[Cob] Curious about the clay

[Henry Raduazo]

Clay is one of the most common substances on earth as such many  
people have it available for free. Just go outside and dig it up.  
With that said every part of the earth differs from every other part  
of the earth. Some people have very pure clay which shrinks  
drastically as it dries some have clay and silt some clay and sand.  
Others have no clay or so little clay their walls will barely hold  
together.
	If you do not have a good supply of naturally occurring clay in your  
area I would not recommend building with cob. A fairly small wall  
that I built in my house as a heat sink weighs 8 tons. I bought 4  
tons of sand ($20.00 per ton) and mixed that with 4 tons of clay rich  
soil that came from digging out the basement of a near by house. The  
contractor was going to haul the soil 60 miles and pay a tipping fee  
to get rid of it, but I was willing to take it for free. Buying that  
much clay at a pottery place would be a bit pricey.
	Anyone who would be a natural builder must first be a scientist and  
then be an engineer. As a scientist you look around your building  
cite and ask What do I have? Rocks? Trees? Clay? All can be converted  
to building materials. Clay is one of the most versatile because it  
has so many uses as a plaster, load bearing material or refractory.  
You need to experiment to find the best mix. Sometimes you need to  
add sand sometimes just straw. You make bricks and then destroy the  
bricks to determine the best combination of materials.
	When you know the best combination of materials then you become an  
engineer and ask yourself "How do I make 8 tons of this stuff?" I  
like to mix with a rototiller on a slab. You may want to mix with  
your feet on a tarp. What ever. You need a lot of stuff to build a  
house.
Ed
On May 7, 2009, at 1:19 AM, Robert J Churchill wrote:
> The word "clay" is used repeatedly but really where exactly is all  
> this clay coming from?  I have no idea where I'm supposed to get  
> all this clay.  For me, it would be easier just to buy clay from a  
> ceramics shop but I don't even know if that would work.  I live in  
> an urban area and it's not like we can just go out and dig up clay  
> at a local quarry.
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