Eric Alperin refers to ice as “the bartender’s flame” — the focal point from which all cocktails are built. Block ice, favored by Alperin, has less surface area and properly dilutes a drink. From the cracking of the tin to the ice going into a mixing glass to an aggressive shake, the sound of ice will tell you what’s happening in a cocktail. He freezes blocks up to two to three days and has a whole chapter devoted to ice in his memoir “ Unvarnished .”