Craft distillers are known for bucking tradition as they experiment with different grains, unusual fermentation and distillation techniques, unorthodox mash bills, and unique finishing casks. Yet relatively few distillers have veered away from the traditional oak barrel, even if some have branched off into unusual oak varieties.
However, some coopers and distillers are beginning to ask about the other inhabitants of the forest—and to take on the challenge of using different types of woods.
Barrel technology has existed for thousands of years, but the earliest vessels were for storing dry goods. For those barrels and tubs, people could use just about any kind of wood because the containers didn’t need to be leak-proof. However, once people began to store liquids such as wine, beer, and mead in casks, the selection of serviceable trees shrank significantly.
“The problem is that there’s a limited number of species that are actually watertight,” says Thomas Collet, owner of ReWine Barrels in Jefferson, Oregon. Early types of lumber used to make casks for storing liquids include yew, fir, and oak. Exactly when barrel-makers discovered which woods would hold water is unclear, but by the first century AD, the amphorae-loving Romans were aware of the achievement. Pliny the Elder writes in awe of the Gauls: “In the vicinity of the Alps, they put their wines in wooden vessels hooped around.” Yet, he notes with amusement, “it has been occasionally seen that these vessels have burst asunder, and there has stood the wine in frozen masses” on the cellar floor.
Barrel technology hasn’t exactly changed much since those early days of cask management—though I haven’t heard of many barrels bursting open with frozen wine. In terms of wood selection, meanwhile, we’ve largely settled on oak as the prime material.
Oak is hard but malleable, so casks made from the ubiquitous wood are durable but relatively easy to craft. The staves are also watertight yet breathable, which means the spirit mostly stays where it should, but important oxygen-driven chemical reactions can still take place. And, of course, the vanilla, spice, and brown-sugar notes imparted by oak casks are both familiar and delicious. (“It’s like they designed it to be a barrel,” Collet muses.)
Furthermore, oak is abundant. Vast forests of American, French, and European oak cover the continents where wine and spirit production take place. For larger producers of whiskey and other spirits, the plentiful nature of oak and its tasty flavors are enough—“If it ain’t broke,” and so on.
However, for craft distillers with a different mantra, adventure awaits.
Branching Out
Rogue Spirits in Oregon began their exploration of different woods partly because they were making their own barrels on site, and the team thought it would be interesting to try trees besides oak. “We had a small cooperage, so we were trying to figure out ways to do something different,” says Kory Neal, head distiller at Rogue. “Larger-scale coopers just can’t pivot quickly or start working with a different wood every day.”
One of the first woods Rogue tried was cherry. However, problems arose before the barrels were even built. “Sourcing was difficult,” Neal says. “It was hard to find a long, straight piece of cherry to even get a stave out of. We overall only made four barrels, and it took a long time to find all that wood.” Once they’d acquired the wood, shaping the staves and putting together the barrels was simple enough, and the wood proved watertight, just like oak.
Once whiskey hit the wood, however, the similarity between cherry and oak staves quickly evaporated. “It's definitely one of the most interesting things we’ve ever produced,” Neal says, “but it is very medicinal. Think Dimetapp—a very artificial cherry.” Besides the intense cherry flavor, Neal says the casks also were “very chocolate- and vanilla-heavy, with a lot of extra baking spices that weren’t in the original whiskey.”
On the other hand, pecan barrels have provided “amazing” flavor, Neal says. Whiskey finished in these barrels also had notes of sarsaparilla, cola, and nutmeg, along with “lots of interesting spices, but not overwhelming in any way.” Unfortunately, despite bringing great flavor, the pecan barrels “really did not want to hold liquid.”
He elaborates: “It was not an angel’s share issue. It was just liquid dripping out of it. We had to constantly work on pecan barrels, knocking hoops, we had to put spiles in, beeswax”—and anything else they could think of to help the leaky casks.
Hybrids & Zebras
Undeterred by this liquid setback, Neal and his team turned next to a combination of woods to achieve the positive flavors without losing liquid. Rogue began to use pecan for the barrelheads, while the staves were made from tried-and-true oak. “When you’re not talking about bending staves,” Neal says, “your heads are way easier to just make into hybrid barrels.”
The reason a cask’s head might stay watertight while staves may leak is simply a matter of construction: “You minimize the weaknesses of the wood,” Collet says. “You’re not bending the head; you’re just joining the pieces, and so there’s less chance for leakage.”
Kō Hana Distillers on Oahu, Hawaii, also has had great success with these mixed kinds of casks.
Kō Hana cofounder Robert Dawson wanted to use koa, a species of flowering hardwood tree endemic to Hawaii; its wood was once used to make dugout canoes. After experimenting with this beautiful wood in a variety of ways, Kō Hana settled on casks made of oak staves and koa barrelheads. After aging first in traditional oak casks, their agricole-style rum is transferred into the koa wood to finish. Koa imparts a dark red color, along with strong notes of black tea and cloves.
Besides hybrid barrels, some distillers are using what they playfully call “zebra casks”—that is, barrels made with staves of alternating wood types. The staves can be a mix of oak species, different kinds of toasts and chars, or a blend of species.
Kentucky’s Bardstown Distillery has won fans with its Origin Series, which is finished in toasted cherry wood and oak barrels. Distilled from a mash of 95 percent rye, Origin Series is aged in a zebra cask of alternating cherry and oak staves. Using cherry for only half of the staves helps to blunt the influence of an impactful wood, while still producing a complex and unique spirit.
Woods from Far and Near
Besides common trees such as cherry and pecan, there is growing interest among consumers in more exotic woods from farther afield.
Several cooperages are now offering barrels made from amburana, cumaru, balsamo (aka Santos mahogany), and even jackfruit wood. Initial studies find that amburana imparts high amounts of cinnamic aldehydes, vanillin, and syringic aldehydes, which impart smoky and spicy notes to whiskey. Yet with the elevated flavor comes an elevated price tag: Barrels made from these tropical woods are often two or three times as expensive as those made from oak.
While some producers are importing wood from far away, others are looking to bring home those interesting flavors by using local species.
“I always wanted to do something truly Hawaiian, something actually endemic, and so that’s where koa came in,” says Dawson at Kō Hana. “This state provided us so much, so I feel like I need to give something back.”
For Kō Hana, koa wood is not just a way to tap into local flavors but also to help conserve natural resources. “We’re the largest conservator of native Hawaiian plants in the state now, in volume,” Dawson says. “We have hundreds of acres of native Hawaiian species.”
Such endeavors that are both flavor-enhancing and conservation-minded will undoubtedly appeal to consumers increasingly aware of the relationship between spirits and our impact on the environment.
There’s still much to learn as distillers experiment with different kinds of trees. It’s hard to imagine any other tree replacing the mighty, plentiful, and watertight oak, but coopers are developing creative ways to use wood that would otherwise be left untried.
Producers and consumers alike are thirsty for new flavors—and there are plenty of trees in the forest.