The practice of finishing whiskey in wine barrels has been around since the 1860s, when scotch producers first utilized Sherry butts as a means of transporting their spirits. But, the tables have now turned and winemakers like James Foster of Stave & Steel currently seek out whiskey barrels – Kentucky bourbon barrels, specifically – as an alternative oak-aging regime for its wines.

This approach is hardly new: By the 1970s, Scotch producers had switched almost entirely from Sherry butts to bourbon barrels. They had also started experimenting with still-wine barrel finishes, although the practice didn’t become an established part of the single-malt market until 2004.  A short decade later, the first whiskey barrel-finished wines – primarily Cabernet Sauvignon, Zinfandel and Shiraz – hit the shelves.

While wine barrels can add fruitiness, body and even sweetness to whiskeys, it’s what bourbon casks can add to wine that intrigued Stave & Steel’s Foster. Foster who is Senior Director of Super Premium Wine for Livermore, Calif-based The Wine Group selected “freshly dumped” Kentucky bourbon barrels and ran trials with a number of different grape varieties before settling on Cabernet Sauvignon. Stave & Steel is California appellated and Foster sourced from sites in Paso Robles, Lodi and Clarksburg for the 2016 release.

“Even just a few drops of bourbon will kill a glass of wine,” said Foster who knew barrels were the key to achieving the style he was seeking. “There’s a tremendous amount of flavor left in these once used new oak barrels,” he said.  Early entries in the whiskey barrel-aged wine category met with some resistance largely because the flavors were really no different from wines that spent longer periods in standard oak barrels.  After a series of trials, Foster avoided that pitfall and dialed in the right length of time the wine should spend being aged. “There’s definitely a recipe that produces a wine with drinkability and Stave & Steel spends about four months in barrel,” he said.

To determine his ideal wine style, he spent time blind tasting through the category where he saw a wide range of styles – from weak to swamped by bourbon and with many wines unbalanced to alcohol.  “I start with a lower alcohol red wine because we’ll see a .5 to one percent increase in alcohol from even a very brief time in barrel.”  The resulting wine is crafted in a style that appeals to tolerant tasters – those who enjoy rich, round, bold but balanced flavors – many of whom are women.

As to why consumers find a bourbon barrel-aged wine so appealing, the bourbon category itself provides some answers. Since 2010 American enthusiasm for bourbon has grown by leaps and bounds; growth that is largely attributed to the renaissance of cocktail culture and Millennials who are keenly interested in home entertaining and amateur mixology.

With the female demographic of whiskey’s consumer base growing much faster than the male, the industry is scrambling to appeal to female consumers with flavored whiskey products. As such, whiskey flavored-wine is a natural fit for women who want bolder flavors.

According to Foster, what sets Stave & Steel apart is the fact that its 100 percent bourbon barrel aged which isn’t the case for brands that may rely on only a small percent of barrel-aged wine in their blend. This technique contributes aromas of vanilla, caramel, smoke and some wood tannins that add more structure to the wine. Vanilla is one of America’s favorite aromas and flavors. It’s one we never seem to tire of and it’s the biggest draw for lovers of oak aromas and flavors in wine.

Because it spends less time in barrel, there’s plenty of primary fruit like macerated cherries, dark plums and ripe blackberries apparent along with secondary notes of umami and brown spices. Quite intentionally it’s difficult to detect any burn from alcohol although the boost the wines gets from the barrel seems to amplify and extend the finish.

A native of Eufaula, Alabama, the picturesque town depicted in the movie Sweet Home Alabama, Foster grew up on the Roseland Plantation and spent his summers in California working alongside his father in a winery. As Head Winemaker at Concannon, Foster also oversees winemaking at historic winery in Livermore and knows his way around a Cabernet Sauvignon vine.  With an estimated 80 percent of California’s 90,000 acres of Cabernet Sauvignon planted to the Concannon Cabernet clones 7, 8 and 11 they form the backbone of the Cabernet industry in California.

Considering Foster’s upbringing, it’s no coincidence that he feels completely at home aging a Cabernet Sauvignon in a bourbon barrel. “I’ve made wine all over the world and I think there’s plenty of room for experimentation,” said Foster. “Bourbon barrel aging is a twist that can reinvent premium Cabernet Sauvignon.”