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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
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.
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