SB: Sprayer news...

[John Kingsley <johnk@magma.ca>]

Hi Folks,

Recently I had the opportunity to play with some
earthen plaster at a plastering workshop run by
7th Generation just west of Ottawa.  The clay plaster
is fun stuff!  I was impressed.

I took along my stucco sprayer to try it out with the
earthen plaster.

[For those new to the list, I have plans for building
a sprayer at:
  http://www.magma.ca/~johnk/strawbale/sprayer/index.html
When I announced this back in March, I had only tried
it on cement plaster and not with earthen plaster]

Not knowing too much about earthen plaster, I added some
water to the mix to allow it to be sprayed (it was too
stiff). With some extra water, the mix sprayed very well.

But the problem was that a week later, when I went back
for the second half of the course, the sprayed sections
of the wall definitely had more cracks in it, most likely
due to the wetter mix.

So there still needs to be some more experimentation.
I suspect adding more sand and more fiber (straw)
to the plaster will help decrease the cracking.

But then again (not knowing much about earthen plaster),
maybe the cracks in the first coat are not really
all that important.  Perhaps the sprayer could
be used on the first coat to build up a thick base
(with some cracks) and then the other (thinner)
coats could be applied by hand, hiding the cracks.

So ... How much cracking is acceptable with earthen plaster?
And will the second coat hide them?

I'd love to hear some comments from the clay gallery.
Hey ... and the peanut gallery too!

Hopefully later in the summer I'll be able to do some
more experiments with earthen plaster and my sprayer.

cheers,
John

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