I think Slate is good at holding heat for a while, but most of these things
are not actually stone. Most are made from resin type materials that have
cured to a solid state and been coloured to look like stone or marble. So
I'd reckon on a web search for "Thermal Resin" would probably come up with a
few good hits.
Why stone ? Chinese restaurants use an alloy plate to keep food hot on
the table. Heated in an oven ISTR.
Also BMW offer an extra (Or the used to ?)on their cars to give
instant heat on a cold morning.Consist of a large slab of aluminium or
somesuch whick takes heat from the engine and stores it over night for
use through the cars heatinh system
Paul Mc Cann
"Big slabs of stone that retain heat. I'm looking for one of those. Any
according to a builder friend of mine marble is very good for retaining heat
he's using it throughout the ground floor of his new house, on top of
underfloor heating, for that very reason.
True, we need mass x heat capacity.
Limestone density 2.1 - 2.85 SHC = 0.8
basalt density = 3.2-3.5 SHC = 0.84 ....MC proportional to 2.94
granite = 2.4 - 2.7 SHC = 0.8 MC proportional to 2.16
sandstone = 2-2.6 SHC =0.92 MC proportional to 2.4
not quite mass x heat capacity but density x specific heat capacity = thermal
heat capacity. The lower the value of rho x cp the less energy moving throught
the body is absorbed by the solid in the first place (THermal diffusivity
= k/(rho x c) so that along with thermal heat capacity lets you see which solid
requires the least heat to get it up to required temp and how much energy is
now stored in it.
email@example.com (Wdyw) wrote in message
Should have added alpha also allows you to work out how the energy is
released during cooling. (all above based on a fixed size of slab
rather than a set mass)
fun and games ...got to spend this week trying to explain to kids why
cp for gases is always larger than cv.
Not necessarily, since you're probably interested in the *volume* of
the 'hot plate' then the denser material will be better. Specific
heat indicates how much heat *per gram* (or per kilo) is required to
heat the material.
I would guess that marble is denser than sandstone by rather more than
the ratio of the specific heats so marble is probably better.
A friends dad had his old storage heater system ripped out and replaced
with central heating. He took the storage heaters apart and removed
the "storage" part of them - basically a large block of some sort of
He laid them as part of a small patio - the heat they gave off late evening
after a day in the summer sun was really quite impressive. Not sure
how they have coped with the weathering though :)
So, a quick trip to the tip might result in an old storage heater that
could be scavanged?
On Mon, 13 Oct 03 08:13:17 GMT, firstname.lastname@example.org (dmc) wrote:
Surely nobody is going to be able to lift out a storage heater, put in
in the boot and then take down the tip?
Or am I just a weakling :-)
Or "they don't make storage heaters like they used to..."
Seriously though - I've dismantled some old Heatstore ones - the metal
panels have come in useful for all sorts of projects, and I've a
couple of the bricks on the bench for keeping the heat in when I'm
doing jewellery work. The rest are on the brick stack outside and
don't show any signs of deterioration after several years.
(Please put out the cats to reply direct)
No stone will keep food warm - they are all much better conductors
than wood etc (with odd exceptions like pumice perhaps) and so will
cool it down, unless the stone is preheated separately. Better to use
an insulating material.
Slightly OT but stone is such a good conductor that 1inch of
polystyrene foam has about same insulating value as 44 inches of
So the old story about stone cottages being warm in winter and cool in
summer is only half true - they are cool in summer but in winter are
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