Whisky Production
The six stages by which barley, water and time become whisky
Malting
The process begins with barley. The grain is first soaked in water for two to three days in a process known as steeping, in order to raise its moisture content and activate the enzymes that will convert its starches into fermentable sugars.
The wet barley is then spread on the malting floor and turned regularly by hand or by mechanical rakes over a period of about a week, during which time it begins to germinate. The moment germination has progressed to the desired point, it is arrested by drying the barley in a kiln. In the Islay tradition the kiln fire may be fed with peat, giving the malt — and later the whisky — its distinctive phenolic character.
Mashing
The dried malt, now known as green malt, is milled to a coarse flour called grist and combined with hot water in a large vessel called the mash tun.
The hot water dissolves the fermentable sugars from the malt to produce a sweet, cloudy liquid called the wort. Three waters at progressively higher temperatures are typically drawn off before the exhausted grain is removed and the wort is transferred to the fermentation vessels.
Fermentation
The wort is transferred to the washbacks — large fermentation vessels traditionally made of Oregon pine or Douglas fir, though stainless steel is now also common. Yeast is added and fermentation begins.
Over the following two to four days the yeast converts the sugars into alcohol, producing a low-strength beer-like liquid called the wash, typically of around eight per cent alcohol by volume. Longer fermentations, of seventy hours or more, tend to produce fruitier, more complex spirits.
Distillation
The wash is distilled twice — occasionally three times — in copper pot stills. The first distillation, in the larger wash still, produces a distillate of about twenty-one per cent alcohol called the low wines.
The low wines are then distilled a second time in the smaller spirit still. The distiller makes the crucial choice known as the cut, selecting the middle portion — the heart — for maturation and setting aside the foreshots and feints. The shape and size of the still and the pace of distillation are decisive influences on the character of the resulting spirit.
Maturation
The new-make spirit is filled into oak casks for maturation. Scotch whisky must be aged for a minimum of three years, though in practice most single malts are matured for considerably longer.
During ageing the spirit draws colour, sweetness and complexity from the oak, while a small percentage of the cask's volume is lost each year through evaporation — the poetic angel's share. American oak casks previously used for bourbon and European oak casks previously seasoned with sherry are the two great traditions of Scotch cask.
Bottling
When the whisky has reached maturity the individual casks are assessed, and a selection are married in a large vat before being reduced to bottling strength with water.
The bottled whisky may be a single-cask expression, the product of a single distillery married across many casks, or a blended composition drawing on the work of several distilleries. In every case the final act of bottling is the moment at which many years of patient craft are finally offered to the world.
