Essential Highlights of an American Whiskey Distillery Tour

Recently Mrs. Wonk and I went on an American Whiskey distillery tour spree, visiting eight distilleries in Kentucky and Tennessee in a little under a week. We’d have visited more except we only had two days in Kentucky, and Mrs. Wonk was starting to get a little itchy from all the talk of mash bills, white dog, and char levels. On this trip we toured:

Each distillery has its highlights, and a series of future posts will spill the details on each. However, after a few visits it was clear that certain elements are present on nearly every tour, so this first post covers the common things in detail, freeing future posts to focus on the unique aspects of each location.

All whiskey starts out as a form of beer – grains, water, and yeast fermenting for several days to turn the sugars within the grain into alcohol. Most American whiskey starts with some combination of corn, barley, rye, and sometimes wheat. The exact ratios for a particular spirit are known as its “mash bill.” One requirement to be legally labeled bourbon is a mash bill of at least 51 percent corn. On our tours in Tennessee and Kentucky, we learned that most corn used there comes from within a hundred miles or so of the distilleries—in the mostly rural farmland that surrounds the major metropolitan areas of Louisville and Nashville. In contrast, barley and rye are “winter grains” and grow better in places like Wisconsin or North Dakota, and are shipped to distilleries on truck or railcar.

The whole grains are milled into a rough grit, and then mixed with water in giant cooker tanks.  The purpose of cooking is to  convert the starches in the milled grain into sugars. The careful control of heat and strategic addition of different grains at the right time creates optimal conditions for the starch to sugar conversion process. An essential ingredient here is enzymes, which are the catalyst in the chemical reaction. The enzymes may be introduced naturally via the use of malted barley in the mash, or added as a separate ingredient.

 

Fermentation Tanks

After cooking, fermentation of the grains occurs in enormous tanks, usually made of stainless steel, but sometimes made of wood. The larger tanks are more than 10,000 gallons in size and over 10 feet wide and tall. Access to the tanks is typically on the 2^nd floor of the distillery building, and they’re typically not covered because the fermentation process emits enormous volumes of carbon dioxide. (Mrs. Wonk gets reminders of Augustus Gloop falling into the chocolate river every time she sees someone lean over a mash tank.) Depending on how far along the process is, you may see vigorous bubbling and feel heat coming off as the result of the fermentation, even though no heat is being applied nor are the contents being agitated.

It’s surprising but very fun that some distilleries let you stick your hand into the fermenting mash to taste a sample. We found that mash which had recently started fermenting was relatively sweet and could almost be consumed as a porridge. Mash that was several days old was much more sour, with a strong beer-like essence – that’s what it is, after all. There’s essentially no risk that all those visitors’ fingers poking at the mash will cause contamination – the sheer quantity of the mash dwarfs any random contamination from random contact. More importantly, the mash is run through the stills and between the heat and 70 percent alcohol, there’s little to worry about.

The sight of a giant, bubbling tun of mash is impressive enough on its own. In distilleries of any size though, there are numerous mash tubs. At Willett, a relatively small distillery by comparison to others we visited, I counted at least seven mash tuns. At the Jack Daniel and Maker’s Mark distilleries, I lost track of how many I saw, and who knows how many you don’t see on the tour?

Another surprising detail of the distillation cycle is that after a batch of mash has been distilled, a small portion of it is held back and used to start the next batch of mash—much like a sourdough starter is used to make batches of bread. This has two beneficial effects:   Yeast still present in the prior batch makes helps ensure that only the desired yeasts (a very precise process with carefully guarded formulas) are fully present in the new batch. In addition, the acidity of the old mash helps ensure that only the desired yeasts strains survive. The process of using old mash to start a new batch is known as “sour mash,” a term that often confuses people who think that sour mash whiskey will taste sour itself. Any mash not used for starting the next batch is provided to local farmers as high-protein, easily digestible livestock feed. There’s essentially no residual alcohol in the spent mash, so happy drunken cows unfortunately aren’t a common sight on the rolling hillsides of Kentucky and Tennessee.

Vendome Column Still

American bourbon and rye spirits share a lot of common aspects with Scotch whisky, but there are critical differences. It’s relatively well known that Scotch starts from malted whiskey, whereas Bourbon must contain at least 51 percent corn, and Rye must contain at least 51 percent rye. What’s less well known is that Scotch whisky is generally made via two passes through giant pot stills. A pot still is a giant closed copper pot topped with a long neck, which the gaseous distillate emerges from. After each batch of mash is distilled, the pot still is cleaned out for the next run.

Although some pots stills are used in American Whiskey production, the majority of the distilled spirits comes from column stills, many of them fabricated by the Vendome Copper & Brass Works in Louisville, KY. Vendome has been making stills for more than a hundred years now. Column stills are upright columns made partially or entirely out of copper. A series of hatch doors ascends up the length of the column for access to the horizontal perforated plates within. Mash is pumped in near the top, steam is pumped in near the bottom, and the still can process mash continuously if desired, as opposed to a single batch at a time like a pot still.

The sizes of a column stills varies dramatically. For example, the stills at St. George Spirits in California are about ten feet tall (my estimate). Thus, I wasn’t fully prepared for the enormous scale of the stills found at distilleries like Jack Daniel’s or Maker’s Mark. They stand several stories high, and some are at least six feet in diameter (again, my estimate). On interesting thing I noticed was that some columns are bare copper, while others are wrapped in a thermal jacket resembling corrugated metal siding. At first I couldn’t figure out why the difference, despite extensive internet searches. Unable to contain my wonkiness, I wrote to Vendome to ask for an explanation. As they put it: “No rhyme or reason.  Some are insulated, some aren’t; some partially, some completely.”

When in operation, the stills exude a lot of heat. I was surprised that when distilleries toured us and others near their column stills, nothing prevents you from walking up and touching them–although that’s typically not a smart move.

Spirit Safe

Much of a distillery tour is about scale – row after row of giant fermentation tanks, enormous column stills, and rickhouses (more on those in a minute) holding thousands of barrels of whiskey. The spirit safe is the eye of the needle that the entire process passes through. As the vapors come off the still, they run through water-cooled condensers and form a steady torrent of fluid that gushes into a copper and glass box about the size of a microwave oven. Through the glass sides you can see the stream of still-warm distillate at about 65 percent alcohol – the actual percentage varies depending on the distillery, but it’s generally in that range.

At this point the new-make spirit is called “white dog,” meaning an unaged spirit. A pipe leading out of the box leads to storage tanks elsewhere, so the box never fills up. However, enough spirit remains in the box to support using a hydrometer, which looks like a floating thermometer in a narrow tube, but is actually measuring the relative density (aka specific gravity) of the liquid, giving the distiller an idea of the relative alcohol content of the spirit currently flowing through the box.

The term “spirit safe” is a reference to the similar spirit safes found in Scottish Whisky distilleries. Those are also made of brass with glass windows, but the primary difference is that Scotch spirit safes have a handle on the outside that allows the distiller to direct the condensed distillate to either the hearts tank (the good stuff) or the heads/tails tank (the bad stuff). This separation of good from bad is only necessary when doing batches in a pot still. Continuously run column stills like in American whiskey distilleries don’t need heads/hearts/tails separation. So then, why the “safe” name? Scotch spirit safes are actually locked, with the key held by a government official to ensure no one takes liquor without taxes being paid on it. American whiskey spirit safes aren’t locked – in fact on several tours, the guide will reach in with a cup and remove some for visitors to sample.

The Rickhouse

After the new make spirit makes its way into new, charred American oak barrels, the barrels need to go somewhere for the several years it takes for American Whiskey to age. The aging process happens in gigantic, wooden frame structures called rickhouses. A typical rickhouse for a larger distillery will hold between 20,000 to 50,000 barrels of whiskey – yes, barrels. Thus, a given rickhouse might easily be holding over one million gallons of whiskey. And the big distilleries have dozens of rickhouses. Let that sink in for a while.

Rickhouses have been around for over a hundred years, and it doesn’t appear that the basic design and construction has changed dramatically in that time. The basic idea is that of a several story high building (five stories seems to be a common height), structurally framed internally with a lattice of 6”x6” oak beams. Special parallel sets of beams run horizontally from one side of the building to the other, designed to hold dozens of whiskey barrels laying on their side for (somewhat) easy rolling. The general effect is that of many parallel rows of barrels forming a layer, and then stacked, layer by the layer from the dirt ground floor all the way up to the roof.

There are no internal walls or niceties of any sort—heating, cooling, or sometimes even electricity. It’s really all about packing as many barrels as possible into a fixed space, allowing just enough space between rows of barrels for someone to squeeze through. Other than the few electric lights, sensors and a small, open elevator for lifting barrels to higher racks, every rickhouse we saw looked like it could have been built 150 years ago with hand tools.  (In fact, Mrs. Wonk spotted a new rickhouse under construction in Kentucky while we were driving—essentially, the internal structural frame is built like a stack of Lincoln logs, and the outer “walls” turn up at the end to shield it from the direct elements.  Mrs. Wonk gets pretty wonky herself when it comes to architecture.)

Because the structures are so large, there can be large temperature variations within a rickhouse. For instance, in the summer, the upper regions will be much warmer than the lower. This in turn affects how the whiskey in a given barrel ages. Some distilleries don’t worry about this too much, and simply blend together enough different barrels to get the desired taste. A few such as Maker’s Mark actually rotate each barrel through different parts of the warehouse to attempt to make the aging of each barrel as consistent as possible.

Something interesting we saw in several rickhouses was a plumb bob – A thin rope hanging from the ceiling down to ground level, with a heavy metal weight at the end. It allows workers to determine if the rickhouse is loaded unevenly or otherwise tilting in an unhealthy manner.

Inside a rickhouse you get the strong smell of the angel’s share – whiskey that’s evaporated through the barrel wood. On average, about 2 percent of a barrel’s content is lost each year to the angel’s share. Outside of many rickhouses you can see visible evidence: The evaporated whiskey encourages growth of a relatively harmless black fungus (or “microflora,” if you don’t want to associate distilling with fungus) called “distiller’s mold” that attaches to the side of buildings, trees, and other non-moving objects. Some distilleries try to mask this by painting their rickhouses black so that the distiller’s mold isn’t as visible. (Mrs. Wonk was a very big fan of Barton’s black rickhouses with dark orange red windows—even she can wonk out over some aspects of distilling…at least those that relate to design.) Others don’t try to hide it – the sight of white sided rickhouses with black swaths up the sides is very common in the region. And just about every tour guide told a similar story of federal agents during Prohibition tracking down illegal moonshine stills by searching for the blackened trees nearby and following the density of black bark until they found the culprits and their hidden equipment.

The rickhouse is typically the spot in the tour where you see a barrel that’s been sawn open to demonstrate that the inside has been charred. You also learn that Bourbon regulations say that only new American Oak barrels must be used and can’t be used a second time. For this reason, used barrels are typically shipped elsewhere, Scotland for instance, for use in aging other spirits that don’t have the same first-use requirements. (Second-hand barrel sales is apparently a huge business, with most barrels selling for near 80 percent of their original cost.)

With these common parts of distillery tours wrapped up, stay tuned for future posts where I highlight the highlights of each distillery we visited.