Published November 1, 2012. From Cook's Illustrated.
We tested three sets of stones in different materials, from granite to soapstone to glass, priced from $12 to $34.
Although many experts claim that whiskey must be slightly diluted to be fully appreciated, beverage stones offer an alternative for those who prefer to sip it neat—but not warm. Simply chill these rocks in the freezer and then plop them in a drink to maintain the optimal temperature (between 57 and 61 degrees, according to the connoisseurs we consulted). We tested three sets of stones in different materials, from granite to soapstone to glass, priced from $12 to $34, tracking the temperature of the whiskey in which they sat for 2 hours and comparing them with whiskey poured into a tumbler that had been chilled in the freezer. None successfully maintained our drink’s temperature for a significant amount of time, but one set landed a stone’s throw ahead of the rest, keeping our whiskey below 63 degrees for 30 minutes. We’d rather just prechill our glasses, which works just as well.