Alcohol is an exceptional solvent. It extracts and holds onto the flavor compounds (phenols, esters, aldehydes, and fatty acids) that give whisky its character. When whisky is maturing in a cask, the interaction between the spirit and the wood is driven by the alcohol concentration. At cask strength (often 55-65% ABV when bottled from the cask), the whisky contains the maximum possible load of these flavor compounds.
The next time you pour a dram, look at the ABV. Ask yourself: Is this intended to be drunk neat, with ice, or with water? Has it been chill-filtered? Would I enjoy it more if it were a few percentage points higher or lower? The answer to that last question is personal.
At first glance, the number on a whisky bottle seems simple. It’s usually a figure between 40% and 60%—43%, 46%, 57.2%—followed by the word “ABV” (Alcohol by Volume) or, in the United States, the term “Proof.” But for the distiller, the blender, the collector, and the casual drinker, that tiny number is a universe of information. It tells a story of legality, economics, chemistry, flavor, and tradition.