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Vermicrete very crumbly after setting - Forno Bravo Forum: The Wood-Fired Oven Community



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Vermicrete very crumbly after setting

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  • Vermicrete very crumbly after setting

    Hi, I've mentioned this in another thread but felt like its a subject deserving its own.
    I mixed the vermicrete for my hearth insulation using 6:1 mix with slightly over 23litres water to 100L of mix because I have a document from my supplier with these instructions saved in my email from a year or 2 ago. Anyway, the mix was VERY dry. It has dried out very crumbly. It shouldn't be a problem because its in a concrete/block box like structure so it can't go anywhere. My oven is now sitting on top and I'm ready to insulate it.
    Anyway, I now find this document (attached)on my suppliers website that recommends I use 40/50% water in the mix. I know this is contrary to all the advice here but from my personal experience mixing this stuff I'm pretty sure it needs to be much wetter than the original 23% water mix or it'll never hold on the dome structure. Has anyone had similar experience? Could my suppliers vermiculite be different from others?


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  • #2
    Re: Vermicrete very crumbly after setting

    Originally posted by RichC View Post
    Could my suppliers vermiculite be different from others?
    I doubt it, vermiculite is vermiculite.

    Vermiculite - Wikipedia, the free encyclopedia
    The English language was invented by people who couldnt spell.

    My Build.



    • #3
      Re: Vermicrete very crumbly after setting

      I think every batch of vermiculite varies a little, but I've found 30 L water to every 100 L vermiculite to be the ideal ratio. If the stuf has got wet then less is required or if using a fine grade more is required. If you end up with water in the bottom of your barrow or bucket then you've added too much water. I've mixed tons if this stuff and the water addition is important to get right.
      23 L water for 100 l verm. Is not enough OMO.
      Last edited by david s; 09-07-2013, 07:08 AM.
      Kindled with zeal and fired with passion.