Although the distillers' art has been understood since earliest times, the subtle aromas and flavours of whisky have never been fully explained, even today. The ancient term uisge beatha, which is Gaelic for the Latin aqua vitae or 'water of life', was corrupted in the 18'" century to usky, and then to whisky. The following description is a generalisation of the process.

It should be remembered that each distillery has its own unique method of producing an end product of the "uisge beatha", enabling them to create their own individual taste for the market shelf.

1. Malting

Best quality barley is first steeped in water and then spread out on malting floors to germinate. It is turned regularly to prevent the build up of heat. Traditionally, this was done by tossing the barley into the air with wooden shovels in a malt barn adjacent to the kiln.

During this process enzymes are activated which convert the starch into sugar when mashing takes place. After 6 to 7 days of germination the barley, now called green malt, goes to the kiln for drying. This halts the germination. The heat is kept below 70°C so that the enzymes are not destroyed. Peat may be added to the fire to impart flavour from the smoke.

2. Mashing

The dried malt is ground into a coarse flour or grist, which is mixed with hot water in the mash tun. The water is added in 3 stages and gets hotter at each stage, starting around 67°C and rising to almost boiling point.

The quality of the pure Scottish water is important. The mash is stirred, helping to convert the starches to sugar. After mashing, the sweet sugary liquid is known as wort. The spent grains - the draff - are processed into cattle feed.

3. Fermentation

The wort is cooled to 20°C and pumped into washbacks, where yeast is added and fermentation begins. The living yeast feeds on the sugars, producing alcohol and small quantities of other compounds known as congeners, which contribute to the flavour of the whisky. Carbon dioxide is also produced and the wash froths violently. Revolving switchers cut the head to prevent it overflowing. After about 2 days the fermentation dies down and the wash contains 6-8% alcohol by volume.

4. Pot Stills

In some mysterious way the shape of the pot still affects the character of the individual malt whisky, and each distillery keeps its stills exactly the same over the years.

In distillation, the still is heated to just below the boiling point of water and the alcohol and other compounds vaporise and pass over the neck of the still into either a condenser or a worm - a large copper coil immersed in cold running water where the vapour is condensed into a liquid.
There are around 100 Pot Still Malt distilleries and Grain, or Patent Still, distilleries in Scotland; but the number working can vary from year to year.

5. Distillation

The wash is distilled twice - first in the wash still, to separate the alcohol from the water, yeast and residue called pot ale - the solids of which are also saved for use in animal feeds.

The distillate from the wash still, known as low wines, and containing about 20% alcohol by volume, then goes to the spirit still for the second distillation. The more volatile compounds which distil off first - the foreshots, and the final runnings called feints where more oily compounds are vaporised, are both channelled off to be redistilled when mixed with the low wines in the next batch.

Only the pure centre cut, or heart of the run, which is about 68% alcohol by volume is collected in the spirit receiver.

6. Spirit Safe

All the distillates pass through the spirit safe - whose locks were traditionally controlled by the Customs & Excise. The stillman uses all his years of experience to test and judge the various distillates without being able to come into physical contact with the spirit.

The newly distilled, colourless, fiery spirit reduced to maturing strength, 63% alcohol by volume, is filled into oak casks which may have previously contained Scotch whisky, bourbon or sherry, and the maturation process begins.


1. Scotch grain whisky is usually made from 10-20% malted barley and then other unmalted cereals such as maize or wheat. The starch in the non-malted cereals is released by pre-cooking and converted into fermentable sugars. The mashing and fermentation processes are similar to those used for malt whisky.

2. The wash is distilled in a continuous or Coffey still, named after its inventor Aeneas Coffey. It has two tall columns - a rectifier and an analyser. Cold wash is pumped in at the top of the rectifier and meets steam. The columns in fact act like a heat exchanger. The alcohol is cooled, condenses and flows away as Scotch grain spirit at about 94% alcohol by volume.

3. The distilled grain spirit is lighter in character and aroma than most malt whiskies and therefore requires rather less time to mature. The bulk of matured grain whisky is used for blending.


While maturing, the whisky becomes smoother, gains flavour, and draws its golden colour from the cask. A proportion of the higher alcohols turn into esters and other complex compounds which subtly enhance each whisky's distinctive characteristics.

By law all Scotch whisky must be matured for at least 3 years, but most single malts lie in the wood for 8, 10, 12, 15 years or longer. Customs & Excise allow for a maximum of 2% of the whisky to evaporate from the cask each year - the Angels' Share. Unlike wine, whisky does not mature further once it is in the bottle.


While the distinctive single malts produced by individual distilleries are becoming increasingly popular, blending creates over 90% of the Scotch whisky enjoyed throughout the world.

By nosing samples in tulip-shaped glasses the blender selects from a wide palate - from the numerous Highland and Speyside malts to the strongly flavoured and peaty Island malts, and the softer and lighter Lowland malts. These malts are combined with grain whiskies - usually 60-80% grain whiskies to 20-40% malt whiskies, and are then left to 'marry' in casks before being bottled as one of the world-renowned blended whiskies.

A blend of a range of malt whiskies, with no grain whisky included, is known as a blended malt.

The way we make Scotch whisky has evolved over several centuries, but the history of Scotch whisky embraces a much wider heritage; that of Scotland and its people.



The ingredients are Barely, Water and Yeast
The barley is at the base of all the process. The quality of the barley has a great influence on the quality of the end product. The barley being used for the production of whisky is carefully selected. It is after all the basic ingredient which will determine the quality of the whisky which will be sold years later. This selection was traditionally the job of the manager of the distillery. Most of the distilleries nowadays buy their malt in a malting plant for economic reasons, this selection is done less and less by the distillery managers, but well by the persons in charge at the malting plant. However, the maltings must respect precise requirements from the distilleries, in order to let them produce their whisky properly, and on the same way year after year. There is no legal obligation to use Scottish barley to produce Scotch whisky. Even if some producers would like to go back to the tradition, most of the distilleries are not concerned by the origin of their barley. The most important thing is the highest sugar content and the lowest price. The combination of those two elements is often the only criteria in the choice of a variety of barley. A great deal of the barley used to produce Scotch whisky is coming from England or South Africa.
Water is another of the most important ingredients in the making process of whisky. The quality of the whisky depends on the quality and purity of the water. Water in Scotland is famous for its great purity. The difference in taste between the whisky coming from various distilleries is partly due to the quality of water used. Water in the Highlands is often peaty, which gives it a brownish colour. Substances, deriving from peat, are carried by the rivers which water is used to make whisky, and contribute often to the original taste of scotch whisky. But water is certainly not the only determining factor in the taste of a malt whisky. The manufacturing process is of course very important in the final taste of whisky. Water is used in several steps during the distillation process. First of all, it is mixed to the grinded malt in order to produce the wort. It is also used for cooling the alcohol leaving the still. Last but not least, water is used to reduce the alcohol at bottling.
Yeast will start the fermentation process. The choice of the yeast is part of manufacturing secret of the distilleries.
The production process of whisky takes at least 3 years. If the spirit do not stay for at least 3 years in an oak cask, it does not deserve the name of whisky. Even worse, it does not have legally the right to be marketed under the name of whisky. To deserve the name of Scotch, the whisky has to stay for this minimum of 3 years on the Scottish ground. Generally, the whiskies marketed as single malt aged for a minimum of 8 to 10 years. Whisky, just like any other alcohol, is the result of natural chemical alterations of sugar.
To produce alcohol, we first need to produce sugar. Sugar is potentially present in barley, which grows easily under the Scottish latitudes. Many alcohols are made from grapes, but the climate of Scotland is not suited for this kind of culture. Nevertheless the manufacturing process remains very similar to the one used in production of alcohol based on other raw material.
Malt is the result of the malting process. The barley is made wet and spread on the malting floor to allow the germination process to start. A succession of chemical reactions change the starch contained in the barley in sugar. Later sugar will change into spirit. The malting art consist of finding the right moment to stop the germination process: not too late but not too early. According to the season, malting takes between 8 and 21 days. Constant attention has to be given to the process. Barley has to be turned over regularly to ensure a constant moisture and temperature and to control the germination of the barley grains.
The end of the germination is triggered by drying the germinating barley over a fire in an oven or kiln. This oven is often heated by peat. The smoke of the peat fire in the kiln is determining the taste of the whisky. Germination is stopped by drying the grains above a kiln. A kiln was often fed with peat. It is the smoke of the peat fire which gives whiskies their particular flavour. The art is in the correct proportioning of peat used to dry the malt.
Malting happens mainly at specialized plants, called maltings. These maltings produce malt according to the requirements of their clients. The same malting company produces thus several kinds of malt. There are however notable exceptions to that rule: Balvenie, Laphroaig, Highland Park, Bowmore are some of the distilleries which produce parts of their own malts and only Springbank produces 100% of their malt. Maltings can be independent, or belong to big concerns, owning their own distilleries, like Diageo (see left picture). Diageo, who owns a great deal of the Scottish distilleries, has created its own malting plants, to supply the distilleries of the group or for local distilleries.
When the malt is dry, it is grinded to make a kind of coarse flour which will be used in the next operations. This flour is called grist. Malt grinding is done with a malt mill in the distillery itself. Nearly all the distilleries use the same kind of mill, traditionally made in Leeds, England.
The grist will be mixed with hot water in the mash tun. Generally one volume of grist is mixed up with 4 volumes of water. In this operation, 3 successive waters are used, at a temperature between 63 and 95°. A mash tun can contain up to 25000 litres and has a double bottom with thin perforations to let the sugared liquid resulting of the brewing operation flow out. A considerable part is then sold as cattle food. In order to facilitate the process, mash tun have rotating blades. The waste is called draff.
The first operation, taking about 1 hour, will change the starch in fermenting sugars. The mix of water and grist looks like porridge. This sugared juice is called wort (on the left picture you can see a wort cooler). The remainders will be brewed 3 to 4 times, in order to get a maximum of wort. The quality of the wort is controlled by the excise men, because it determines the amount of spirit which will finally be produced. This is the base of the taxation of the distillery.
In order to start the fermentation of the wort, yeast is added. The action of the yeast on the sugar of the wort will produce alcohol and carbon dioxide. The wort starts bubbling, which will sometimes result in strong vibrations of the wash back, despite its impressive size. Traditional wash backs are made of Oregon pinewood or scottish larch. However, more and more stainless steel wash backs are used nowadays, because they are easier to maintain. The result of the fermentation of the wort is a kind of beer with a percentage of approximately 8%. Till now, there are no substantial differences in the process of making whisky, and the making of beer. From now the difference between the process will become obvious. Beer will be perfumed with hops, while whisky will be distilled without alterations.
The distillation is the process used to separate alcohol from water and other substances contained in the wash. Distillation is made in stills. Water evaporates at 100° while alcohol does from 80°. Alcohol will thus be transformed in vapour and raises into the still before water itself begins evaporating.
In Scotland distilling pots are used. The size of the stills is fixed by the law. This is due to historical reasons, related to excise rights. Edradour has the smallest legal stills of Scotland. If the stills were a bit smaller, the distillery would lose its licence. Stills are in copper, because this material has a great influence on the physical process of separation of the waters and the spirits. The quality of the dram we will enjoy a few years later depends partially on the copper surface being in contact with the liquids during the distillation process. The shape, the height, the length of the lyne arm etc. are also very important in the making of the taste of the future whisky. If a distillery has to add or replace a still, it will always try to get a still with the same capacity and the same shape, in order to guarantee a constant quality to the whisky.
Traditionally, the stills were heated with coal or peat, depending on the areas and possibilities. Currently, nearly all of them are heated with vapour, because this method gives more control on the process. The fuel used to heat the vapour is generally petrol, but sometimes coal is still used.
Scotch whisky is double distilled, with some exceptions to this rule, like Auchentoshan which is distilled three times, just like Irish whiskey. The distillation process occurs in two stages in two still with different capacity and shape. The first distillation occurs in the wash still whose capacity can be between 25.000 and 30.000 litres and transforms the wash in "low wine", at about 21% of alcohol. If the stills were originally heated with a naked fire, generally from coal or gas, the current stills are heated by a serpentine within the still, where the vapour is circulating. The alcohol vapours are cooled outside the still by condensers. The traditional condensers were serpentines immerged in a great open wooden back, containing cold water. Currently, most of the distilleries use vertical tubular condensers, because the output is better. Waste of the first distillation is called "pot ale" or "burnt ale", and is transformed to feed cattle too. The low wines resulting from this first distillation are kept in the low wine receiver and will be used as the basis for the second distillation.
The second distillation occurs in a spirit still which is generally smaller than the wash still, as there is less liquid to process. During the second distillation, only the "distillation heart", the part which has between 63 and 72% of alcohol, will be casked. The heads and tails, also called feints, will go to the feint receiver, and reused mixed with the low wines of the next distillation. To separate the feints from the distillation heart, a spirit safe is used (see above picture). In past times this spirit safe was used for the determination of the quantity of alcohol produced , to calculate the taxes due by the distillery.
The distillation process is unique for each distillery using pot stills. This means that all the whiskies produced by a certain distillery are treated on the same way, with the same malt, the same stills on the same way by the same people. So, why can they be so different from each other? The answer to this question is in the aging process, the casks used, the nature of the warehouse, the taste of the air and some other criteria.
If the surrounding air has an influence on the taste of whisky, one must realize that many distilleries bring their casks to a central place near Edinburgh for their aging. Why? The influence of the air on the taste of whisky - is it myth or reality? There is one thing for sure however, and that is that the role of quality of the barley, the making process, and the nature and quality of the casks where it was aged is very important. According to some specialists, this could be good for 95% of the final quality of a malt whisky. To have the right to bear the name of whisky, a grain spirit must be aged at least for 3 years in an oak cask. Unlike Cognac which is stored in new casks, the Scottish always use second hand casks.
The oak casks are classified by capacity. The shape of the casks is mainly due to historic reasons, related to storage problems on ships. Sherry was carried on Spanish gallions, and the slender shape of the butts was the best for storing on this kind of ships, while the Portuguese Port was stored in a more bulbous cask, which was easier to carry on Portuguese merchant ships. Often whisky is aged for a while in bourbon casks finishing his aging period of 6-12- months in some kind of other cask, in order to give it some new fragrances, before bottling. This explains the "wood finish" mention on some bottling's.
A whisky cask is always a second hand cask. It generally contained Bourbon or Sherry. Other casks are used too, like Port, Madeira and more rarely Claret or rum. Some of them are very expensive, probably because of the rarity of the casks. However, there is a question about this wood finishes. If the aim is to give some new and pleasant fragrances to the whisky, it is clear that this method is used sometimes to hide some distillation errors. Often, the casks are warmed up before transferring the whisky, in order to accelerate the fragrance transfer. Such practices are not acceptable, because the consumer has no way to know about this.
There is a very big cask industry. There are about 100 active distilleries all over Scotland. The average production of each of them is between 1.200.000 and 2.000.000 litres a year. To deserve the "Scotch label", whisky must stay at least 3 years on the Scottish territory in oak casks. Assuming that the annual production is about 150.000.000 litres, the absolute minimum of whisky stored in Scotland is 450.000.000 litres.
This only to guarantee the legal right to be called Scotch whisky. This is without taking in account the huge quantity of whiskies which are aging for 10 to 30 years. On the other hand, the casks used for storing whisky are never new ones. It is thus very important to maintain the casks in good state. Some distilleries have their own cooperages but most of them prefer outsourcing this to specialized companies. There are lots of cooperages in Scotland, and the most famous of them is the Speyside Cooperage, situated half way between the Glenfiddich distillery and Dufftown (see above picture). This cooperage has about 300.000 casks in stock. All of them need reconditioning. There are about 20.000.000 cask all over Scotland. A cask can be (re)used for a maximum of 60-70 years.
The angels share:
The advantage of oak for maturing alcohol is that it is not airtight. It lets surrounding air enter the cask which explains the salted taste of a whisky aging near the sea, but it also lets evaporate the whisky it contains. It is generally admitted that between 1 and 2% a year evaporates this way. Evaporation can affect the water contained in the cask, but also the alcohol itself, resulting in a diminution of the alcohol percentage. That is called "the angels share". However, this percentage is theoretical, because this could result in a strange situation, as old whiskies (30 years and more) would lose their right to be called whisky. Indeed, assuming a whisky has about 70% of alcohol when it leaves the spirit still, and loses about 1% of alcohol a year a 30 years old whisky would just have a percentage of 40%, which is the lowest limit for a whisky. The angels share is indeed the part of alcohol which escapes to excise rights. Excise rights are calculated on the amount of alcohol coming out of the still and not on the amount of water. As this amount is diminishing over the years, the marketed whisky would be taxed using the alcohol percentage it had when it was distilled.
The nature of the warehouse is also very important. A damp or a dry cellar will influence the evaporation of the spirit differently. In a dry concrete cellar, water will evaporate mainly, letting a dryer whisky with a higher alcoholic percentage. In a damp warehouse with a beaten-earth floor the alcohol will evaporate, letting a rounder whisky with a smoother taste.
Bottling is the last step before putting the whisky on the market. Unlike wine, whisky does not mature anymore in the bottle. So 12 years old whisky stays 12 years old even 12 years later, and does not become a 24 years old one. When bottling, some residues are left in the whisky. The effect of this is that whisky looks "cloudy", and this is not always appreciated by the consumer. That's why distilleries found out the "chill filtering", which removes all this residues. The problem with chill filtering is that it also removes parts of the fragrances and of the taste. With the current revival of single malt, more and more bottlers bottle their whiskies without chill filtering.
During bottling, the alcohol percentage is reduced. This is the other operation where the quality of water has a great influence on the taste of whisky. The minimum percentage of alcohol for whisky is 40%. Most of the bottles are marketed at this percentage, because the excise rights are calculated on the alcohol proportion in the bottle. The excise rights are particularly high in Great Britain, but in other countries they are lower. That's why on the international market, whiskies are frequently bottled at 43%. For some technical reasons, the ideal percentage for bottling without chill filtering seems to be 46%. Most of the non chill filtered whiskies are marketed at 46%.
Often whisky is not diluted when bottled. That's called cask strength bottling. Generally, the casks are mixed before bottling, to get a more standardized product, just like great wines. When the whisky comes from just one cask, it is called "single cask".
Most of the distilleries do not bottle their own whiskies, but let this happen at specialized plants. Exceptions among others are Glenfiddich, Springbank, Bruichladdich and Loch Lomond. Even if they do not bottle themselves, the responsibility of the bottling stays from the distillery. This is called "official bottling". This operation happens often in the suburbs of Edinburgh where several bottling plants are installed, belonging to distilleries or to independent bottlers.


Further pages on this story - Facts of Scottish Whisky

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© Crann Tara 2006