[Cob] cob stoves & light straw

[Amanda Peck]

Back in the summer I spent in rural Mexico, I didn't think to look at the 
inside of a (giant) horno (oven) about 10 steps from where I was sleeping.  
But I'd guess it might become very low-fired.  Brick kilns made of unfired 
adobe-like block are how Nader Khalili got the idea for ceramic houses.  
When I used to put little shapes of the local clay into the fireplace when I 
was a kid, they sort of fired, somewhere below the level of terracotta pots.

That doesn't mean that you COULDN'T fire it.  (The stoneware at the art 
department at the University of Hawaii worked with back in the 60's was 
fired with waste packing wood)  Not sure if there would be a 
layering/cracking problem with some fired/some not fired--beyond the level 
of normal use.

One of the classic articles on clay-coated organic matter--this one was 
wood-chip--claims this:

"Depending on the system you're using, the weight ranges from 1000-1500 
lbs/cubic yard of dry mix. The insulative value for a 12" exterior wall with 
plaster can be up to R-25, depending on the quality of the woodchips, clay, 
and the density with which the mixture is packed. Vapor barriers are 
unnecessary because of clay's inherent property as a diffusing water 
reservoir and the capacity for moisture dispersal."

That's from: http://www.foxmaple.com/proclay.html

I don't know what that claim is based on, whether it applies directly to 
straw as well.  I did see a lot of "dependings" in the sentence.

.....................
Brad asks Two unrelated questions:

1.  Does the inside of a cob oven become fired, like pottery in a kiln?

2.  Does anyone know the typical density and R-value of dry light straw,
also how wide the panels can be compared to their depth.  Or can anyone
suggest where such data might be found? (light straw = straw soaked in a
clay soup, then packed densely to fill spaces, clay acts as fire retardant
and mould inhibitor).



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