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Re: GSBN:Clay plastered wall passes 1-hour test!

I want to add a couple of things to what Bill and David have  said.

Firstly, I underestimated the importance of the plaster on the cool  side.
When we applied it I was unaware of it's function regarding a fire  on the
opposite side.  So it was not as thick as it should have been (only  3/4" and
slightly less in some places) and not enough chopped straw was  added.   This is
what caused the crack when the wall was moved into  place and coupled to the
furnace.  We had the material on hand and time to  patch it but we did not.
Thus the oxygen took the big suck from the fire  and there was our weak spot.  It
was a bit of a cliff hanger there at  the end.  Water did indeed leak out
near that crack on the cool side  during the hose test but Mike the Fire Guy said
seepage doesn't count and gave  us a passing grade.  I love that guy.

Matts and Tracy certainly made the right call on the type of earthen
plaster.  We have this beautiful gray clay occuring in some caliche here in  central
Texas and it is my favorite for plaster because it is hard and is very  crack
resistent.  Since this is present with caliche it has lots of  limestome
aggregate in it.  The fire would have exploded that  limestome plaster away in
quick time, I believe.  In fact, there seems to  be some limestome or talc or
chalk or gypsum particles in the red clay (I have  noticed them before but not
given them much thought) and where these white  particles were (they seemed to be
no closer than every 12 inches or so) the red  plaster had popped off and
exposed their little white heads.

So, notes on passing an earth plaster on straw fire test:   Plaster the cool
side well.
Use a silica clay.   And, I think, cobbing the gaps would be  better than
stuffing as it would give more attachment for  the plaster.
Perhaps with a better plaster job on the cool side and cob in the  gaps we
could have gone for the 2 hour test.

All in all it was a beautiful thang.  Thank you Bruce, David,  Matts, Ben,
Bill and both Mikes, Cougar and Nicholas and Kindra and CASBA and  the God of
Hellfire for having a little mercy...heaven knows we need that.

Frank Meyer

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