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jukenut 07-17-2008 01:49 PM

Thoughts ?
Hi all,
I poured the oven insulated base this past weekend. I used vermiculite, mixed with portland
cement, 5:1 ratio. ( I did not skimp on the cement, I was even a little generous) i checked the
base a couple of days later, seemed a little soft, spongy. I have not worked with vermiculite
before, maybe I am just used to cement and its firmness. Thoughts ? Oh I should say I dry
mixed the vermiculit and cement, and then added water gently.

This weekend I am planning on assembling the oven, my plan is to use refractory cement on the
joints, lay about 2 inches of vermiculite on the oven, blanket wrap the oven, chicken wire &rebar,
and another 4 inches of vermiculite. Of course I am not going to do this all in one shot, it would be over a few days.

I did print and read one of the intallation manuals on line here, I am going to re-read tonight.


SpringJim 07-17-2008 02:02 PM

Re: Thoughts ?
Anthony, the vermiculite/perlite layer tends to be a bit "spongy" kind of like styrofoam to me.....and I think the less portland (or less well mixed), the more fragile the material tends to be.

nissanneill 07-17-2008 09:26 PM

Re: Thoughts ?
Hi Jukenut
the vermiculite cement is more like a cork consistency but will harden up a little more over time. I certainly would not put any more Portland cement into the mix as the insulasting effects are reduced as the portland works more like a heat soak than insulating. The 1:5 ratio is exactly as I did mine with no problems.


asudavew 07-18-2008 08:12 AM

Re: Thoughts ?

Originally Posted by jukenut (Post 37454)
, lay about 2 inches of vermiculite on the oven, blanket wrap the oven, chicken wire &rebar,


I think the general consensus is to use the blanket first. It's the better insulator and will hold heat in the oven longer than vermiculite. Then follow that with your vermcrete.

Other than that, I think you have the right plan going.


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