The Art of Whisky Distillation
Distillation is at once the simplest and the most exacting of the whisky-maker's crafts. Its principle — that alcohol and water may be separated by the careful application and removal of heat — has been understood since the medieval period. Its practice, however, remains one of the great disciplines of the industry.
In the classic Scottish tradition, distillation is carried out twice, in a pair of copper pot stills known as the wash still and the spirit still. The wash still receives the fermented wash and produces a distillate of some twenty-one per cent alcohol known as low wines. The low wines are then distilled a second time in the smaller spirit still, from which the master distiller draws the spirit that will one day become whisky.
The cut is where craft meets judgement — the moment at which the distiller decides what shall become whisky and what shall not.
The second distillation is the moment at which the distiller's judgement is most decisive. The distillate emerges in three portions. The first — the foreshots — is high in unwanted volatile compounds and is set aside. The last — the feints — is low in alcohol and heavy in oily congeners, and is likewise set aside. Only the middle portion — the heart of the run — is filled into cask for maturation. This choice is called the cut, and the precise point at which the cut is made and closed is one of the most closely guarded traditions of every distillery.
The character of the resulting spirit is shaped in the most surprising way by the shape and size of the still itself. Tall, narrow stills of the kind used at Glenmorangie encourage a slow reflux, in which the heavier vapours fall back into the pot and only the lightest ascend. The resulting spirit is delicate, floral and fragrant. Short, squat stills of the kind used at Lagavulin or Macallan produce a heavier, oilier spirit, richer in body and more assertive in character.
Copper itself is central to the process. In the course of distillation the vapours interact with the metal, and the copper removes sulphurous compounds that would otherwise carry through into the final spirit. This is the reason the great distilleries have always used copper pot stills, and the reason a still is periodically retired and replaced by an exact replica when its walls have thinned beyond a certain point.
Copper is not merely the material of the still; it is a quiet participant in the making of the spirit.
The continuous or column still, patented by Aeneas Coffey in 1831, works on a different principle. Instead of a series of batch distillations, the column still allows for a continuous process in which the wash enters at the top of a tall column and the distillate is drawn off at a chosen point according to strength. Column stills produce a lighter, purer grain spirit that is essential to the blending tradition.
Whether performed in pot or column, distillation is the moment at which the whisky-maker chooses what to include and what to set aside. It is the moment at which the character of the finished whisky is most decisively determined. Everything that follows — cask, warehouse, time — refines what the still has already made possible.