[Cob] Curious about the clay

[Dean Sherwin]

Good answers on the topic of clay & soil mix.  Getting friendly with 
an excavator seems like one good way of getting your hands on that 
soil modifier.  Isn't there a simple test for the presence of enough 
clay, something like:  Take a moist handful of subsoil, press it into 
a ball in your hand, see if it stays together.  If it does there is 
enough clay.  Cut it in half with a pocket knife.  If the cut sides 
are slick and shiny, there is too much clay.
Dean Sherwin

At 03:00 PM 5/7/2009, you wrote:

>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
> >
Dean Sherwin CPE
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