Cob: Masonry heaters

[Darel Henman]

Joy,
  the iron will expand and shrink quiker than the cob I have heard. 
This is not good.
To offset any deliterous affects due to this however, perhaps one could
create a buffer space between the pipe and the cob and filling it with
air or some other more conducive yet soft spongy material or even use a
fire brick material. ?

Diatomaceous earth (long dead planton remains) probably also be used.  
It is often formed (somehow, like a clay consistency) and then dried
into a fire brick.  
Diatomaceous earth is used as filters for wine, and other drinks.


It is also a material that is now being used in place of sand in some
wall mortars.

Darel

Banks wrote:
> 
> I'd like more info on cob heaters, too, but with metal 'innards' like a
> draft-controlled firebox to direct heat to a cooktop & oven.  Could this be
> done?   The thermal mass & safety of a cob exterior, combined with the
> utility of an old fashioned cookstove.....
> 
> I wonder how the cob would hold up.  Would the iron change sizes with
> heating/cooling, crumbling the cob.   If anyone's tried this please let me
> know.
> 
> Joy