Pouring the Hearth

[fmottahe]

Hello,

I would like the experts opinion about the following question:

In section 4 of the instructions for Pompeii oven, 2 alternatives are provided:
1) Using FB board, or alternatively,
2) using insulating concrete (cement plus vermiculite).

I have seen a 3rd option in books about earth ovens (using empty bottles plus perlite and clay slip).

What do you think?
Is there any discussion of this or other techniques in this forum?

Thanks,

[Neil2]

1) Use FB board, or alternatively,
2) use insulating concrete (cement plus vermiculite/perlite)

[fmottahe]

Thanks for your reply, but I was trying to get some opinions on option 3 (bottles plus perlite and clay slip).

[dmun]

Glass, broken or in bottle form is not an insulator. Clay isn't either. Neither is sand, or gravel, or broken masonry, or rock salt.

We aren't living in the middle ages. We have access to modern materials, and we should use them. The cost of insulation is small compared to the cords of firewood you would have to burn to heat up an uninsulated oven.