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The Basics Series: The Alchemy of Whisky-Making

How Do We Distil the Elixir of Life? 


This post isn’t about the Philosopher’s Stone. My apologies for the misleading headline.

(Image Source: Harry Potter and the Sorcerer's Stone (Warner Bros. Pictures,  2001))


The Celtic peoples who lived in the Scottish Highlands and Ireland had a term for the highly concentrated alcoholic spirit distilled from fermented barley- “uisge beatha”- meaning elixir of life. This term evolved over the ages and became Anglicised to “whisky” that we are familiar with today.

In a way, this is a tutorial about how to make the Celtic elixir of life. It remains unclear why the Celts called whisky the elixir of life, considering that overconsumption would have taken them to meet their maker.  

The alchemy of making of whisky involves 5 essential steps and 5 essential ingredients. The steps involved are malting, mashing, fermentation, distillation and maturation. The ingredients involved are water, grain (whether barley, wheat, corn or rye), kilning fuel (whether peat or charcoal), cultured yeast and oak barrels (with various oak species and seasoning). 

These 5 steps and 5 ingredients are important “levers” that affect the resulting whisky. Adjust any of these 10 factors and one would significantly affect the whisky’s taste.


Step 1: Malting

The malting process involves 2 ingredients: (1) grain and (2) peat or coal.

All whisky starts as raw grain – whether it is barley, wheat, corn or rye. In the case of “single malt whisky”, barley is the main ingredient. During the malting process, raw barley is steeped in water, then spread out on a large floor at a temperature-controlled room to allow the grain to undergo germination. This is intended to convert starch in the grain into sugars.

A traditional barley malting room at Springbank Distillery (Image source: Malt and Oak blog)


The germination process would take up to a week. During this process, the distillery staff may take shifts every few hours to laboriously aerate and turn the barley using a shovel to promote even germination and prevent mould. 

Once the barley has partially sprouted, all the barley is place in a large kiln for heating and drying. The damp malted barley is placed on a wire mesh resting floor above an oven. The oven is then fired up to toast the sprouted barley above. The temperature does not go beyond 70°C to ensure that natural enzymes within the barley are not destroyed.


Malted barley being smoked and dried at 45° to 65° (Image Source: Ewan Graham)


A whisky maker has a choice of 2 types of fuels to use for kilning – this has a huge impact on the taste of the whisky and determine whether it would have a “Highland” style or an “Islay” style.

If coal is burnt, any flavours imparted would be relatively neutral. The barley would not retain any smoky character. Using such barley, the resulting whisky is non-peated and generally sweeter. 

On the other hand, if peat is burnt in the kiln, aromatic smoke permeates the malt and is absorbed as a smoky flavour in the barley. It is with such barley that smoky, peated whiskies are created. Sometimes, peat also imparts a slight medicinal taste.

Men harvesting peat in Islay (Image Source: Whisky Advocate)


As a brief aside, the first whiskies in Scotland and Ireland were historically all peated. Parts of the industry (and the New World) then began to shift away from peat towards a more neutral tasting coal. The harvesting of peat also has implications for conservation and climate change.


Step 2: Mashing

Next is the mashing process which two ingredients: the (1) malted barley and (2) hot water. 

The dried malt is placed in a mill and ground up into the consistency of coarse flour. This coarse flour is then mixed with hot water in a large tank (called a mash tun). Hot water is added in three batches, starting at around 67°C with later batches rising to almost boiling point. The mixture now resembles porridge, and is known as “mash”. This process essentially agitates the enzymes from the barley, and further catalyses the conversion of starch into more sugar.

A look inside a mash tun (Image Source: Whisky Magazine)


The mash is then strained, extracting a sweet, sugary and malty liquid known as “wort”. 

One should add that the source of the water adds an important dimension to the taste of the whisky. Every distillery appears to swear by the quality of their water source and extol the virtues of the water’s unique influence on their whisky’s character. Distilleries steeped in tradition would obtain water from the nearby spring or loch (what they call a lake in Scotland), and the different mineral composition within the water can be felt by discerning whisky tasters. For instance, Glenmorangie sources water from the nearby Tarlogie Springs, which is rich in magnesium and calcium. This hard water imparts a very subtle crisp and sweet taste.


Step 3: Fermentation

Next up is fermentation process. Three main ingredients are involved: (1) the wort, (2) cultured yeast and (3) while not technically a raw ingredient- the fermentation time.

Fermentation in a washback (Image Source: Undiscovered Scotland)


The wort is poured into a large wooden vat (or washback) where it meets cultured yeast (that is, specifically cultivated strains of yeast). Fermentation then occurs. This is a complex chemical reaction where a huge range of flavour compounds are created, resulting in fruity-smelling esters (ethyl-2-methyl butyrate), buttery-tasting flavour compounds (diacetyl) and biscuity flavour compounds (maltol). However, the most important reaction is this:

C6H12O6 (sucrose) → 2 C2H5OH (ethanol) + 2 CO2 (carbon dioxide)


The chemical structures of flavour compounds bind with the taste receptors in our mouths thereby creating the distinctive flavours we are familiar with. (Image Source: Department of Chemistry and Chemical Biology at Harvard University)


The resulting substance is a malty-tasting beer-like liquid which clocks in at about 7%-10% ABV. This is known as “distiller’s beer”

This process of fermentation can take anywhere from 48 to 100 hours. And here is why we considered time an ingredient. Fermentation for a shorter period of time (ie below 50 hours) tends to create more alcohol and cereal taste. Fermentation for a longer period (i.e. over 60 hours) tends to result in less alcohol, but more complex and a sweeter tasting spirit. A longer fermentation period of up to 100 hours is also credited for creating more fruitiness, and is adopted at Springbank Distillery and Chichibu Distillery.


Step 4: Distillation

Next, we have the distillation process, where the only ingredient involved is the distiller’s beer.

The process of distillation extracts alcohol and lighter compounds, creating a resulting liquid with a high alcoholic content. As the stills used for distillation are copper, the copper also helps to strip out undesirable flavours.


Pot stills at the Springbank Distillery (Image Source: Springbank Distillery)


Traditionally, a series of pot stills are used. Pot stills are less efficient than column stills at extracting alcohol. However, pot stills are favoured by orthodox sects. Ironically, their inefficiency in extracting alcohol is desired exactly because it allows more flavourful compounds (from the malt) to be retained in the resulting spirit. Nothing in the world would make a long-established distillery change the size or shape of their precious stills. This is because much of a whisky’s subtle character are forged by the still itself.

The distiller’s beer is poured into the first still, where it’s fired up. The most volatile substances, like alcohol, evaporates off the beer and into the still neck, eventually reaching a condenser at the top, which rapidly cools down the vapours to turn them to liquid once again. The resulting liquid, which is about 20% ABV, goes into the second still for a repeated process.

At this point, the distiller has two choices. He could end at the second distillation, and what we have would be “double-distilled whisky”. Alternatively, he could go through another round of distillation to create “triple-distilled whisky”. What’s the difference? More on that later.


Distilled spirit emerges from these valves to be analysed by the stillman (Image Source: Glenfiddich Distillery)


The resulting final spirit flowing out from the still is around 60%-70% ABV. Not all of this is drinkable! The resulting spirit is further separated by a valve into three “cuts”: (1) the head cut / foreshots, (2) the middle cut / heart, and (3) the tail cut / feints. As the spirit pours out of the tap, the stillman excludes the initial head cut (or foreshots), which are deemed too flavourless and removed from the drinkable spirit. The subsequent middle cut (or the heart) is then collected and used to make whisky. The tail cut, along with the head cut, are then recycled for re-distillation. 

Whether a whisky is double-distilled or triple-distilled affects its body. Lighter and smoother-tasting whiskies could have been triple-distilled. This is because the additional round of distillation sieves out heavier compounds. Triple-distillation is often used by Irish distillers to create their very light, sweet and almost-effortless-to-drink Irish whiskey the likes of Jameson.    

The “cutting” of the spirit also affects the body. An earlier cut is clean, estery, lighter-bodied and sweeter. As one goes down to the later cuts of the spirit, more heavy compounds are introduced. Based on this logic, Glenfiddich Distillery creates its famous sweet and light-tasting spirit by only using the lightest part of the distillate to make whisky. The stillman must execute a very early and small middle cut, essentially saving only the lightest compounds and sweet esters to be matured into whisky.


Step 5: Maturation

The final step is maturation, which involves 2 ingredients: (1) the new make spirit, (2) the cask used and (3) time.

Technically, it is inaccurate to refer to the new make spirit from distillation as whisky. Unless it has been matured for at least 3 year, new make spirit cannot be sold as “whisky” under Scottish and Irish law. Until then, the substance is informally known as white dog or moonshine. 

Maturation conventionally takes place when spirit is stored in oak barrels for years. The spirit interacts with the microscopic pores of the oak; the oak imparting wood sugars, vanillin and oak lactones (vanilla and coconut-like aromas), and at the same time, the oak also draws out undesirable or harsh-tasting compounds in the spirit, such as sulphur. 

The spirit slowly becomes smoother, obtains more balanced flavours and draw its amber colour from the oak. By the end of 3 years, the spirit is finally true whisky.


“Quiet Please!” Whisky sleeping in barrels at the Macallan Distillery (Image Source: Macallan Distillery)


Why is an older whisky so much more expensive than a younger whisky? It is because a good proportion of liquid in the barrels is quietly stolen by angels during this period. Through the maturation period, whisky evaporates through the porous barrels at a rate of 2% a year. This is proportion of lost whisky is known as the “Angels’ Share”. This phenomenon cannot be avoided, but it also helps to smoothen the liquid reducing the ABV of an almost undrinkable, high-proof spirit into a soft and smooth whisky.

After the angels have claimed their share, the remaining whisky is much smoother and complex in flavour, but unfortunately scarcer.


Image Source: Jooce Garrett


Bottling the whisky


Once the whisky is sufficiently mature, it would be bottled at a minimum of 40% ABV. This usually involves slightly diluting whisky from the barrel (usually at 60-65% ABV) to suit the palates of drinkers who dislike the harshness that usually comes with high alcohol content.

Some caramel colour (industrially known as E150a) may be added by the distillery to make the whisky look more appetising, or appear like it has undergone a longer maturation period. The whisky may also be chill-filtered to remove natural sediments and to prevent it from becoming cloudy.

And there we go – a quick and essential primer on how whisky is created! Just as we ought to learn how food gets from the farm to our dining tables, whisky enthusiasts should know how whisky is made. A little knowledge on how each step and each ingredient could affect flavour goes a long way in helping us appreciate subtle nuances in the complex flavours of each whisky.