Strawbale Archive for June 2001

"It is true that dry hydrated dolomitic lime in bags can often be inferior.
That is because most of it is manufactured for industrial chemical uses...It
is not very "fat".  This is due to the high-temperature hydration process
burning the lime and making it too crystalline...just like slaking quicklime
with too little water.

"The masonry market is a very small part of the lime industry and most
emphasis has been on dolomitic Type S (pressure hydrated) limes. Even these
limes are really not expected to perform like the old quicklime slaked "fat"
limes, and are mostly promoted to be used in ASTM mixes of 1 part cement,
1/10 part lime, 3 parts sand, etc.

"However, GenLime makes a very different product in that their hydrating
process is better controlled, resulting in a plasticity index of over 400,
while ASTM for Type S is a plasticity of over 200.  Quite a difference.  The
barely passing plus or minus 200 plasticity limes are suitable to be added
to cement mixes, but in my opinion are marginal for lime-plus-sand plasters
and stuccos.

"I think this is where the problem arises. Soaking the dry hydrate for a
couple weeks seems to help.  Slaking high calcium quicklime below 200*F is
much better, and aging the resulting putty provides an even better product.

"I think that Type S can be produced with high plasticity as is the case
with
GenLime- and some of the other companies some of the time- but for the most
part the Type S limes barely pass the ASTM specs.  The specs were derived
from what the industry could do economically because the market for "fat"
lime is too small to be economically addressed.  The total US lime market is
about 25 million tons; the total Type S market is ony 400,000 tons."
Thanks again to Harry for this perspective.

Some advise getting your Type S lime "fresh" from your supplier, but I don't
know how much difference this makes.  We recently used 50% Type S, and 50%
hydraulic lime, but I know of only one source of hydraulic lime in the US,
and its back east, and therefore expensive to get to AZ.

Senor Steen's article on "The Benefits of Prickly Pear Cactus Gel in Lime
Plaster" is also in issue #29.  It has been done for hundreds of years, and
seems to be a Good Thing, where it is available.  You cook the cactus
yourself.

Issue #33 has a very interesting article on "The Discovery and Use of
Carbide Lime", by Kaki Hunter and Doni Kiffmeyer (okokok@lasal.net, they may
have workshops ), which
is a waste product from the generation of acetylene that can be obtained for
free.  This is an interesting possibility that uses an industrial waste
product that already exists, all over the country, and is possibly the best
quality lime you can get for plaster.  It is caustic, like all lime, of
course, and  TLS
warns:"Accessing carbide lime from the waste pits can be problematic-
proceed with caution".  If you want to pursue this possibility, Kaki and
Doni write: "Check the phone book for local acetylene gas manufacturing
plants. Ask if they generate their own acetylene... and what they do with
the left over "generator slurry".  Explain the use you have for the lime.
Most people are happy to help.  A few states such as California have
outlawed the process of making backyard acetylene because of the leftover
caustic waste situation.  By developing a beneficial use for the carbide
lime residue, we coud solve an environmental problem that would suit
everybody."

Enough for now- Good luck!
Bill





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