With thanks to whiskycorner.co.uk, here's a detailed description of the whisky making process.
Malt whisky production begins when the barley is malted, by steeping the barley in water and then allowing it to get to the point of germination. Malting releases enzymes that break down the starches in the grain and help convert them into sugars. When the desired state of germination is reached the malted barley is dried using heated air. Many (but not all) distillers add smoke from a peat-heated fire to give smoked, earthy flavours to the spirit.
Today only a handful of distilleries have their own maltings; these include, Balvenie, Kilchoman, Highland Park, Glenfiddich, Glen Ord, Bowmore, Laphroaig, Springbank and Tamdhu. Even those distilleries that malt their own barley produce only a small percentage of the malt required for production. All distilleries order malt from specialised maltsters.
The dried malt (and in the case of grain whisky, other grains) is ground into a coarse flour called “grist”. This is then mixed with hot water in a large vessel called a mash tun. The grist then steeps in the hot water for a variable amount of time.
This process is referred to as “mashing”, and the mixture known as “mash”. During the process of mashing, enzymes that were developed during the malting process are allowed to convert the barley starch into sugar, producing a sugary liquid known as “wort”
The wort is then transferred to another large vessel called a “wash back” where it is cooled. The yeast is added, and the wort is allowed to ferment. The resulting liquid, now at about 5-7% alcohol by volume (ABV), is separated from solid matter by filtering, and is a rudimentary form of beer called the “wash”.
The next step is to use a still to distill the wash. Distillation is used to increase the alcohol content and to remove undesired impurities such as methanol. There are two types of stills in use for the distillation: the pot still (for single malts) and the Coffey still (for grain whisky). Most Scotch malt whisky distilleries distil their product twice; exceptions include the Auchentoshan distillery and Springbank’s “Hazelburn” brand, which retain the Lowlands tradition of triple distillation. A third method is unique to the Springbank distillery’s “Springbank” brand, which is distilled “two-and-a-half-times”. This is achieved by distilling half the low wine (1st distillation) for a second time, adding the two halves together and then distilling the complete volume a final time.
For malt whisky the wash is transferred into a wash still. The liquid is headed to the boiling point, which is lower than the boiling point of water. The alcohol evaporates and travels to the top of the still, through the “lyne arm” and into a condenser – where it is then cooled and reverts back to a liquid. This liquid has an alcohol content of about 20% and is called “low wine”.
The low wine is distilled a second time, in a spirit still, and the distillation is divided into three “cuts”. The first liquid or cut of the distillation is called “foreshots” and is generally quite toxic due to the presence of the low boiling point alcohol methanol. These are generally saved for further distillation. The stillman looks for the “middle cut”, which he places in casks for maturation. At this stage it is called “new make”. Its alcohol content can be anywhere from 60%-75%. The third cut is called the “feints” and is generally quite weak. These are also saved for further distillation.
Grain whiskies are distilled in a column still, which requires a single distillation to achieve the desired alcohol content. Grain whisky is produced by a continuous fractional distillation process, unlike the simple distillation based batch process used for malt whisky. It is therefore more efficient to operate and the resulting whisky is less expensive.
The maximum distillation purity prescribed in the Scotch Whisky Regulations is 94.8% ABV. This allows the spirit to have a rather high level of alcohol purity – approaching that of neutral spirits, and it contrasts with the maximum of 80% ABV allowed for “straight” American Whiskey. High levels of alcohol distillation purity can give the whisky a lighter (but less rich) flavour. In practice, Scotch single malts are generally not distilled to very high levels of alcohol content, so that they can retain more of the flavour of the original wash.
Dilution prior to aging
Most new-make malt whisky is diluted to about 62.5% ABV, before it is placed in casks to mature.
Once distilled the “new make spirit” is placed into oak casks for the maturation process. Historically, casks previously used sherry were used (as barrels are expensive, and there was a ready market for used sherry butts). Today, the casks used are typically sherry or bourbon casks, but with many now coming from northern France with its huge supply of aged white oak casks used in both white and red wine production. Sometimes other varieties such as port, Cognac, Madeira, Calvados, Beer and Bordeaux wine are used. American whiskey production is a nearly inexhaustible generator of used barrels, due to a United States regulation requiring the use of new, freshly charred oak barrels in the maturation of bourbon and many other types of whisky.
The ageing process results in evaporation. So each year in the cask causes a loss of volume as well as a reduction in alcohol. The 0.5—2.0% lost each year is known as the angel’s share. The distillate must age for at least three years in Scotland to be called Scotch whisky.
Colour can give a clue to the type of cask (sherry or bourbon) used to age the whisky, although the addition of legal “spirit caramel” is sometimes used to darken an otherwise lightly coloured whisky. Sherried whisky is usually darker or more amber in colour, while whisky aged in ex-bourbon casks is usually a golden-yellow/honey colour.
Vatting and dilution
With single malts, the now properly aged spirit may be “batted”, or “married”, with other single malts (sometimes of different ages) from the same distillery. The whisky is generally diluted to a bottling strength of between 40% and 46%.
Occasionally, distillers release a “Cask Strength” edition, which is not diluted and usually has an alcohol content of 50-60%. Many distilleries are releasing “Single Cask” editions, which are the product of a single cask that has not been batted with whisky from any other casks. These bottles usually have a label that details the date eth whisky was distilled, the date it was bottled, the number of bottles produced, the number of the particular bottle and the number of the cask that produced the bottles.
Many whiskies are chill-filtered before being bottled. In this process, the whisky is chilled to near 0°C (32°F) and passed through a fine filter. The aim is to remove some of the oily/fatty compounds produced during distillation. The chill-filtering prevents the whisky from becoming hazy when in the bottle, when served, when chilled, or when water or ice is added. This only happens at an alcohol content below 46%ABV.
Generally bottled whisky over 46%ABV indicates that it is non chill-filtered or unchill-filtered, as the spirit generally remains unclouded at this alcohol level. Many whisky enthusiasts believe that chill-filtration removes some of the flavour and body from the whisky, which is why some consider unchill-filtered whisky superior.
E150A caramel colouringis commonly added to Scotch whisky prior to bottling, to give the whisky a more rich and well-aged appearance. No other additives are allowed in Scotch whisky. This contrasts with the rules governing Canadian whiskey production, which allow the addition of other flavourings as well as caramel, and with the rules governing American whiskey, which do not allow additives in “straight” whiskey. The use of the caramel additive must be disclosed when the whisky is sold in some jurisdictions, although not in Scotland itself.
Water and Ice
Many whisky connoisseurs believe that you should not add any water because you are tasting the whisky in its true natural form with all of the original distillery characteristics and flavours.
By adding a small dash of water to a whisky, you can open up different, new and subtle flavours that you previously hadn’t experienced. This is especially true when drinking cask strength whiskies that have higher alcohol levels (this can be up to and over 60% ABV in some cases). With cask strength whisky the alcohol and resulting burning in your mouth can overpower even the most prominent flavours. By adding some water, this dilutes the alcohol and reduces its effect, giving both the prominent and more subtle flavours a chance to shine through. Imagine drinking orange squash concentrate without any water and then with water, it’s essentially the same idea. How much water you add, if at all, is entirely up to your own taste.
Ice is slightly different, rather than enhancing flavours, it actually inhibits them as the ice makes the temperature of the whisky drop rapidly. It is the same as when you drink a good white wine that has been chilled down too much. It will be more refreshing and calm the burn, but can make the taste dull and flat. The taste will start to open up and reveal its full character once the whisky start to warm up.