#11  
Old 03-31-2008, 11:45 AM
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Default Re: Sorry - another Vermiculite Question

When I did my vermiculite layer, I got worried because mine was very coarse and everyone was using fine grain stuff... maybe its another of those things where it doesn't really matter much either way so long as you get the hydration and concrete proportion right?
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  #12  
Old 03-31-2008, 02:01 PM
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Default Re: Sorry - another Vermiculite Question

That's kind of my issue.

What I have is very fine - almost like sand. To be on the safe side I'll probably get the Isol board but still want to pour a smaller insulated hearth...

My main question is should the "fine" stuff be okay? 5 to 1 ratio as well?

Thanks
Dick

PS - George - I did see your response but want to get a consensus. This is something I can't change once my floor is down...
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  #13  
Old 03-31-2008, 05:29 PM
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Default Re: Sorry - another Vermiculite Question

Otter,
You can't hurt my feelings. I would do the same! I thought you said you could take it back and exchange it?
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  #14  
Old 03-31-2008, 07:03 PM
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Default Re: Sorry - another Vermiculite Question

George,

Thanks!

I can - and I think I will take it back for the perlite... I'll probably put down a 3 1/2 inch layer (extra height and insulation) and then 2 inches of Iso board on top... That should bring my oven height to ~43".

Thanks
Dick
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  #15  
Old 04-01-2008, 07:07 AM
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Default Re: Sorry - another Vermiculite Question

I like that! Lots of insulation under the floor. Great idea!
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Old 04-02-2008, 06:22 PM
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Default Re: Sorry - another Vermiculite Question

Done,

Traded 4 bags of Vermiculite for Perlite.

Is the ration 5 to 1 or 6 to 1? My Pompeii version 1.2 says 5:1 but I see postings that say 6:1? Is it a big difference?

Thanks
Dick
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  #17  
Old 04-02-2008, 08:30 PM
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Default Re: Sorry - another Vermiculite Question

Everyone chooses their own path. I did 5 to 1. 6 to 1 gives it higher insulative properties, at least I believe. I also believe that it makes it weaker due to the reduced amount of cement in the mix. People do what they think will be best in their own ovens. I followed the plans on that one.
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  #18  
Old 01-19-2009, 12:21 AM
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Default Re: Sorry - another Vermiculite Question

I used vermiculite for the outer insulation on the dome - 5:1 mix with cement, funny to work with really but it ended up OK. I put a rockwool blanket on the outside of the brick dome first, then alfoil, then about 3" of vermiculite/cement. The dome insulation appears to be very good - the hottest fire barely warms the outside. However, (too late to change it now), I used 3" AAC slabs under my hearth, and the floor of the oven cools off way quicker than the roof and walls. If I could do it again I would use a 5 or 6 inch layer of vermiculite under the hearth, because under that is a huge concrete slab heat sink. Not so good.
But -we pulled the first pizzas out last night - magical! Now we just need some cooler weather, around here it is about 40 degrees C each day and we are often not allowed to light fires at all!
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Old 01-19-2009, 02:29 AM
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Default Re: Sorry - another Vermiculite Question

I think the 5:1 ratio is the go for the insulation under the oven floor because you need some strength there, but on the outside of the dome you only need sufficient cement to hold the stuff in place. A 5:1 ratio would mean far more weight in cement than vermiculite and reduces its insulation value enormously. I've found a 10:1 for the dome insulation is sufficient. Anyone else have ideas on this?
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  #20  
Old 01-19-2009, 03:29 AM
Peasant
 
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Default Re: Sorry - another Vermiculite Question

The reason I used the 5:1 mix was that any weaker and the mix would not stick together at all. Maybe it depends on the particular texture of the vermiculite you have? It sounds as if it varies quite a bit.
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