In January 2016, Mrs. Wonk and I crossed the pond to spend eight days the Islay and Speyside regions of Scotland, visiting as many whisky distilleries as possible during an all-too-brief visit. We battled snow, hail, fierce winds, flooded railway tracks, comically narrow roads, and tire-killing curbs. In the end, it was the trip of a lifetime, visiting thirteen distilleries and experiencing profound moments several times per day. Over the next dozen or so posts, I’ll share the stories of each distillery through words and photos.
We also made appearances at Ardbeg and Aberlour, but circumstances prevented a full tour.
Having recently visited nearly every major Bourbon distillery in Kentucky and Tennessee, the images and techniques of the bourbon world were fresh in my mind as we worked through the Scottish whisky homeland. I found myself constantly comparing and contrasting how similar yet so different the distilleries of Kentucky and Scotland are. Sure, anybody can see the difference between Kentucky’s towering column stills and the rows of gleaming copper-bellied pot stills in Scotland. But there many more subtle differences that the untrained eye doesn’t pick up. I’ll highlight some of them along the way.
With your tickets booked and plans made, let’s now take a look at the critical elements of single malt whisky production. By covering the common elements in this post, it frees me up in subsequent write-ups to focus on what’s unique to each distillery. You probably don’t need to read about the difference between a wash and spirit still a dozen times, and I certainly don’t want to repeat myself a dozen times either (and Mrs. Wonk is really, really tired of hearing it).
At any given distillery, you may not see all that follows. It really depends on how the facility operates and how extensive their tour is. But taken collectively, this forms a primer on the whisky making process from start to finish.
Whisky as a Chemical Process
All whisk(e)y starts from grains such as corn, wheat, rye, and barley. These grains all primarily consist of starchy carbohydrates. For now, let’s focus on just barley, as it’s the only grain used in single malt Scotch whisky, and also happens to be the simplest to explain.
The most concise way to describe the path from grain to Scotch, rye, bourbon, or whisky is as follows:
Grain –> (starches + enzymes) –> simple sugars –> beer (wash) –> raw spirit –> barrels –> whisk(e)y.
Germination of the barley kernels creates a slug of enzymes alongside the starch in the barley kernel.
The mashing process (described later) uses these enzymes to convert the starch into simple sugars.
The subsequent fermentation process turns the simple sugars into an alcoholic “beer.”
The distillation processes concentrates the desired alcohol (ethanol) and desired congeners, while removing water, undesired alcohols (e.g. methanol), and evil-tasting congeners.
While the above explains the process conceptually, let’s see how it’s manifested at a single malt Scotch whisky distillery.
Water is the life blood of whisky production. Not only is it an essential part of the mash (along with malted barley, described next), it also cools the vapor coming off the stills and cleans equipment between runs. Distilleries use an insane amount of water, and since they’re frequently located in remote areas, the water can’t be easily supplied in sufficient quantify by municipal supplies. That’s why you’ll find distilleries located alongside streams or rivers.
The word “glen” is Gaelic for valley, and streams naturally flow through the many valleys of Scotland—thus the many distilleries with “glen” in their name. (Mrs. Wonk: All the glens. So many glens.) If you’re lucky, you’ll get to see the distillery’s water source during your visit, like we did at Lagavulin and Bowmore in Islay, and the Glenrothes in Speyside.
Unlike bourbon which uses a recipe (mash bill) of several different grain types (typically, some combination of corn, rye, barley, and wheat), single malt Scotch whisky must be made from 100 percent malted barley.
Creating malted barley is essentially tricking the dry, dormant barley kernels into thinking they’re working hard to grow a plant, then suddenly stopping that initial growth. The process begins by soaking thousands of pounds of dry barley kernels with water, then slowly churning the wet kernels periodically. During this time, the inside of the kernel madly creates enzymes, which are critical for converting starches to sugar. After a few days, the first small plant shoots start sprouting from the kernels, and the kernel is at its optimal point in terms of enzyme content. The next step is to bring this plant production to a screeching halt, as the distiller has other plans for this kernel. In the next section, I’ll cover exactly how it’s stopped.
This malting process is a crucial step. If you were to use unmalted barley, the essential sugars wouldn’t be created from the starches in the grain. Incidentally, malted barley enzymes are also critical in bourbon making, although in bourbon, the malted barley component is typically around 10 percent of the overall mash bill.
In the distant past, just about all distilleries malted their own barley in giant barns, where the barley was spread out in a thick layer covering a vast area of concrete floor. Periodically, workers (or later machinery) churn the malt with shovels to keep the resulting heat from germination from building up. As we saw and practiced firsthand, it’s a slow, labor intensive process that requires constant monitoring and is deeply affected by factors like the outside temperature and humidity.
Only a few distilleries still make their own malt these days. Instead, the vast majority is made at gigantic malting plants using drums, rather than traditional malting floors. Distilleries simply order malt created to their specifications and have it delivered via grain trucks that fill the roads everywhere in Scotland.
The distilleries who still malt their own barley are able to make only a fraction of what the distillery requires, so they use a mixture of their own maltings as well as malt from a central malting plant. If you have the chance, absolutely prioritize visiting a distillery that does their own malting. It’s a step back in time and a real treat to see how it’s done. Bonus points if you can get a charming master distiller to give you a private lesson in malt shoveling.
After the barley grains have had their long bath and are just starting to sprout, it’s time to stop everything, leaving a kernel full of starch and enzymes ready to be mashed and fermented.
How do you stop a sprouting kernel? Warm, dry air. Without water, the plant growth stops in its tracks. These days, you could simply fire up the equivalent of an enormous hair dryer and get to work. However, imagine how distilleries would have done it back in the early 1800s, before electricity was available. The obvious way to create heat is to burn something — wood or oil, perhaps. However, on the windswept, relatively un-forested island of Islay, the most readably available burnable substance is peat–layer upon layer of decayed plant matter, cut in chunks from the local bogs.
Peat burning at Laphroaig
Regardless of the heat source, the drying process looks like this: At ground level is a furnace where peat or some other fuel source burns. The hot air, heated by the combustion, flows upward through a chimney that widens dramatically the higher it rises. The top of this (now very wide) chimney is capped by a room with a very finely grated floor. The wet barley is spread out evenly on this floor. As the warm air rises though the grated floor, it dries the malted barley, which is churned occasionally to achieve even drying.
The top of this room is the ceiling of the building. The hot, smoky air exists though small vents in the top. This whole setup (furnace, chimney, and drying room) is commonly known as a kiln.
From the outside the building, the kiln roof resembles a Japanese pagoda. The vents are near the very top, just underneath the flared top cap. You’ll frequently see pagoda roofs remaining at distilleries even if they long ago stopped malting.
Islay is known for their heavily smokey whiskys. The smokey flavor comes from their local use of peat as a heat source. The distinctive peat smoke infuses the malted barley with a ton of phenols. Despite being highly reduced by the subsequent fermentation and stilling phases, enough of these phenols remain in the final product to give peated whisky a uniquely smokey characteristic.
At the risk of the stating the obvious, if the distillery doesn’t malt their barley, they don’t have malting floors or peat kilns.
Distilleries go through prodigious amount of malted barley, and to ensure a ready, uninterrupted supply, they keep a large amount on hand in giant malt bins, each which can easily hold a school bus. Malt is removed as needed via a gravity-fed chute, which empties into a long rectangular box below. An augur screw drive moves the malt along to the milling area.
The milling process cracks open the hard barley kernel, exposing its inner contents, including the all-important starch and enzymes. Large milling machines process a never-ending stream of malted barley kernels through a series of narrowly spaced rollers to crack open the kernels.
After running through the mill, the grain is some mixture of the following:
Contrary to what you might think, you wouldn’t want all grits or all flour in the mash. Each of the three components plays a role in the mashing, and distilleries have a very clear target of what the ratios should be for their particular mash. Typically, the ratios are something like this:
- 70 percent grits
- 20 percent husks
- 10 percent flour
How can you measure what ration of grain, husks, and flour is coming out of the mill? The answer is ingeniously simple: A series of sieves with different screen sizes are stacked– the coarsest screen on top and the finest screen on the bottom. A sample of the mill output goes into the top of the stack, which is then shaken thoroughly to sift the components. Whatever ends up in each sieve is weighed, and ratios are calculated and confirmed.
With the malted barley milled to the correct rations of grit, husks, and flour, the mix is added to giant, multi-thousand gallon metal vats along with hot water at a precisely controlled temperature. These vats, known as mash tuns, have large agitator arms or rakes that continuously stir the thick porridge of barley and hot water.
During their luxury stay in the world’s largest hot tubs, the enzymes busily convert the starches into simple sugars. After an hour or so, the liquid drains out through small slots at the bottom of the mash tun and into a holding tank. The slots are small enough that very little barley escapes. Next, a hotter batch of water fills the tun, and the process plays out again. Some distilleries repeat the process a third time with yet even hotter water.
The resulting liquid from these two or three dunks in hot water is a sugary mixture known as wort. The next stop for the wort is fermentation, but not until it’s cooled to the point where yeast can thrive, rather than die off from the heat.
As for the milled barley, now depleted of nearly all its sugar and starch, it’s typically provided to local farmers for use as cattle feedstock or other uses. Lucky, lucky cows.
Fermentation Vats (Washbacks)
After cooling, the sugary wort goes into yet another kind of tank. Known as washbacks, these tanks hold many thousands of gallons and are several floors tall. Some tanks are metal, others wood. If made of wood, Oregon pine is frequently the variety used—a little bit of the Pacific Northwest in Scotland.
Fermentation starts by adding a yeast strain (proprietary to that distillery) to the wort. Soon the washback’s contents are foaming and frothing way, with large bubbles forming on the surface. In full swing you can feel the heat coming off the fermenting wort, and although you can’t see it or smell it, a large amount of carbon dioxide as well. At a chemical level, the yeast is converting the sugars into various types of alcohol (mostly ethanol, hopefully), as well other chemical compounds knowns as congeners. I’ve written about congeners in detail in the past, but here’s it’s sufficient to know that there are hundreds of different congeners, and each provides a different aroma and taste–some good, some bad. During the distillation phase (described next) the bad-tasting congeners are minimized and the good-tasting congeners concentrated.
The typical fermentation of Scotch whisky is between two to four days. While this may seem like a long stretch, it’s relatively short compared to molasses fermentation times for Caribbean rums, which can last up to four weeks in some cases.
The end result of fermentation is “distiller’s beer” or “wash,” at around 8 percent ABV. Some tours will pull out a small sample of the beer from a washback and let you taste it. Although I wouldn’t drink it every day, I found it reasonable enough. Mrs. Wonk, not so much.
If there’s one iconic image from Scotch whisky making, it’s a row of gleaming copper pot stills with their tall necks and round bellies. My heart always beats a little faster when I’m in their presence. It’s in these kettles that the low-proof distiller’s beer turns into new make spirit, ready to go into barrels for their long slumber.
Without going into a full discussion of how distillation works (I’ve covered it in detail previously), the general idea is that the liquid in the still is heated. Because the various wash components boil at different temperatures, things that boil at lower temperatures are the first to rise up through the neck, where they can be cooled back into liquid form via a water jacket and subsequently collected.
In most cases, single malt whisky is distilled twice; in some cases, distilleries such as Auchentoshan distill three times. The first distillation occurs in what’s called the wash still. In goes wash at around eight percent ABV, out comes “low wines” at around 23 percent ABV, which is stored in a low wines receiver, i.e., a tank.
The wash still is a brute force separation of ethanol from the undesired water, which boils at a much higher temperature. Essentially, everything that boils at 173F or lower (the boiling temperature of ethanol) goes into the low wines. Everything that boils above 173F, including the large amount of water, doesn’t make it into the low wines. The wash distillation takes several hours.
The second still in the process is called the spirit safe. It’s filled with low wines, which are heated; the compounds with lower boiling points rise through the still neck first, followed by compounds with successively higher boiling points. The first things that come off are colloquially known as the heads, and don’t go into the final whisky. The last things that boil off are known as the tails; these also don’t go into the final whisky. It’s the portion during the middle of the process–known as the hearts–which is isolated as new make spirit. The typical ABV for distillation coming off the spirits still is around 68 percent ABV.
It’s natural to wonder how the heads, hearts, and tails don’t all end up in the same tank. The answer is a brass box with large windows, known as a spirit safe. As the cooled, condensed liquid flows toward the appropriate tank, it passes a point where a lever positions a short diverter pipe directing the flow to the desired tank. When collecting heads, the lever is set one way and directs the spirit to one tank. When collecting hearts, the lever changes positions and the spirit flows to a different tank.
You can actually see the liquid flowing through the short diverter section on its way to the correct receiving tank. Also in the spirit safe are hydrometers, which resemble a large thermometer floating partway out of an oversized glass column filled with spirit. The hydrometers indicate the ABV of the spirt flowing through the spirit safe at the moment, helping the distiller know when to transition from heads to hearts to tails.
For historical reasons, the spirits safe is locked and can’t be easily opened by just anybody, hence the “safe” portion of the name. Traditionally a government tax agent held one of the required keys for the lock. This (in theory at least) prevented distillery workers from redirecting new make spirits to their own illicit containers, thus avoiding paying the tax man his due.
The heat source for boiling the stills comes in two forms. The modern way is a coil through which steam passes, transferring its heat to the liquid in the still. Oddly, you rarely see images of these heating units inside the stills. I was quite lucky during our Bowmore tour to get a great shot, with flash, of the interior of a still. It’s far more elaborate than a simple coil and looks more like a Saturn rocket motor than a heat exchanger.
The old fashioned way of heating the pot still is via direct fire–quite literally, flames underneath the still to heat it. Direct firing is relatively rare these days — we saw it only at Glenfiddich. An interesting issue with direct firing is that the high heat at the very bottom can burn the organic compounds in the wash. To prevent this, direct-fired stills have a contraption known a rummager, essentially a set of copper chains dragged around in a circle against the bottom of the still to prevent scorching.
When you first experience pot stills in Scotland, they may all look very similar to each other. (Mrs. Wonk still thinks they all look pretty much the same.) But if you look closely, you’ll notice important differences. Some are almost spherical with tall, skinny necks. Others are more pot-bellied. The stills at Lagavulin are renowned for their pear-like shape. Some have a balls in the neck, others don’t. You’ll also find radically different angles of the lyne arm, the short section at the top of the neck that angles sharply to the side. All of these differences impact the component ratios of the final spirit, thus giving it a specific flavor profile. Simply put, the shape of a distillery’s pot stills isn’t just aesthetics. It plays an important role in shaping the distillery’s signature flavor profile.
An easy way to tell a wash still from a spirit still is to look for the small glass windows on the still’s neck. Wash stills have these windows; spirits stills don’t. The distiller can peer through the windows to see how the boil is going. Wash stills and spirits stills are frequently paired together and reside next to each other.
The use of paired pot stills (wash and spirit) are a key difference between bourbon and single malt production. In America, nearly every major distillery proudly displays its column stills made by Vendome in Louisville, Kentucky. The Scottish equivalent is pot stills made by Forsyths, in the Speyside region. There is at least one instance of crossover though: At the Woodford Reserve distillery, you’ll find three pot stills made by Forsyths, used for a small part of Woodford’s bourbon production.
Once distilled, the raw distillate goes into barrels for aging. Per Scotch whisky regulations, the aging must be in oak barrels for at least three years. However, unlike bourbon which must be aged in newly charred, first use oak barrels, Scotch whisky allows far more latitude with the barrel’s background. Much single malt whisky is aged ex-bourbon barrels shipped over from the U.S. Another major source of barrels is used sherry casks from Spain. Many single malts like Glefarclas, Glendronach, and The Macallan have a distinctive sherry note to them; that sherry influence isn’t accidental. Scotland was using sherry barrels long before a ready supply of ex-bourbon barrels from America became available.
Barrel aging naturally occurs in unheated warehouses, where countless barrels are stacked in rows and tended for years at a time. If you’re fortunate enough during your visit, the guide may pop the cork of a barrel or two, and draw out a sample for tasting. To do this, they use a metal pipette roughly three feet in length, called a valinch, to poke down into the barrel and draw up several ounces of whisky. My best valinch by far was at Lagavulin on my fiftieth birthday, where I used one to pull a few precious drams of 50 year whisky from a barrel with “1966” painted on its end.
If you drive through Kentucky bourbon country, you’ll see giant, five-story, metal-sided rickhouses dotting the fields and hillsides, but particularly concentrated near the distillery that owns them. Thus, in most cases, the majority of a bourbon distillery’s warehouses are in a somewhat constrained area. In contrast, some Scotch whisky distilleries, particularly on Islay, send a fair amount of their whisky to aging warehouses far away on the mainland.
Another noticeable different between Kentucky bourbon and Scotch whisky aging is the style of warehouse. Scotland uses two types primarily–rack and dunnage. A racked warehouse is similar in concept to a Kentucky rickhouse: Large racks, several stories high, holding barrels laying on their side in rows. A dunnage warehouse is much smaller in scale, typically one story high, with stone or brick walls and an earthen floor. Barrels are stacked no more than three high, end to end. These conditions provide for higher humidity and more even air circulations, at the expense of far fewer barrels stored. Dunnage warehouses, like we saw at Bowmore, Laphroaig, and Glenfarclas, are considered to create better whisky, while costing more to operate.
There are more than 100 single malt whisky distilleries in Scotland. As certifiably wonky about such things, I found each of the eleven we visited to be vastly different from the others, and given a chance I’d go visit the remaining 90 or so. Mrs. Wonk has a different take: By the fourth tour that started with an introduction of barley malting, she was about ready to take over and give the tour herself. Yes, they all have quite a lot in common, but the more you know, the more you appreciate the unique feel and history of each distillery.
With this brief introduction to most of the equipment, processes, and lingo of single malt Scotch whisky completed, future posts will feature one distillery at a time. Using the basics laid out here, I will focus on the unique details and key sights without re-explaining the basics each time. First stop: Islay – isle of smoky peat bomb whiskys–and a few that aren’t. Stay tuned!