As the "flavor monsters" in the whiskey world, cask-strength whiskeys excite as rare treats. Bourbon distillate is typically diluted with water before hitting the charred-oak barrel, since federal regulations say that the bourbon cannot go into the barrel at more than 125 proof. Water evaporates out of the barrel as the whiskey slumbers in a hot warehouse, so you often see the proof is higher when the barrel is emptied than when it was filled. Therefore, most bourbon is cut with water again before bottling to bring the proof down to a desired strength, such as 40 percent ABV or perhaps a bold 50 percent. Cask-strength bottlings have not been cut with any water and feature full-flavored, high-octane whiskey straight from the barrel. This style offers great flexibility, because you can add whatever amount of water you like to bring the whiskey to your preferred strength. (You can always bring a whiskey at barrel-proof down to 40 percent or 50 percent alcohol, but you can never make a 40 percent ABV whiskey taste stronger.)
Jim Beam released Booker's as the first cask-strength bourbon in 1988. The whiskey's power amazed bourbon lovers with nuances of tobacco, oak tannin, chewy caramel, and fall spice. Others that titillate discerning taste buds are George T. Stagg, Parker's Heritage, and Wild Turkey's Rare Breed. Wild Turkey's Master Distiller, Jimmy Russell, firmly believes in distilling at a lower proof to capture more flavor so its cask-strength whiskey is the lowest strength in this category at around 108 proof. It's loaded with cinnamon and nutmeg spice. Parker's Heritage is rich with dried fruit and toffee notes and has a very dry, woody finish. Stagg's proof differs with each release (it has been as high as 141) and so does the flavor profile, but it typically displays an incredibly concentrated, layered complexity each time, and at 15 years, a bit of smoky wood dominates the finish.
Be warned: Drinking undiluted whiskey over 100 proof can be dangerous in more ways than one. Booker Noe, for whom Booker's is named, loved telling the story of how his wife blew the oven doors off when cooking with undiluted Booker's. What's more, a little addition of water unlocks the subtleties of that concentrated flavor; you need not prove your vigor by drinking cask-strength whiskey straight.
Image Credit: Nicola Kast