Stove top slab addition: Granite do any good? (vs. Soapstone)

[Beowulf]

Had much fun doing the firebrick in the old QF. Now that I have a diamond blade, I got to thinking about cutting up some granite left over from a kitchen project a few years ago and putting about 3" of it on top of the stove.

Here's the thinking:

The QF has a cowling in the back (rear heat shield) that the blower forces air through. It comes up about an inch higher than the stove top and directs air in a roughly laminar flow across the stove top to help heat the room. The blower is on a thermal switch that cuts it off when the back wall of the firebox drops below about 200 F.

The stove cycle keeps the blower on through most mornings, until time to reload. I usually get up to a reasonably warm downstairs, of say 66 F, prior to reloading the stove. Let's say the room was about 76 F when the stove was set for the night.

What I'm wondering is, would putting maybe 3" of granite on the stove top act as enough of a heat storage sink to give us a little warmer morning temperature in the room?

I would anticipate three layers, with the bottom layer having a couple of channels in it for the air to flow through from the back of the stove.

I hear all the love for the soapstone stoves, but the old QF is what I have, as well as some spare granite and now the means to shape it.

Thoughts?

 

[vvvv]

the pan under the outlet, full of water, will retain more heat & have better conduction i think

 

[Beowulf]

the pan under the outlet, full of water, will retain more heat & have better conduction i think

yeah, but then my wood would get all wet! ;-)

 

[madison]

My vote is NEY.

Besides looking weird I would offer a few thoughts off the top of my head (so it may not be worth anything)..
1. Could the extra weight of the stone on top of the stove damage the stove, stove legs, and/or hearth?
2. Could the trapping of heat/prevention of heat convection off the stove top damage the stove body?
3. The opposite affect could also be, in the morning it would take longer to heat up the area....

I say put that diamond blade away before you hurt yourself.

 

[jhjove]

I wonder if granite may be more easily cracked when exposed to high temps?
For my stove I build small fires in the beginning of the heating season to drive
the moisture out of the soapstone. I have to think granite would fall into this category.
But it may not hold up well to consistently high temps. Just guessing....

 

[Todd]

I think Hearthstone use to make a stove out of granite? I wouldn't do it, stove wasn't designed for it.

 

[ddddddden]

Soapstone has twice the heat storage capacity of steel. Granite has ~1.7x, so I think it would do the heat reservoir thing fairly well. Dunno 'bout stacking slabs on top of the Quad. . .maybe just stack some on the hearth or lean it against the wall. There's lots of soapstone info on a Tulikivi page called "The characterirtics of soapstone." Unfortunately, I can't get the full URL, so if any moderator would like to correct my link, that'd be swell. www.tulikivi.com/www/kotien.nsf Interestingly, Tulikivi says that soapstone is not very porous, 0.08% vs. 0-30% for other types of building stone. Could the seasonal "break-in" fire to drive the moisture out of soapstone be unnecessary?

 

[woodgeek]

Heat storage is product of mass, specific heat and temperature swing. If the granite doesn't get to stovetop temps, its not worth the trouble.

 

[firefighterjake]

Most likely you will not get the desired result that you're hoping to achieve . . . namely the granite acting as a massive heat sink and releasing heat long after the fire has died off. I suspect you may get some effect, but just putting a stone top on a steel or cast iron stove does give the stove the same characteristics of a soapstove stove . . . I know.

You may have noticed in another thread that I did something similar to you . . . albeit with only an inch of soapstone. I noted some heat retention, but it was pretty minimal.

Moreover, as others have mentioned putting three inches of stone on top of a stove is a pretty heavy load . . . and I would be a bit leery of placing the bulk of the stone right on the stove top without an air gap underneath . . . hard to say what effect this may have on the insulating qualities and heat dispersion from your stove.

That said . . . if you would like to "dress" up the stove a bit and want to play with the tile saw I would say go ahead and cut a single granite slab as a topper . . . but I would suggest limiting yourself to just a single 1 inch or so and I would put the stone up on some stone pads to give yourself a half inch or so of air space . . . I personally think it might look kind of pretty . . .

 

[Backwoods Savage]

I believe there has been experiments with all types of stone and other objects to "store" heat and hopefully reap the benefits later. Most things will to a certain extent, but most prove to be not worth the time.

Many, many moons ago people used to place rocks on and around their heating stoves or furnaces to "store" heat. However, most of those were used to warm beds or take along in a car or buggy to keep the feet from freezing. As for helping to heat the home, I seriously have my doubts with most things of this nature. But then, this idea might be worth trying anyway. Some things just have to be tried even if they say it can't be done.

 

[madison]

If the idea worked, the stove companies would already be all over it.

 

[Battenkiller]

Heat storage is product of mass, specific heat and temperature swing. If the granite doesn't get to stovetop temps, its not worth the trouble.

Yeah, and mass being not so much in this case. Also, granite has only about 1/3 the thermal conductivity of soapstone, so it will be three times as effective as an insulator. With temp drops of 50-100º that have been observed by members with extra soapstone, I think you are asking for problems.

If you have a bunch of it, it probably wouldn't hurt to fashion a stand for it and put it near the stove, but I don't think you will gain anything by putting it right on top.