alternative insulation??? Other Oven Types Discuss alternative insulation??? in the Pizza Oven Design and Installation forums; Without proper insulation, it gets very hot, and will bleed out the heat from the floor you need for cooking. ...

[dmun]

Without proper insulation, it gets very hot, and will bleed out the heat from the floor you need for cooking. My oven has two and a half inches of mineral wool board (HW insblock14) and the support slab remains cool to the touch at full pizza heat.

And no, you're correct, sand is not an insulator.

[Grasshopp3r]

Could he use crushed glass as an insulator? How fine would the glass need to be in order to be effective? Small pieces or as fine as sand?

[Janine M. LeGrand]

Hi Dan Qui,
I was wondering how your oven turned out. I think we face similar challenges--I am trying to build an oven in rural Uganda so obviously supplies are limited. On the suggestions people have given me, one suggested clay mixed with straw for insulation, and another mentioned that some earth builders use glass bottles (not broken I think for the airspace) in earth for insulation. Did you ever finish your oven? What did you end up using? Does it work well?

[dmun]

Broken glass is a proven no-go: it's as useless as sand as an insulator.
The whole-upright bottles is an interesting idea, it would maintain an insulating airspace. Maybe jars with straight walls would have more strength than necked bottles. Hmm. I'm wondering about air expansion within the bottles. If you could top the bottle/jar layer with a sheet of expanded metal lath, it would prevent air from being trapped in the bottles.

[SpringJim]

Originally Posted by james

I've also heard the old fashioned product called "Expanded Clay" -- argille espanso.

James

I used this expanded clay balls in Spain James (BFB) and it is only so-so. Works, but still loses too much heat in my opinion. The BenjaMia Bakehouse Oven with the Pelite insulation is proving far superior with very little heat transfer.

I would not discount the mud/clay mixture though. I think that has been used for years. I saw a field oven at Colonial Williamsburg built that way. As long as you have an inner fireproof layer, like bricks or clay, I think you could use a high straw content outer layer with good success....especially in places like the amazon jungle!!!!

[charlesaf3]

density can make up for a lot of insulation value. I'd guess even sufficient dirt underneath would do it - anything that entrains air would be ideal.