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Re: GSBN: Earth plasters
Thanks for your submission and insight. The first I'd heard of 'fermenting'
straw (or paper) was from some friends from NZ, Sven and Sarah Johnston,
who hosted a workshop and a guest presenter was Tom Raven, the colorful
Frenchman, who uses a fermented mix, like bakers use a yeast starter for
baking breads. Tom swears by this fermenting and concurs with you on added
durability of the earth plasters. The Johnstons found they had some mold
issues, maybe as a result of this mix tho. Have you experience any issues
with molds? Maybe you'd care to chime in Sven?
Colorado Straw Bale Association
> [Original Message]
> From: Graeme North ecodesign@...
> To: GSBN GSBN@...
> Date: 10/10/2007 3:08:32 PM
> Subject: Re: GSBN: Earth plasters
> We have found the addition of pulped paper as a fine fibre very very good.
> Its made either from office paper or newspaper ­ it can be made by
> soaked paper into a concrete mixer with lots of water and just letting it
> roll until completely broken up , then draining off excess water before
> It gives a very fine fibre which is enormously beneficial in terms of
> increasing strength, and durability of earth plasters. If it ferments a
> even better (all ferment seems to help earth plasters ­ using water that
> had a bit of straw left in it for a week or two to start to fizz is good
> well) ­ there appears to be some enzymic reaction that takes place
> paper or ferment water and clay that helps workability and durability.
> Paper pulp eliminates dusting from earth plasters ­ helpful especially if
> the soil is a bit silty. It also sticks well ­ we use it over
> pre-compressed straw without meshing.
> We also use it as a finishing plaster over drywall ­ a very nice finish
> it sticks like ...glue.
> It is also very effective as an additive to earth bricks as well ­
> robustness, durability, and also lowers density giving better insulation.
> The amount of paper pulp that can be added can be quite high - we often
> up to around 30% or so by volume to plaster , and have made mud bricks
> up to 50% paper pulp ­ cardboard houses anyone?
> I am currently looking at building with cob and mud brick mixes using
> roughly 2 parts clay-soil, 2 parts wood shavings (long fibered rippings)
> straw, and 1 part paper pulp ­ very tough, very light, easy to work, and
> looking promising. Very good insulation, and very nice to use as gravity
> increases ­ remember that there is plenty of evidence that gravity doubles
> in strength very thirty years.
> As to lime over earth ­ I¹ve found it works well so far IF there is good
> keying and wetting ­ if the initial earth is a cob type mix with lots of
> (straw) fibre with plenty of fibres left hanging out of a rough surface,
> then that is good too for tying the layers together.
> I¹ve just lost a patch off a bit of a small experimental earth plastered
> whitewashed straw wall where the earth plasters layers were not keyed well
> together. Keying is good.
> Graeme North Architects,
> 49 Matthew Road,
> RD1, Warkworth,
> New Zealand 0981
> Ph/fax +64 (0)9 4259305
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