On paper, the whiskey-making process seems remarkably easy. You need to mash (corn, barley, wheat, or rye in most cases), ferment, distill, and age it. That’s it. Seems pretty simple, right? Well, it’s a lot more complicated than that. And while all of the steps are important, in my decades of writing about alcohol, I’ve learned that none are as important as aging. Without spending some time maturing in a barrel or cask for months, years, and decades, it would simply be white whiskey or moonshine and wouldn’t ever reach the pinnacle of aroma and flavor of a mature, nuanced whiskey — and certainly not something you’re excited about drinking.
Wood maturation adds a lot to the overall color, aroma, and flavor of the whiskey. The distilled spirit melds with the charred wood and gains color ranging from amber to dark caramel and flavors like oak, vanilla, toffee, cinnamon, tannins, and many more.
Different barrels are used to mature whiskey
Not only is the aging process important, but so is the barrel used. You can’t just grab some random wood lying around, craft it into a barrel, add distilled whiskey, and assume your expression will be flavorful after a few years of aging. The right barrel and wood are extremely important.
Below, you’ll learn about the different barrel types used by various styles of whisk(e)y. Not just the wood used, but the type of cask as well.
What is a whiskey barrel?
Before we take a deep dive into the aging process, it’s important to give a little background on the barrel itself. This cylindrical wooden vessel is crafted of boards bound together to create an airtight seal. Often charred or toasted to caramelize it and allow the whiskey to better interact with the wood, the barrel adds the color, aroma, and flavors that whiskey drinkers expect when they crack open a bottle of their favorite whiskey.
A well-made barrel is very important. I’ll go as far as to say that the craft of making barrels in a cooperage is just as important as the art of distilling and aging whiskey itself. You need the craftsmanship of a talented cooper and specific woods to make the whiskey you know and love.
Oak barrels
When it comes to maturing whiskey, oak is the king. There’s no wood type more popular than oak. The most common oak barrel is white American oak. It’s commonly used for bourbon whiskey and Tennessee whiskey, but you will find Irish whiskey and single malt Scotch whisky aged in this type of wood. It’s well-known for adding flavors like toasted vanilla beans, caramel, and oak.
French oak
French oak is another popular choice. Adding flavors like chocolate, caramel, and vanilla, it’s used by many bourbon and American whiskey brands as well as single malt Scotch whiskies. European oak imparts flavors like raisins, chocolate, spices, and wood and is a popular choice for Irish whiskey and single malt Scotch whisky.
Japanese Mizunara Oak
A lesser utilized, but exciting choice is Japanese Mizunara Oak. Known for its spice, leather, coconut, and vanilla flavors, it’s popular for limited-release whiskeys throughout the world, but widely used for aging Japanese whisky.
Garry oak
Garry oak isn’t as popular as the others, but you’ll find some American single malt whiskeys using it for the spices, molasses, caramel, and dried fruit flavors it adds.
Other barrels
Now that we’ve explained the prowess of oak as a maturation vessel for whiskey, it’s time to get into the previously used barrels distillers use for aging and finishing.
Ex-bourbon barrels
The most well-known is ex-bourbon barrels. These casks that previously aged bourbon whiskey are very popular for aging and finishing single malt Scotch whisky and Irish whiskey. Like the bourbon itself, these barrels add flavors like toffee, vanilla beans, cinnamon, and oak.
Ex-sherry cask
Another widely used aging and finishing vessel is ex-sherry cask or sherry-seasoned barrels. Very popular in the single malt whisky world, these barrels add flavors like sweet sherry, dried cherries, spices, and candied nuts. Many single malt Scotch whisky distilleries like The Macallan, Tamdhu, Glenfarclas, Aberlour, Glendronach, and The Dalmore use ex-sherry and sherry-season casks both for aging as well as finishing.
Other barrels include ex-port barrels (known for their dried fruit and spices) and ex-rum barrels (known for their coconut, oak, vanilla, tropical fruit, and spices). The latter is a popular choice among American whiskeys and single malt Scotch whiskies brands, including Angel’s Envy, Westward Whiskey, and the Balvenie.
Bottom line
Now that you’ve learned a little about the various barrels used to mature and finish, hopefully, you have more understanding about the importance of barrel aging. When whiskey is distilled, it’s clear and immature. To create the bourbon, rye whiskey, single malt Scotch whiskey, Irish whiskey, and Japanese whisky you love, it needs to spend months and years aging in barrels.
