentage of portland cement,the stiffer the mix will be and the lower the insulation value and vice versa. I went with 8:1, right in the middle. I made a slurry of the cement in water and added it to the vermiculite in a wheelbarrow and added just enough water for it to become (gently) combined, or in cook's terms, incorporated.


    • #3
      Re: Vermiculite Questions

      Yes, garden variety vermiculite is what you want. You may want to try calling any local growers or landscape suppliers. The Lowes around me only sell the small bags at a pretty steep price. The plant growers usually have the large 4 cu. ft bags for $18-$30.
      5:1 ratio is recommended for the under hearth insulation. If using the same for the dome, you can stretch it to 8:1 or even 10:1. Yes this is the ration of vermiculite to p cement


      • #4
        Re: Vermiculite Questions

        Hi All,
        I'm busy cooking and eating, all the time, but finally I am Builiding my first oven, likely a 36 in. ID Pompeii style!
        Wondering how thick my support slad should be ? Hearth is 48 x 48 in. and plan to use 10 pieces of 1/2 rebar in slab. Then a second slab of vermiculite - concrete mixture on top of the slab. Is this correct so far ?
        thank you !


        • #5
          Re: Vermiculite Questions

          Originally posted by eatingmorefood View Post
          Hearth is 48 x 48 in.
          You should go a little bigger than that for a 36" oven.

          My 34" WFO build

          Weber 22-OTG / Ugly Drum Smoker / 34" WFO


          • #6
            Re: Vermiculite Questions

            How big should my Pompeii oven be if My hearth plan is 48 in x 48 in ?
            Would you think I am crazy to build it next to my WOOD DECK ?
            What are the chances of sparks jumping out ?


            • #7
              Re: Vermiculite Questions

              George is right: 36+9+8 = 53, not counting cladding or enclosure, and you'll need more for the entry side unless you're planning a corner opening.
              My geodesic oven project: part 1, part 2


              • #8
                Re: Vermiculite Questions

                Hi Dmun,
                Your oven is amazing. Thanks for the reply, maybe it will be 32 inch ID ....
                Wondering how thick my support slad should be ? Top of concrete blocks stands at 48 x 48 in. ( I could pour slightly larger) plan to use 10 pieces of 1/2 rebar in support layer of the slab. Then a second slab of vermiculite - concrete mixture on top of the slab. Is this correct so far ? Plan to use my large supply of 14 in x 16 in. x 1 in. pizza stones (cutting them up).
                Would you think I am crazy putting this oven 1 foot from my wood deck ? I want to be able to cook off the high deck. The oven will have a door, of course. Do many sparks pop out the front of your oven?
                thank you !
                EatingMorefood - Chef