Making whisk(e)y requires 5 main process steps: Milling, Mashing, Fermentation, Distillation, and Maturation. Additionally, when making Malt Whisk(e)y, a 6th process step occurs first… Malting

In general, about 30-40% of the flavor comes from the distilled spirit and 60-70% comes from maturation.

When creating the distilled spirit, the types of grains, the yeast strain, and how the spirit was distilled each contribute to the flavor.

During maturation, the type of wood, how the surface of the wood was treated prior to filling, whether or not wine or another spirit was previously matured in the cask, how long the spirit ages in the cask, and where the cask is warehoused all impact the flavor.

Malting … only when making Malt Whisk(e)y

Approximate Time: 48 to 96 hours

Malting creates a dried grain with sugar-rich starches.

The first phase of malting requires steeping the barley in warm water and then resting it several times, to trick the seeds into germinating. This breaks down the cell walls and exposes the starches to the surface of the grain.

At just the right moment, when the cell walls have been broken down, but before the young plant starts to use up the starch, the germination process must be stopped.

This is done by drying the grain, now called ‘green malt,’ in a kiln. If peat is burned during kilning, the smoke will coat the malt and impart a smoky flavor to the finished whisk(e)y.

• 

• 

Milling

Approximate Time: < 2 hours

Regardless of the grain or type of whisk(e)y, all grain must be milled. Milling grinds the grain into grist, which makes the starches accessible, so that they can be converted to sugar, and eventually, alcohol, in subsequent process steps.

Mashing

Approximate Time: 2 to 8 hours

The distiller pours the grist into a large tank, called a mash tun, and then gradually and systematically adds hot water to the grist to extract as much sugar as possible from the grain. The mash bill is the recipe that defines which grains are used and in what proportions. Mashing creates a sugary liquid called wort.

Fermentation

Approximate Time: 48 to 96 hours

Fermentation converts the sugars contained in the wort into alcohol. The distiller pumps the wort into a fermentation tank, or washback, and adds yeast to it. The yeast acts upon the wort, digesting the sugar, and producing alcohol and carbon dioxide. The resulting liquid is called wash (or beer). It is a strong, sour beer, typically ranging from 8% to 10% Alcohol By Volume (ABV).

Distillation

Approximate Time: 2 to 8 hours

Distillation separates the alcohol from the wash to create distilled spirit, called new make at 60% to 70% ABV. Distillation takes advantage of the fact that alcohol boils at a lower temperature than water.

• The wash is heated to a high temperature slightly below the boiling point of water; and alcohol evaporates.
• The alcohol condenses and is captured in another vessel. There are several different methods of distillation, depending upon the type of stills used and the type of whisk(e)y being made.
• Coffey or Column Still: This is the primary distillation method for all single grain whiskeys, bourbon, and rye. It uses a process of continuous distillation, which provides for improved efficiency in comparison to traditional pot stills, but generally produces less flavor. Some bourbons and ryes use pot stills for more flavor.
• In Scotland and Ireland, malt whisky & pot still whiskey must be made in copper pot stills. They are typically operated with 2 or 3 stills connected sequentially, to raise the alcohol to the final 60-70% ABV. Pot stills are run in batches, and usually cleaned between runs.

• 

• 

Maturation

Approximate Time: 2 to 25 (or more) years

Maturation ages the new make in oak casks, turning it into whisk(e)y. This imparts good flavors from the wood and filters out some unwanted ones from the spirit. The distiller typically puts the new make spirit into the barrel at 60 to 65% ABV.

In Scotland and Ireland, maturation must be for a minimum of 3 years.

In the USA, for straight whiskey, it must be matured at least 2 years. However, it can still be called whiskey as long the spirit has come into contact with wood.

As stated earlier, 60-70% of the flavor comes from the casks in which the whisk(e)y is matured. For a good overview of the different types of casks used and their influence on flavor, click here: Casks Used In Maturation

Blending & Bottling

After maturation, the whisk(e)y is ready for bottling. To be called whisk(e)y, it must be bottled at a minimum of 40% ABV. 50% ABV is equivalent to 100 proof. So, 40% ABV corresponds to 80 proof. Whisk(e)y bottled at greater than 50% ABV is known as “over proof.”

Most commercially-available bottled whisk(e)y is blended from multiple casks, along with water, to bring the alcohol content into the range of 40% to 50% ABV. There are, however many over-proof whiskies available, as they are growing in popularity. It’s obviously much less expensive for a distillery to make lower proof whisk(e)y, however, since they can blend more water with the spirit and fill more bottles per cask. Also, many countries tax liquor based upon the ABV … an added incentive to make low ABV liquor.

Cask (Barrel) Strength & The Angel’s Share

A “cask strength” or “barrel strength” whisk(e)y is one which is bottled at the full ABV at the end of maturation.

As whisk(e)y matures, due to the porous nature of the casks and various climatic factors, a certain amount of evaporation occurs. This evaporation is known as The Angel’s Share, because some of the whisk(e)y has disappeared into the heavens. There are a lot of happy angels up there!

Various factors can affect the final ABV of a whisk(e)y as it matures.

In dry climates, where there is wide seasonal temperature variation (i.e. Kentucky), the angel’s share can be anywhere from 2% to 5% per year; and, water tends to evaporate at about the same rate, or slightly faster than alcohol. So, if you started with 500 liters of spirit at 63% ABV, after 10 years of maturation, you might have between 240 and 400 liters of whiskey. And, it would be in the range of 60% to 70% ABV.

In cool, moist climates with less temperature variation (i.e. Scotland & Ireland), the angel’s share is typically around 2% per year; and a high proportion of the angel’s share is comprised of alcohol. So, if you started with 500 liters of spirit at 63% ABV, after 10 years of maturation, you would likely have around 400 liters of whiskey. And, it would be in the range of 55% to 60% ABV.

The angel’s share, coupled with the fact that the barrels are sitting in a warehouse and not being sold, are two reasons why whiskies with older age statements (i.e. 18 yr) cost more than younger age statement (i.e. 10 yr) ones.

Cheers! / Slainte! / Kanpai!

Further Reading

From Diageo: The Making of Whisky