Why 40%? Historically, it’s believed that this concentration best carries the flavor compounds (congeners) from the cask. Below 40%, the whisky can become cloudy and lose its characteristic “mouthfeel.” Many entry-level blends and single malts (e.g., Johnnie Walker Red, Glenfiddich 12) are bottled exactly at this legal minimum to maximize value for producers. You’ll encounter three main ranges of alcohol content in Scotch: