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Vermiculte, Perlite and bulk Pumice

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  • Vermiculte, Perlite and bulk Pumice

    i don't see anyone talking about using pumice which is easy to get by
    the cubic yard from rock and soil sources and is less expensive?
    are the insulating properties similar?


  • #2
    Pumice is an excellent alternative. Perlite is a form of pumice in
    fact and perlite is often used as an alternative to vermiculite in
    concrete applications (in fact often more frequently then vermiculite
    for many concrete uses). Perlite is usually easier to find in a usable
    format -- small discrete particles as it is used both as a soil
    additive (in large bags -- 3-4 cu ft usually costs about what 4 of the
    small qt bags will) and as a concrete filler. It's poured into the
    cores of block walls before filling with concrete to reduce the amount
    of concrete required. In this use it is usually coated with silicone
    so make sure you get non-siliconized perlite if you use that. Pumice
    is usually easier to find out west than back here in the east.



    • #3
      jim - thanks so much for your answer!

      is it safe to say than that pumice can be used in the same thicknesst
      as vermiculite for insulating our bread ovens? (where avaible easily
      like here in ca)

      i found pumice at a soil and rock supply retailer nearby in a mix of
      sizes ranging from 2-7millimeter in diameter and bought a cubic yard
      for $40 while i was still planing on building a earth-friendly mud
      oven, but than run into the pompeii designs.......pumice is used
      regularly for landscaping purposes ....

      i have already used a 6-inch layer of pumice/portland cement for the
      insulation of the hearth....

      james asked me why i considered using pumice at the first place. price
      and availability was one factor, the other was that vermiculite and
      perlite (as does portland cement for that matter) require a lot of
      energy to be produced while pumice is just ground up lava stone.



      • #4
        Great question. We've been having some trouble locating bulk supplies of vermiculite -- I
        guess there was some question about asbestos contamination --- so I've been
        investigating alternatives. Pumice seems to be a great idea. I know they use it in concrete
        forms. Where did you find your source? We're up in Sonoma county, CA.



        • #5
          John and Simone,

          This makes a lot of sense, though I have to admit to not knowing the
          exact insulating properties of the two. Perlite and vermiculite are
          very similar, but I don't know about bulk pumice. Jim probably does,
          and I am sure he will let us know if he does. :-)

          I will do some research as well. Once we know the thermal property,
          it is easy to calculate thickness relative to Vermiculite, where
          hands-on experience shows that 4"-6" is definitely sufficient. My
          oven here has less than that, and my stucco exterior never gets hot.

          John, I bought my vermiculite at Home Depot in Windsor (my second
          home), in the garden section.

          Here is a link on vermiculite and asbestos. It appears to have more
          to with mining and production than use, but you can make your own
          call. As Simone noted, it takes energy to "pop" it.

          Last, can we move this thread to the new Forum? It's a good one. I
          will copy these over under Yahoo-Archive, and give the thread a
          catchy name.

          Pizza Ovens
          Outdoor Fireplaces


          • #6

            hi leslie and john

            american soil product has a big supply yard right here in richmond bordering el cerrito.(ca)
            coming from sonoma you take 80 south and get off at central av.
            make an immediate right onto san joaquin road. follow the road for about
            1/2 a mile and you will see it on your left. it is sandwiched between 80 and 580.
            great place!! you can buy stuff in cubic-, half cubic yard or in smaller bags.
            #510 540 8011 - you can also find them on the web.

            are you building a bread-oven? love to hear more about it.
            we live in el cerrito and you a certainly welcome to come by. i am
            almost done with my pompeii.



            • #7
              beginning stages

              Hey everyone, we are starting our pompeii oven this weekend-woo-hoo!

              I'm reading through many of the threads and JUST want to be sure I have a few things straight:

              -It's okay to just dry stack the cinder block and coat with quickrete on the outside for stability? I think Bob has done this on his oven, and it seems to be working great for him, I just want to be sure that in my climate and hard winters this would still work.

              -I can use EITHER perlite, vermiculite, or pumice on the stand with the concrete? I can just choose which one based on availability and price? Seems like everyone has tried something different. Does it matter in the end which is used? Are they equally easy (or hard) to work with?

              Anyone that has opinions on either of these matters, please let me know-

              Thanks Elizabeth


              • #8
                Re: Vermiculte, Perlite and bulk Pumice

                if your going to stack your blockk you should use the quickrete SURFACE BONDING CEMENT. it has fiberglass strands in it that give it its strength. I also used rebar and filled every other core in the block, dont know if it was necessary but i figured it couldnt hurt. I also used it for the final layer on my dome after Quickrete assured me it would be okay to use with the minimal heat it will receive. I also added color and the acrylic fortifier to make it waterproof.


                • #9
                  Re: Vermiculte, Perlite and bulk Pumice

                  I am building a Pompeii oven in Albuquerque and am trying to decide whether to use perlite, pumice or red lava rock mixed in concrete as additional insulation to the 2" ceramic fiber blanket I am using to insulate the dome of my oven.

                  I am building the Pompeii Oven in my kitchen and will enclose everything in brick from the floor to the ceiling. I want to fill the void above the dome with concrete mixed with either, pumice, perlite or red lava rock which I can obtain locally. I might use all three and see how it is to work with them.

                  I did find a page that said in a post that perlite has a higher insulation value than pumice.

                  "yep that they are however each has a specific insulation value. pumice being the lowest and perlite being the highest. in order to get the insulation values you have to use more materials. so you end up spending just as much to get
                  4 times the pumice as you would for a two 2 cubic foot of perlite."
                  Crushed Lava Rocks vs Perlite or Vermiculite (wood burning stoves forum at permies)

                  I found another page that give info on perlite's insulative value.
                  "Perlite's R-value is nearly 3.0 per inch at 6-lbs./cu. ft. density."
                  Supreme Perlite Company - The Northwest's Leading Manufacturer of Perlite Products.

                  I would love to find a table that lists the insulation values of all three.

                  I found a source for perlite at Condeck Concrete
                  ConDeck Concrete Installer -

                  4 cubic ft bag $11.00 (weight 33 lbs)
                  56 cubic ft bag $125.10 (weight 615 lbs)

                  I found pumice at CR Minerals in Espanola, NM
                  Amorphous Silica - Crystalline Silica - Filtration - Silicosis

                  $25 per yard

                  I also found pumice at Buildology
                  Gravel & Landscaping Materials | Retaining Walls, Pavers Albuquerque

                  $170 per ton

                  I have found red lava rock at various sources for about $70 to $78 per ton