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Poured hearth, questions about concrete and insulation... - Forno Bravo Forum: The Wood-Fired Oven Community

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Poured hearth, questions about concrete and insulation...

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  • Poured hearth, questions about concrete and insulation...

    First the questions:

    I read somewhere that if you add some washing-up liquid to the water in the cement, you can get away with using far less water for the same workable consistency because it reduces the surface tension of the water - does anyone know anything about this? I tried it on some smaller projects and you do need less water, but I didn't on the hearth as I was worried it might reduce the strength or something.

    I've been looking for insulation and someone suggested using stonewool. Someone else gave me some (10 year old) glasswool that they used on their oven, though not enough for the entire insulation. I googled both products and was a bit worried by some of the results. One company wanted the equivalent of about 500 USD just for insulating slabs to put under the oven! However, I did locate vermiculite... I'll put the information in the vermiculite thread in a moment. The only thing is, my hearth is alread quite high - I'm worried I'll have to use a step ladder when I use it.

    So, stonewool, 10-year-old glasswool, stepladder, keep looking, what do you think?

    Anyway, here are the picks. I used my tried and true learning-by-doing-hope-no-one-ever-sees-this method of construction, and its still standing. Btw, the righthand corner is not in fact lower than the rest, it just looks that way because the frame walls are uneven...
    Attached Files
    "Building a Brick oven is the most fun anyone can have by themselves." (Terry Pratchett... slightly amended)

    http://www.fornobravo.com/forum/f8/p...pics-2610.html
    http://www.fornobravo.com/forum/f9/p...nues-2991.html

  • #2
    Re: Poured hearth, questions about concrete and insulation...

    So, after all the advice , I decided to go with the Vermiculite. I put it down two days ago, and now, like everybody else, I'm suddenly worried. In this case that the Vermiculite particles were too big... they're 4-8 mm and the consistency is more like chocolate coated popcorn than oatmeal. All the pictures I can find seem to show a different consistency. How big is the US Vermiculite then? Will I be ok with mine?

    Sorry to whitter on, but you all know what Vermiculite is like. Hope someone can reassure me...
    Frances
    "Building a Brick oven is the most fun anyone can have by themselves." (Terry Pratchett... slightly amended)

    http://www.fornobravo.com/forum/f8/p...pics-2610.html
    http://www.fornobravo.com/forum/f9/p...nues-2991.html

    Comment


    • #3
      Re: Poured hearth, questions about concrete and insulation...

      What was your mix? 5 to 1?

      And did you just wet it until you could squeeze just a bit of water out of it?

      If so, from what I've read, it should firm up nicely in about a week.

      It should eventually feel and act like cork.

      But this is just what I have read.
      My thread:
      http://www.fornobravo.com/forum/f8/d...ress-2476.html
      My costs:
      http://spreadsheets.google.com/pub?k...Xr0fvgxuh4s7Hw
      My pics:
      http://picasaweb.google.com/dawatsonator

      Comment


      • #4
        Re: Poured hearth, questions about concrete and insulation...

        Yeah, I think I got the mix right - actually I thought the stuff was quite fun to work with. It seems to be firming up ok, too.

        The thing is, its going to be more like cork made from popcorn than cork made from oatmeal. As it were. I mean it was a really chunky mixture.
        "Building a Brick oven is the most fun anyone can have by themselves." (Terry Pratchett... slightly amended)

        http://www.fornobravo.com/forum/f8/p...pics-2610.html
        http://www.fornobravo.com/forum/f9/p...nues-2991.html

        Comment


        • #5
          Re: Poured hearth, questions about concrete and insulation...

          I think you will be fine.

          It's recommended to use the fine grains, but the coarse ones will work too.
          My thread:
          http://www.fornobravo.com/forum/f8/d...ress-2476.html
          My costs:
          http://spreadsheets.google.com/pub?k...Xr0fvgxuh4s7Hw
          My pics:
          http://picasaweb.google.com/dawatsonator

          Comment


          • #6
            Re: Poured hearth, questions about concrete and insulation...

            can a extra thick layer of fine grade vermiculite be used instead of the fire bricks to make the hearth ? anyone tried that yet or does it crumble and end up on the bottom of your pizza ??

            Comment


            • #7
              Re: Poured hearth, questions about concrete and insulation...

              Originally posted by barbarian View Post
              can a extra thick layer of fine grade vermiculite be used instead of the fire bricks to make the hearth ? anyone tried that yet or does it crumble and end up on the bottom of your pizza ??
              Nah. The vermiculite is for insulation purposes. The bricks hold heat, provide thermal mass, and create a hard surface to cook your pizza on. You pour a concrete layer for strength, followed by a vermiculite layer for insulation, and then a layer of bricks for thermal mass and heat storage.
              My thread:
              http://www.fornobravo.com/forum/f8/d...ress-2476.html
              My costs:
              http://spreadsheets.google.com/pub?k...Xr0fvgxuh4s7Hw
              My pics:
              http://picasaweb.google.com/dawatsonator

              Comment


              • #8
                Re: Poured hearth, questions about concrete and insulation...

                Thanks .. duh I should have used my brain..
                I have done 9 hours straight of reading I just stumbled on one thread discussing a similar question.... I am not kidding I just paused 30 min. for dinner
                this is the date of my subscription to the forum LOL
                Date: September 14, 2007 2:33:40 PM EDT
                this is awesome and pathetic at the same time

                Originally posted by asudavew View Post
                Nah. The vermiculite is for insulation purposes. The bricks hold heat, provide thermal mass, and create a hard surface to cook your pizza on. You pour a concrete layer for strength, followed by a vermiculite layer for insulation, and then a layer of bricks for thermal mass and heat storage.

                Comment


                • #9
                  Re: Poured hearth, questions about concrete and insulation...

                  Originally posted by barbarian View Post
                  Thanks .. duh I should have used my brain..
                  I have done 9 hours straight of reading I just stumbled on one thread discussing a similar question.... I am not kidding I just paused 30 min. for dinner
                  this is the date of my subscription to the forum LOL
                  Date: September 14, 2007 2:33:40 PM EDT
                  this is awesome and pathetic at the same time
                  Obsessed already?

                  I understand......... trust me!
                  My thread:
                  http://www.fornobravo.com/forum/f8/d...ress-2476.html
                  My costs:
                  http://spreadsheets.google.com/pub?k...Xr0fvgxuh4s7Hw
                  My pics:
                  http://picasaweb.google.com/dawatsonator

                  Comment


                  • #10
                    Re: Poured hearth, questions about concrete and insulation...

                    Originally posted by asudavew View Post
                    Obsessed already?

                    I understand......... trust me!

                    Yup I caught the bug

                    Comment

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