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Perlite Question - Forno Bravo Forum: The Wood-Fired Oven Community

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Perlite Question

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  • Perlite Question

    Fellow builders:
    I've gotten to the point of getting ready to mix and pour the insulating layer of Perlite and Portland cement. I opened the bag of perlite for the first time and found that is sand like in consistency. Is that too fine to mix with Portland and pour? Should I junk the stuff and buy something else. Vermiculite in quantity seems to be tough to find here in Austin

    Thanks

  • #2
    Re: Perlite Question

    I think that that is too fine. Look for a coarser grain - something like 1/8 inch or better particles.

    Comment


    • #3
      Re: Perlite Question

      Sounds a bit too fine to me, as well. I used Vermiculite for the insulation slab - was labeled "medium grade" and until I reached the bottom 25% of each bag it was fine. The bottom of each bag was like brown talcum powder (a lot of settling), needless to say, I wasn't thrilled with the waste.

      I switched to perlite for the dome (over 2" of blanket). The perlite was purchased from an online shipping products supplier, they sold about a half dozen different grades/sizes. Again, I chose medium. The perlite was much more consistant throughout the bags, it was about the size of Grape Nuts Cereal. As others have mentioned, it is much easier to judge whether you have mixed the portland thoroughly because of the white color.

      The bottom line - I think you need it a bit courser, makes the mix more "airy" and adds to the insulation value (my opinion).

      RT

      Comment


      • #4
        Re: Perlite Question

        Originally posted by RTflorida View Post
        ...

        I switched to perlite for the dome (over 2" of blanket). The perlite was purchased from an online shipping products supplier, they sold about a half dozen different grades/sizes. Again, I chose medium. The perlite was much more consistant throughout the bags, it was about the size of Grape Nuts Cereal. As others have mentioned, it is much easier to judge whether you have mixed the portland thoroughly because of the white color.
        ....
        RT
        RT, can you tell us the website where you bought your perlite?

        Thanks!
        Toby

        Comment


        • #5
          Re: Perlite Question

          Re Perlite question:
          Thanks, Neil, Florida. I am worried about this question of vermiculite grade/size. Is there an official view? It isn't mentioned in the instructions as you probably know (and sorry, I am not familiar with Grape Nuts cereal coming from Australia). Size of rice grains? A pea? Big as the end of your thumb? I bought one bag (vermiculite grade 1) and it's just a bit bigger than coarse sand, so I guess that's no good. Help!

          Comment


          • #6
            Re: Perlite Question

            Neither grape nor nut.
            Attached Files
            -David

            Comment


            • #7
              Re: Perlite Question

              I found my perlite at a hydroponics store, they had all grades from fine to coarse and the price was very reasonable

              Comment


              • #8
                Re: Perlite Question

                Only kind I've found so far was Miracle-Gro and it's not cheap.. if someone has an online source please post it!
                Shay - Centerville, MN

                My Outdoor Kitchen/Pompeii WFO Build...

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                • #9
                  Re: Perlite Question

                  I found perlite in bulk at a local hydroponics store, and at a good price

                  Comment


                  • #10
                    Re: Perlite Question

                    here's where I bought mine: the shipping is more than the product.

                    Krum Horticultural Perlite Garden Plant Soil Aerator A - eBay (item 250465932618 end time Aug-15-09 05:36:32 PDT)
                    My geodesic oven project: part 1, part 2

                    Comment


                    • #11
                      Re: Perlite Question

                      "A pea? "

                      Coarse perlite is a mix of sizes but averaging about that size or a bit smaller. Some people have had success with the medium grade - which would average about "rice" sized.

                      Comment

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