Whisky or whiskey is a type of distilled alcoholic beverage made from fermented grain mash. Various grains (which may be malted) are used for different varieties, including barley, corn (maize), rye, and wheat. Whisky is typically aged in wooden casks, generally made of charred white oak.

Production

Distillation

A still for making whisky is usually made of copper, since it removes sulfur-based compounds from the alcohol that would make it unpleasant to drink. Modern stills are made of stainless steel with copper innards (piping, for example, will be lined with copper along with copper plate inlays along still walls). 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.

Column stills are frequently used in the production of grain whisky and are the most commonly used type of still in the production of Bourbon and other American whiskeys. Column stills behave like a series of single pot stills, formed in a long vertical tube. Whereas a single pot still charged with wine might yield a vapour enriched to 40–50% alcohol, a column still can achieve a vapour alcohol content of 95.6%; an azeotropic mixture of alcohol and water.

Aging

Whiskies do not mature in the bottle, only in the cask, so the “age” of a whisky is only the time between distillation and bottling. This reflects how much the cask has interacted with the whisky, changing its chemical makeup and taste. Whiskies that have been bottled for many years may have a rarity value, but are not “older” and not necessarily “better” than a more recent whisky that matured in wood for a similar time. After a decade or two, additional aging in a barrel does not necessarily improve a whisky.

While aging in wooden casks, especially American oak and French oak casks, whisky undergoes six processes that contribute to its final flavor: extraction, evaporation,oxidation, concentration, filtration, and colouration.

Extraction in particular results in whisky acquiring a number of compounds, including aldehydes and acids such as vanillin, vanillic acid, and syringaldehyde.

Packaging

Most whiskies are sold at or near an alcoholic strength of 40% abv, which is the statutory minimum in some countries[8] – although the strength can vary, and cask-strength whisky may have as much as twice that alcohol percentage.

Types

Whisky or whisky-like products are produced in most grain-growing areas. They differ in base product, alcoholic content, and quality.

  • Malt whisky is made primarily from malted barley.
  • Grain whisky is made from any type of grains.

Malts and grains are combined in various ways:

  • Single malt whisky is whisky from a single distillery made from a mash that uses only one particular malted grain. Unless the whisky is described as single-cask, it contains whisky from many casks, and different years, so the blender can achieve a taste recognizable as typical of the distillery. In most cases, single malts bear the name of the distillery, with an age statement and perhaps some indication of some special treatments such as maturation in a port wine cask.
  • Blended malt whisky is a mixture of single malt whiskies from different distilleries. If a whisky is labelled “pure malt” or just “malt” it is almost certainly a blended malt whisky. This was formerly called a “vatted malt” whisky.
  • Blended whisky is made from a mixture of different types of whisky. A blend may contain whisky from many distilleries so that the blender can produce a flavour consistent with the brand. The brand name may, therefore, omit the name of a distillery. Most Scotch, Irish and Canadian whisky is sold as part of a blend, even when the spirits are the product of one distillery, as is common in Canada.American blended whisky may contain neutral spirits.
  • Cask strength (also known as barrel proof) whiskies are rare, and usually only the very best whiskies are bottled in this way. They are bottled from the cask undiluted or only lightly diluted.
  • Single cask (also known as single barrel) whiskies are bottled from an individual cask, and often the bottles are labelled with specific barrel and bottle numbers. The taste of these whiskies may vary substantially from cask to cask within a brand.