where to get a stone that holds heat?

[Big Bill]

You know like they have slabs of stone on hostess trolleys for keeping food warm while it's served? Big slabs of stone that retain heat. I'm looking for one of those. Any ideas please?

BB

[BigWallop]

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.

[in2minds]

"Big slabs of stone that retain heat. I'm looking for one of those. Any ideas please?" [..]

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.

Les

[Huge]

Kiln shelves. Any art supplier.

[Peter Ashby]

Surely for a role in heat retention you have to know the heat radiance of the two as well? Oh and the density would come into too since specific heat is per kg.

Peter

[Steve]

specific heat capacity of marble 0.88 specific heat capacity of Sandstone 0.92. = Sandstone is "better".

Steve

[Steve]

True, we need mass x heat capacity.

Limestone density 2.1 - 2.85 SHC = 0.8 (ditto marble)

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

Steve

[Wdyw]

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 (alpha) = 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.

[Big Bill]

It do, but only for printers.

BB

[Big Bill]

Fuck it, I'll buy a trolley.

Unscientific BB

[Big Bill]

Now that sounds more sensible. I used to do pottery, funny enough.

BB

[dmc]

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 concrete/stone stuff!

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?

Darren

[DrJohn]

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.

[usenet]

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.

[Bob Mannix]

I think the answer is dead easy. Concrete is similar density to marble and has a hugely larger specific heat capacity (3.35 onstead of 0.88). Build your own very cheap, very effective slab.

[Mr Fiendish]

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.

Barley Twist (Please put out the cats to reply direct)

[jacob]

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 limestone. 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 f..ing freezing.

cheers

Jacob

[The Natural Philosopher]

Open up any storage radiator.

[Paul Mc Cann]

snip

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 Bill]

HEY! I SAID I WAS GONNA BUY A TROLLEY - OK??? :-)

BB