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Distillation here at Lochranza is very slow—it runs at a rate of around six to seven litres per minute. And it’s not because of the laid-back nature of the island. Every detail of our distillation process, from the speed of our runs, to the shape of our stills, has been designed to enhance those rich, fruity flavours that develop during fermentation. 

But what exactly is distillation? And how does it impact the final flavours we taste in whisky? 

What is distillation?

If fermentation is where alcohol is created, think of distillation as the process of concentrating that alcohol. It’s how we turn the wash (a low-alcoholic beer that’s produced during fermentation) into a new make spirit (the liquid that will mature in casks for a minimum of three years to become whisky). 

How does distillation work?

Distillation works by separating alcohol vapours from the liquid. Once separated, these vapours concentrate into a much stronger spirit. 

It all happens in the stills. Typically made of copper, stills are essentially giant kettles. Now, if you remember back to your chemistry lessons in school, water and alcohol have different boiling points. When we heat up the liquid, the alcohol evaporates and rises up the neck, leaving water and other elements behind. 

Most single malts in Scotland are double distilled—first in the wash still, and then in the spirit still. The wash still increases the ABV (alcohol by volume) to around 20%–30% and produces a liquid called the “low wines”. By law, whisky has to be at least 40%, and so, the production team runs the low wines through the spirit still before they collect the new make spirit at around 60%–75% ABV. 

Through the condensers at the top of each still, the alcohol vapours concentrate and cool down, transforming into a clear liquid. This clear liquid then pours through the spirit safe, where the production team needs to separate it into three parts: the heads (foreshots), the heart (middle run) and the tails (feints). 

• The heads contain methane alcohol and some ester compounds
• The heart contains ethanol alcohol (the kind we want) and those clear, flavourful compounds. This is the majority of what makes up the “new make spirit” that will become whisky. 
• The tails are mostly water, but also contain some heavier, earthier phenols. 

What impact does distillation have on flavour? 

Distillation is an intricate process with many elements that influence that final flavour of the whisky. It’s both a science and an artform. 

How copper impacts the flavour of whisky

Not all stills are made from copper. Throughout history, people have distilled spirits using  stainless steel, glass and even clay. However, copper has been the whisky-makers still of choice for centuries. 

Copper reacts with alcohol to filter stronger compounds like sulphur (which give you that smoky flavour) and create softer compounds like ester (which are responsible for a light, fruity flavour). 

How distillation rate impacts the flavour of whisky

Distillation rate refers to how quickly (or slowly) it takes for the alcohol vapours to separate from the liquid. 

You get a faster distillation rate by boiling liquid in the still with a hard, aggressive heat. And you get a slower distillation rate by boiling the liquid with a gentler heat.

With a fast distillation rate, the alcohol doesn’t spend much time in contact with the copper. And so, you get more of those smoky, sulphur-y flavours. In contrast, you get a lighter, fruitier spirit with a slow distillation rate. 

How the shape of the still impacts the flavour of whisky

The shape of the still has a great impact on how much contact the alcohol vapours have with the copper. And it’s all to do with something called “reflux”.

“Reflux” is when the alcohol vapours don’t leave the still as a gas straight away. Instead of quickly escaping to the condenser, they get caught in a cooler part of the still, change to a liquid, and drop back down to be boiled again. 

Distilleries design their stills to either encourage or discourage reflux. For example: a large bulbous still with a wide neck and a downward-facing lyne arm is designed to discourage reflux. Once the alcohol turns to vapour, it’s quickly guided out of the still and into the condenser. But a lantern-shaped still encourages reflux. The alcohol gets caught in the cooler part of the still, and turns back into its liquid form. 

But what does this mean for flavour?

Stills with more reflux cause the alcohol to spend more time in contact with the copper, resulting in a softer, fruitier spirit. And stills with less reflux move the alcohol vapours quickly away from the copper, giving us more of those heavy notes. 

How the cut point impacts the flavour of whisky 

Different compounds and flavours boil at different temperatures. The art of the “cut point” is knowing when to separate the heads, heart and tails of the spirit to get the desired taste. 

Although the heart is the “creme de la creme” of the distillation, there are some favourable compounds to be found in the heads and tails—each contributing to the final flavour. Many distilleries take elements from all three parts to make their unique new make spirit. 

• The heads contain compounds that give you subtle grassy, floral and citrus notes. 
• The heart contains esters responsible for most of those sweet, fruity flavours like apple, pears and banana. 
• The tails contribute heavy, earthy, oily flavours that are often associated with peated whisky. 

Distillers who cut their spirit early, will collect more of those light, fruity flavours from the heart and heads. And distillers who cut their spirit late, will create a combination of both light and heavy notes from the heads, heart and tails. 

How does Arran Whisky distil its new make spirit?

Let our Brand Home Ambassador, Phoebe Hall, take you through the process…

“Our spirit style is light and fruity with an oily mouthfeel: Think pears, apples and orchard fruits with a vanilla-like sweetness. We use both fast and slow acting yeast, to hit our average fermentation time of 75 hours. Even at this early stage, those fruity characters really come through. The wash at Lochranza tastes a lot more like a traditional flat apple cider, than a beer. 

From there, our single malt is double-distilled in copper pot stills. The first distillation produces a liquid that’s about 23% alcohol and the second raises its ABV to an average strength of 69%. 

Our stills themselves are small, with long, narrow lyne arms that are fairly level (they sit at almost a 90-degree angle). This design encourages reflux and allows the alcohol vapours to have plenty of contact with the copper—filtering out the strong, sulphurous compounds and nurturing more of the fruity esters we want. Likewise, our distillation speed runs at a leisurely six to seven litres per minute, meaning the alcohol and copper can react for a longer period of time. (Our flow rate is one of the slowest in Scotland! Roughly 6 litres per minute. It takes around 2 hours to collect our heart of the run).

Our cut point is fairly broad, but quite early—anywhere between 75% and 63.5%. This means we avoid the dark, heavy flavours of the tails (which can swamp the character and override those lovely  fruity esters) and instead, craft our new make spirit with the lighter flavours that you find in the heart and heads. All of this contributes to Arran Single Malt’s signature fruity character.”

Want to try it for yourself? Shop any of our whiskies online or visit our home at Lochranza for tours and tastings.