Originally Posted by b1os
So, do the stainless steel ones work better? I don't really know a lot about physics, but I'm quite certain that water retains heat (and therefore coldness) much better than stone or -- especially -- metal. So my idea of the ideal non-diluting cooling device would be something along the lines of a stainless steel "frame" in form of a cube that is filled with distilled water (obviously such that the frozen distilled water fits perfectly in the inner setting). Or probably silver (doesn't it react less to food in general -- ignoring egg and such?).
Quick Googling informs me that soapstone has a significant higher heat capacity than steel, but the density is a lot lower. It's probably a wash in terms of cooling drinks. Silver would be worse than steel I believe. Nothing plausible is going to come close to water (ice), especially since it can melt and remove heat that way as well.
The best for cooling without dilution would probably be something like those reusable ice cubes. Little plastic fruits with water in them
I've heard of people using frozen grapes to chill wine.
The stones (or steels) are just more aesthetically pleasing. You can always fish them out and add more if you need more chilling.