Then, Scotch whisky–makers started experimenting with new ways to enhance whisky in the 1980s, and bourbon distillers followed their lead. "Growing up in the industry you'd hear old-timers say you can't make barrels out of maple or other species," says Chris Morris, master distiller for Woodford Reserve Distillery. "But with the handcuffs off, due to the experimentations in the Scotch whisky industry, we said 'it's about time to see what we can and can't do.'"
To change whiskey, a master distiller has to change one of the whiskey's flavor sources. Most distillers choose to alter the wood during the aging process.
Morris recently launched Woodford Reserve "Four Wood," the seventh release in Woodford Reserve's annual Master's Collection, which sees Morris alter one of the five sources of the whiskey's flavor—grain, water, fermentation, distillation or maturation. Focusing on the time the whiskey spends in the barrel for 2012, Morris put standard six- to seven-year-old Woodford Reserve in a maple wood barrel as well as former sweet wine casks to lend more chocolate, nutty and dark cherry flavors not usually found in bourbon. Much like the original Woodford Reserve mingled with the new charred American oak barrel, the "Four Wood" chemically reacted with its barrel wood to produce a particular set of flavors. The former fortified wine barrels had wine soaked into the wood and are larger than standard whiskey barrels, giving the Woodford Reserve a larger surface-to-whiskey ratio as well as the small-scale fruity flavors that remained from the barrel's former alcohol.
In an effort to create a spicier-finishing whiskey, Maker's Mark added toasted French white oak staves to its existing bourbon barrel for its 2010 Maker's 46. "French oak has a different flavor profile than American oak—it’s spicier," Boswell says. "The French oak wood is lighter, a less dense wood. The oxygen interacts with the spirit differently than the American oak barrel."
French white oak packs nine times more tannic acid than American oak, Boswell says. When the Maker's Mark hits the barrel and mingles with the French and American oak, the whiskey takes on both woods’ profile characteristics. With the French spice and American sweetness, Maker's 46 delivers a spicy, rich caramel whiskey that leaves its flavor on the tongue longer than traditional Maker's Mark.
Aging has even gone beyond stationary warehouses. For its Ocean-Aged Bourbon, Jefferson's Reserve placed several barrels on a 126-foot ship and let the casks cruise at sea for nearly four years. The increased oceanic air pressure (compared with its warehouse), along with the Panama Canal's extreme heat pushed the whiskey deeper inside the wood, causing the wood sugars to caramelize and add a rumlike black hue. The whiskey breathed a little easier, too, says Trey Zoeller, who co-founded Jefferson's Reserve. "The porous nature of the barrel not only allows for evaporation of bourbon out of the barrel, but also [for] the barrel to breathe in the salt air, giving it a briny taste," Zoeller notes.
But Wheatley's Buffalo Trace Distillery may hold the record for whiskey experimentation. Since 1987 the company has conducted more than 1,500 barrel experiments for its Experimental Whiskey collection. These tests included studying sections of the tree to determine which heartwood should go into which stave and making a French oak barrel three times the size of a standard barrel. In the latest experiment Wheatley charred a regular bourbon barrel for 3.5 minutes instead of the standard 55 seconds. "We could not have gone a second more," Wheatley says. "The barrel nearly fell apart."
As for the whiskey—well, some people liked it, some didn't. And that's the standard reaction to the whiskeys that break tradition. Many whiskey purists despise these new-age whiskeys, saying distillers are trying to fix something that's not broken. "I've developed thick skin over the years," Morris says about the negative reviews. "Everything I do is about making [whiskey] better."