Single malt whisky is malt whisky from a single distillery.
Single malts are typically associated with single malt Scotch, though they are also produced in various other countries.
National varieties
United Kingdom
Scotland Under the United Kingdom's Scotch Whisky Regulations, a "Single Malt Scotch Whisky" must be made exclusively from malted barley (although the addition of E150A caramel colouring is allowed), must be distilled using pot stills at a single distillery, and must be aged for at least three years in oak casks of a capacity not exceeding .The Scotch Whisky Regulations 2009 , The National Archives, 2009.The Scotch Whisky Regulations 2009: Guidance for Producers and Bottlers , Scotch Whisky Association, 12 February 2009.
Regulations in other countries largely follow the Scotch model, though permitted practices vary. For example, United States regulations state "[t]he adopted criteria for American single malt whisky specify that the product be a type of whisky that is mashed, distilled, and aged in the United States; is distilled entirely at one U.S. distillery; is distilled to a proof of 160 or less; is distilled from a fermented mash of 100 percent malted barley; is stored in oak barrels (used, uncharred new, or charred new) with a maximum capacity of 700 liters; and is bottled at not less than 80° proof. In addition, the criteria allow for the use of caramel coloring as long as its use is disclosed on the product label. The regulation will also allow the use of the term “Straight” for an American single malt whisky that is aged for at least two years."
England English single malt is currently defined by the English whisky GI and British Standards Institute guidance (BS 8636).
The geographical indication (GI) for English whiskydefines English single malt as whisky produced from malted barley grown in the UK using English water, that is milled and fermented in England, batch-distilled in pot stills with sufficient copper contact at a single distillery in England to a strength of less than 94.8% ABV, matured in wooden casks of no more than 700 litres for a minimum of three years, and bottled at a minimum of 40% ABV with no added flavouring or additives other than E150 caramel colouring.
English single malt differs from traditional single malt production in several respects. Mashing and fermentation may take place away from the distillery though it must still occur in England, different types of stills may be used so long as there is sufficient copper contact, and any type of wooden cask may be employed for maturation. Differences in the rules governing single malt production, particularly those relating to mashing and fermentation, have given rise to a dispute between Scotch whisky and English whisky producers.
Wales Welsh single malt whisky is defined by the Welsh single malt geographical indication (GI). It must be produced from malted barley and water sourced in Wales, and the whisky must be mashed and fermented, distilled, matured, and bottled entirely in Wales.
United States Single malt whisky in the United States is defined by the Alcohol and Tobacco Tax and Trade Bureau (TTB). Under TTB regulations, U.S. single malt whisky must be produced from 100% malted barley grown in the United States and distilled to no more than 160 proof (80% ABV) at a single distillery in the country. The spirit is matured in used, charred new, or uncharred new oak barrels with a capacity of no more than 700 liters, all within the United States. No neutral spirits may be used in its production, and the only permitted additive is E150 caramel coloring, which must be disclosed on the label.
Denmark Danish single malt whisky is defined by the Danish Whisky Manifesto, which was established on 16 April 2025 by ten Danish distilleries. According to the manifesto, Danish single malt must be mashed and fermented in Denmark, produced from 100% malted barley grown in Denmark, and matured for at least three years in wooden casks in Denmark. A variety of distillation methods are permitted. No additional sweeteners or other additives are allowed.
Production Barley, yeast, and water are the only ingredients required in the production of (barley-based) single malt whisky. All single malt goes through a similar batch production process.
There are several types of single malts available from distilleries including single barrel single malts which are the product of a single batch that was stored for three or more years in a single oak barrel. These single-barrel variants afford the opportunity for the consumer to see the influence of different types of storage on the same whisky (e.g., first-use bourbon whiskey barrels, port pipes, etc.). The more common form of single malt is a marrying at the bottling time of various batches that are mixed or vatted to achieve consistent flavours from one bottling run to the next.
Malting
Barley is "malted" by soaking the grain in water for two to three days and allowing it to germinate. This process releases enzymes, which convert unfermentable starch (which is insoluble in water and not available for fermentation by yeast) to fermentable sugars. Traditionally in Scotland, germinating seeds were laid on a malting floor and regularly turned. After three to five days, when the optimum amount of starch has been converted to fermentable sugars, germination is halted by heating the seeds with hot air.
Many distilleries once used a kiln to heat the germinated barley. The "pagoda roof" (many now false) that ventilated the malt kiln can still be seen at many distilleries both in Scotland and in other countries. However, most of the distilleries now use commercial "maltsters" to prepare their malt.
In most cases, some level of smoke from a peat-heated fire is introduced during heating to add phenols, a smoky aroma and flavour to the whisky. Some of the more intensely smoky malts have phenol levels between 25 and 50 parts per million (ppm). Islay malts have a reputation for being the peatiest. More subtle malts can have phenol levels of around 2–3 ppm. Entirely non-smoked (non-peated, unpeated) malts are made by the Glengoyne Distillery, which only uses hot air for drying.
Mashing The malt is milled into coarse flour (grist) which is made of husks (20%), grits (70%), and flour (10%), to which three courses of hot water are added to extract the sugars.
The extraction is done in a large kettle (usually made of stainless steel) called a mash tun. At first, the hot water dissolves the sugars (maltose) and enzymes (diastase) in the grist. Then the enzymes act on the starch left over from the malting stage, continuing the conversion to sugar, and producing a sugary liquid called wort. Typically, each batch of grist is mashed three times or so to extract all the fermentable sugars. The first water is injected at about 60 °C, the second portion at about 72 °C and the third and final portion at about 88 °C. The wort from the first two water courses is drained into "washback" vessels for further processing, whereas the third course is retained as the first charge in the next batch.
Fermentation
Yeast is added to the wort in a large vessel (often tens of thousands of litres) called a washback. Washbacks are commonly made of Oregon pine or stainless steel. The yeast feeds on the sugars, and as a by-product, produces both carbon dioxide and alcohol. This process is called fermentation and can take up to three days to complete. When complete, the liquid has an alcohol content of 5 to 7% by volume and is now known as wash. Up until this point the process has been quite similar to the production of beer.
Distillation
The wash is then distilled. The wash is heated, boiling off the alcohol, which has a lower boiling point than water; the vapour is collected and cooled to condense it back into a liquid form.
Scottish regulations require single malts to be distilled in pot stills. In other jurisdictions, column stills may be used.
The initial distilled spirit produced by a pot still, known as low wine has an alcohol content of about 20 to 30%. The low wines are then pumped into a second still, known as the spirit still, and distilled a second (and sometimes a third) time. The final spirit, called "new make spirit", generally has an alcohol content of 60 to 70%.
Dilution prior to aging Most new-make malt whisky is diluted with water to about 60% alcohol by volume (ABV) or so before it is placed in casks to mature (62.5% is specified as a maximum in U.S. law for making straight whisky). The aged spirit is then diluted with water to reduce it to bottling strength (typically 40-50% ABV). Since large amounts of water are used during the process of whisky production, water supplies are a key factor for the location of any distillery.
Maturation
The "new-make spirit" (above 60% a.b.v.), or unaged whisky, is then placed in oak casks to mature and to reduce its alcohol content to expedition levels (40-45% a.b.v.). By law, all Scotch whisky must be aged for a minimum of three years in oak casks, though many single malts are matured for much longer. The whisky continues to develop and change as it spends time in the wood. Typical maturation periods are in the range of 10-15 years; longer periods of twenty years or more occur, but are rare and costly. During the time it spends in the wood, a significant percentage of each cask's content will evaporate. The lost part is known as the angel's share.
Reused casks
The selection of casks can affect the character of the final whisky. Outside of the United States, the most common practice is to reuse casks that previously contained American whiskey, as US law requires several types of distilled spirits to be aged in new oak casks. To ensure the continuity of supply of used oak casks, some Scottish distilling groups enter a contract with US manufacturers for casks used at least once; once a cask has passed through a first bourbon maturation in the United States, it is sent to Scotland to be refilled. Bourbon casks impart a characteristic vanilla flavour to the whisky.
Sherry casks are also commonly used. This practice arose because sherry used to be shipped to Britain from Spain in the cask rather than having been bottled, and the casks were expensive to return empty and were unwanted by the sherry cellars. In addition to imparting the flavours of their former contents, sherry casks lend maturing spirit a heavier body and a deep amber and sometimes reddish colour.
Stainless steel shipping containers, however, have reduced the supply of wooden sherry casks, to the extent that the Macallan Distillery builds casks and leases them to the sherry cellars in Spain for a time, then has them shipped back to Scotland.
Other casks used include those that formerly held port wine, madeira, rum or cognac.
Vatting, dilution, and bottling
To be called a single malt whisky in Scotland, a bottle may only contain whisky distilled from malted barley and produced at a single distillery, distilled entirely in pot stills. The regulations of other countries may allow malted rye.
If the bottle is the product of malt whiskies produced at more than one distillery, the whisky is called a blended malt or vatted malt, or pure malt. If a single malt is mixed with grain whisky, the result is a blended whisky. Single malts can be bottled by the distillery that produced them or by an independent bottler.