Saturday, June 14, 2014

Oven In Progress (con't)

The happy oven builders (I hope they're) are at it again for another session. They have just finished filling the void between the stone base with rubble and topped off with perlite insulation. They used 8" of perlite insulation with some bottles in the middle which may add to the insulation value. 
It looks like they mixed Portland cement in with the perlite, but none is necessary. Portland cement creates thermal pathways for the heat to escape, so it is best left out of the base. The perlite alone will easily support a top concrete slab. 
If you're insulating the outside of the dome with perlite, then you need some Portland cement to hold it all together. 6 parts perlite to 1 part Portland.


 Stay tuned for the next work day

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