[Cob] vermiculite, pumice, perlite suppliers?

[raduazo at aol.com]

Masonry grade lime has been fired to a very high temperature to drive off CO2 and water. The water is then added back to the mix and it is dried. When you add water to this mix and put it up an a wall and keep the wall moist for a couple of days the lime absorbs CO2 from the air and turns back to limestone on the wall. 
Gardening grade lime is just ground up lime stone which has not been fired has not had the CO2 removed and thus it remains a powder. It never hardens because it is already limestone.
 
-----Original Message-----
From: Shannon C. Dealy <dealy at deatech.com>
To: Amanda Peck <ap615 at hotmail.com>
Cc: coblist at deatech.com
Sent: Thu, 22 Sep 2005 07:34:33 -0700 (PDT)
Subject: Re: [Cob] vermiculite, pumice, perlite suppliers?


On Thu, 22 Sep 2005, Amanda Peck wrote: 
 
> What's the difference between masonry grade and gardening grade, (which might > not be available in the gardening sections of the stores, but rather through > greenhouse or professional garden suppliers)? 
> ...................... 
> 
> Shannon wrote (snipped into nothingness) 
> masonery grade perlite 
 
Horticultural grade perlite is open celled in order to absorb and retain water for propagating plants, masonery grade is closed cell for use as insulation. If you use horticultural grade for a stove (as I once did years ago), it will suck up tremendous amounts of water when you are trying to mix it with your clay slip (if you don't use lots of water you won't be able to get the clay slip to coat it), and it will take forever to dry out, during which time your stove won't be working as well as it should (after 50 hours of almost continuous running on my stove at the time, a large percentage of the perlite was still wet, though I was running a thicker insulation layer than normal). Don't use horticultural grade perlite! 
 
Shannon C. Dealy | DeaTech Research Inc. 
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  | Embedded Systems, Real-time, Device Drivers 
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