All bourbon is whiskey, but not all whiskey is bourbon—so the saying goes. By the same token, all whiskey is aged in a barrel, but not all is aged in a Kentucky bourbon barrel. It has to be made from a certain wood—and no second-hand barrels will do; it needs to be prepared the right way, and it needs to last years. Join us as we delve deep into the charred depths and discover a little more about these silent heroes.
WHAT MAKES KENTUCKY BOURBON BARRELS SO IMPORTANT?
THEY'RE MADE OF THE RIGHT STUFF
One of the secrets to a great whiskey barrel is the wood all bourbon casks are made from: American white oak. It’s been used since the beginning and for good reason. White oak is prized by coopers (the craftspeople who construct and maintain barrels) for the same reason it was the preferred wood of shipwrights for centuries: its strength, dense grain, and resistance to rot.
So white oak has a lot going for it, but how do these elements affect our bourbon? Well, strength means the barrels are hardy enough to spend many, many years in the rickhouses where bourbon ages. The dense grain contributes to overall water-tightness but also lowers evaporation, reducing how much whiskey is lost to what’s known as “the angels’ share”.
Last, but perhaps most importantly, white oak is packed with flavor-enhancing compounds—more on these below.
UNIQUE CHARACTERISTICS OF A BOURBON BARREL
So, apart from oak, what are whiskey barrels made of? Well, did you know that Kentucky bourbon barrels are constructed without any glue or nails, so no stray flavors get into the whiskey? Instead, the cooper uses precisely cut wooden staves that fit together perfectly. The wood is then heat-treated with steam or flame to make it pliable enough to bend and shape. After the wood reaches the desired shape, metal rings are forced into place around the outside, where they can’t affect the whiskey inside but hold the staves together. And so, a barrel is born.
A BOURBON BARREL'S BAPTISM BY FIRE
It’s when the interior of the barrel is charred—here amid the flames, smoke, and blackened wood—that the soul of bourbon can be found. The inside walls are exposed to intense heat and flames, which result in the flavor compounds we mentioned earlier.
THE CHAR LEVELS
The skill of creating bourbon is found in each decision made along the way. One of those choices is how much to char your barrels. The easiest way to understand char levels is to think of them as a sliding scale. Some flavors like bread, toast, and coconut present better at lower levels of char. Conversely, if you’re looking for a smoky vanilla kick, then you’re better off at high char levels. Distilleries will choose the level of char depending on the flavor profile they are trying to create in a bourbon.
# 1: a 15-second char. A light toast with sweetness and oaky flavors
# 2: a 30-second char. A medium-light char with coffee and hints of vanilla
# 3: a 35-second char. A medium char with spice, vanilla, coconut, and caramel notes
# 4: a 55-second char. A rich char with strong vanilla, spice, smoke, and tobacco notes
You can discover more about the essential characteristics of exceptional bourbon here. Apart from added flavor, the newly charred barrel also acts as a filter. As the bourbon ages, the carbon in the char removes impurities from the liquid. At Wild Turkey, we favor the deep # 4 char, to ensure the bold character of our whiskey. This is also known as alligator char due to the barrel interior’s rough texture and shiny appearance, like the reptile’s skin.
THE BARREL AGING PROCESS
Bourbon distillate fresh out of the pot still is known as white dog, and it’s a feisty character. It’s clear, strong, funky, and needs taming. This is where the art of barrel aging comes into play. Once filled, the barrels are stored in a rickhouse. Although they are resting, they are not inactive. The conversation between barrel and bourbon is a dynamic process, and the slow march of time and fluctuations of the seasons transform the liquid.
In summer, heat causes the liquid to expand and seep into the wood. Here, it absorbs the flavors produced by charring while having impurities removed. During the cooler season, the liquid contracts again, reabsorbing those compounds into the whiskey. This pumping process is often referred to as the breathing of the barrel.
As flavors develop, so does color. With every breath, the barrel imparts pigment into the liquid. During this aging process, the bourbon also undergoes oxidation, where alcohol molecules interact with oxygen from the air. Over time, this interaction helps smooth the harsh edges of the spirit, resulting in a more refined and balanced bourbon. In total, as much as 70% of bourbon’s flavor and 100% of its color comes from the barrel.
The management of the rickhouse is something we take very seriously at Wild Turkey. Our goal is always to create the most stable conditions possible to reach the pinnacle of maturation. To achieve this, our finest barrels are placed in the center cut—floors three to five of our seven-floor rickhouses. Here, the temperature and humidity fluctuations are the most consistent. By avoiding extreme fluctuations, our bourbon ages gracefully and develops rich flavor profiles.
As Wild Turkey Master Distiller Eddie Russell says: “The best aged whiskey barrels are hand selected by me, and only from the center cut of the rick house – since that’s where the optimal maturation occurs. Adamant about quality, I will only use the natural, weather-driven process for maturation – never air conditioned or heated ‘because it’s the right thing to do”
Now, we get to the million-dollar question: how long is bourbon aged? By law, straight bourbon has to be aged for at least two years. Wild Turkey 101 is blended from barrels aged at least five years, including some older.
Some of our Wild Turkey releases are a lot older.
Because for us, the ultimate answer is always: as long as it takes. Every barrel is a little bit different, and our Master Distillers Jimmy and Eddie Russell are experts in selecting barrels at just the right moment.