The typical unifying characteristics of the different classes and types are the fermentation of grains, distillation, and aging in wooden barrels.

[18] The practice of medicinal distillation eventually passed from a monastic setting to the secular via professional medical practitioners of the time, The Guild of Barber Surgeons.

[18] The earliest mention of whiskey in Ireland comes from the Annals of Clonmacnoise, which attributes the death of a chieftain in 1405 to "taking a surfeit of aqua vitae" at Christmas.

The distillation process was still in its infancy; whisky itself was not allowed to age, and as a result tasted very raw and brutal compared to today's versions.

In 1707, the Acts of Union merged England and Scotland into the Kingdom of Great Britain, and thereafter taxes on distilled spirits rose dramatically.

[22] In America, whisky was used as currency during the American Revolution; George Washington operated a large distillery at Mount Vernon.

It also was a highly coveted trade good, and when an additional excise tax was levied against it in 1791, the Whiskey Rebellion erupted.

The operation was soon shifted to nearby Solan (close to the British summer capital Shimla), as there was an abundant supply of fresh spring water there.

[25] In 1823, the UK passed the Excise Act, legalizing distillation (for a fee), and this put a practical end to the large-scale production of Scottish moonshine.

[26] By the 1880s, the French brandy industry was devastated by the phylloxera pest that ruined much of the grape crop; as a result, whisky became the primary liquor in many markets.

Although specific methods may vary among distilleries, whisky production broadly comprises four primary stages: grain preparation, fermentation, distillation, and maturation (aging).

The soaked grains are then transferred to large containers where germination occurs, initiating the metabolic process that converts starches into sugars.

This process is subsequently halted by drying the grains with hot air, a procedure also known as kilning, at the end of which the product is malt.

In the production of Scotch whisky, the air used for kilning is heated by burning peat bricks in a furnace, imparting the characteristic smoky flavour to the malt.

The ground malt is introduced into a mashtun, a large vat containing hot water, and is agitated for approximately thirty minutes or more.

Once complete, the resulting liquid, known as wort, which contains the extracted sugars, is separated from the mash, cooled, and transferred to the washbacks, or fermenting vats.

The yeast metabolizes the sugars, producing alcohol, carbon dioxide, and congeners, which can influence the flavor profile of the whisky, either enhancing or suppressing desirable characteristics.

[33] The decision to transfer either the entire wash or only the most liquid portion into the still is at the discretion of the distiller, and each choice affects the flavor profile of the final product in distinct ways.

The simplest standard distillation apparatus is commonly known as a pot still, consisting of a single heated chamber and a vessel to collect purified alcohol.

[43] Principal whisky producing areas include Speyside and the Isle of Islay, where there are nine distilleries providing a major source of employment.

In many places, the industry is closely linked to tourism, with many distilleries also functioning as attractions worth £30 million GVA each year.

[48] The main difference defining a Tennessee whiskey is that it must be filtered through sugar maple charcoal before aging, known as the Lincoln County Process.

The historic popularity of Canadian whisky in the United States is partly a result of rum runners illegally importing it into the country during the period of American Prohibition.

Distillers operated in London, Liverpool, and Bristol until the late 19th century, after which production of English single malt whisky ceased until 2003.

[64] The distilleries producing French whisky include Glann ar Mor and Warenghem in Brittany, Guillon in the Champagne region, and Grallet-Dupic in Lorraine.

Scotch malt whiskies were divided into five main regions: Highland, Lowland, Islay, Speyside and Campbeltown.

[67] Puni is an Italian distillery in Glurns that makes single malt whisky, including Alba, which is matured in Marsala casks.

[102] The distinctive smoky flavour found in various types of whisky, especially Scotch, is due to the use of peat smoke to treat the malt.

Fusel oils are higher alcohols than ethanol, are mildly toxic, and have a strong, disagreeable smell and taste.

[109] In an experiment, whiskey aged 3 years in orbit on the International Space Station tasted and measured significantly different from similar test subjects in gravity on Earth.