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Vermiculite with no blanket

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  • Vermiculite with no blanket

    Hi, hope I don't get a collective groan but have searched and not found an answer.
    Can I skip using ceramic blanket and apply only vermiculite as an insulator on the exterior of the dome?
    Thanks in advance

  • #2
    Yes you can, but vermiculite cement is a much poorer insulator than the blanket. Of course, if you built a "house" for the dome, there's nothing stopping you filling the resulting cavity with vermiculite. That will work well, but vermiculite cement is a poor insulator.
    My 42" build: https://community.fornobravo.com/for...ld-new-zealand
    My oven drawings: My oven drawings - Forno Bravo Forum: The Wood-Fired Oven Community

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    • #3
      Ok, thank you, appreciate it.

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      • #4
        Has anyone seen or experienced any cracking in the outer render as a result of not having the blanket as expansion joint between the dome and perlite/vermiculite concrete?

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        • #5
          Originally posted by Petter View Post
          Has anyone seen or experienced any cracking in the outer render as a result of not having the blanket as expansion joint between the dome and perlite/vermiculite concrete?
          Yes, two friends of mine built such an oven and the outer render has cracked badly.
          My 42" build: https://community.fornobravo.com/for...ld-new-zealand
          My oven drawings: My oven drawings - Forno Bravo Forum: The Wood-Fired Oven Community

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          • #6
            Great info, Thanks a lot!

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            • #7
              What Grade of Vermiculite should you use When applying to your Dome & Floor areas ?

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              • #8
                Yes I’ve cracked the outer shell of an oven that had no blanket. The problem is that a very thick vermicrete layerwill still have a lot of moisture deeper in and particularly where it contacts the inner dense dome.If this suddenly turns to steam you’re in trouble. I simply rendered another layer over the cracked outer shell after several more drying fires to drive out the moisture. After that experience I began doing layers of vermicrete no thicker than an inch and a half thick, with a week of drying before adding a subsequent layer. When the safer blanket became cheaper I started using it instead of a vermicrete only insulation layer.

                Any grade of perlite or vermiculite will work, but the finer grade requires more water and as it is a problem to remove, it’s not a great choice. The coarse grade doesn’t hold together so well, particularly with the leaner mixes. I compromise and use a medium grade.
                Kindled with zeal and fired with passion.

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