Cask Strength: The Surprising Connection Between Bourbon and Scotch

So you like your scotch? Drink more bourbon.

Just as with a glass of fine wine, one of the joys of imbibing any Scottish whisky is experiencing the full expression of terroir: the peat, the spring water, the amount of rainfall during a particular growing season; all of these factors influence the final outcome as the barley undergoes its life cycle, from malt to mash to spirit.

Quaff a dram of Laphroaig 10, and you’ll immediately grasp those emanating notes of peat and smoke, two very recognizable phenols characteristic of the label. One can get caught up in the romance of a sensory journey to a particular idyllic fen in Scotland. But after the the aromatic veil of peat and smoke subsides, somewhere on the endnote, you might detect a round vanilla and caramel finish that’ll likely bring you back stateside. What you’re picking up in your Laphroaig is actually the influence of American oak barrels that have aged American bourbon.  

Over the last century, American bourbon barrels have become integral in Scottish whisky production from Islay to Speyside, imparting a New World influence on the world’s most revered and lauded labels. Casks that once matured Wild Turkey, Jim Beam and Woodford are shipped off to live out second lives as newcomers to an Old World tradition. The practice has become so commonplace, in fact, that 90 percent of Scottish whiskies are finished in ex-bourbon barrels.

The story begins in 1919 when both the American whiskey industry was brought to its knees by the Volstead Act, and while the legal arm of the Temperance Movement couldn’t reach across the Atlantic, Prohibition pummeled the whisky industry in Scotland as well. Whisky-producing locales which had flourished because of the U.S. market were devastated.

But once the teetotaling tyranny of the Volstead Act was repealed, the thirst of the American public was reawakened, and world-wide whiskey production resumed in earnest to quench it. Despite (or due to, depending on who you ask) the fact that America was sinking into the Great Depression, the demand for whiskey catapulted and production was thrust into overdrive.

Any American distiller worth their malt understood the importance of the cask in the production of whiskey; the best aged their spirits in virgin oak barrels which imbued their bourbons with predictable, reliable flavors. Across the pond, however, whisky producers used anything they could get their hands on, as long as it was made of oak. “People simply didn’t understand the relationship between wood and whisky back then,” explains Mitch Bechard, National Brand Ambassador for Glenfiddich. Prior to the 1940s, most of the time they used old sherry or wine casks sourced from Europe, but there are some toe-curling accounts of distillers using old fish barrels rolled off the pier.

This all changed in 1938, when the U.S. government passed a bill mandating the use of virgin American oak casks in bourbon production in an effort to shore up the logging and coopering industries still recovering from the Depression. As a result, a surplus of used bourbon barrels amassed. Scottish distilleries saw an opportunity and enthusiastically offered to take these unwanted barrels and give them a second life filled with new spirit. This historical opportunism would evolve into a lasting relationship for decades to follow.

Though the journey of a barrel could end any number of places, it’s unlikely a landfill is one of them.

Aside from the benefit of a plentiful supply, ex-bourbon barrels became quickly prized for the qualities they impart upon a spirit during the aging process. “Ex-bourbon barrels deliver a nice balance of flavor where the oak doesn’t dominate the maturing spirit but still adds significant sweetness and oak character,” explains Sebastien Derbomez, the USA ambassador for Monkey Shoulder.  “The intense oak flavours have all been removed by bourbon leaving soft, sweet, vanilla oak notes.” This softer finish results in a spirit less tannic than those aged in sherry or wine casks, making it more palatable and accessible for those just starting to explore Scottish whisky.

It’s these qualitative benefits that have cemented the ex-bourbon cask’s place in the production of Scotch. But others have caught on to the virtues of American oak; bourbon barrels are now used in the production of Japanese whiskey, tequila, beer and even hot sauce.

Casks can be reused in Scottish whisky production up to four times before they lose their aging potential, but what happens to these barrels after they’ve served their time? Though the journey of a barrel could end any number of places, it’s unlikely a landfill is one of them. Some barrels go on to become the wood chips that flavor smoked Scottish salmon, while others could be repurposed into furniture. Walk into any given bar in Dufftown, where Glenfiddich is made, and it’s likely you’ll be seated upon a stool that once aged a whisky — and an American Bourbon.

Interested in learning more on the scotch and bourbon markets? Read more.

Nancy Lippincott
Nancy Lippincott

Nancy Lippincott is SHIFTed's Managing Editor. Trained in anthropology, she brings a holistic, culturally observant approach to storytelling. Her background spans both hyperlocal journalism and and global digital-media brands; she spent five years managing Park Slope Reader, a boutique print quarterly, and also contributed to PopSugar and

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