Essential Highlights of an American Whiskey Distillery Tour

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.

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

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 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.)