Cob Need some *cob* help

[Patrick Newberry]

> 
> I don't think this is exactly good news for me.  When I followed
> your instructions, I ended up with what appears to be about 85%
> sand followed by 15% silt.  Being there were only two distinguishable
> parts, I'm guessing that there is next to zip in the clay department.

Do you have any clay round you?


> 
> Is there by chance a product on the market that I can add to make up
> for the missing clay?  Is adding straw necessary?

I've heard folks say it is not necessary. Most things I've built have 
used straw but not everything, everything did have some clay however. 
Actually I heard the straw reduces the compressive strength of the 
brick but helps in other areas. 

> 
> When making tests bricks, is the time it takes to dry a factor in
> whether you have a *good* brick?
I've never heard, other than too quick causes more cracks.


> 
> How does one test for durability?  Should the brick be able to
> withstand a drop from a certain height without breaking?

Oh yea you can take a ball of  your our mix  and throw it up to see how 
much it smashes down. If it looses it's shape then there isn't 
enough clay. Ken Kern made a type of lever with a piece of diminsional 
lumber and put a plate on the lever and push down to test the strength. 


> 
> Lastly, for now ;), when making a structure such as a goat pen, does
> one need to lay some sort of cob foundation to build the cob onto or
> can one merely start building on flattened earth (or sand in my case)?

No you'll need some type of foundation. You could use rocks, cement, 
stablized earth in bags, I guess even presure treated lumber. The key 
is you want to separate the earth that make your walls and the earth we 
walk on. 

Pat
http://www.gnat.net/~goshawk 
"There is No Hope, but I may be wrong."