On distillery tours, bourbon production may seem like it’s just a bunch of valves and pipes. These are the pipes of the Bernheim Distillery in Louisville.
Before the corn, malted barley, rye, and wheat meet in a fermentation tank, they’re sent to their respective storage bins or augers that mill the grains into a slightly coarse flour. Corn has its own silo, as does barley, but rye and wheat alternate storage time in a single bin. If a distillery does not use wheat, then the rye enjoys its own bin. The milled grains sit for anywhere from an hour to three days, or until the distillery workers are ready to cook the grain.
What happens next depends on the distillery and its proprietary procedures. Typically, the smaller the facility, the more hands-on the process.
On distillery tours, bourbon production may seem like it’s just a bunch of valves and pipes. These are the pipes of the Bernheim Distillery in Louisville.
At the MB Roland Distillery in western Kentucky, the small crew pours fifty-pound bags of local white corn into a hammer mill, milling the grain and sending it to the cooker. The corn is mixed with malted barley, wheat, or rye and a sour mash for a mixture that resembles a giant pot of white corn grits. MB Roland founder Paul Tomaszewski told me: “The mixture is held to two hundred degrees Fahrenheit for sixty minutes and then is pumped through a heat exchanger to reach one hundred and forty-eight degrees Fahrenheit, when the remainder of the malted barley is mixed in. Immediately, the heavy starches begin to convert to simple sugars and the mash goes from thick and starchy to light and watery with a sweet taste and aroma. The mash is then brought down to ninety degrees, pumped into a six-hundred-gallon fermentation tank, and remains in a climate-controlled room for the five- to seven-day fermentation period. Following fermentation, the mash is blended together, again by hand with an electric mixer, before being pumped into the still.”
In contrast to MB Roland’s hand mixer standing over the tank, larger distilleries are automated, and workers dictate stirring with the push of a button. Jim Beam’s Claremont facility boasts twenty-one forty-five-thousand-gallon fermenters. You could fit seventy-five MB Roland fermenters inside one Beam tank. This doesn’t make one process better than the other; rather, large distilleries tend to look more like factories, and the so-called craft distillers frequently execute most fermentation steps by hand.
At Bernheim and other fully automated distilleries, a worker sits behind a computer monitor and observes the grain unload from a semitrailer and pushes a button to move all grain through to the cooker. Bernheim starts with pouring corn and a little malted barley into the cooker to induce enzyme activity. Yeast and water are added about the same time.
At the Buffalo Trace Distillery, fermentation takes place in large tanks with ducts to suck out the carbon dioxide. The yeast converts sugars into ethyl alcohol and carbon dioxide, which are released into the air via bubbles rapidly popping to the surface.
“While the tub is heating up, we will add corn with a little bit of pre-malt. We will then heat all the way up to two hundred and twelve Fahrenheit and hold for a bit. On the cooldown we will add the flavoring grain, rye or wheat, at around one hundred and seventy Fahrenheit, then followed by the malt once the temp is below one hundred and fifty Fahrenheit,” says Denny Potter, co–master distiller for Heaven Hill.
It’s in this cook and the fermentation where bourbon’s flavors begin to develop. When yeast is added, the tub begins producing ethanol, other alcohols, esters, aldehydes, and other compounds collectively known as congeners. These congeners greatly contribute to the taste of bourbon and are influenced by the yeast, grain, grain-to-water ratio, water, cooking temperatures, fermentation conditions and length, and available oxygen.
You could say that yeast is the leading flavor component or the flavor starter, depending on whom you talk to. During the cook, the grain’s starch is converted to sugars. The yeast, a live, single-cell organism, feeds on sugars. As a byproduct of its sugar feast, yeast creates ethyl alcohol in the process of alcoholic fermentation.
Distillers use two types of yeast: a propagated wet yeast and a dry yeast.
Yeast is literally everywhere. It lives on us, near us, and in the places where we eat, sleep, drink, drive, and swim. Early Egyptians and other ancient peoples used yeast to make bread as well as to make alcohol. But it was not known to be a living organism until Louis Pasteur identified it as such in the late 1860s. Through a microscope, Pasteur determined yeast was responsible for alcoholic fermentation; since then, yeast has become the most underrated and perhaps the most important aspect of making bourbon. It imparts flavor and can dictate the whiskey’s floral or spicy characteristics.
Both types offer virtues over the other style. Dry yeast remains true to the master culture every time, while the propagated wet yeast is less faithful but begins fermentation quicker.
There are two basic types of yeast—baker’s yeast and brewer’s yeast. Brewer’s yeast consists of several types that are propagated from barley malt, fermented grape juice, distilled wine, fermented molasses, and fermented rye malt. Today, specialized laboratories maintain strains for current and prospective whiskey clients that range from dry yeasts to propagated yeasts. One of these yeast houses is Ferm Solutions, which is the sister company to the Wilderness Trail Distillery in Danville, Kentucky.
According to Ferm Solutions, both dry and propagated yeasts offer unique advantages. Dry yeast is consistent every time, because it comes from the master culture each time the distiller makes a new batch. This consistency limits mutations, ensuring that even after ten or twenty generations, the dry yeast strain will not change into something else. Activated dry yeast requires much less labor, too, while yeast propagation requires intense concentration and skilled labor. But propping yeast is a labor of love and activates the fermentation process quicker. The yeast type is really a matter of preference. Dry yeast users like Heaven Hill will argue for the consistency of dry yeast, while former Seagram’s distilleries MGP and Four Roses will swear the propagated wet yeast yields better whiskey.
But all distilleries value their yeast strains.
Most established brands have been using their particular yeast for decades and have it meticulously stored, both professionally and privately: Jim Beam has had the same yeast since Prohibition and stores strains at several production employees’ houses. Jim Beam’s great-grandson Fred Noe keeps the yeast in his man cave’s corner refrigerator, because one can never be too careful about the family yeast strain.
The yeast helps yield the flavor profile a brand desires, and no brand tells this story better than Four Roses. The whiskey maker’s identity is practically intertwined with its yeast. Today, Four Roses uses five proprietary yeasts that are linked to its former parent company, Seagram’s, which had a production strategy of using ten unique recipes to make bourbon. Seagram’s operated five Kentucky distilleries and achieved this target formula strategy with two grain recipes using the so-called V yeast. As each of the distilleries closed—Old Prentice (now Four Roses), Cynthiana, Fairfield, Athertonville, and Calvert—Seagram’s created a new yeast to compensate for losing that distillery’s uniqueness in the target formula. By the time Seagram’s went out of business, Four Roses used five unique yeasts that absolutely set the whiskey apart: V is light fruit; Q is floral essences; K is spicy, nutmeg, and cinnamon; O is fruity with hints of a milk stout; F generates herbal essences. If you taste five Four Roses products side by side with different yeasts, you can absolutely tell a difference.
In truth, Four Roses is the anomaly of bourbon distillers. Nobody else uses five yeast strains; or at least, nobody admits they do. There are so many flavor factors going on in fermentation that it’s difficult for individual brands to truthfully know their yeast’s impact on the congener production. “The mashbill affects congener production, because each grain has its own sugar and protein profile, which is converted to its own signature flavors during fermentation. This is pretty elementary and can be equated with how bread tastes when you make it with wheat versus rye,” says Dr. Pat Heist, founder of Ferm Solutions and the Wilderness Trail Distillery in Danville, Kentucky. “The ratio of one grain in a mashbill relative to another is one part of the recipe. The other important component is how much water is added to how much grain? For example, at our distillery [Wilderness Trail], our mashbill is sixty-five percent corn, twenty-five percent wheat, and ten percent malted barley. This is added to water to yield a sugar content of about eighteen percent Brix; sugar can also be expressed as [degrees] Balling. Other distilleries may use more or less water resulting in a higher or lower sugar content [as measured in] Brix. The higher the sugar, the higher the resulting ethanol and congener concentration. The more congeners produced, the more likely they will be pronounced in the finished spirit. Many chemical changes also occur during aging, which is obviously a big component, probably the biggest, of taste.”
The particle size of the milled grains can influence how quickly the starch breaks down into fermentable sugars, but the hope is that the yeast acts quickly on the sugars to mitigate growth of bacteria. Bacteria contribute to their own set of metabolic byproducts that can influence the flavor of the distillate. According to Heist, some distilleries purposely add bacteria into the mix either by undercooking the barley to allow survival of bacteria or by doing a side fermentation with bacteria and then adding this mix to the mash, much like backset is added in the sour-mash method. “Organic acids are a big contributor of flavor to the distillate and are produced by both yeast and bacteria. Each has their own unique acids, but they also produce some common acids,” Heist says. “Much of these organic acids and other congeners are governed by the yeast strain, but also things like temperature of fermentation, pH, osmotic stress, level of dissolved oxygen, availability of nitrogen and other macro- and micronutrients, agitation versus no agitation, whether or not there are contaminating bacteria or wild yeast, length of fermentation, how the material is treated between the end of fermentation and distillation—moving to an open-top beerwell can lead to evaporation of ethanol or infusion with oxygen, for example. Whether the sugars are in the form of maltose or glucose, [which is] enzyme dependent, could also influence byproducts lending to flavor differences.”
In other words, there’s a lot going on during fermentation. But given the success Four Roses has had with its five yeast strains and marketing its yeast, I suspect other brands will begin championing their yeast a little more. Many of them have a great story to tell. For example, after Bill Samuels Sr. closed his family distillery, he professionally stored his yeast in the Midwest. When he started Maker’s Mark, he brought this yeast out and tested it against other yeasts, including the original Stitzel-Weller yeast. The yeast that won this tasting panel is still used today. Which one this was depends on whom you ask, however, and Maker’s Mark has never played up this story in its marketing.
One area that distillers do not fall short on marketing is the water. In fact, to read a Kentucky bourbon brochure, you’d think Kentucky water was the essence of life and grows hearty men and women. According to the Kentucky Department of Travel, an official state agency, “While it may not be scientifically proven, it’s believed that Kentucky’s pure-filtered limestone water provides the state’s Thoroughbreds with the competitive edge to reach the winner’s circle so frequently.” Why let science get in the way of telling a good story?
Kentucky is blessed with limestone-filtered water. If the water is pulled from an open source, such as this one, state and federal laws still require industrial filtration. Most distilleries filter the water again onsite.
It’s true that Kentucky enjoys underground Paleozoic-age aquifers along with Illinois, Indiana, Ohio, and Tennessee. But Kentucky’s access to these limestone-filtered waters—through streams, springs, and rivers—became commercialized earlier thanks in part to the access to springs, streams, and rivers. In Kentucky, the water flows over limestone, filtering out unwanted minerals and iron. This is one of the chief reasons distillers made Kentucky home: the water is perfect for making whiskey. Today, distillers are not pumping water directly from a lake or stream and into the still; they must purify it. Most facilities have purification systems onsite and were originally established at the location due to the proximity to good clean water. Distilleries located within city boundaries, such as Louisville’s Bernheim or Brown-Forman’s 354, are pulling city water for distillation. “We’ll run water through carbon filtration before it goes to the mash, so it’s already disinfected, cleaned, and even more so than it needs to be. Because of the carbon filtration, we pull out any kind of taste or odor elements that might be in that water,” Bernheim’s Potter says.
The limestone-filtered, purified water is pumped into the tank around the same time as the corn, malt, and yeast. Distillers add the secondary grain as the tub fills, along with the backset. The backset is a thin, milky liquid from the previous distillation that helps kick-start the fermentation. By adding a backset, also called spent beer or sour mash, the distillers are injecting the previously fermented grain’s and yeast’s flavors to the current fermentation. Furthermore, this technique reduces the chances for bacterial infections. The backset lowers the pH, counteracting the grains’ high sugar and starch content, which raise the pH. Distillers could also lower the pH by using food-grade acids, but the backset is much more economical and traditional for bourbon makers.
At the Bernheim distillery, the backset is achieved after the still turns alcohol into vapor during the distillation process. The remaining mash falls to the bottom of the still, where it’s pumped to an area that separates the mash’s grain and liquid. “It’s a simple screen that we run the material over,” Potter says. Some of the liquid will fall through and be collected in our backset tank while the remaining grain-and-water mix flows across the screen and into a separate tank, where it will either get picked up by farmers or be neutralized and sent down the drain.” Within hours, the backset is then pumped into the fermenters and or mash tubs. But there are times the backset is not used, and this is a benefit of operating an automated distillery. “It doesn’t happen often because we abide by the rules of a sour-mash process. However, there are some rare times where you need to dump the backset because it causes too much risk of bacterial contamination,” Potter says.
They ideally want an overall fermenter pH of 5.4 on the scale of 0 to 14 and a backset pH around 3.7. Many distillers choose to keep the fermenter between 4.8 and 5.4 pH. If the overall mash falls below 3.7 pH at Bernheim, it’s a red flag. At this level, the mash is getting highly acidic, increasing contamination risk and hurting the yeast, which results in off-putting flavors. In low-pH situations, a backset with a pH hovering around 3.5 would continue to decrease the pH and drastically increase bacterial infection potential. In this case, the worker who quarterbacks every step of the fermentation from a computer simply presses a button that indicates “water mash” instead of “sour mash,” and water is added to the fermenter. “We will try to use some backset, just not as much as usual,” Potter says. “There are times where it is impossible to use any backset, such as when you start up your distillery after a prolonged shutdown. No backset is available, so you are forced to go water. Some distilleries got a little colorful with their marketing terms in that they will call this a ‘sweet mash.’ All that means is that they did not use backset; they used water. And typically is not something you do on purpose.”
Another Bernheim worker in the so-called Head House pays close attention to the water mash, lowering the temperature to ensure the pH balance is at a steady 5.4. Another reason distillers hold onto the traditional sour-mash technique is the leftover liquid is pumped into the city sewer lines, and it can lead to a costly monthly sewer bill.
Bernheim’s controlled temperature fermenters bubble up, releasing carbon dioxide and creating alcohol—or, as one Bernheim worker told me, “it pisses out alcohol and shits out carbon dioxide.” On the first day, the yeast is active converting starch to sugar and bubbling like a pot of oatmeal cooking. As the fermentation progresses, the bubbles form more slowly, less vigorously, as there is less gas to escape. On the final day, usually around day five, the mash looks like a smooth soup. If need be, distillers can produce beer in as few as three days or as many as seven; manpower and barrel availability dictate how quickly Bernheim turns grain into fermented liquid or distillers beer. How long the fermentation takes varies by distillery, but some believe a lengthier fermentation yields fruitier bourbon.
Once the beer is ready, though, it is pumped to the still. And like every other aspect of creating bourbon, the distillation imparts its own unique flavors to the whiskey. Distilleries have been known to take the same mash to two different stills, using the exact same temperatures, just to see if the stills produce the same consistent whiskey. And the fact is, no two stills have ever yielded the same distillate. Each has its own nuances that make its end product special.
First, it’s important to note that bourbon is usually double distilled. The Irish are known for triple distillation, and vodka makers will distill dozens of times. Tradition has dictated that bourbon distillers only distill twice, ensuring some vegetable oils survive the process. At its Versailles, Kentucky, location, Woodford Reserve triple distills with its pot stills, but the final bottled product also includes a mingling of bourbon from Brown-Forman’s Louisville distillery, which uses a traditional continuous column still.
Most of the larger distillers use a towering column still that is frequently referred to as a continuous column still, a prototype that Irishman Aeneas Coffey invented in 1830. The concept of Coffey’s design was essentially to use perforated copper plates to remove oils during distillation, which created distillate at higher proofs and was much more efficient than pot stills. Coffey’s design redefined alcohol distillation and eventually made its way to America.
The larger bourbon distillers use continuous column stills. This workhouse beer still churns out whiskey for MGP Ingredients in Lawrenceburg, Indiana.
At the Corsair Distillery in Nashville, this pot still makes a lot of whiskey. Those who use pot stills swear by their ability to keep the grain’s subtle nuances but admit they are harder to clean than a column still.
How it works: The beer (mash) is fed into the vessel, which boils and separates the ethanol from the grains and water. Each compound boils at different temperatures. One compound, methyl alcohol—methanol—is naturally occurring in some fruits and vegetables. Thus, the fermentation byproduct carries over into the distillation process, where methanol boils at 148 degrees Fahrenheit. If the still does not achieve higher temperatures than this, then methanol, which smells like turpentine, becomes the predominant distilled liquid and, if consumed, it could cause blindness or kill. That’s why home distilling is illegal and the government cracks down on people making whiskey in their basements. Fortunately, bourbon distillers are cranking up the heat and getting the still to boil high enough—173.1 degrees Fahrenheit, or 78.37 degrees Celsius—to turn the beer’s ethanol into vapor. Once the lower-boiling-point compounds turn into vapor, they are cooled to condense into a liquid known as distillate. With column stills, distillers re-distill the distillate to further remove the methanol. Using pot stills, they’ll discard the portions of the batch known as “heads” and “tails”—the beginning and end of the distillation, which contain high concentrations of methanol—before re-distilling the so-called heart of the first run.
Inside the column still are perforated trays, usually fifteen to twenty, that strip the alcohol out of the fermented beer, forming a vapor. This portion of the column still is referred to as the beer still, and it strips solids from the concentrating ethanol. After going through the beer still, the alcohol hits the beer condenser, where heat transfer reduces a thermodynamic fluid from the vapor into a liquid. This liquid, the first distillate, is called low wine; it’s a raw 90 to 125 proof and not meant for drinking.
From here, at most continuous-still operations, the low wine is fed into the second distillation vessel, a doubler or a thumper. The difference between the two: the still feeds liquid to a doubler and vapor to a thumper. While the column still could pass for a skyscraper in small Midwestern US towns, the doubler or thumper is typically a sexier-looking and much smaller pot still that removes the impurities and further concentrates the low wine into the so-called high wine.
Vendome Copper & Brass Works makes and refurbishes all the major Kentucky bourbon distilleries’ column stills. Vendome’s Mike Sherman tells me that the distilleries don’t like changing a thing when it comes to their stills, even if it would mean being more efficient. For example, the majority of Kentucky distillers’ column widths range from Wild Turkey’s sixty-inch diameter to Buffalo Trace’s eighty-four inches. Maker’s Mark’s three stills are by far the smallest of the larger distillers at thirty-six inches wide. When Maker’s Mark was expanding, Sherman offered to create a larger still for greater capacity. “We tried to convince Maker’s Mark that they could go from a thirty-six-inch to just replace it with a bigger still and get twice the production, but they didn’t want to have anything [to do] with that,” Sherman says. “They wanted to go back with exactly a second thirty-six-inch system. … Normally when somebody calls and says, ‘Hey, our beer still is worn out, we need another one,’ you don’t even have to ask if they’re going to change anything, because the answer is always no. They want exactly what they got.”
The majority of America’s still manufacturing takes place at Vendome Copper & Brass Works in Louisville, Kentucky. Operating since the early 1900s, Vendome employs specialty welders and craftsmen. The skill of copper welding is a rare talent because copper is a soft metal that requires finesse and firmness at the same time.
At a 1792 Barton warehouse, barrels stretch as far as the eye can see. Each distillery has its own method of aging whiskey, and this is an all-natural warehouse, tempered only by the occasional open window.
Where Vendome has found some experimentation is in the microdistillery arena, also called the craft-distillery industry. The American Distilling Institute gives the label of “craft” to independently owned distilleries with maximum annual sales of fifty-two thousand cases. For this genre, Vendome produces smaller column stills, hybrids that are half column and half pot still, as well as traditional pot stills. “When people come to us, the first things we’re trying to find out from them are how much do you want to produce? How many cases or how many proof gallons a year or a day are you trying to produce? What size? Once we get an idea of how much people want to produce, not only in the first year but the second, third year, fourth year, they get kind of a business plan, then we’ll size the equipment so they can kind of grow into the equipment,” Sherman says. “The majority [of smaller producers] are using pot stills, but more smaller distilleries want a smaller continuous setup.”
Whereas Buffalo Trace’s continuous still is eighty-four inches in diameter, the smaller distilleries use column stills that range from twelve to twenty-four inches. No matter the size, column stills offer a level of consistency over pot stills. In many respects, a column is a distiller’s autopilot; once the still is set and the distiller knows exactly how he or she wants it to run, the steam flows and the column goes. A pot still needs a more hands-on distiller to keep the distillate flowing.
With pot distillation, the distiller outfits two stills, wash still and spirit still, both heated from underneath by either steam coils or fire. The wash—an industry term for distiller’s beer—is poured in the pot and boils. Vapors pass through the still’s neck and a water-cooled condenser known as the worm, which looks like a winding copper snake. The worm condenses the vapor to create the low wines, which are distilled again in the spirit still, a smaller pot still that further condenses the low wine into high wine. Whereas the column still’s final distillation will reach the distiller’s targeted proof level, the pot still set up will typically range within 5 proof points.
No matter the still, the regulation is very clear about the maximum proof levels allowed for bourbon in its final distillation—160 proof. But the truth is most distillers are falling into a sweet spot between 120 and 140 proof. The lower the proof as it comes off the still, the more character and vegetable oils survive the distillation. Vodka comes off the still at 190 proof. The US government defines vodka as “odorless” and “tasteless” because not many flavors or aromas can survive a distillation of 190 proof. In fairness to vodka, though, the Polish, Russian, and Swedish production methods offer more nuance for the final product, and there are indeed good vodkas in liquor stores.
Once it comes off the still, the distillate is cut with water and placed in the barrel. Many old-school distillers will say the majority of whiskey’s flavor comes from top-notch distilling, but contemporary research suggests they’re wrong. Bourbon is all about the barrel.
When distillate enters the barrel, it’s clear as water. The wood chemically changes the whiskey, altering its color, filtering out unwanted properties, and adding notes of caramel, vanilla, coconut, citrus, fruits, and the most impressive smells and tastes you can possibly imagine. The wood is everything to a whiskey, with some studies indicating it makes up 75 percent of a product’s flavor profile. And the type of wood is paramount to a good whiskey.
US regulations indicate oak must be used, but why oak? Early distillers tried other types of wood, but oak proved to be more durable and liquid tight and to not inject sulfuric or skunky flavor notes like some woods do. In fact, oak offered lovely flavors and aromas that became a staple in all whiskeys.
These logs are earmarked to become future Woodford Reserve barrels. The forester looks for tall, straight trees that are about seventy-five years old and have sections of wood about four to six feet with no knots or defects.
After much research, cooperages and foresters have determined that the chemical makeup of oak is perfect for whiskey. According to the Independent Stave Company, the world’s largest cooperage, within a couple percentage points, oak is made up of 45 percent cellulose, 25 percent lignin, 22 percent hemicellulose, and 8 percent of oak tannins. They’ve determined the lignin removes vegetal notes while adding vanilla characteristics; the hemicellulose gives the wood sugars or the caramel aspects to the whiskey. When the wood is charred, vanilla, spice, toast, smoke, coconut, mocha, and vanilla are locked into the wood and ready to be extracted by a distillate.
Oak has several species, and bourbon’s regulations do not dictate what type of oak is used. Due to availability and success, American white oak, specifically Quercus alba, is the main tree used for making whiskey barrels. However, many distillers are currently using French oak—Quercus petraea and Quercus robur—in everyday bourbons. French oak has nine times the tannins as American, giving these bourbons a spicier flavor profile. Distillers are also using the likes of Mongolian and Japanese oak in experimental products, but these will never become the norm due to supply and cost. In fact, even American white oak is getting harder to come by. Since 2012, there’s been a shortage of barrels, making it more difficult for established distilleries to lay whiskey down in the wood and for start-up distilleries to age fresh distillate.
Increased bourbon demand is contributing to the barrel shortage, but the lack of quality wood is even more to blame. Most oak used for bourbon barrels comes from the Ozarks and Appalachian forest regions. Here, heavy rains can keep logging crews from entering the timber tracts, while freezing winters, heavy winds, and tornadoes ruin a tree’s chance to become a bourbon barrel. When selecting oak to be used for bourbon barrels, foresters analyze a tree for defects. Knots, broken limbs, crooked bodies, and out-of-line bark indicate minerals and water were redirected to compensate for the tree’s imperfections. If a tree loses a limb in an ice storm, it redirects its energy to compensate for the lost limb.
Coopers need about four to six feet between knots in the wood to make a bourbon barrel, as well as a tree that is clean below the limbs and has a trunk with ten to twelve growth rings per inch. Back in the old days, loggers cut any tree they wanted for barrel-stave logs. This randomness yielded leaky barrels with wood either too soft or hard. Today, science-minded foresters look for oak around sixty to seventy-five years old.
“Older trees are not as photosynthetically active as an average stave tree of sixty years old to seventy-five years old,” says John Williams, a forester for the Dunaway Timber Company, one of Brown-Forman’s contracted stave mills. “Nutrients in older trees slow down.”2 A defective or older tree’s scarred insides produce fewer of the wood sugars needed to give bourbon its rich vanilla and caramel flavor notes.
The ideal logs for bourbon barrels are also desired by high-end furniture manufacturers. But the United States’ twenty stave mills, which contract with private landowners to find good barrel timber and convert logs into staves, are willing to pay a premium to make sure a tree is used for a bourbon barrel versus an executive’s desk.
Once the stave mill manufactures the log into staves 5.5 inches wide and 37 inches long, either the stave mill or the cooperage stores the staves outside for a process that is called seasoning. I believe this is the single most important factor for creating a barrel that yields spectacular whiskey.
“When we air-season wood, we actually let the wood stand in stacks of the barrel staves,” says Brad Boswell, whose Independent Stave Company makes the majority of the US whiskey barrels. “The wood is slowly degrading because of the microbial activity that grows and feeds off the wood. The rainwater, snow, and the natural elements leach out the tannins out of the wood.”
Once the logs are turned into staves, they sit outside, where they air dry or are “air-seasoned,” leaching out unwanted microbial particles. This process varies by brand but typically takes between six months and two years.
In my experience, the longer the staves are seasoned, the more complex the whiskey is. The staves for basic, everyday products such as Jack Daniel’s and Jim Beam are seasoned for six months before being transformed into barrels, while a more premium product such as Woodford Reserve is air-seasoned for nine months. Staves for some bourbons are air-seasoned for as long as three years.
Once dried, the staves are steamed, hand-assembled into a barrel, and proprietarily toasted and charred. Bourbon brands boast about their charring methods in their television commercials, but the fact is, nobody is really doing anything special in the charring arena. All major brands either use a no. 3 char, which is achieved using about 45 seconds of direct and constant flame, or a no. 4 char, 55 seconds of the same. As a part of its Experimental Collection, the Buffalo Trace Distillery experimented with a no. 7 char, or 210 seconds (3.5 minutes) of pure flame, for its #7 Heavy Char Barrel Bourbon release in 2013. The wood was burnt to a crisp and barely held together to age the whiskey. Master distiller Harlen Wheately said the barrel wouldn’t have lasted another 30 seconds.
Within a day of its creation, a normal charred barrel is filled with fresh distillate and the whiskey penetrates the wood, typically 75 percent through the stave. “As the barrel breathes, that leads to esterification of the spirit,” says Chris Morris, the master distiller for Woodford Reserve. “When we get a barrel that yields a really fruity whiskey, I know that part of the barrel came from a faster-growing tree with softer wood. A portion of the barrel breathes more, and we get a fruitier barrel. Sometimes, those staves will do more leaking.”
Leak hunting isn’t exactly the sexiest job in the business. Crews walk the warehouses, smelling and looking for leaks; if a barrel leaks, well, that’s lost whiskey. Leak hunters use old-fashioned cedar pegs, hammers, and other tools to fix those beloved barrels from leaking the good stuff.
Speaking of leaks, as the whiskey ages in the barrel, about 3 to 5 percent a year is lost to evaporation. This lost whiskey percentage is affectionately referred to as the “angel’s share.” Distilled spirit is thinner than water and will evaporate through the wood. It will also leak out of the barrel; if the wood has a microscopic tear from the chainsaw, a baby worm boring through it, or a woodpecker pounding its beak deep in the wood, the stave can have microscopic holes not detected in the cooperage tests or visible by the naked eye. The whiskey will drip out of the wood slowly. Sometimes the wood sugars contain the leak, forming a sappy, stalactite-like tar that plugs the leak. For the times these natural defenses don’t fix the leaks, distillers will occasionally deploy leak hunters, who carry a small eight-ounce hammer with a sharp edge to scrape wood fibers; an arsenal of cedar pegs; and a stainless-steel punch with a round bar stock and pointed tip for maximum precision to crush the cedar deep into the oak stave to stop the leaking. Without these three simple tools—the hammer, steel punch, and cedar pegs—the leaking barrel drains dry.
Once fixed, a leaky barrel intrigues people buying personal barrels for their retail outfit, bar, or personal drinking usage. Former Buffalo Trace leak hunter Anthony Manns noticed during samplings for barrel selections that the “crappier” the barrel is, the better it sells. “A barrel that looks like hell is a little sweeter and smoother than a pristine barrel,” Manns says. “You won’t see a lot of people pass up a beat-up barrel.”
Theoretically, more oxygen enters a leaking barrel, and the evaporation rate increases from 3 to 5 percent to upwards of 15 percent if the leak is not contained. But does it really affect the flavor? “Overall the leaking barrels do not leak out enough to change the flavor, although there is a threshold where once enough has leaked out that the volume to surface area changes enough to affect the flavor,” Wheatley told me for Whisky Advocate. “If half the barrel leaked out, it would alter the flavor as it aged.”
I wish there were a way to point you in the direction of some bourbon from a leaky barrel, but there’s simply no way of telling when you purchase a bottle in the store. I’ve tasted hundreds of barrels of bourbon, and the top ones always had a little wear and tear, as Mann pointed out. Of course, tasting straight from the barrel can be shocking to the palate.
The barrel-proof whiskey is upwards of 140 proof and contains flecks of black coal from the charring process. By the time you buy the product in the liquor store, the whiskey has been filtered and water has been added. An argument can be made that proofing and filtration are paramount to a bourbon’s flavor.
The most common filtering method is chill filtration, in which the distillers cool the aged bourbon down to about 18 degrees Fahrenheit and use a cellulose paper type to filter out the aldehydes, fats, proteins, and esters that will eventually cloud up (or “flock”) a bottle if not taken out. The chill filtration might alter the bourbon’s subtle nuances, but distillers receive a great amount of returns if they don’t do this. When unknowledgeable bourbon enthusiasts see an unopened bottle cloud up from the fats and oils, they are likely to return and never buy the product again, believing there to be something wrong with it. For that reason, distillers filter bourbon. Occasionally, they will not chill filter a product, but they almost always disclose that fact on the label. Several Four Roses private-barrel selections, Elijah Craig Barrel Strength, and George T. Stagg are examples of non-chill-filtered bourbons, and you can certainly detect a difference in the product.
There are other filtration methods, such as the simple barrel-char removal and particle removal filters. Next to chill filtration, the carbon treatment filtration is the most common technique used in bourbon. When used properly, carbon filters can filter out impurities and not bind to alcohols. Woodford Reserve and Angel’s Envy use carbon filters, and both brands are able to effectively filter out the unwanted properties without altering the percentage of ethanol.
Unfortunately, the filtration style is not widely promoted by the brands. It’s a real shame, because some whiskeys are genuine products of their filtration systems. Michter’s, for example, has a state-of-the-art filtration system that yields a much different whiskey than the distiller from where they purchased their whiskey. Michter’s Willie Pratt is able to rid the product of flocking but also keep the primary essence or flavors that cause the flocking. He once filtered a single rye whiskey thirty-two ways, and each sample tasted like its own unique product. Michter’s products taste as if they’ve never been filtered. Yet they don’t talk about this unique aspect of their processes on their label.
I’ve found that whiskey companies tend to shy away from marketing the technology involved with their products, citing instead the romance of Kentucky or of craft distilling, thus sparking the spirited debate for technology’s place in whiskey. As far as I’m concerned, if technology makes better and more consistent whiskey, then long live the high-tech filtration systems and automated distilleries.
At a pristine Heaven Hill warehouse, bourbon barrels enjoy a little Bardstown sunlight. Each will lose 3 to 5 percent of its volume a year to evaporation, a portion called the “angel’s share.”
In Kentucky, there are few smells better than what you can get standing in the front and center of a bourbon warehouse, commonly referred to as a rick warehouse, rackhouse, or rickhouse. The aromas of oak, vanilla, coconut, caramel, and spice fill the air. If the smell of bourbon didn’t lead to a DUI charge, distillers would probably turn the warehouse smell into an in-car air freshener.
These beautiful pieces of 1800s architecture are made of thick wood beams and sturdy wood floors that will hold up to nine stories of barrels, stacked three high and more than a dozen deep, but warehouses vary from distillery to distillery. Some, such as Jim Beam’s, have aluminum-skinned siding. Others, such as a few at Buffalo Trace and at the MGP Ingredients Distillery, enjoy original brick or stone surfaces. Some distilleries choose to open the windows to maximize airflow; others close them tight and control the temperatures.
These warehouses are part mystery, part science, and they’re all living, breathing barrel domiciles that dictate the flavor profile of bourbon. Four Roses uses single-story warehouses because they offer a more consistent product, while Jim Beam and others prefer multi-story warehouses, fully admitting the seventh floor gets much hotter than the first and thus yields a different whiskey than down below. Woodford Reserve strictly controls its temperature, never letting the warehouse get too hot or too cold.
The extreme Kentucky weather pushes the whiskey deeper inside the barrel, which expands during the summer months and tightens in the winter. Occasionally, the pressure is so strong the barrel bung will pop off. And the location of the barrel affects the amount of pressure it endures. There are so-called “honey holes” in the warehouse that get the optimum heat and coolness for whiskey.
At Jim Beam, the legendary master distiller Booker Noe called floors seven through nine the center cut of the warehouse because they age more consistently. Noe theorized the bolder flavors were up top. But up until recently, these theories were passed down from distiller to distiller—today, distillers are actually studying them.
Buffalo Trace launched its Warehouse X experimental lab to study the different types of warehouse aging. The small brick-and-concrete warehouse stores up to 150 barrels, but the four independent chambers allow variables to test the aging methods. The variables include natural light, temperature, airflow, and humidity.
Since this studious attempt by Buffalo Trace began in 2013, the University of Kentucky has begun its own efforts to study barrel aging. Once a mystery, aging bourbon is now a science.
When Kentucky Artisans Distillery opened its facility, it almost immediately ran out of room to store barrels. So what do you do when you need warehousing space in a pinch? You purchase containers to store barrels. “You’d be surprised how well these containers age whiskey,” says distiller Tripp Stimson. “Warehouses are expensive!”
