Cob cob and cisterns

[goshawk at gnat.net]

> 	 this is kind of an aside - maybe pat newberry might know best:  does 
> anybody know why it is inappropriate to mix straw with clay if one is making 
> bricks for a fired structure 'a la nader khalili'?

Remember Superadobe and Nader's fired sturctures are two different 
animals. You can use straw in superadobe (I often do at the ends of 
bags) but I've never seen any pottery or fired bricks with straw so 
my guess is that the straw would disintergrate and the weakend 
structure would still not gain that much in insulation value from the 
air pockets. 


i was wondering about 
> methods for air-entrapment with ceramic structures - i thought maybe firing a 
> cob structure might result in a strong, water-resistant but relatively 
> light-weight semi-porous (ie. higher r-value) ceramic structure. or does the 
> straw expand too much when it is burning, causing the clay/adobe to crack? 
> 
> 	the reason i mention this is that i was wondering whether the steam 
> from the sweatlodge might saturate the cob with so much moisture that the 
> building would slump after a while, reducing the strength of the dome. i've 
> never built anything with cob, i was just curious whether you thought this was 
> a valid consideration. i'm trying to get a feel for how the material behaves 
> over time. i would imagine (based on no experience whatsoever) that cob in a 
> humid environment would act like wax in warm environment - that it would 
> basically melt, but really slowly. what do y'all think? 

My one experience in a sweat makes me beleive that the cob would do 
fine from the inside (outside rain damage is another thread). But 
anyway back to the sweat, we place rocks in a very hot fire and then 
placed the rocks in the sweat. We did throw a bit of water from time 
to time on the rocks and we did sweat like pigs but it still was more 
like a sauna and not a steam bath so I think you'd be find from the 
inside.


> 
> 	i'm especially interested in the possibilities of using n. khalili's 
> methods for producing ceramic structures for creating water cisterns or even 
> methane digesters. or what other ways are available to make airtight/watertight 
> containers other than metals, plastics or concrete? 

again don't forget, superadobe is a differnt meathod from firing a 
house or cistern or what ever. 



Pat
L&L
Pat
& the Maukly crew
email: goshawk at gnat.net
http : http://www.gnat.net/~goshawk