A whisky’s final flavour can come from various parts of the production process, and the character of the spirit still – and how it is operated – can play a key role, as Gavin D Smith explores
PHOTOS: PETER SANDGROUND / MIKE WILKINSON / HORST FRIEDRICHS / JEREMY SUTTON-HIBBERT
In double malt whisky distillation, the second stage takes place in the spirit still, sometimes referred to as the ‘low wines’ still, where the character of spirit being produced may be heavily influenced and its strength is significantly increased.
The spirit still is filled with the contents of the low wines and feints receiver, which contains low wines from the wash still and remnants from the previous run of the spirit still. This liquid has a strength of around 25% abv.
The size and shape of the still has a direct effect on ultimate spirit style, as has the manner in which the still is operated. A still with a long, narrow neck will produce a significant degree of what is termed reflux.
This is where heavier, oilier compounds with a higher boiling point than lighter compounds condense as they rise up the still and the temperature drops, causing them to fall back towards the boil pot of the still, where they are re-vaporised.
Conversely, a still with a wide and short neck will produce fewer temperature variations and therefore a lower degree of reflux, with heavier compounds reaching the head of the still and being carried over into the condenser, leading to a heavier, fuller-bodied spirit. In terms of size, large stills offer a greater degree of copper contact for the liquid they contain than small ones, so they tend to produce a lighter spirit.
Greater reflux and consequently lighter spirit character may also be generated by the inclusion of a ‘boil ball’ between the still’s pot and neck, with this larger, cooler chamber creating higher levels of condensation.
Another factor in spirit style is the design of the lyne arm, or lye pipe, which connects the still head to the condenser. An ascending arm will allow for more reflux, while a descending arm is likely to be instrumental in the development of a fuller-bodied spirit.
ABOVE: Alistair McDonald, distillery manager at Clydeside, where the spirit still has a boil ball to increase reflux during distillation
The greatest stylistic contrast between pot stills at high-profile Scottish distilleries concerns Glenmorangie, with its very long-necked, elegant stills and the small, squat vessels in place at The Macallan. The influence of still design is apparent in the two very different spirits they produce.
During spirit distillation, the initial ‘heads’, or foreshots as they are known, are separated from the desirable ‘heart’ of the run using the brass-bound spirit safe that is a feature of virtually every Scottish distillery. The undesirable ‘tails’, or feints. are also separated in the same fashion.
The heart – at around 70% abv – is directed into the spirit receiver, while the heads and tails are returned to the low wines and feints receiver to be re-distilled with the next batch of low wines.
Each distillery will operate it own cut points to separate the three elements of spirit produced, with many modern distilleries adopting automated cut points, usually determined by time. Some, however, still rely on the skill of individual stillmen, who judge cut points by spirit colour and aroma. At Glen Scotia in Campbeltown, the single pair of stills is controlled by two hand-turned valves per still, with distillery manger Iain McAlister noting that:
“We start to cut to the heart of the run at 72/73% abv and cut again at 63% abv. We run relatively slowly, at 280-300 litres per hour. The harder you run it, the more you burn off and lose positive character.”
ABOVE: The famously long-necked stills at Glenmorangie are in stark contrast to the short, squat vessels used at The Macallan
Cut points may vary significantly, even with heavily-peated whiskies. Bruce Perry, global brand manager for Torabhaig distillery on Skye, says: “When we distil, we cut high, at 64% abv, which is very high for a peaty whisky. We are able to collect the guaiacols, the fragrant, earthy notes, whereas other distillers of peaty whiskies will probably cut at 68 or 69% abv, which gives more cresols and therefore iodine and tar-type characteristics.”
Iain McAlister has already referred to the speed of distillation, and a slow rate of distillation, using gentle heating, leads to a greater degree of reflux and consequently a lighter spirit. Rapid heating drives off vapours more readily, reducing reflux, leading to a heavier style. Meanwhile, at Glen Ord distillery, stills are run slowly but very hot in order to produce intense, grassy spirit.
As distillers seek to reduce their carbon footprints and move away from the use of fossil fuels, heat recovery technologies, including Mechanical Vapour Recompression (MVR) and Thermal Vapour Recompression (TVR), have become important aspects of the distilling process.
MVR and TVR are designed to capture and recycle heat generated in the distillation process that would otherwise go to waste, and the result can be a reduction of up to 40 per cent in the amount of steam required for distillation.
Overall, the process of double distillation increases alcoholic strength from around 25% abv to approximately 70% abv, and the actual business of making what will become whisky after three years is at an end. For the spirit, however, there may be many stylistic changes to come during maturation.
ABOVE: Torabhaig’s still size and shape were dictated by the size of the listed byre that’s the distillery’s home on Skye
“It is the Highland still-man who, in the final analysis, has the final say in determining the character of the whisky. The precise moment in the distilling process when the feints or impure spirits are separated from the whisky which is run into the spirit receiver is at the discretion of this high functionary. Very carefully with his sampling beads [to determine strength] he keeps testing the whisky ‘run’ until, reduced with water to some 30 degs under proof, the spirit remains clear in the glass. At the close of distillation he has only to run some of the feints for a short time into the spirit receiver to give the whole a pungent, feinty objectionable flavour, more readily detected on the palate ten years later than there and then in the crystal distillate. The great still-man, like the great poet, is born, not made.”
‘Caledonia’, Harpers Wine & Spirit Gazette, 18th June 1948
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