The others are correct that the fires in a masonry stove are built using very well seasoned wood and are not damped but rather are allowed to burn very fast and hot. Creosote is unburned wood byproducts produced by incomplete combustion. Complete combustion of the wood in the firebox results in no creosote to condense on cooler chimney walls. From what I have read the masonry stove chimney walls remain very clean in spite of the fact that they meander around and travel long distances before venting to the outdoors. I've also read that they frequently are designed with a shortcut bypass which is opened to let the fire catch and create a draft and then shut once the fire is drawing well.
The concept behind masonry stoves is that the wood is burned very fast and hot (usually fires last about an hour) extracting maximum heat from the wood burned and storing it in the large mass surrounding the chimney channels. Once the fire is out the chimney and/or combustion makeup air vent are closed to stop the draft and trap the heat in the stove mass where it is given off by radiation slowly and evenly throughout the day.
If you search masonry stoves, Russian stoves, ceramic stoves, etc on the Internet you will find lots of interesting articles about the subject. It sure makes you think about how inefficient our methods of heating with wood are.
JN
Is the ultimate efficiency known? The modern EPA stoves here in the US are rated higher than 70% efficiency. I wonder how much better the ceramics do?
I have this stove, and they rate it at 75% efficient. But what does that actually mean? I really don't know...but except for the front, the walls, top, bottom, back are all soapstone. The front is supposed to radiate quickly to give you some immediate heat, but the rest is very slow to heat up, but does stay hot for a good long time. But, the only rating of the Russian or Finnish stove I have found said it was 90% "combustion efficiency." What does THAT mean? Are we talking apples to apples here, or is the stove really 15% more efficient, or even more that the soapstone stove I use?
http://www.hearthstonestoves.com/wood-stoves/stove-details?product_id=20
I read for the ceramics, etc, they start two short fires per day mostly, and then close off the damper completely when the fire is burned out so the heat cannot leave the chimney. I read the the only downside is that you have to anticipate the need for heat, since you will not get that heat quickly, nor will you be able to stop heating quickly should the heat not be needed.
I would love to have a ceramic, at least to try, but people in the US need to realize, if they do not already, that the stoves here are ~50% more efficient that in the past, and that can make a big difference...for those who are not ready to build a Russian stove of their own.
Ok, a bit more...this site claims at the bottom that the EPA efficiency includes combustion efficiency and heat extraction efficiency combined.
http://www.chimneysweeponline.com/wscompe.htm