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Re: GSBN:Borax in plaster



Hello Andr?, hello everybody!

Borax was used in several carpentry works as repellent agent (diluted with
water, then we sprayed the timber) and that seemed fairly good to stop
insects from attacking the wooden structure. But in plaster, it dont seem to
me that it would   be   of any  significant efficiency, as termites or many
other woodeaters dont eat the plaster, but travel through tiny cracks and
reach the wood, wich is their food. Even if they chewed some plaster to make
their way, they dont really ingest  it,  so it is not the proper repellent
mixed with plaster. On the other hand I totally agree with Matt's
experience, considering that it chemically weakens the plaster. As borax is
a kind of salt, and we all know salt combinated with cements or  plaster
type products weaken the final dryed mix; that is because  of the
interaction with the Hydrogen molecules , "blocked" by the salt and
unavailable for completing plastering hardning process.
In SB construction, adding natural lime to plaster (especially if mixed
with chopped straw) is an excellent and non toxic repellent (most insects
and rodents hate lime). I often use a mix inspired from the "platre de
paris" (Paris plaster)  in wich initially, sand in variable proportion, is
mixed with a preparation of 1 third plaster, 2 thirds lime, then add water.
The mix is longer in time and more flexible than pure plaster, you may add
some water if getting too stiff, but still has to be used within a good 1/2
hour. This mix can be excellent both in and outdoors. If needed, put lots of
chopped staw instead of sand, and you'll get an rellly great  straw
plastering.

A+     Lorenzo
----- Original Message -----
From: MattsMyhrman@...
To: GSBN@...
Sent: Wednesday, July 12, 2006 2:12 AM
Subject: Re: GSBN:Borax in plaster



In a message dated 7/10/06 2:08:43 PM, forum@...:


I remember reading that one can also add borax to the earthen plaster to
avoid
mould. Does any of you have exp?rience with borax in the plaster. And how
much
would you advice to use?



Dear Andre',

Several years ago I experimented with borax and boric acid in plaster, to
see
if I could prevent a grass--eating termite that we have here from eating
straw that is surrounded by mud plaster either where the first coat of
plaster was
pushed into the surface of the bales, or where chopped straw was mixed with
the plaster.   I introduced the borax and boric acid by creating a saturated
solution of the chemicals in water, and then using this water to mix the mud
plaster.   The chemicals didn't seem to prevent the termites from ingesting
the
mud and, even worse, the addition of the chemicals greatly reduced the
strength
of the dried plaster.   I'd be very wary of using this approach.

Best wishes from Matts-a pox on that borax-Myhrman


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