Can thickness be added to a stove?

[cbrodsky]

I disagree a bit here. Though I agree that soapstone is not magical, I feel that a typical soapstone stove's heat capacity is enormous, especially considering that its walls are upwards of two inches thick AND all walls meet at RIGHT ANGLES, ie, excess mass exists here, purely out of the shortcomings of working/machining the material. On the other hand, mass positioned next to a cast or steel stove is unlikely to reach two hundred degrees in temperature...far less than the five hundred degrees that the soapstone can attain prior to its decline portion of the cycle.

But mostly, my point was/is that unless someone is available to close the air intake at the start of said cycle-decline, heat will be supplied to 'combstion' air when there really is no combustion taking place....and will, thus, NOT be available to the living space. OBVIOUSLY, this flies in the face with soapstone stove marketting propaganda. I've been making this point for some time....I date my involvement with HearthNet to 1998....but with very little acceptance. However, it DOES seem as though there is a little less resistance (here) to that thinking ....perhaps, some folks are 'coming around'.

Just noticed my post never showed up earlier... I'd argue a couple points above.

The specific heat capacity of soapstone is not markedly different from cast iron:

Soapstone = 0.23 BTU/lb-F
Cast iron = 0.16 BTU/lb-F

Either type of portable stove has similar weight in lbs. so the Soapstone holds a little more heat, but I wouldn't say enormous.

On the other hand, the thermal conductivity is enormously different:

Soapstone = 45 BTU-in/hr-ft2-F
Cast iron = 520 BTU-in/hr-ft2-F

I think this difference, coupled with the design elements you discuss above, are much bigger factors in why a soapstone stove is "different" from other stoves. You are slowing down the rate of heat transfer from the core of the stove. This lets a slower burning fire stay hot longer inside the stove, and deliver less peak heat, but for a much longer period of time. It also explains why even after you get to coals, it takes a long time for all that heat to exit the stove.

Additionally, in any stove, one should be adjusting air intake to control flue temperatures once up to temp. In a metal stove, the rate of heat loss is higher, so you will need to feed more oxygen to maintain a clean burn. In a stone stove, you should be damping down that oxygen rate to achieve reasonable flue temperatures or as you note, you're wasting heat. By slowing the combustion air rate, you are stretching the burn time of the wood while still keeping a hot fire - you just don't put out as much peak heat.

This issue of controlling air correctly is not unique to one stove or the other. In general, it's just good practice all around. Ideally, this should happen throughout the cycle... would be a fun project to have a thermocouple driven actuator that did all this for you for peak efficiency

-Colin