[Cob] Making good cob

[Earthed]

Dear cob fanatics,

I have just read what Jill Hogan wrote On Mar 4, 2005,and need to reply as
what she says is very misleading. Jill stated:

"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."

1. Good and bad cob can be made with feet, a tractor, a cement mixer, horses
and probably by many other methods. Many of the buildings on our website
www.earthedworld.co.uk were built using cement mixer cob. Kevin Mcabes
houses are all built using tractor cob. Clay is the glue which holds the
sand and straw together, see what Ocean Liff-Anderson says.

2. Lumps of subsoil with very high clay content do not usualy 'dissolve'
when soaked. Which is a shame, because it means if your soil has a lot of
what looks like potters clay in it you are going to have more work to do!
Clay will quite happily sit in water without doing anything for a long time,
hence it is used to line ponds and pits in landfill sites. To make good cob
from this type of subsoil you will need to break it down, usually better
done when it is dry, because clay becomes plastic and sticky when wet,
making it harder to break up.
We know this becuase we have built cob structures using many types of
subsoil. You need to keep in mind that many of the older cob buildings here
in Devon and Cornwall have only around 15% clay in the cob mix, the rest is
silt, sand, rock and straw.
If your soil dissolves in water then it probably has a lot of silt and sand
in it and you may be in for an easier ride!

Happy cobbing,
Alan Cameron-Duff
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