Want a bourbon that rested in Bordeaux casks? A rye with notes of Pinot Noir? How about an American single malt that’s been in both kinds of barrel? All this and more is available, thanks to the ubiquitous practice of cask finishing.

The technique originated in Scotland. Two master distillers there, David Stewart of Balvenie and Bill Lumsden of Glenmorangie, share credit for inventing cask finishes, which largely remained the province of scotch until 2011, when Angel’s Envy debuted its port-finished bourbon. Nowadays, just about every American whiskey maker includes cask finishing in their repertoire, as it’s a quick way to create a new product (which is, unfortunately, the primary driver of whiskey sales these days). Port, sherry, rum, and other spirits’ barrels are popular options, as are red wine casks—a category that encompasses everything from anonymous “Grand Cru” and “French oak red wine” [sic] to well-known names like Chappellet and The Prisoner.

But successfully finishing American whiskey in red wine casks is not as easy as just siphoning from one barrel to another. Distillers and blenders have a lot to consider, starting with what they want from the wine cask. “It’s either going to alter the whiskey in a way that adds new flavors, or enhance the whiskey and elevate flavors that are already there,” says Miles Munroe, master blender at Westward Whiskey, which offers a Pinot Noir finish among its core lineup of American single malts.

Because bourbon, rye, and some American single malt undergo primary maturation in new charred oak, what works for cask finishing in Scotland doesn’t necessarily translate here. American whiskey makers must work with a bold, oak-forward profile in a way that neither overpowers nor detracts from the existing maturation notes, nor loses the impact of the finishing cask altogether.

“I don’t want to kill the original profile of the bourbon,” says John Rempe, master distiller at Lux Row, whose portfolio includes wine cask-finished bourbons like Blood Oath, Ezra Brooks, and Daviess County. “When I’m finishing with a wine, I’ll generally do it with the youngest whiskey that doesn’t have all those really developed flavors” so as not to disrupt the more mature profile of older whiskies. And, he adds, doing a partial finish enables him to take a more precise approach with the final blend.

There are other considerations too.

Cask Quality

Whiskey makers universally agree that the quality of the cask is paramount. “You can’t fix that later,” says Lisa Roper Wicker, a master distiller and blender who started her career as a winemaker. But what’s important for the cask when it holds wine doesn’t always matter when it’s used for whiskey—and can sometimes be downright destructive.

Many winemakers assume that they should add sulfur to an empty cask, to prevent microbial growth, but this ruins it for whiskey finishing. “Whiskey is a sponge for those sulfur notes and you can’t get them out,” Wicker says. “That ruins the whiskey.” When assessing wine casks, she rejects any that have a whiff of sulfur, as well as those with a vinegar aroma, the telltale sign of acetobacter. Nobody wants a whiskey that tastes like sauerkraut.

So whiskey makers look for wine casks that have only been rinsed, or even fresh casks when they can get them. It helps to be located near wine country. Westward is in Portland, Oregon, so Munroe often gets casks from Willamette Valley wineries like Remy and Suzor. “Winemakers here do, on average, four vintage fills before they consider a barrel somewhat neutral,” he explains. “For me, there’s still so much life in that barrel. I can put whiskey in there anywhere from a few months to over a year, and continue to get good extractive flavors from that cask.”

Some distilleries, like Bardstown Bourbon Company, go so far as to ship just-dumped casks in refrigerated trucks, which preserves the delicate remains of the wine and avoids spoilage. It’s an expensive proposition, but worth it for the flavor impact—and to be able to showcase a high-profile winery name like Phifer Pavitt or Silver Oak.

Increasingly, distillers are reconditioning casks: filling them with a gallon or two of wine, swishing it around, and then dumping it out just before adding whiskey. It's a method of restoring some of the flavors that a fresher wine cask would impart. “Some barrels are almost dry and wouldn’t have much wine influence in them,” Wicker explains. “Reconditioning puts them all in uniform condition. That’s how some finishes are coming out super consistent.”

The Right Match

Not every red wine cask works for every whiskey, even for American whiskies that have fairly consistent new-charred-oak profiles. Wicker, who consults for a number of producers, challenges them to consider the base whiskey style as well as the wine. Will an earthy Burgundy work well with a wheat whiskey? Maybe not—but it’s often a great match for bourbon. On the other hand, American single malt encompasses a wide range of flavors and thus, as a category, has more flexibility in finishing cask choices.

Both oak species and the wine itself make a big impact at the finishing stage. French oak has a tighter grain than American oak, and the wood has usually been seasoned for several years, which reduces astringency and softens tannins. Thus when used for whiskey, a French oak cask often creates a velvety texture and adds a creamy element. A common note from French oak red wine casks is earthiness, sometimes described as “forest floor” or even “leaf decay.” But the aromas and flavors can be much more specific too: Cabernet Sauvignon imparts jammy red berry notes; Cab Franc, green pepper; Merlot, plumminess.  

Munroe, who works with many individual wineries, says that terroir and the winemakers themselves also influence a cask’s finishing impact. He recently created a blend called Vintner’s Cuvée, incorporating casks from four different wineries: Pinot Noir, Syrah, and Tempranillo from Dominio IV, and Cabernet Sauvignon from Sonoma’s Jordan Wines and Vasse Felix in Margaret River. “I compare winemakers to American single malt makers,” he says, explaining that, more than base ingredient, what matters most is “the style of the maker.”

Before undertaking a full finish, Wicker tests potential combinations by adding a few drops of the wine in question to a glass of the whiskey. “I call it roughing it in, getting an idea whether it’s going to be a good match or not,” she says.

Time and Texture

At the start of its life, whiskey goes into a barrel and gets ignored for several years, until it reaches maturity. But during the finishing process, distillers monitor the liquid closely. “I’m sampling all the time,” Rempe says. “You can over-finish whiskey in wine barrels. It can become extremely tannic and you can get such a bitter note.”

Additional texture from tannins can also affect the whiskey’s flavor and its ideal final proof. Although he regularly puts together batches of Westward’s core Pinot Noir single malt, Munroe spent the better part of a year creating Vintner’s Cuvée. He was going for a specific flavor profile—earthy, fresh strawberry, a note he often finds in Dominio IV wines. “I could get to this point where I was getting close to the flavor profile, but if something was off with the tannins it would mute that subtlety,” he says. “It took eight or nine months of tinkering with different blends at different ratios, and trying different ABVs as well.”

The Brokerage System

Most whiskey makers don’t have direct relationships with wineries to get the casks they need, although they often wish they did. Instead, they go through brokers, who may or may not be able to supply details about the casks’ origins, the type of wine they held, or even the oak type. “That part of the market isn’t super sophisticated,” Wicker says.

With the brokerage system, there’s no possibility of inspecting casks ahead of time, so she and other experienced whiskey makers assess them when they arrive with the “sniff test”—literally, smelling for off notes. Wicker sends back casks that don’t pass. Less experienced distillers, however, don’t always catch these flaws, or understand why they matter, which is how some truly awful finishes end up in bottle.

And that can be a tragic end to an otherwise good whiskey. Wicker recalls mistakenly filling some sulfited barrels, saying ruefully, “It still haunts me to this day.”

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