The idea of tasting a whiskey that comes straight from the barrel has been an enticing selling point in recent years, but the growing popularity of "cask strength" spirits is a bit more than just a nebulous term meant to conjure images of tough men, dark wood, and stiff drinks.
If we put you on the spot, you might be a little confused about what cask strength actually means, because there are a lot of things cask strength is not. First of all, cask strength whiskey is not still-strength whiskey, nor is it the highest proof the spirit can possibly be.
Cask strength is whatever comes out of the barrel (cask) after a certain number of years of aging. Rich Varga, Master of Scotch for both The Glenlivet and Aberlour, explained the aging process best: "When the heart of the new make production comes off [the end of the distillation process], it is anywhere from 68-72% ABV. It then goes into a nice long sleep where flavor and color increase and alcohol ABV naturally decreases."
That number isn't always straight from the still — in fact a lot of distillers bring the original proof down before barreling. "Generally the spirit is going in at 127 proof (63.5ABV)," says Varga, "as this is the ideal range of ABV for maturation to manage the Angel's Share."
But that's technical information. What it means for consumers is that you have to be more conscious of what's actually going on behind that "cask strength" label. No two cask strengths are going to be the same. The worst of them may have needed watering down to be at their optimal flavor profile. The best of them come right out ready to drink, and change and evolve in amazing ways as you dilute them.
That's the selling point for cask strength: experiencing various evolutions of flavor in one glass. Varga says, "The philosophy behind cask strength whisky is that people can receive the real deal, undiluted with water from the distillery, and dilute if/as they see fit. Most suppliers will dilute down to 40-42ABV, but there are varying personal opinions on this practice."
It's not just about sipping. Cask strength whiskeys have their place in cocktails that benefit from over-proof whiskeys, like the Julep, in which dilution by melting ice is part of the drink.
But for the purpose of sipping, most are meant to be diluted at some point — either with some water or a slow-melting ice chunk. Gradual dilution means you're getting to see the whiskey at various proof points, starting with the strongest.
Varga says cask strength is about "experiencing them at the fullest natural potential. I suggest first trying neat and then… do with the untouched dram what you will. Add your preferred level of water, or even a small cube. Ice tends to lock down the flavor of scotch, but the addition of ice can be helpful for enjoying the intense flavor of a cask strength whisky."
The Glenlivet's recent Nadurra First Fill is one of those new cask strengths to the market. Varga says they did very little in determining the final profile of the whisky. "We like to say with Nadurra, we don't determine the ABV, Mother Nature does." Nadurra means natural in Gaelic, and so Varga says, "Whatever the whisky is at the time of bottling, that's what we go with. We're aiming for a flavor profile that best captures the essence of the distillery. We don't add anything to it or take anything out." But what does all of that do to flavor?
The Glenlivet Nadurra, for its part, has more bright, tropical fruit notes and richer hints of vanilla from the virgin oak. Aberlour's cask strength A'Bunadh is heavier, bolder, and takes the deepest raisiny, praline spices from its ex-sherry casks. Because they're both bottled around 60 percent, there's some room to add water and watch the flavors evolve. That means no two drinks will be exactly the same — which gives you a great excuse to keep sampling.