“Whiskey is what beer wants to be when it grows up.” – Anonymous

You may have heard this classic phrase before, but did you know that there’s some scientific truth behind it? How whiskey is made is a fascinating process. Here’s why.

According to Mike Pomranz of Eater Magazine, “all whiskey begins life as beer.” Pomranz explains that both whiskey and beer start by fermenting grains to release sugars that are later turned into alcohol by yeast. “The primary difference with whiskey is that this fermented product is never intended to be drunk,” he says. Through a complex process of distilling and aging, whiskey evolves into the far more sophisticated and mouth-watering spirit we know and love.  

As a whiskey enthusiast, you probably have some working knowledge of how it’s made, but a quick refresher on the nuts and bolts of this proud tradition never hurts. And the more you understand the craft, the more you can identify the distilleries that make the perfect whiskey for your unique palette. So let’s review.

Whiskey Ingredients

Grain Mash. This is typically a mixture of grains such as malted barley, rye, wheat, or corn, depending on what type of whiskey is being made.

Water. For many distilleries, a unique water source is a point of pride. Whether it be a Scottish loch or an alpine river, a distillery’s water source is often as big a part of the brand identity. Jack Daniels Whiskey, for example, attributes some of its classic flavor to the “crisp, cool, 56-degree water” of Tennessee’s Cave Spring Hollow. According to the company, the limestone in this cave removes iron and other impurities from the water, which is used to make every bottle of Jack Daniels produced worldwide.

Dr. Craig Wilson, master blender at Diageo, conducted research showing that a whiskey’s water source can have an important impact on flavor. For example, soft water can produce heavier whiskey, while hard water may produce lighter, sweeter spirits. Along the same line, he found that water with higher levels of organic matter can produce fruitier flavors in a finished whiskey.

Yeast. Last but certainly not least, yeast turns fermented grains into alcohol.

How Whiskey is Made: Step-by-Step

1. Malting. The grain is soaked in water until it reaches a saturation point, then spread out and sprinkled with water for roughly three weeks until it begins to sprout. Germination produces an enzyme called amylase, which is responsible for converting the grain’s starches into sugars. The grain is then dried in a kiln, halting the germination process.
2. Mashing. Grains are ground up and put into a large tank called a mash tun (or mash tub) with warm water. The amylase converts starch into sugars, and after several hours of mashing, a thick, sugar-rich liquid known as mash is produced. Even if malt whiskey is not the distiller’s final goal, some ground malted grain will be added to this mix to help convert the starches to sugars.
3. Fermentation. Once cool, the mash is transferred into large fermentation tanks. These can be closed (Scotland) or open (United States). Yeast is added at this stage, and goes to work quickly turning those converted sugars into alcohol. Fermentation usually takes about 48 hours, but some distillers experiment with longer fermentation periods or different strains of yeast to achieve a specific flavor profile. The remaining liquid contains between 5-10 percent ABV. From this point, the liquid (also called “distiller’s beer”) could be brewed and turned into beer, or put into a still and distilled into whiskey. We all know what the right choice is here.
4. Distillation. In the still, the liquid is purified through heating and vaporization, removing impurities that can affect flavor. To begin, the distiller’s beer enters the still from the top as steam enters from the bottom. The beer slowly drips through the plates, and alcohol is condensed into a liquid. This initial distilling produces “low wine,” which is unusable. After a second distillation (or more, depending on the type), “high wine” is produced. At this stage, the liquid has increased to approximately 70 percent alcohol. The temperature at which the liquid is distilled determines the proportions of water, alcohol and congeners. Before whiskey is finalized, distillers will remove the unpleasant-tasting congeners by boiling them off or pouring them off the surface.

Both of the main types of stills (pot stills and column stills) are made of copper, known for its purification capabilities. Pot stills, often used in Scotland, need to be cleaned after every batch. Column stills are able to produce much larger quantities of whiskey because of their continuous distillation process.

5. Aging. Barrel aging is what gives whiskey its distinctive flavor. Barrels are made from oak that has been dried, or “seasoned.” The process can be done quickly in a kiln, but most whiskey producers opt to let the wood dry outside. There, it is exposed to the elements for six to 24 months. The process of natural decomposition begins, and fungi helps soften tannins and break down the wood in preparation for barrel aging. Once seasoned, the wood is shaped into barrels and the interiors charred with open flames of up to 600°F. Distilleries make individual decisions about how long to char the barrels (anywhere from a few seconds to a few minutes). The higher the char level, the more the spirit will seep into the pores of the oak once in the barrel.

Once the barrels are ready, they are filled with the distilled spirit and stored in warehouses (or “rackhouses” as they’re often called in the U.S.) for at least two years. The temperature and humidity levels of the barrel storage location affect the final characteristics of the whiskey. Barrels can be reused (typically no more than three or four times), and distillers take into account the previous contents when strategizing the new spirit’s desired flavor profile.

6. Bottling. After barrel aging is complete, whiskey is bottled (always in glass). Adding water ensures that distillers achieve the desired ABV, which must meet or exceed 40 percent. For large operations, a bottling run will be made up of many barrels, but when one barrel is bottled, we get that elusive single barrel release.

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