[Cob] Mechanical cob vs. instruction by cob "experts"

[ocean]

Clay slip, uniformly mixed with sand and straw by a mixer/tractor will 
form a cob mix as strong as a foot mixed blend, in our experience.  The 
microscopic level described in the previous posting by M.A.T. is nice 
theory, but not the only truth!

The key is to understand that the clay acts as the "glue", much like 
Portland cement, to hold together aggregate - sand - and fiber - straw. 
  This is the essence of cob.  If you can get a uniform amount of clay 
to coat each grain of sand and each fiber of straw then you will have 
strong cob.

Cement mixers, bobcat/tractor cob, horses stomping or humans stomping - 
all can make good cob or lousy cob, depending on the ratios and mixing 
of clay/sand/straw/water.

A problem I've observed before on the coblist electronic forum is 
repeated in this discussion - here we are discussing cob without any 
clay or sand or straw to feel, touch, stomp on, or otherwise physically 
experience.  It's very hard to conceptualize how to make "good" cob 
without a physical demonstration of the process.

I recommend taking a class or workshop taught by an experienced 
teacher, either through Cob Cottage Company, Becky Bee, Kleiworks, or 
some other cob building educational organization.  Or as an 
alternative, have an apprentice from one of the above organizations 
come and lead a workshop for you.  This way you'll have 
hands-on/foots-on demonstration of how to make structurally superior 
cob.  And you'll never again wonder whether your cob is strong enough 
to hold up your house.

Ocean Liff-Anderson
_____

Steward, Ahimsa Sanctuary  http://www.peacemaking.org
Proprietor, Intaba's Kitchen  http://www.intabas.com


On Mar 4, 2005, at 8:22 PM, Jill Hogan wrote:

> The secret of an earth house staying together is that earth and clay 
> are made up of platlets and as in a pottery pot even when it is dry 
> before it is fired it will maintain its form, This is due to a 
> magnetic attraction between the platlets caused by moisture. So the 
> secret of a good cob mixture is to get the platlets lying parallel. 
> When you use a mixer it tears the platlets apart as opposed to the 
> stamping with feet like wedging clay for pottery you get the platlets 
> lying flat together. Hence buildings built this way have stood for 
> hundreds of years. There are no short cuts
>  
> Secondly solving the clay issue simply put you clay in a tub cover it 
> with water and it will dissolve. When you need to add it simply take 
> it out of the tub with a spade and add it to your mixture.
>
> Jill
> McGregor Alternative Technology Centre "MAT"
> Tel: 023 6251533
> www.mat.org.za
> info at mat.org.za
>  
> We teach new (truly ancient) ways of living that respect the earth as 
> a living spirit"
>  
> "We respect each other for who we are"