[Cob] Lime life cycle...

[Ocean Liff-Anderson]

CaCO3 + extreme heat = CaCO (quicklime) - extremely volatile powder,  
can explode when water is added!
CaCO + H2O = Ca(OH)2 (hydrated lime) + extreme heat(!) - this is the  
"slaking process", yield is good for lime plasters, lime washes, etc  
- be sure to keep under water!
Ca(OH)2 + CO2 = CaCO3 (calcium carbonate) - also known as "chalk" or  
agricultural lime, inert ingredient, can't be used in lime washes or  
plasters

if hydrate lime "dries out" then it reacts with CO2 to form CaCO3 -  
"agricultural lime" - as per Shannon's explanation

Good luck!
Ocean

On Oct 7, 2008, at 11:10 PM, Shannon Dealy wrote:

> On Tue, 7 Oct 2008, Carrie wrote:
>
>> I was just about to mix up some lime for a lime plaster, and I  
>> discovered
>> that my lime is dry.  It has been sitting in a covered 5 gallon  
>> bucket for
>> some months; I guess I should have checked it sooner, alas.  I  
>> have added
>> more water to it but I have a couple of questions:
> [snip]
>
> Once the lime has been wet and allowed to dry it is useless for  
> plasters
> (particularly if it has been drying for any significant amount of  
> time).
> What you have now is essentially a very expensive form of agricultural
> lime (suitable as a soil additive if your soil happens to need  
> it).  You
> can keep lime pretty much indefinitely so long as there is a layer of
> standing water covering the top of it, but once the water drops  
> below the
> surface of the lime (allowing contact with the air), the reaction will
> begin with that top layer and as the water level continues to drop,  
> air
> (specifically carbon dioxide) will eventually react with the rest  
> of it.
>
>
> Shannon C. Dealy      |               DeaTech Research Inc.
> dealy at deatech.com     |          - Custom Software Development -
> Phone: (800) 467-5820 |          - Natural Building Instruction -
>     or: (541) 929-4089 |                  www.deatech.com
>
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