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Heaven Hill Distillery. Bardstown, KY © 2019
Think Wisely. Drink Wisely. ®

Whiskey’s transformation from white dog to smooth spirit is nothing short of miraculous. The raw distillate acquires flavor, color, character and aroma after years inside of a charred white oak barrel. Here’s a look at the science, and magic, behind our barrels.

1

The Barrel

In a world of bountiful resources, millennia of evolution, and centuries of technological advancements, the mighty oak tree reigns supreme as “king of the barrels.” Its unique grain and chemical makeup provide for liquid-tight lumber that gets stronger as it’s curved into barrel shape. What’s more, its distinct sugars, waxes, fats, and oils impart a complex combination of flavors that are unique to Bourbon.

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2

Charring

Distillers char the inside of their barrels at varying levels, ranging from Level 1 (15 seconds) to Level 7 (3.5 minutes) and beyond. We char at Level 3 (40 seconds), which leaves a ¼-inch-deep layer of char inside the barrel. This process caramelizes the oak’s sugars and creates a dense layer of smoky sweetness waiting to be dissolved.

By breaking open the wood’s cell walls through charring, the spirit gains access to flavor compounds such as caramelized wood sugars, vanillin, and spice.

Lighter char levels tend to produce more fruit esters and spice notes, while heavier char levels release desirable oak flavors into the spirit more quickly.

Charred wood filters the spirit by trapping undesirable aromas within it, and creates chemical components that turn clear distillate brown as it matures.

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Adding the Distillate

This is where the science and magic really ramps up. When the distillate is added, the liquid penetrates the charred layer to access the newly caramelized layer, and the char filters the liquid. We barrel our whiskey at 125 proof (62.5% alcohol). The water dissolves the oak’s sugars and the alcohol extracts compounds that add depth, complexity, and character.

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4

Aging

Good Bourbon comes to those who wait. As temperature fluctuations cause the oak to expand and contract, the liquid seeps beyond the char and caramel layers to interact further with the oak, extracting deep notes of spice and wood. Liquid evaporates, oxygen enters, and chemical reactions create even more flavors and aromas. On average we lose 6% the first year because of soakage then 3% every year after that.

Water dissolves wood sugars that contain the sweeter vanilla and caramel notes. Alcohol extracts tannins that give the spirit complexity, depth, and a drying sensation on the palate.

Liquid evaporation allows oxygen to enter, causing many chemical reactions, like esterification. Esters are chemical compounds within whiskey that produce fruity aromas and sweet flavors.

Sometimes a whiskey’s flavor is less than desirable due to too many years in the barrel, or because of excessive evaporation (a.k.a. the “angels’ share”) under prolonged heat exposure.

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5

Effects of the Environment

After we tailor every step of the process, obsess over every specification, and determine the ideal aging period, there are a multitude of uncontrollable factors that can affect our Bourbon. Everything from the year’s average temperature to the barrel’s rickhouse position will impact the liquid inside, and no two barrels ever age the same.

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