[Cob] more on plasters & cob time

[Barbara Roemer and Glenn Miller]

We just returned from a workshop at the Steens' Canelo Project in AZ.  The
Japanese master plasterer used 90% straw in some of his finish plasters, and
as little as 10% (by volume) in others, depending on the surface he wanted
to create.  Additionally, in Japan it's typical to let the clay and straw
sit together for a year so the elements can "marry."  The straw breaks down
so thoroughly that it almost disappears, but apparently the fiber is still
there strengthening the plaster.  We saw "plaster" corners that were 3"
thick, both on straw bales and on cob bricks.  Finish plaster was done atop
those already thickened edges, sometimes another inch or so thick.

My own experience echoes Shannon's.  The mixes I've used for 1/2" plaster,
for 2" plaster, for 2-12" thick cob, and for floors are all very similar.

Cob has always seemed painfully slow to me, but friends here are speeding up
the process with tractor and tiller cob and also using form boards so they
can do much bigger lifts at a time.  Mechanical mixing means a drier mix,
which also can be stacked higher before spluging.  Two people can put up a
cob wall of 20' in two days.  It's moving closer to rammed earth but does
not contain concrete.

Barbara