Making Whisky

making whisky poster

The history of whisky-making is engaging, beguiling, and at times, rather troublesome. The essence of whisky-making is distillation. As far back as the 2nd millennium BC, the ancient Babylonians employed the practice to make perfume and aromatics. And we know that by the 13th century Italian monks were distilling alcohol from wine to make brandy.

But it isn’t until 1494 that the first written evidence for the distillation of alcohol from grain appears in the written record.  It seems, King James IV of Scotland placed an order to a Friar John Cor for approximately 500 bottles of “aqua vitae.” By the 16th century, the practice of whiskey-making was intrinsic in Irish and Scottish culture. And distilling whisky played a fundamental role in securing the future of the fledgling American colonies.

It is doubtful that the whisky our ancestors drank would compare favorably to a modern dram. But that has more to do with how whisky maturation has evolved that it does with the fundamentals of whisky-making. Read below to gain modern insights into the ancient practice of whisky-making.

So you want to make some whisky. Making whisky is a six-step process. Depending on the style of whisky you are making, some of the steps differ slightly in the procedure. However, it all starts in the same way; harvesting a quality crop of grain. In some cases, the distiller will malt the grain but in all cases, he or she will mill the harvested cereal.

Malting

Malting begins with steeping the grain in water three times, with air breaks in between. This process initiates germination. After a few days, the maltster transfers the grain to large drums and blows in humified air to control the temperature to prevent the germinated grain from overheating.

Over several days, the grain sprouts, and the cellular structure within the grain begins to break down. Malting produces enzymes critical to converting starch into soluble sugars during the mashing stage.

malted wheat

Malted (germinated) wheat

The malter heats the grain and then quickly dries it to prevent full germination, preserving as much of the sugars as possible. Today, malters heat the grain in closed kilns. In the past, however, they spread the germinated grain on a perforated mesh malting floor (open kiln). Below the floor, they burned peat. As the smoke from the open peat kiln wafts upwards, it imparted a smoky character to the grain. Today, most maltsters use hot air to dry the grain, and if they desire a peaty character, they introduce smoke directly into the kiln.

Typically, distillers, malt only barley. However, but some may elect to malt rye and sometimes wheat to impart unique characteristics to their whisky.

Milling

Milling the grain into a coarse flour or grist is the second step in preparing the grain. The distiller mills all types of grains, not just barley. They then grind the grain into a mix of husks (20%), large particles called grits (70%) and a fine flour (10%). Getting the proper ratio is critical to the mashing process to follow. Too fine a grist will clog the equipment; too coarse will cause the water in the mash tun to drain too quickly and not optimize the harvesting of sugars.

The grist below is now ready for the next step, mashing.

barley wheat and corn grist images

Mashing

Okay, now that we have the prep work out of the way we can get down to business.

The milling process broke down the husks and exposed the starch compounds. The grain is now ready for mashing. During the mashing process, the distiller adds hot water to the grist. He/she does this in three-four steps, called rests.

Malts and corn whiskies are typically made from a single grain; the former being 100% barley, the latter being a minimum of 80% corn. However, for most whiskies, an American Bourbon, for instance, distillers use a combination of grains. A  typical Bourbon consists of; corn (min 51% to 79%); rye (8-35%) or wheat (18-20%) and malted barley (5-12%).

The proportion of each grain influences the character, taste, and aroma of the final whisky. In addition to contributing to the flavor profile, the enzymes within the malted barley also assist in converting starches to sugars.

Once the mix is determined the distiller places it in the mash tun, a large container with rotating arms or rakes that constantly agitate the mix. Traditionally this was done in large wooden tubs, but most distilleries now use a lauter tun, a large stainless steel vat. Enclosed within the tun is a series of rotating rakes, which constantly stir and agitate the mixture optimizing the conversion of the starches into sugars.

Hydrating
traditional mash tun

Rakes agitating mash in the mash tun.

Hot water (around 65°C, 149°F) is added to the grist at a ratio of approximately 1:4 (grist to water), creating a mixture with the consistency of porridge. The hot water gelatinizes the starch molecules enabling natural enzymes (amylase) present in the mix to breakdown starches into soluble sugars, mostly maltose. The rakes stir the mix for about an hour, and then the water is extracted and cooled down to 20°C (68°F). This solution, now called wort, is set aside and readied for fermentation.

The distiller then adds hotter water (around 75°C, 167°F) to the remaining grist, and agitates it further. The hotter water is more effective at extracting harder to remove sugars. Once drained, this mixture is also set aside, ready to be fermented.

The character of the wort influences the flavor of the final spirit. If the wort is cloudy and contains husk or flour particles it will produce a malty, nutty and spicy spirit. A clearer wort produces a spirit with less cereal character.

A third (85°C) and sometimes even a fourth filling, known as sparging, with even hotter water (95°C, 203°F) might occur. The hotter water, the more efficient the extraction process but unfortunately, water at these temperatures also kills the amylase enzymes, and the mashing process concludes. The solution from these last one or two rests is not brought forward to the fermentor but rather is added to the water to use for the first round of mashing the next batch of grist.

The grist, solids, remaining after the third or fourth series, referred to as draff and is high in protein and fiber. This byproduct is often pelletized and made into animal feed.

lauter tun

Modern lauter tun and wort kettle

Fermentation

Up until now, the process has been pretty straight-forward, but it’s during fermentation that things start to get interesting. And if you didn’t pay attention in chemistry class (and I didn’t) it can get a bit confusing. We noted that during the mashing process enzymes break down starches, converting them into sugars. Interesting in itself, but it’s during fermentation that things begin to heat up (pun intended).

During this stage, the distiller takes the sugary wort mix created during the mashing phase and moves it to a large vessel called a washback. She/he then adds yeast to the solution. The yeast makes up around 2-2 ½ % of the wash. It may not sound like much, but these little fellas do incredible work. First, the yeast breakdowns the sugars in the wort mix into alcohol and carbon dioxide; second, it creates conditions favorable for certain bacterias to transform some of that alcohol into flavor compounds such as esters.

closeup of whisky wort

Fermenting wort

The fermentation process occurs in two phases. In the first phase, the yeast takes the sugar molecules present in the wort and converts them into alcohol.  The yeast interacts with the sugar (C6H12O6) and creates two molecules of ethanol (C2H5OH), and two molecules of carbon dioxide plus heat. The chemical equation is as follows:

C6H12O6 ->  2 x C2H5OH + 2 CO2 + heat

In the second phase, the alcohol content builds up and depletes the sugar molecules. The alcohol content and generated heat then suppress the yeast allowing certain bacteria to go to work. Lactic acid bacteria transforms some of the alcohol into new compounds. These are acids, aldehydes, esters, and long-chain alcohols called congeners. These compounds have a pronounced effect on the fruity aromas and flavors detected in the final product.

Duration

The entire process can last from 48-96 hours; however, distillers usually achieve maximum alcohol content within the first 50 hours. After that, it’s more about producing esters and other compounds. Wash produced in 50 hours or less, considered a short fermentation, produces more cereal flavors. While fermentations greater than 60 hours become more complex as the esters and long-chain compounds build up. No matter the length of the fermentation period the maximum amount of alcohol produced is between 5-8% (ABV).

wood and metal washbacks

Metal and Wood Washbacks

This drama is played out in a receptacle called a washback, traditionally made of wood but cast iron and steel washbacks are also common. Wood washbacks have lost favor because they wear out over time and are difficult to maintain, requiring a thorough cleaning after every wash. Although many believe the wood can add additional flavor to the wash, most feel its contribution does not justify the additional costs in maintaining the tubs.

Distillation

By following a relatively straightforward procedure, we’ve taken freshly harvested grain, converted it into a sugary wort, and then converted that into a beer-like mixture (wash) with an alcohol content of 5-8%. Simple enough.

However, it’s at the distillation stage that things begin to get complicated and where experience separates the master from the pupil. It’s not that the distillation process itself is complicated. It’s quite straightforward; alcohol vaporizes at approximately 78°C (173°F) whereas water vaporizes at 100°C (212°F). Therefore, all the distiller has to do is draw off the vaporized alcohol, condense it and voila, she/he has made whisky. Well, technically not whisky but a highly concentrated mixture of alcohol. That’s distillation in a nutshell.

But it’s not that simple because the alcohol solution we’ve created may either delight you or possibly kill you. You see, not all alcohols are created equal, and some are downright lethal. We need to remove toxic alcohol and other less desirable compounds before our concoction is ready for the cask.

How we do this depends on the type of still, we’ll be using, but the concept is pretty much the same. Column stills and hybrid stills use a flow process yielding different concentrations of alcohol at different levels in the column. The higher you go, the purer the alcohol. Whereas, with pot still whisky, distillers make in batches, using two to three separate stills.

I’m going to use the pot still to discuss the distillations process. Most whiskies go through a double distillation, and some distillers run the mixture through a third distillation, the Irish in particular. (Click the button below for more information on the different types of stills and associated distillation processes.)

Whisky Still Types

First Distillation

We begin by adding the wash from fermentation to the “wash still.” The liquid is heated, and when it reaches 78°C (173°F) it begins to boil and become turbulent. At this point alcohols and other compounds called congeners, begin to vaporize and rise from the solution up the neck. Some vapors condense and slid back into the solution where they are boiled again. This is called reflux.

However, the lighter alcohols remain and pass to the lyne arm and then onto the condenser where it liquifies. The process takes four-seven hours, and the end product referred to as “low wines,” has an alcohol content of 20% to 25%.

The spent wash, the liquid remaining in the wash still, has a residual alcohol content of 1% and contains proteins, minerals, and other trace elements. The distiller sells this byproduct as a high-quality animal feed.

double distillation diagramSecond Distillation

The low wines are then fed into a second still, often referred to as a “spirit still” for a second distillation. This process takes approximately eight hours, or about twice as long as the first distillation. The distiller reheats the solution, and once again, alcohols and other compounds begin to vaporize. The first distillate, called “foreshots” or  “heads” contains undesirable elements such as methanol and fusel oils. This product has little value and is either discarded or cycled back to the “low wines” of the next batch.

At this point the distiller begins to collect the “hearts,” the part of the solution that contains high concentrations of ethanol (drinking alcohol), as well as congeners and esters (flavor & aroma profiles) that contribute to the character of a spirit.  This portion of the run, collected in the “spirit safe” is referred to as new make spirit and will be passed along to the cask for aging. The hearts generally have an alcohol content of 60% – 65% alcohol by volume.

However, the process is not yet complete. The distiller continues to draw off additional alcohols and congeners, called “taints” or “tails.” They are lower in ethanol but higher in congeners and esters. They also contain amyl alcohols that contribute to the mouth-feel and finish of a spirit. The taints are collected and added to the low wines to generate more flavor and character in the next batch.

triple distillation diagram

Third Distillation

As it was stated, most whiskies are produced using a double distillation process. However, some distillers run the spirits through a third distillation. The Irish, in particular, use the third distillation for many of their whiskies. However, several Scottish distillers also employ the third distillation as do other distillers around the world.

Distillers opt for the third distillation because it yields a slightly higher alcohol content. But it also captures lighter, fruity flavors and aromas. You will recall that heavier, more water-soluble compounds are left behind in each stage of distillation. During the third distillation, the distiller cuts the run into heads, hearts, and tails. But during this process, the focus is capturing those elusive esters and congeners in the heads and tails. By altering the cut points the distiller can create a broader range of flavors.

The third distillation creates a smoother whisky with strong fruity hints.  It also increases the alcohol concentration to approximately 80% ABV. However, most distillers dilute the whisky before casking.

Aging

We are almost there just another few years, and we’ll be ready to enjoy the fruits of our labors.

What? Can’t wait, you say?

Well, we could drink it now, but it wouldn’t be whisky, it’d be “moonshine,” “white lightning,” hooch,” or if it’s barley-based, “poteen.” But go ahead and have a sip; we can’t blame you. After all, that’s pretty much the way our ancestors drank it, whether they be in the highlands of Scotland or the hollows of Kentucky.

But you might be missing out on the best part of making whisky. You see, we are at the point where the magic is about to begin. It’s here where we take our clear new make spirit and transfer it to rustic oak barrels. Place it in a barn or cellar for 2, 5, 7 or even 25 years or longer and wait, just wait.   Why? Because what eventually comes out of those barrels is not what went into them, it’s a whole lot better!

radial structure of oak

Note the Medullary Rays running perpendicular to the growth rings. This growth pattern contributes to the water tightness of the oak stave. Note also the char layer penetrating into the wood.

So, what happens when you age a new spirit in wooden barrels, oak barrels in particular? Scientists have a pretty good grasp on the maturation process, but they will be the first to admit there is still plenty going on that they don’t quite understand. But most experts agree that maturation is responsible for as much as 60 to 75 percent of the taste of a finished whisky.

Aging whisky in wood casks influences its quality and character in it at least four ways:

  1. Certain compounds in the wood are very effective in extracting unwanted compounds from the new spirit, sulfur compounds in particular. By charring the inside of the barrel we optimize compound extraction.
  2. Charring also “opens up” the wood and facilitates the transfer of desirable compounds deeper within the wood, lignins, and vanillins (for vanilla-like taste), lactones (for a buttery flavor) and tannins or “wood spice.”
  3. Also, employing a barrel previously used to age port, wine or sherry, imparts flavor profiles from these products on the new whisky.
  4. Lastly, pigments within the wood also contribute to the color of whisky. The depth of color is dependent on several factors:
    • The type of wood, for example, charred American oak casks imparts more color than European oak casks.
    • The product previously stored in the cask; sherry casks give a whiskey an auburn-like look, while Scotch whisky matured in Bourbon casks is much lighter in color. Port cask maturation can even lead to a pinkish appearance.
    • The number of times the distiller has previously used the cask. The more often a distiller uses cask, the less impact it has on coloring the whisky.

But the barrel is only a part of the story. Time and location also play an important role in the maturation process.

Generally speaking, aging improves the quality of a whisky. But age doesn’t always mean quality. Remember the adage, garbage in, garbage out. Well, it’s the same with whisky. If the fermentation or distillation process went poorly, aging will not produce a miracle.

Also, not all whiskies age alike. For instance, many feel that Kentucky Bourbons reach perfection between 6-7 years, and a Scotch may optimize at about 25 years. It’s also important to note that whisky can be aged too long, and its quality and character may begin to diminish over time.

Another factor that affects aging is the location; well, more specifically, climate. Part of the reason Kentucky Bourbons require a shorter maturation time is that the climate in that region is hot and humid. Warmer temperatures accelerate the maturation process and affect how the whisky interacts with the wood. While in Scotland, the temperature swings are more dramatic, driving the whisky deeper into the wood facilitating more but slower interactions.

whisky barrels stored on racks

Bourbon Casks Aging Warehouse Basement

Location is not just geographical. The location within the warehouse can have a profound effect on a whisky’s maturation. Casks located on the upper racks on the south side of a warehouse may age faster than casks located on the bottom rack along the north wall. Two to three degrees in average temperature will impact the chemical reactions occurring within the cask and can have a profound effect on the character of a whisky.

Bottling

Alright, simmer down, we’re almost there.  It’s almost time to put it into the bottle. But we may, or may not, have a couple of more things to do, depending on how we want to present our whisky.

The first thing we’ll need to decide is how potent a dram we want to serve up. If you recall, the alcohol by volume (ABV) was around 65% when we finished distilling. Perhaps a little higher if we ran it through a third distillation.  It may be running a wee bit lower now that the Angels have taken their share. We can bottle it at that strength, and we’ll have a “Cask Strength” whisky to offer.

However, that’s pretty powerful stuff, and to be honest, the high alcohol content kinda messes with our ability to detect all those subtle aromas we’ve worked so hard to capture.  So more than likely we’ll want to bring that concentration down a bit by cutting it with purified water. We probably will not use water from our original source.  More than likely we will use treated water, free of all impurities including naturally occurring minerals and trace elements. We are not going to risk contaminating the whisky now, we’ve worked too hard and waited too long!

One thing to keep in mind, we don’t want to drop below 40% ABV, or the long arm of the law will reach out and stop us from labeling our fine whisky, whisky.

Finally, it’s time to bottle our whisky, right? Maybe. But there are just a couple more things we might want to consider. Hey, this ain’t Kool-Aid we’re making, this is a work of art, and we want it to be perfect. Okay, okay want’s next you ask.

sample bottles and a blended whisky

The whisky in the glass is a blend of whiskies from the adjacent bottles.

Blending

Do we want to mix it with some other casks to balance out the aromas and character of the whisky? Or we might even want to add some grain whisky to fine-tune the taste, look, and feel of the whisky. This step may be important if we intend to market our whisky under one brand name. After all, consistency is important so as not to confuse our future customers.

So, if either of these options appeals to us, we’ll send the cask over to the blender, and she/he will take our whisky and mix it with a bunch of other whiskies. If the blender uses only other malts, we’ll up with a “blended malt” or “vatted malt.” If they use grain whisky, we’ll have a “blended whisky.”

But we’re not going to do that; we’re going with what we got. Great, you say; finally, we bottle it right? Not necessarily. We have just one more thing we can consider.  If we brought our whisky down below 46% ABV,  we may want to run our whisky through a chill filtration process? And why do we want to do that you ask?

two glasses of whisky comparing chill-filtration

The dram on the left shows the result of adding water to a non-chill filtered whisky with an ABV below 46%. (photo attributed to http://www.c2-spirits.com)

Chill Filtration

Well, our whisky contains some naturally occurring oils, fatty acids, esters, and proteins. They came in with the grain and the wood contributed some more while in the cask. These contribute to the texture, mouthfeel, and finish of the whisky.  They also help enhance the flavors. Above 46% ABV, the whisky holds the compounds in solution. However, if the ABV is below 46%, adding water (when diluting at the distillery or adding water or ice to your glass) causes the compound to fall out of solution, causing the whisky to appear cloudy. And sediment may even form at the bottom of the bottle.

Tiny little compounds (natural or not) floating in their whisky puts some folks off so we can run our batch through a series of microfilters at 0°C (32°F) to -4°C (24.8°F). This process removes the flock (those tiny compounds) and gives us a nice clear whisky. But keep in mind chill-filtering is mostly for cosmetic purposes. And some folks claim it compromises the quality of the whisky, affecting the color, flavor, and viscosity of the whisky. If we elect to go this way, we might want to add some spirit caramel (E150a) for color.

Okay, now that we are sure we have the whisky where we want it as far as ABV, character, flavor, and clarity we are finally ready to bottle our whisky and reap our reward.

Though fascinating to observe on a large scale, bottling is a pretty straight-forward process. We simply select a nice looking bottle, slap a label on it and pour our whisky in and cork it.

Congratulations! We did it; we made whisky. Not comes the best part, savoring our spirit and pondering the mysteries of life!

Sláinte!