I’m a sucker for wine cask-finished whiskeys (well, just whiskeys, really, but sometimes I pretend to have a palate). The Glenmorangie Madeira Wood was one of my first Scotch love affairs, and I recently discovered the new Basil Hayden Red Wine Cask Finish, which blends Kentucky Straight Bourbon with bourbon partially finished in red wine casks to pretty spectacular (i.e. delicious) effect.
This led me to ponder the question of why it is so delicious, which led me to investigate the whole finishing process. Transforming raw materials into drinkable liquor is fascinating—and a lot more complicated than the still on that old TV show M*A*S*H led me to believe (if you don’t get this reference it’s because you aren’t quite as finely aged as I am). A lot of spirits are aged (also called “maturing”) in order to make them palatable, because when a spirit is initially distilled it’s often pretty raw stuff. Bourbon, for example, starts off life as a clear liquid with none of the charm or taste notes of a good bourbon—those come from an initial aging in barrels made of charred American oak (so-called white whiskey usually uses a different recipe, or mash bill, because it’s not going through this process). According to Wine Magazine, barrel aging is where bourbon gets the majority of its flavor, and all of its color.
There are some specific requirements around aging—to call a whiskey a bourbon, for example, it must be aged in oak barrels for at least two years. Scotch has to be aged at least three years in used bourbon barrels; añejo tequila between one and three years, typically in used whiskey or wine barrels; and aged rum has to have spent at least one year in a bourbon barrel somewhere.
So if so much effort goes into aging a spirit, why is finishing so important to (some) spirits?
What is finishing?
Finishing describes the process of giving a spirit a specific flavor and color profile by storing it in a vessel—commonly wood barrels that have previously matured a spirit, but not always. It’s a secondary aging process involving transferring the already aged spirit to a second vessel in order to get the desired flavor profile and color. Think of it this way: You distill something into a clear alcoholic liquid. You age that in a barrel, where it transmorgrifies into whiskey. Then you age the whiskey in a second barrel that held red wine and it turns into, say, Basil Hayden Red Wine Cask Finish.
The chemistry of maturing and aging is complex, but it boils down to three basic interactions:
Subtractive: The interaction between the wood and the spirit removes unwanted or undesirable flavors.
Additive: Time spent in the barrel pulls color and flavor notes from the vessel into the spirit.
Interactive: As the spirit sits in the vessel, it interacts with the vessel material (e.g., wood) as well as oxygen.
This is essentially the same process that goes on in the initial maturing process, which transforms the clear distillate produced in the distillation process into what you recognize as whiskey or rum or tequila. The finish brings in secondary flavors—for example, adding a touch of wine to a whiskey.
There’s one other aspect of finishing: Resting. Some spirits are “rested” in a “neutral” vessel made of something like stainless steel or glass. These materials don’t interact with the spirit at all, so there’s no additive or subtractive process going on. According to Master Distiller Harlan Wheatley, this neutral resting allows a spirit to settle down and mellow without adding any additional flavors to it. Resting is a common practice with white spirits like pisco or tequila, but is also employed with whiskey and other spirits.
For a long time, certain spirits were never finished. According to VinePair, spirits like vodka and gin aren’t traditionally matured or finished because they don’t contain as many compounds that can interact with, say, a wood barrel. While vodka might be rested in a neutral vessel like a stainless steel barrel, it wouldn’t be finished in a cask. But that perception is actually changing—increasingly you’ll see “barrel rested” or “barrel aged” vodkas and gins as distilleries experiment with new categories. Technically, this means those spirits are no longer legally considered vodka (which the Alcohol and Tobacco Tax and Trade Bureau [TTB] defines as “without distinctive character, aroma, taste or color”) or gin (which the TTB only recognizes in its un-aged form), but that doesn’t mean these experiments aren’t worth drinking.
Finishing comes down to engineering the final product by exposing it to specific materials and conditions over a specific time period, and there are several different ways to finish off a liquor. One of the biggest considerations is what the barrel held before you put the whiskey in it, as the wood of a barrel will absorb the flavor of what’s inside it, then leech that flavor back into whatever it holds next, creating a complicated history of flavors.
Here’s are how some spirits are commonly finished.
Whiskey
While a wide range of spirits are finished these days, it’s especially common in the whiskey world. The most common finishing for whiskey is in wood barrels or casks, including:
Bourbon barrels. A lot of whiskey is actually finished in bourbon barrels, because bourbon can add notes to other whiskeys they normally wouldn’t obtain from their own aging process.
Wine casks. Whiskey is frequently finished in wine barrels to pull the fruit and spice flavors from different wines into the spirit. Sherry, port, madeira, and marsala are common barrels—different wines are chosen based on what will complement the whiskey’s flavor profile.
Rum barrels. If you want a sweeter whiskey flavor, you can finish it in rum casks.
Those are just the most common. You can find whiskeys finished in vermouth, maple syrup (!), brandy, and beer barrels.
Gin
Finishing gin is increasingly popular, and the spirit becomes a little whiskey-like in the process, typically taking on a brown color and a hint of that whiskey flavor. Most barrel-aged gins are finished/aged in unused, new wood barrels. While these can include traditional American or French oak, gin producers can get pretty creative and have bespoke barrels created just to complement their product.
Barrel-finished gin is often used as a substitute for whiskey in cocktails, bringing along those juniper and spice notes that whiskey lacks and changing the whole experience. Whether that’s good or bad depends largely on whether you regard gin as a civilized spirit or the devil’s liquor.
Vodka
Like gin, vodka was once considered a white spirit you couldn’t age or finish (though it wasn’t uncommon to “rest” it in a neutral container made of steel or glass), but that attitude is also changing. After all, flavored vodkas are pretty common these days, and if you put vodka into a non-neutral vessel like an oak barrel, it will go through the same additive, subtractive, and interactive process in there as whiskey does (albeit to a lesser extent) emerging with a “honey-like” hue and a distinctive flavor.
Vodka is often finished in both charred and un-charred oak barrels, but you can also find barrel-finished vodkas that spent time in wine barrels, and bourbon or other whiskey barrels.
Rum
Rum typically only goes through a single maturation process in bourbon barrels, but in recent years there’s been an explosion of finished rums. These “cask-finished” rums mature in bourbon barrels as usual, then spend a few months in other casks, most commonly wine casks. Sherry, port, and cognac casks are frequently being used to finish off rum. But rum has also been finished in whiskey barrels other than bourbon, and even in tequila barrels.
Tequila
Tequilas vary in terms of maturation: Blancos are bottled immediately (or a minimal amount of time) after distillation, while reposados are aged up to a year and añejos aged at least a year and as long as three years. Like vodka or rum, tequilas aren’t traditionally finished, but it’s becoming more popular these days. You can find tequila finished in Scotch barrels, bourbon barrels, and wine barrels, particularly sherry casks.
Brandy
You may be seeing a pattern here: You don’t traditionally think of brandy being “finished” in secondary vessels, although an initial maturation in oak barrels is very common, and some brandies (like pisco) are legally required to rest in neutral vessels for a period of time. But we see more and more brandy being finished in wine barrels, and even whiskey barrels.
Finishing can add flavor and complexity to a spirit, especially if the vessel material and previous occupants of that vessel are chosen very precisely to craft a specific flavor profile. While some people argue that finishing something like gin is just a marketing gimmick, in the end all that matters is whether you enjoy the expression or not. Which means you have the pleasant task of sipping a lot of spirits ahead of you.