Which type of stone has the poorest thermal conductivity?
March 8, 2010 11:09 PM   Subscribe

Which type of naturally occurring stone has the poorest thermal conductivity? low cost and ability to be cut into a slab shape are desirable.

I want to make a small counter top out of stone that feels relatively warm to the touch. Should I just go with concrete or is there a naturally occurring material that has poorer thermal conductivity?
posted by Infernarl to Science & Nature (11 answers total) 2 users marked this as a favorite
Probably pumice.

But the literal answer to your question is meerschaum. However, you ain't gonna be cutting slabs of the stuff. And it ain't cheap.
posted by Chocolate Pickle at 11:34 PM on March 8, 2010

Doing a search for "ceramic foam" gets lots of hits.
posted by XMLicious at 11:49 PM on March 8, 2010

The problem with all of those things is that they'd make a terrible counter-top because they're soft. Any stone hard and dense enough to not take dents or to wear away (e.g. marble or granite) is also going to be a pretty good thermal conductor.
posted by Chocolate Pickle at 12:40 AM on March 9, 2010 [1 favorite]

Or, thinking outside the box, I saw an article in Fine Homebuilding where they placed an electric radiant floor mat (like what you'd install under the tile in your bathroom floor) under the granite countertop (it was a kitchen island).

Leave the switch on 'low' (and/or add a timer) and you're sure to have a warm counter no matter what stone/cement surface you choose.
posted by jpeacock at 2:03 AM on March 9, 2010

Soapstone might work:

Soapstone has a greasy feel (hence the name), can be ground to a powder or carved, has a high fusion point, low electrical and thermal conductivity, superior heat retention and high lubricating power. It is chemically inert.

Concrete would probably be a poor choice:

A couple of years ago, Martha Stewart spent some shows showing off the new kitchen studio. There were acres of soapstone, counters and sinks. That was when I remembered it fondly from my long ago years as a lab rat. For many years soapstone was the material of choice for lab sinks, counters and such. The stuff is just about indestructible. In one chemistry lab I worked in it had been in place for well over 40 years. If you like the rustic look of soapstone, I can't think of a better material.

Concrete will fizz under lemon juice and is dependent upon sealers. At one point, I was a materials technologist. We had a saying . . . "Man who paint concrete really stupid." From a materials' technology standpoint, I can't imagine a worse choice for kitchen counters. Over the years, I would get "government job" questions from architect friends asking what to do with a problem concrete counter. My answer usually came in the form of "Get a jackhammer."
The real disasters are the sealers, of whatever polymer, that forms a film. Without getting too technical, concrete has terrific strength in compression, almost none in tension. Whatever polymer film will set up stresses as it cures. This may occur over a surprising length of time, months maybe. Bottom line, the stresses will eventually pull apart the cement part of the concrete at the interface. The interface may be a few thousandths of an inch down in the surface if the sealer had good penetrating power. Now you have peeling and a real mess. ...

posted by jamjam at 2:17 AM on March 9, 2010 [1 favorite]

I don't think high thermal conductivity is the reason stone feels cold. When I touch a stone, the heat is sucked out of my finger but it isn't transmitted down to the core of the stone. It's just stuck right there at the surface.

The problem is the high(ish) specific heat of stone. An amount of heat that lowers my finger by 3 degrees only raises the stone 1 degree, say.

(Except now that I type that out I'm not so sure. Presumably the human body's specific heat is near that of water, which is actually much higher than stone. Maybe that's not true right at the surface of the skin though?)

Maybe you can just build the counter in a sunny spot and let thermal mass keep it warm until morning?
posted by DU at 4:36 AM on March 9, 2010

Pumice is a great insulator. When I went to Craters of the Moon several years ago, there was a spatter cone made of the stuff that had a pile of snow inside it (this was at the end of August).

I don't think you'd want to use it as a counter top, because of the porosity, though.
posted by ArgentCorvid at 4:57 AM on March 9, 2010

posted by aramaic at 6:13 AM on March 9, 2010

I'm not sure I'd worry about concrete as much as Fifi in Jamjam's link seems to. I'm not saying it's not correct, but I haven't seen the same concerns voiced elsewhere and we're getting to a point where lots of people concrete counter tops have been around for a while.
posted by Kid Charlemagne at 6:23 AM on March 9, 2010

A possibility might be to have a layered structure (think stone plywood), especially if the very surface layer is quite thin and the layers beneath have very low thermal conductivity.
posted by JMOZ at 7:13 AM on March 9, 2010

Does it need to have the feel of stone, or just the look? You could take a slab of whatever stone you like and use one of those pour-on finishes. That would put a quarter-inch glossy insulating layer over whatever cold stone you might have underneath, so it would be warm to the touch. It won't feel like stone, though.

One advantage of this would be that your stone doesn't have to have a perfectly smooth top, since the finish would fill in any holes.
posted by echo target at 7:45 AM on March 9, 2010

« Older Moving away from email at work   |   Ant farm: fun or creepy? Newer »
This thread is closed to new comments.