Cob Red Georgia Clay

[Shannon C. Dealy]

> On Sun, 16 Jul 1995, Solar Girl wrote:

You might want to check the date setting on your computer.

[snip]
> 1.    I have access to red clay from Georgia (Florida soil is awfully
> sandy &/or silty), and I wondered if anyone knows of any pros or cons to
> using Georgia clay (a pro might be that the house would be a ready-made
> warm red tone). I have not yet gotten my cob books, but I'm wondering if
> there are any particular properties of clay that make it good or bad?
> Or is any old clay okay?
[snip]

The purpose of the clay is to make things stick together, as long as it
will do this, it should work, though some clays are definitely better than
others. "Stickier" clays in particular may tend to work better since
they provide a stronger bond, and they can allow you to use less clay
which means less shrinkage and cracking during drying.

> 3.    Last and not least, does the straw need to be straw?  Could it be
> dried grass clippings, weeds, spanish moss or hay?

The name of the game is fiber, it doesn't really matter what the source is
as long as it provides adequate strength and you are prepared to deal
with any limitations of the type of fibers you use.  The sand clay mixture
has to be able to bond to the fiber, and shorter fibers provide less
surface area for the sand/clay to "grab" onto.  In addition, the longer
the fibers are, the better they tie together the cob, though really long
fibers make it difficult to work with the cob once you are done mixing it.
Really long fibers can make a completed batch almost impossible to
to break up into usable chunks.  Generally you will probably want fibers
that are at least 6" long, though I find 12" to be about the optimal
length for what I have been working with.  I have been building lately
with the native grasses growing near the building site which has a variety
of weeds, vines, ferns, etc. mixed in.  It all seems to work quite well,
as long as I remove all of the thistles and blackberry vines (major ouch
during barefoot mixing :-0 I have occasionally missed some).  I did make
test bricks using this stuff first to make sure I would be happy with the
result.

Shannon C. Dealy
dealy at deatech.com