[Cob] lime putty

[Sigi Koko]

I use Mississippi Lime, their vertical hydrate product, which is low
temperature fired so few burned, inert particles.  I buy it from a whole
saler (I'm in PA, so that is Univar near Harrisburg, but
www.mississippilime.com lists distributers by region).  I make sure it is
fresh (ie, not more than 6 weeks old).  I soak it in ample water for at
least 6 weeks until it is the consistency of sour cream.  During soaking
make sure there is always at least an inch of water on top to prevent
carbonation.

The plaster is 1 part sour cream consistency lime putty described above
mixed with 3 parts mason's sand (very angular shaped sand) in a mortar
mixer.  It goes on beautifully, is very workable, can be burnished in the
final coat for a very smooth finish if desired, and can be pigmented as
desired.

Note that this is hydrated lime, so mixing with water is simply rewetting
the lime, NOT the explosive chemical reaction you get with calcium oxide
(also called lime).   So, the process is much safer, but definitely wear a
mask to prevent breathing in the lime dust.  And when working with lime in
any form, keep all of your skin completely covered, as lime is extremenly
caustic.  I also keep a bucket of water with some vinegar in it to
neutralize anything...trowels, gloves, hands if they accidently get lime on
them, etc.

Finally, I do not recommend "going down to the lumber yard and buying a bag
of slaked lime and tossing it in a barrel of water and waiting a day and
go."  You will likely be buying something that has a lot of carbonated inert
particles that are indistinguishable from good hydrate.  The end result is
poor, soft, powdery plaster.  A bummer after the work that goes into
application.

Hope this helps.
Sigi Koko, principal
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