[Cob] Good clay?

[Bill&Julie]

Hello Dave,,  ô¿ô

The Shake Test, is not all hokas-pokos...
And friend of mine is a Soils Specialist with the DNR,
and they use Screens to do most of the seperating.
But they weigh each stage to classify what they have.
And when they get to the dust and clay they use a water
shake to divide that down. But then they dry those
divisions in an oven, and then they weigh them too...

Side note: They use Olive Oil to sub-divide the
various sizes of polishing grit of crushed diamonds.
Shake/stir, and stand 10 minutes, and what settles
out is one grit, pour off the oil, shake/stir and let stand
for a 30 minutes, and what settles out is another grit.
ECT, ect,  You will find this procedure on page 1138
of the 25 edition of the Machinery's Handbook.

I read about this, when polishing die parts in a machine shop.

~¿~  bill


----- Original Message ----- 
From: "Dave Brown" <quahog at netnet.net>
To: <coblist at deatech.com>
Sent: Wednesday, May 03, 2006 10:08 PM
Subject: [Cob] Good clay?


> This is my first venture into the world of cob.  I intend to build a
> cob oven in the back yard.  This area of WI has plenty of good
> clay.  A fraction of a foot of topsoil, then clay, and clay, and more
> clay ... right in my backyard.  Or so I think.  This area used to be
> big brick making, predominately red brick from the local red clay.
>
> I tried the shake and let it settle test.  After 24hrs I find that
> there is almost no sand or grit in the bottom of the jar.  I don't
> recognize any silt at all, and the slurry is still thick as a melted
> chocolate/strawberry McShake.  It appears to me as if I've got instant
slip.
>
> I know that there are some doubts cast about the shake test, but I
> think it's at least given me an idea of what I have to work
> with.  What's the next best step to take to determine if what I have
> is good clay or is it silt masquerading as clay?  Or would it just be
> best to simply use it for what I think it is and make a series of
> trial cobs (varying sand amounts and with/without straw?
>
> Suggestions?
>
> Dave Brown
> Green Bay, WI
>
>
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