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Post by lisaroch on May 19, 2012 12:03:33 GMT -8
We are building a stove using the materials suggested in the Rocket Mass Heaters book (Ianto Evans & Leslie Jackson). We are confusing by the type of perlite needed. At our local perlite plant the three types are insulation (choice of cryogenic, masonry fill, loose fill or treated) construction (aggregates- choice of plaster or concrete) or horticultural (choice of Luna Rock, A20 or gladstone). We bought the aggregate (plaster) kind (as recommended by the salesman when I explained how we would be using it), but it seems very fine in consistency. We don't want to use the wrong kind. Any suggestions? www.pennperlite.com/ |
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Post by canyon on May 19, 2012 13:22:33 GMT -8
This is something that is confusing in the book and if Lisa Jackson does the editing that has been recommended the new version upcoming will have some different wording. In the book they say only to use "masonry grade" but that can be dificult to find and when I special ordered it I found that it was very fine indeed. So now I use a roughly 50/50 blend of "masonry grade" and the much larger "horticultural" grade. I also have not hesistated to use the straight horticultural grade when necessary (available at greenhouse/gardening supply stores) with plenty good results. My suggestion is to blend the fine stuff you have with the larger particle variety for a good varied particle size mix.  |
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Post by woodburner on May 21, 2012 13:45:33 GMT -8
I think it would be an easy matter to crush some horticultural grade to a finer size.
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Post by Donkey on May 22, 2012 21:33:08 GMT -8
Seems best to just leave the stuff large. There's usually enough fines in the bag to not need to crush anything.
A wide variety of particle sizes is the ticket. Big ones is good if there are enough of the little guys to fill in the voids between. The voids are good too as long as the whole mess sticks together. And the reason they need to stick together is that you can't really trust whatever you put the stuff in to hold it. If there are ANY cracks or pin-holes, loose pearlite will find a way to get out and blow around the works.
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Post by Donkey on May 22, 2012 21:34:01 GMT -8
I mean really, the voids ARE the point.. Voids mean insulation and the more the merrier.
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Post by johnmaster on Dec 21, 2012 9:27:40 GMT -8
So is the idea to use a center core steel stube that will eventually rot away and leave simply the clay slip/perlite hardened tower as the burn chamber? My current plan for a 6" system has a repurposed piece of insulated stainless flue pipe (the heavy kind with the refractory insulation between the walls of the stainless pipe) with a bunch of the perlite slip mush around it pcked into a thick stainless tube I found at the scrap yard as the outer riser peice. The layers would basically be stainless/insulation/stainless/perlite/stainless. Am I setting myself up for failure or is this a good way to go? I don't know exactly what's on the inside of a stainless flue tubing but the thing is heavy!
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Post by Donkey on Dec 21, 2012 14:29:03 GMT -8
With stainless steel in a six inch system, I expect it should last a while. You probably don't need all that many layers either. Just the inside and outside layers is how I'd approach it.
But, yeah.. If I'm using black stovepipe or something like that, I just assume the metal will burn out and prepare for it.
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