Cob: Perlite

[Mike Carter and Carol Cannon]

Check Out: http://www.schundler.com/techperl.htm
(For more than you wanted to know.  )
Around here it is sold in large paper bags, about $4 for a couple of cubic
feet.
Make sure to use a mask when handling.
We have used it in chimney and flue mixes; it is a good insulator.
I have never seen it float except during wash-up of our mixer.
Would have to agree that cob strength could be adversely affected by adding
enough to do any good insulation-wise.  If used as part of plaster,  I'd put
a hard layer over it on the outside.
Proven that insulation is best on outside of mass - hence the term
"outsulation".

Mike
>
>That's perlite.  I don't know WHAT its made of.
>
>However, perlite, the white styrofoam-like stuff, is just about
>waterproof.  You could use it as a cob additive, but you would have to
>mix it pretty thouroughly as it has a tendency to "float out".  It is
>very, very lightweight.
>