Single Malt whisky has existed for centuries but it’s really only in the last few decades that the popularity of this particular style of whisky has become a truly global phenomenon. 

Scotland’s single malt whiskies are at the pinnacle of the malt whisky category, but both Irish and Japanese single malt whiskies are also very popular and today exciting new wave single malt whisky is being made as far afield as India, Taiwan and Australia.

But what is single malt whisky and why is it now seen as the best kind of whisky in the world? Let’s start with a look at how single malt whisky is made.

The key stages in making single malt whisky are as follows:

1. Malting: Preparing the barley grains to convert the starch inside themselves into sugars.
2. Mashing: Adding hot water to produce a sugary liquid called Wort.
3. Fermentation: Adding yeast to the Wort to turn the sugars into alcohol - basically, making a beer called Wash.
4. Distillation: Turning the wash beer into a spirit by heating it in a Still. Alcoholic vapour rises up inside the Still and is condensed back into a liquid, producing a clear, highly alcoholic spirit. 
5. Maturation: The spirit is filled into wooden casks and left to mature.

Malting 

What is Malt? In single malt whisky, it’s barley that has had its germination process begun (by soaking the barley in water) and then stopped (by heating and drying it). 

Malting barley begins the process of converting the starch inside the grain into fermentable sugars. When germination begins, the barley uses an enzyme called Amylase in its husk to convert the starch inside the barley into sugar. Heating and drying the germinating barley stops the process before the seed can grow too much. 

The heating/drying process is called Kilning. For most malt whisky, hot air is used to dry the germinating barley, but for some whiskies peat smoke is also used. Peat smoke contains compounds called phenols which bind to the husk of the malted barley and give a peaty, smoky flavour to the final whisky.

To make Single Malt Scotch Whisky, only a recipe of 100% malted barley may be used. Other whiskies use a mixed recipe (often called a Mashbill) including other grains such as corn, wheat or rye.

Mashing 

The barley grains are ground in a mill into a coarse, floury substance called Grist and are then doused with hot water inside a large vessel called a Mash Tun. The resulting porridge-y Mash is stirred to complete the conversion and extraction of sugars from the grain - as the mash is stirred, the remaining starch dissolves in the hot water and is converted by the amylase into sugars. The sugary liquid in the mash is called Wort and is drained away for the next stage, leaving behind a thick mass of spent grains called Draff.

In Grain Whisky, malted barley and unmalted grains are milled separately and then mashed together so that the amylase from the malted barley can convert the starches from the other grains into sugars.

This is one of the reasons that Grain Whisky is cheaper to produce than Single Malt Whisky - malted barley is expensive compared to the other types of grains, which don't undergo the expensive, time-consuming malting process, while the efficiency of the amylase in malted barley means that only a small amount is needed to make grain whisky.

Fermentation 

The Wort is piped from the Mash Tun into the Fermentation vessels. These are very large wooden tubs or steel tanks called Washbacks, where yeast is added to begin fermentation. Yeast is an organism that ingests sugar and excretes alcohol. This process usually lasts between 2-5 days and turns the sugary Wort into an alcoholic liquid called Wash, which is basically a strong beer.

Distillation 

Distillation is the process of boiling the alcohol out of the wash and then condensing it in a much smaller amount of liquid.  For single malt whisky, the wash is piped into Pot Stills - essentially enormous copper kettles - where the liquid is heated by steam-heated pans inside the still.

Pot stills are made out of copper for several reasons - copper's malleability works well for the construction of the unusual shape of whisky stills, but also the copper itself is crucial in distillation for the reduction of unpleasant sulphury compounds that would otherwise affect the final flavour of the spirit.

Single malt whisky is distilled at least twice, although there are some distilleries in both Scotland and Ireland who distil their spirit three times, and others who do a mixture of double and triple distillation.

As alcohol has a much lower boiling point than water, the vapour that comes off the wash is rich in alcohol. This vapour rises rapidly up inside the neck of the wash still which narrows to a pipe at the top (known as the Lyne Arm). From the lyne arm the vapour is piped through a Condenser, where it is cooled and condenses into a liquid which is stored in a tank called a Receiver.

The liquid from this first distillation in the wash still is called Low Wines, and is generally at an alcoholic strength of around 20-30%. The spent wash left in the wash still is called Pot Ale and is often combined with the draff from the mash tun and converted into feed for livestock.

The low wines are directed from the receiver into a second still, called the Spirit Still, where the same process happens again, concentrating the alcohol within the liquid that forms in the condenser.

The condensed spirit from the second distillation runs through a glass chamber called the Spirit Safe, where the heart of the spirit is separated from the unpleasant or toxic compounds that arrive at the start and the end of the distillation. 

These are called the Foreshots and Feints (or heads and tails) of the distillation and are diverted away from the ‘middle cut’ which is the good spirit that will eventually become whisky. The foreshots and feints are kept in a separate receiving vessel and then returned to the spirit still to be redistilled with the next batch of low wines from the wash still. 

The timings for the ‘cut points’ - the moments when the foreshots and feints are separated from the heart of the spirit - are crucial. If the cuts are made too early or too late they can result in the loss of perfectly good spirit, or spoil the entire batch.

Now that we know how single malt whisky is made, let's have a look at how the single malt whisky market has developed in modern times.

The Fall and Rise of Single Malt Whisky

The Scotch whisky that took over from Cognac as the world’s most popular distilled spirit in the late 1800s was of course blended Scotch whisky, and even today the vast majority of Scotch whisky made, sold and consumed is blended whisky.

Nowadays, though, while blended Scotch whisky is still the dominant category in sales and volume, single malt whisky is acknowledged as a superior drink in terms of flavour and complexity. Of course, these have always been established facts among connoisseurs of malt whisky, but given today’s exalted prices for the oldest, rarest single malts it’s incredible to think that fifty years ago most Scottish producers didn’t think enough of their own single malt whisky to consider it worth bottling. 

Prior to the late 1960s, the commercial possibilities of single malt whisky were almost completely ignored by most producers. Single malt whisky was made almost exclusively for blending purposes, and the majority of malt distilleries had no official bottling. Fans of single malt whisky had to scour through specialist merchants for independent bottlings of single malt from pioneers such as Cadenhead’s and Gordon & MacPhail; outside of Scotland itself the choice rarely extended beyond the occasional bottle of Glenfiddich, Glenlivet or Macallan.

All this was soon to change, although more by necessity than from any savvy business decisions - rather, the revolution in single malt whisky that took place in the 1980s and 1990s was the consequence of a self-inflicted commercial disaster that resulted in the loss of some of the world’s greatest distilleries.

The modernisation of many of Scotland’s single malt distilleries that took place in the 1960s and 1970s was, in retrospect, a turning point in Scotch whisky history affecting both the character of Scotland’s national spirit and the destinies of many of the places that made it.

During this period most producers were seeking to increase output. Sales of blended Scotch whisky were buoyant and the modernisations were used as an opportunity to greatly expand capacity across the industry in order to meet the confidently-predicted extra demand as blended whisky continued its expansion in world markets.

There were two very significant problems with this scenario. 

The first was that in the modernisation of the distilleries throughout the 1970s, something crucial in single malt whisky was lost. In short, the baby got thrown out with the bathwater as quality was sacrificed for quantity. 

While distilleries were ripping out old malting floors, speeding up fermentation and distillation times, installing new stills, converting from direct fired to steam heating, replacing worm tubs with shell condensers, and changing barley strains and yeast types to squeeze out ever greater yield, they didn’t realise that all these changes were going to have huge ramifications for the character of their spirit.  

At the time, the character and purity of the water used in the distillation process was seen as sacrosanct and crucial to the final product. It was only later that it was discovered that, despite being whisky’s main ingredient, the water’s contribution to the character of the spirit was absolutely negligible. 

It transpired that as long as the water was clean and uncontaminated, the whisky would be fine and changing the water source would have zero discernible impact on the final product. Yet even today some distilleries are still trotting out this disproven myth of the importance of the water to the distillery’s output. 

What the great modernisers of the 1970s hadn’t realised was that all the quirks and individuality of their whiskies were actually coming from everything that they had rushed to get rid of in the drive for efficiency and greater output.

The character of a whisky distillery’s new make spirit rests in the barley that it is made with, and how it is fermented and distilled. Changing any aspect of either fermentation or distillation can have profound consequences on the spirit’s characteristics, even before it goes into the cask for ageing.

The first problem, then, was that the extra whisky that was made following the modernisations was not as good as the spirit made at the old, unmodernised distilleries. The consequences of this mistake were not discovered until much later, by which time it was too late to fix. 

The second, more immediately serious problem faced by the newly-modernised and expanded distilleries was that the extra demand they had been adapted to fulfil never materialised.

Towards the end of the 1970s, whisky fell out of fashion: a resurgent cognac had become the choice of mature sophisticates, while younger spirits drinkers turned to cocktails and vodka. At the same time, the overseas markets failed to take off as expected.  Instead of the predicted jump in global demand for whisky, sales flatlined and then fell off a cliff.

The result of the Scotch whisky industry’s over-optimism was a catastrophic whisky lake, with millions of litres of unwanted single malt whisky sitting getting older in warehouses all over the country. The consequences were inevitable; whisky companies cut back on production and between 1983 and 1985 no fewer than sixteen of Scotland’s single malt whisky distilleries were forced to close; a further six distilleries shut their doors permanently before 1994.

This dreadful, needless calamity still haunts the Scotch whisky industry today - but from the ashes of their greatest failure, the distilleries inadvertently stumbled into a slow and painful revival.

Prior to the 1980s, the accepted general wisdom in the industry was that 8-10 years of maturation was more than sufficient for single malt whisky; having casks of 15 or 20-year-old whisky in your warehouse was considered by many distillers to be poor cask management.  

But in the late 1970s and early 1980s, with hundreds of thousands of casks of maturing whisky and very little demand, the distillers were faced with a problem of what to do with their surplus stock. Many began adding older casks of whisky to their blends and a lot of new official bottlings were released from distilleries that previously had not bothered bottling their single malts at all.

At the same time, those distilleries that already had standard bottlings, notably Macallan, Highland Park and Glenmorangie, began releasing older expressions - indeed, Macallan’s Anniversary bottlings, arguably the very beginning of today’s luxury whisky category, first appeared in 1983 at the height of the crisis.

By the late 1980s most of the big name distilleries had 15-year-old or 18-year-old editions and some, like Springbank and Macallan, were bottling even older single malts. In the meantime, though, an enormous number of casks of single malt whisky had been sold to independent bottlers at knock down prices by distillers desperate to make ends meet.

Inevitably the nimble independent bottlers such as Gordon & MacPhail, Cadenhead’s, the Scotch Malt Whisky Society and later Signatory and Douglas Laing, were able to fast-track top quality casks of aged single malt to the market. These indie bottlings were enthusiastically received by a new audience of whisky fans who often found to their surprise that the cheaper independent bottlings were frequently much better than the official releases.

The growing interest in the single malt category through the late 1980s and 1990s led to the bigger companies seeking to replicate the success of the independent bottlers. Diageo’s predecessor United Distillers released three seminal collections in the shape of the Classic Malts range, the Flora & Fauna series and the cask strength Rare Malts Selection between 1988-1995. 

Both the Classic Malts and the Flora & Fauna series are still going strong today, while the Rare Malts range was eventually replaced by the Diageo Special Releases, now in their 20th year and the most important event in the calendar for the promotion of long-aged prestige single malt whisky.

Throughout the 1990s and well into the present century the whisky industry was preaching a constant sermon that older whisky was better in order to shift their ageing stock, and prices for aged whisky were rising accordingly. It was only around the mid-Noughties that many companies suddenly realised that this mantra was going to become problematic when they no longer had aged whisky to sell, as the production gaps from the shutdowns of the 1980s began to bite.

Thus it was that the next broad trend in official bottles of single malt Scotch whisky emerged - the rise of the No-Age-Statement (NAS) bottling. For many of the large producers, this entailed the necessity of switching their message from ‘Older = Better’ to ‘Age Doesn’t Matter’. 

NAS bottlings were introduced to take the pressure off sales of age-statement distillery bottlings as stock became squeezed. The NAS trend is very frequently combined with the other defining style of single malt whisky that emerged in the late 1990s - the ‘finished’ whisky. Finishing is the art of reracking whisky from its original cask into a second type of cask - usually a wine cask, although rum and other spirits are also used.

The advantages of combining NAS with Wine Finishes are obvious on paper - most drinkers are looking for complexity, a quality that is generally in short supply in young whisky. By moving a maturing whisky from ex-bourbon or refill casks into a fresh wine cask, the young whisky will pick up new flavours (usually of cooked fruit) within a very short period. 

Not all of these whiskies are as successful as their aspirational price tags would suggest, but when it is done correctly, ‘finishing’ a whisky can definitely result in an interesting dram, though not always one that would encourage repeat purchases. Most NAS whiskies are therefore marketed as limited editions. 

The single malt whisky market today, it goes without saying, is unrecognisable from the situations of forty, thirty or even twenty years ago. The whisky available now from most distilleries is also very different from its ancestors - a consequence of the previously-mentioned rush to modernisation in the 1970s. 

The best spin that can be put on this scenario is to argue that the top and bottom limits of quality have narrowed - so there is less bad and less brilliant whisky but overall the quality of the average whisky has gone up. This is a difficult position to defend when one tastes the standard bottlings of single malt whisky from the 1970s and 1980s, which are almost universally better than their modern-day equivalents.

All of this is not to say that there is no good single malt whisky being made today - on the contrary, there is plenty of great whisky available today, and much of it is young whisky. This is thanks to the improvements in the understanding of the importance of fermentation, distillation and, most significantly, maturation - the wood policy at most distilleries is now meticulously micro-managed.  

Sadly, the quality of available new sherry casks today is markedly inferior to the superb sherry casks used in the 1960s-1970s due to the collapse of the sherry industry in the meantime. This has had a profound effect on the general standard of sherry-matured whisky, which tastes very different to its forebears from the golden age - although it is argued within the industry that the 1988 ban on the use of paxarette (a concentrated sherry-like syrup) is also a factor here.

In practice, the best young single malt today is that simple, unpretentious whisky that has been matured for 8-12 years in refill casks. These whiskies allow the wood to do its job of removing the undesirable harsher notes in the spirit and adding some oak influence - but not too much to hide the character of the spirit, a trap that many wine-finished NAS whiskies are still falling into. 

It is ironic that the distilleries that follow closest to the best practices of the pre-modern era - slow fermentation, unhurried distillation, traditional casks - are producing the best quality and most successful modern whiskies of today.