Whisky today is universal, but it is most frequently associated with Scotland, Ireland and the USA.  

Scotch Whisky is a spirit with a minimum alcoholic content of 40% and is distilled in Scotland on Pot Stills and/or Column Stills from a recipe of 100% malted barley or a mix of malted barley and other grains.

The resulting spirit must be aged in oak casks in Scotland for a minimum period of three years before it can be called Scotch Whisky.  No other ingredients apart from water, yeast and grains can be used, and the final product cannot be artificially flavoured - the only permitted additive is caramel colouring (E150). There’s a few other rules and some qualifications to the above, but this is the essence of it.

We’ll get into the specific types of Scotch Whisky shortly, but first let’s run through how whisky is made. 

Making Malt Whisky

The creation of single malt whisky depends on five key processes: malting, mashing, fermentation, distillation and maturation. 

The 'malt' in single malt whisky is malted barley - but what is malting? Malting is a process that turns starches inside the barley grain into fermentable sugars and it's an essential first step in making whisky. 

Malting

At the beginning of the malting process the grains of barley are steeped in water and then laid out or poured into a large horizontal ‘drum’ to begin germinating. During germination, the barley begins converting the starch inside the grain to sugars, and produces a small shoot called a rootlet. This is why germinating barley must be constantly turned - otherwise the rootlets would all grow together and the barley would turn into one big sticky lump.

The barley’s germination is then stopped by heating and drying the grains, usually with hot air but sometimes also with peat smoke (if you want to make smoky whisky). This stage is called Kilning, and it dries out the husk and locks the sugars into the grains before the barley can grow any further. The barley is now malted.

Mashing and Fermentation

The next key stage is mashing and fermentation, which is basically exactly the same as making beer. The malted barley is ground into a coarse flour called grist and hot water is added in a vessel called a Mash Tun, creating a thick, porridgey mix called Mash. More hot water is gradually added and the mash is stirred to dissolve the sugars. 

The sugary liquid from the mash tun, called Wort, is piped into a fermentation vessel called a Washback, where yeast is added and fermentation begins. Fermentation is the process where the yeast converts the sugars in the wort into alcohol, making a beer called wash. 

Distillation

The wash is then distilled, either two or three times, in copper pot stills. The wash is heated in the first still (called the Wash Still), and the alcohol vapourises, rising up the still to the neck, where it is directed by a pipe called the Lyne Arm into a Condenser. 

In the condenser, the alcohol vapour is cooled and condenses back into a liquid with an alcoholic strength of around 20-30%. This liquid is usually referred to as Low Wines. The spent wash left in the wash still is called Pot Ale and is drawn away. Pot ale is sometimes combined with the barley residue from the mash tun (known as Draff) and converted into feed for livestock.

The second distillation takes place in the Spirit Still. The low wines are pumped into the still and heated as before. This time, however, when the spirit percolates down from the condenser it is piped through a special glass chamber called the Spirit Safe. 

The spirit coming from the still is separated into three parts in the spirit safe. The liquids from the start and end of the distillation are known as the foreshots and feints, or the heads and tails of the spirit. These contain unpleasant or toxic compounds and are diverted away to a separate receiving tank for redistillation with the next batch of low wines.

This leaves the middle section of the spirit run, known as the Heart of the spirit or the Middle Cut. The middle cut is piped from the spirit safe to a tank called a Receiver. Each distillery will have slightly different 'cut points' in the spirit run between the foreshots, the heart and the feints, depending on the style of spirit they want to make.

This spirit is called New Make Spirit and will eventually become malt whisky, but first it must be filled into oak casks and sent to a warehouse to mature. The new make spirit is a clear liquid and is usually around 70% alcohol. Most distilleries dilute this spirit down to 63.5% before filling it into their casks.

In whisky-making, every decision about how to carry out these different processes is crucial. Most people know that the type of cask used for maturation is important, but the cloudiness of the wort, the duration of fermentation, the shape of the stills, the speed of distillation and even the type of condenser are all huge factors that will have a profound effect on the final character of the whisky.

Continuous Distillation

Grain whisky is distilled in a Column Still, also known as a patent still, continuous still or Coffey still. A column still is composed of two large metal columns (hence the name) known as the Analyser and the Rectifier. Both of these columns are filled with horizontal perforated metal plates. 

The cold wash is pumped down through the rectifier in a coiled pipe. The wash is heated in the pipe as it travels down through the rectifier, because it is meeting hot vapour coming in from the Analyser. 

This warmed wash is then pumped into the top of the Analyser, where it meets steam that is piped in from the bottom of the column. As the wash trickles down through the perforated plates, alcohol is vapourised and rises back up.  By the time the Wash reaches the bottom of the analyser all the alcohol in it has been vapourised and the spent Wash is drawn away.  

The mix of steam and alcoholic vapour rises and is piped into the bottom of the second column, the Rectifier, which is filled with another series of horizontal perforated plates. Here, the vapour meets the coiled pipes carrying the cold Wash. Cooled by the pipes, the vapour condenses into alcoholic liquid on the plates and is then vapourised again by the steam, rising up to the next plate where the process is repeated. At the same time, the heavier, oilier lower strength alcohols - the Feints - cannot rise all the way up the rectifier and eventually fall down to the bottom, where they are pumped back to the analyser. 

This elegant process continually strips the liquid from the alcohol, producing a purer and higher strength spirit on each plate as it travels up the still. The distiller can then draw off the spirit near the top of the still at their chosen strength. There is a Condenser at the very top of the rectifier, where the most volatile higher alcohols - the Foreshots - are condensed and drawn off for redistillation. 

This is a much more efficient process than pot still distillation, and can be run continuously, while pot still distillation can only be done in batches. Continuous distillation gives a high yield of a higher strength spirit and uses cheaper materials, meaning cost savings are significant over pot still distillation.

Maturation: The newly-distilled spirit is diluted from its natural strength down to around 63.5% and filled into oak casks. It is then matured in bonded warehouses for a minimum of three years. The majority of oak casks used to mature Scotch whisky are ex-bourbon barrels called Hogsheads that typically hold around 250 litres. 

The other traditional type of cask for Scotch whisky maturation is the Sherry cask, but nowadays many different types of wine and spirit casks are also used.  The most common of these are red wine, port and rum but Sauternes, Madeira, Calvados and even Champagne casks are sometimes used.

While it matures in the cask, the whisky interacts with the oak, gaining colour and flavour and losing some of the harsher edges of the raw new make spirit. Because of the porous nature of the wood, a small amount of the liquid and alcohol inside will evaporate over time - for tax purposes this loss is calculated at 2% alcohol per year, although in practice it may be significantly more or less for individual casks. 

As more air enters into the cask the oxygen also reacts with the whisky inside, creating new compounds in the whisky. The longer the whisky matures, the more these interactions with air and oak will affect the final flavour.

Grain Whisky is typically aged for shorter periods because the majority of this type of whisky is used for young blended Scotch whiskies. Single malts, on the other hand, are sometimes left to mature for decades before being bottled.

So much for the process of making Scotch whisky - let’s now have a quick run through the different types.

Scotch Whisky: To be classified as Scotch whisky, all the steps involved in making the whisky - from mashing and fermentation through to distillation and maturation - must have been carried out in Scotland. The maximum strength of the spirit taken from the still before dilution and ageing must be less than 94.8% and the maximum permitted size of the barrels used for ageing is 700 litres. 

Single Malt Scotch Whisky: To be known as Single Malt Scotch Whisky, in addition to all of the above conditions, the spirit must be made only with malted barley using pot still distillation at a single distillery in Scotland. Mixing together two or more single malt whiskies from different distilleries creates what is known today as Blended Malt Whisky (formerly known as Pure Malt or Vatted Malt). Single malt Scotch whisky must also be bottled and labelled in Scotland. 

In addition to the Single Malt Scotch Whisky classification, a geographical indicator of the region in which the distillery is located may also be used. These regions are the Lowlands, Highlands (including Islands), Speyside, Islay and Campbeltown. If this geographical term is used on a whisky’s label it must be placed before the rest of the classification, so Highland Single Malt Scotch Whisky is correct but Single Highland Malt Scotch Whisky is not.

Grain Whisky: Grain Whisky is the name applied to any whisky that has been made from a mashbill containing less than 100% barley, or any whisky that has been made on a column still. A mashbill of 100% malted barley distilled on a column still must be classified as a Grain Whisky, even though the same recipe distilled on a pot still would be Single Malt Whisky.

The most common grains for this type of whisky are wheat, corn and rye. However, Grain Whisky recipes must contain a small amount of malted barley, as this contains the Amylase enzyme required for the fermentation process to occur. 

Like malt whisky, grain whisky can be further classified either as Single Grain Scotch Whisky (if it’s from a single distillery) or Blended Grain Scotch Whisky (if the spirit was distilled at two or more distilleries). The same geographical indications as for Malt Whisky may also be used, eg Lowland Single Grain Scotch Whisky.

Blended Scotch Whisky: Mixing Scottish malt and grain whisky together produces Blended Scotch Whisky, the most common type of whisky sold today. Most blended Scotch whiskies are made by mixing several different malt and grain whiskies, with some blends containing whiskies from dozens of different distilleries.

The most recognisable examples of Blended Scotch Whisky in the UK are Johnnie Walker, Bell’s, Teacher’s and Famous Grouse, although other brands such as Chivas Regal and Ballantine’s are well known in international markets.