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Perlite vs. Vericulite final Insulation layer - Forno Bravo Forum: The Wood-Fired Oven Community



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Perlite vs. Vericulite final Insulation layer

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  • Perlite vs. Vericulite final Insulation layer

    I am waiting the 3 weeks for my 6" Cladding to dry and am wondering if I should use Vermiculite loosely, mixed 6:1 with portland cement, or use Perlite.
    I build a brick wall up from the base, so now I have a 5" gap between the cladding and the final wall, so I can pour anything in there. Is one better than the other. They both cost exactly the same, and the Vermiculite says 100% Asbestus free certified on it.

    Thanks for any suggestions.


  • #2
    Re: Perlite vs. Vericulite final Insulation layer


    I am waiting the 3 weeks for my 6" Cladding to dry
    why wait, get some 'gentle' fires going, not to bake the oven but add alittle heat to encourage the drying process. It will get the air moving, drive a little heat into the dome and accelerat the evaporation process. Remeber to take it gently. See what moisture is coming out through the bricks before increasing the temperatures.

    As far as your insualtion, I would be tempted to line the back of your outer wall with a thicker 'caterers aluminium foil' and pour in vermiculite. This will give the best (well at least in my opinion), as 5" is all that is needed, the foil will add that extra protection and keep it dry should moisture get through the bricks in a wet period.

    Prevention is better than cure, - do it right the first time!

    The more I learn, the more I realise how little I know

    Neillís Pompeiii #1
    Neillís kitchen underway


    • #3
      Re: Perlite vs. Vericulite final Insulation layer

      I chose the medium grade vermiculite from ULINE shipping supplies.. Worked fine for me.. and as i understand, Vermic is 100% natural.. I dont know if the perlite is or not.. If you are Just filling the voids, you dont need to mix with portland.. only pour it in.. you can mix it,, Im not sure if that makes a difference ... Maybe someone else can verify that ??
      you can sometimes buy premixed vermicrete from a Pool building supply company..


      • #4
        Re: Perlite vs. Vericulite final Insulation layer

        Vermic is 100% natural..
        They're both naturally occurring minerals with the strange property of "popping" like popcorn when heat treated. This is what perlite looks like:

        This is what vermiculite looks like:

        Vermiculite is the short mineroligical name for hydrated laminar magnesium-aluminum-ironsilicate which is similar to mica in appearance. Vermiculite is light-weight, fire-resistant, odorless, absorbent, and expands into accordian shaped pieces when heated also known as being "Exfoliated". These pieces of exfoliated vermiculite insulation sometimes resembles worms, hence the prefix "vermi" which is latin for worm.
        My geodesic oven project: part 1, part 2


        • #5
          Re: Perlite vs. Vericulite final Insulation layer

          If you mix vermiculite or perlite with cement and water you then have the problem of removing the water by a combination of air movement, temp. and time. Add the stuff dry and you have less water to remove from your oven. Be careful about using a foil layer for added insulation. It does a great job of locking in the moisture. I tried this and my oven took months to dry properly. At least poke lots of little holes all over the foil to allow the steam out.
          Kindled with zeal and fired with passion.


          • #6
            Re: Perlite vs. Vericulite final Insulation layer

            "This is what perlite looks like:"

            That's what the "un popped" stuff looks like. (If if looks like the above photo, don't use it.)