Vermiculite/Perlite volume loss into concrete? Tools, Tips and Techniques Discuss Vermiculite/Perlite volume loss into concrete? in the Pizza Oven Design and Installation forums; You can compress the stuff when you apply it, but that will reduce its insulation. I've found the perlite breaks ...

[david s]

You can compress the stuff when you apply it, but that will reduce its insulation. I've found the perlite breaks down a bit more than vermiculite. The mix will take approximately double the amount of water than an equivalent concrete mix that uses hard aggregate.

[dmun]

It comes in four cubic foot increments: it's not like you can order it by the pound...

[kebwi]

Actually, I got several garbage bags of left over vermiculite for free today. It might have some rockwool mixed in. I hope not too much. This is the right stuff, right (see pic)?

[ThisOldGarageNJ]

It might have some rockwool mixed in (see pic)?

If you think you have rockwool mixed in, maybe you can pour some out in a cardboard box, go thru it with a yard blower,,,from what I have read you dont want any rockwool in there as it can stink when it burns off from the heat... hopefully you can blow out the rockwool and just the heavier vermiculite will stay in the box... and from what I can see in the pic it looks ok
Mark

[kebwi]

Hmmm, does anyone think the vermicrete will get hot enough to burn the rockwool if there is an inch or two of Inswool beneath it (I'm referring to the dome of course), unsure about the hearth).

Likewise, does anyone know if the rockwool is dangerous? When it burns do I not want to be inhaling the stuff that supposedly makes it smell bad?

[ThisOldGarageNJ]

Before I stucco'd my dome, I had the 2-3 inches of kaowool and 3-4 of vermicrete. The outside of the vermicrete never got over 150 degrees,, and that was with the fire from hell,,,, I would see if I could find an MSDS for rockwool and get the temp it ignites at... Your probably okay,, Just remember you are still breathing that stuff when you are working with it.. Maybe just hose it down will wash the loose wool off

Mark