I’m thinking about using some large soapstone tile to build up a small batch feedRMH. It will have a regular firebrick firebox and a ceramic riser, but I was thinking of using soapstone to enclose the bell where one would normally put a steel drum and I would facade the firebox in soapstone as well. Anyone see any reason I shouldn’t do this?
Using the soapstone as a facade is a lovely idea. I don't know how well it will stand up to riser temperatures, though.
I would use the steel drum and then enclose it with a built-up screen of soapstone, arranged so that there can be some slight airflow between tile and riser drum, with strategic perforations arranged by gapping the tiles. Doing so might provide air intakes and outlets at the bottom and top, increasing the heat exchange between the riser and the air, but also trapping more of the radiant heat in the soapstone lattice/tile facing.
Some drawings or pictures of the tiles you're talking about could help. But this sounds interesting. Please keep us in the loop, and good luck.
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Proceed with caution. do some heavy research and inquiry on the water containing properties(if any) of soapstone. Because if it contains much water...... it COULD POP/CRACK or 'explode' . Also... as stated.... the thermal properties... how well it stands up to heat etc.
i wish i had these answers for you.... but i don't.
if high heat doesn't hurt it.. i think it will be quite lovely!!
(isn't soapstone a bit expensive? How'd you get enough to consider doing this? no need to answer that if you don't want. )
Encasing with soapstone will be beautiful.
Using it directly around the riser could be a problem.
I suggest bricking the whole riser and just covering with the soapstone.
Of course if you have bunches of soapstone, then give it a go and let us know how well it works!
I'm confused, because soapstone is often lauded as THE material to use for a masonry heater. It is most certainly not safe to use in place of refractory masonry products in the core of heater, (RMH or masonry) but it's considered just about ideal for the mass/facade. Many feel it has the best thermal properties of any natural stone, absorbing a great deal of heat and releasing it slowly to the surrounding space. Soapstone is to masonry heaters as cob is to rocket mass heaters.
Soapstone is an ideal material for thermal mass, but is not an ideal insulator. What you want around your riser is an excellent insulator that can stand very high temperatures. The ceramic fiber is that already.
You can perfectly well make an enclosure of brick instead of a steel barrel; the top third or so, at least, should be firebrick so it will last under the heat stress. This can be faced with a solid soapstone layer for additional mass and good radiating properties. You will not get the same instant heating as you get with a bare steel barrel. I would always build in an access panel to be able to inspect and repair the riser if needed, and if well located, this access panel could serve some instant radiator function.
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