Vermiculite (Grade #3 or #4) - Forno Bravo Forum: The Wood ...
01-27-2014, 01:26 PM. Re: Vermiculite (Grade #3 or #4) I've tried coarse, medium and fine vermiculite and all work ok for a 5:1, but for a leaner mix like 10:1 I've found the finer stuff works better. Some have argued that the coarser stuff would theoretically insulate better. I'm undecided about this and any difference would be marginal anyway.
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