[Cob] How warm must it be to work?

[Peter Kaulback]

Great, thanks for the heads up!

It still quite warm here, so I have some time still (provided the farm 
proceeds comfortably).

Peter Kaulback

Shannon C. Dealy wrote:
> On Sat, 23 Oct 2004, Amanda Peck wrote:
> 
> [snip]
> 
>>I don't think that cob, or pure clay/sand or even clay/sand/perlite mixtures
>>"set" the way that lime or concrete does.  So the problem is freezing while
>>it's still too wet not to get ice crystals extruding an inch up from the
>>clay the way I vividly remember from my red clay childhood.
> 
> 
> This is essentially correct, when a cob type mix freezes while still
> significantly wet, it puffs up like popcorn from the expansion of the
> ice crystals and loses integrity.  I don't know the specifics of your
> design or mixes, but for many ovens, the simplest thing is to build a
> small fire in them to dry them out, this can however have a down side if
> your mix shrinks to much the oven will crack (potentially in many places).
> Kiko once made an miniature oven in two hours  for me to use in a display
> at a local festival (dried it by firing it) it did crack, but was still
> good enough for our needs.  Of course doing it this fast is not the best
> approach (we were both to busy to spend any real time on the oven), but
> for a larger oven and a smaller fire, you may find the results to be a
> reasonable trade off.  Another (safer) way to dry it faster is to just put
> one or two fans near it, but even this can crack a drying mix if it dries
> to quickly.  Cracking is caused in part by uneven drying -- one section
> dries and gets hard while an adjoining area is still soft and shrinking,
> results in them pulling apart, since the hard area can't move with the
> section that is still drying/shrinking.
> 
> 
>>Or it's too cold to mix barefoot.
> 
> [snip]
> 
> As one of the few people dumb enough to build with cob in winter in a
> moderately cold and very wet climate, it's only to cold to mix if the
> mud cracks when you stomp on it :-)
> 
> 
> Shannon C. Dealy      |               DeaTech Research Inc.
> dealy at deatech.com     |          - Custom Software Development -
>                       |    Embedded Systems, Real-time, Device Drivers
> Phone: (800) 467-5820 | Networking, Scientific & Engineering Applications
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> 
> 

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