Editorial · Technical History
Production Process
Six stages of production, each described through its documented technical and industrial history.
Malting
Malting converts raw barley into a fermentable material. The grain is steeped in water to initiate germination, spread out while enzymes develop and then dried in a kiln to arrest the process. The method is documented in medieval monastic brewing records long before it was applied to distillation.
Floor malting, in which the germinating grain is spread across a stone floor and turned by hand with wooden shiels, remained standard practice until the twentieth century. It is labour-intensive and its output is small relative to modern equipment.
Centralised commercial maltings using drum and Saladin box systems replaced floor maltings across most of the industry from the mid-twentieth century. Fewer than ten distilleries in Scotland retain working floor maltings, generally producing a fraction of their requirement.
Where peat is used as kiln fuel, phenolic compounds in the smoke are absorbed by the grain. On Islay this practice reflects the historical absence of any other abundant fuel on the island.
Mashing
Mashing extracts fermentable sugars from the malted grain. The grist is mixed with hot water in a mash tun in successive waters of increasing temperature, and the resulting liquid, known as wort, is drawn off for fermentation.
Early mash tuns were open wooden vessels stirred by hand or by a simple rake mechanism. Cast iron and later stainless steel vessels with mechanical rotating gear replaced them progressively through the nineteenth and twentieth centuries.
The introduction of the semi-lauter and full lauter tun improved extraction efficiency and clarity of wort. The degree of clarity is recorded as influencing the character of the spirit subsequently produced, and distilleries document their mashing regime accordingly.
The spent grain remaining after mashing, known as draff, was historically returned to local agriculture as cattle feed, a practice that tied distilleries closely to the farms surrounding them.
Fermentation
Fermentation converts the sugars in the wort into alcohol through the action of yeast, producing a liquid of low strength known as wash. The role of yeast was not understood scientifically until the nineteenth century, and earlier distillers relied on brewing practice and locally maintained cultures.
Fermentation vessels, termed washbacks, were traditionally constructed of Oregon pine or larch by coopers. Wooden vessels are harder to clean than steel and require regular repair, but the microbial population resident in the wood is documented as contributing to the fermentation.
Fermentation length varies significantly between distilleries. Lagavulin employs an extended period of up to 75 hours, considerably longer than the industry average, and such regimes are recorded as a deliberate element of production practice.
Stainless steel washbacks were adopted widely from the mid-twentieth century for reasons of hygiene and durability, and the retention of wooden vessels is now generally a documented heritage decision.
Distillation
Distillation separates alcohol from water by evaporation and condensation. The apparatus derives from the alembic documented by scholars writing in Arabic between the eighth and tenth centuries, transmitted into Europe through Iberian translation schools and medieval monastic medicine.
Copper was selected initially because it is malleable and conducts heat efficiently over a direct fire. Its retention reflects a documented chemical function: copper reacts with sulphur compounds in the vapour stream and removes them from the spirit.
Still geometry determines the degree of reflux, the proportion of vapour that condenses and returns to the still before reaching the condenser. Glenmorangie is historically documented as operating the tallest pot stills in Scotland at 5.14 metres, while Lagavulin uses small onion-shaped stills.
The continuous column still patented by Aeneas Coffey in Dublin in 1831 allowed uninterrupted production of grain spirit at high strength and low cost. It did not replace the pot still but operated alongside it, supplying the blending trade.
Maturation
Maturation was not a designed stage of production. Casks were the standard transport container of pre-industrial Europe, and the observation that spirit held in wood for extended periods differed from newly distilled spirit appears in commercial correspondence before it was understood chemically.
Bonded warehousing, under which duty became payable on release rather than on production, made long maturation economically feasible and established it as a documented commercial norm during the nineteenth century.
American white oak, Quercus alba, and European oak, Quercus robur, contribute differently. United States legislation requiring new charred oak for bourbon has supplied the Scotch and Irish industries with the majority of their casks for a century. Japanese Mizunara oak entered use during the Second World War when imported casks became unavailable.
Spirit is lost through the staves during maturation, recorded in the industry as the angel's share, conventionally documented at approximately two per cent of volume annually in Scotland and considerably higher in warmer climates. Scotch and Irish whiskey both require a minimum of three years in cask.
Bottling
Until the late nineteenth century whisky was generally sold by the cask to merchants, who matured and bottled it themselves. The merchant-bonder system operated on that basis in both Dublin and Edinburgh, and Redbreast originated within it.
The shift to distillery and blender bottling in glass with printed labels introduced standardisation. Strength, volume and origin became stated on the container, and the regulation of those statements followed.
Blending and vatting are carried out before bottling. An age statement records the youngest component in the bottle rather than an average, a conservative convention embedded in legislation across producing countries.
Modern legal requirements, including minimum bottling strength and rules governing regional and category designations, are set out in instruments such as the Scotch Whisky Regulations 2009 and equivalent national codes.
