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Vermiculite/perlite confusion - Forno Bravo Forum: The Wood-Fired Oven Community



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Vermiculite/perlite confusion

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  • Vermiculite/perlite confusion

    During my initial research I found the super expensive bags of vermiculite and perlite at Lowes. They were in transparent bags so I could see what they looked like and I remember them being gray and rather large in granularity, several mm if I recall.

    Then I found a super cheap source of perlite at a masonry store and this morning bought three 4 ft^3 bags without a second thought (I anticipate using five or six eventually). This stuff was much whiter, ivory perhaps. More to the point, it is much finer than the stuff I saw at Lowes. It looks like laundry detergent, grain size of half a mm perhaps? My concern is that smaller grains might pack tighter, leaving less "fluff", less air, and weaker insulation.

    Are there different types of perlite and did I get the wrong kind? The bag even lists insulation as a possible application, so that gives me hope.

    My final decision for perlite over vermiculite was based on the facts that it is the cheaper of the two and reportedly has a slightly higher insulative R value.

    Shouldn't I want something with large grains so it will pack loose with large air pockets? Is this a vermiculite/perlite distinction (which implies that I am not remembering the appearance of the perlite at Lowes accurately) or does perlite come in different grain sizes...and would I be correct in assuming I want the largest grains possible for the loosest fill?

    BTW, my application will most likely be concrete, not loose fill, since I'm doing a dome, not an enclosure, although I am considering the approach of a rebar-chicken-wire stucco dome with a dead space around the brick dome and filling it with loose fill as opposed to concrete, haven't decided yet. Obviously, the hearth is concrete either way.

    Thanks a lot.

    Website: http://keithwiley.com
    WFO Webpage: http://keithwiley.com/brickPizzaOven.shtml
    Thread: http://www.fornobravo.com/forum/f21/...ttle-7878.html

  • #2
    Re: Vermiculite/perlite confusion

    i found the fine stuff did not create a very good layer, as it became one with the concrete and was not oatmeal-ish enough. So i tore it out. This vermiculite was from McClendon's. The good, coarse grained, setup well, and looked just like oatmeal vermiculite came from DeYoung's in Woodville.


    • #3
      Re: Vermiculite/perlite confusion

      Thanks. Rats. Thought I was set up on this. It was only $15.40 a bag at Salmon Bay in Ballard (pretty near where I live in Lake City).

      EDIT: Actually, I just called DeYoungs and their prices are $26.98 vermiculite, $15.98 perlite, so effectively identical to Salmon Bay for perlite.

      Thanks again.
      Last edited by kebwi; 09-21-2009, 01:02 PM.

      Website: http://keithwiley.com
      WFO Webpage: http://keithwiley.com/brickPizzaOven.shtml
      Thread: http://www.fornobravo.com/forum/f21/...ttle-7878.html