How Whisky is Made - Single Malt

surgar and barley

1. Malting

All single malt whisky starts its life as simple barley, and as we know alcohol is created by fermenting sugar. So, before anything else, sugar is needed. Fortunately, barley is packed full of starch, which can be broken down to release its sugars. The traditional method for this is to steep the barley in water, and then spread it across the malting floor to let it germinate. The barley is left on the floor for around five days, during which time it needs to be turned and flipped to ensure all grains germinate evenly – this is done by hand, at precise intervals.

Once the starch has become sugar, the germination process is stopped by drying the barley in a kiln, and it’s at this stage that the unique peat can be used to impart its characteristic smoky notes. With or without peat, the barley is dried using hot air from a fire below, and we then have our malt ready for the next step.

(That’s quite a chunk of work, so no wonder most distilleries source their malt from large, purpose-built maltings. A few distilleries do still produce their own malt, Laphroaig, Springbank, and Bowmore, are good examples of this.)

milling illustration

2. Milling & Mashing

With the malt ready, it’s time to mill it into a coarse flour, called grist. The grist will be added to hot water to extract the sugars, so the coarseness of the grist is vital – too fine or too coarse will prevent the sugars from properly being extracted.

To extract the sugars, the grist is mixed with hot water (a process called mashing, done so in something called a mashtun) at varying degrees. Mashing is done three times, with the temperature of the water being increased each time – to help extract every drop of sugar possible. Though the final extraction doesn’t result in high enough sugar levels, and thus is reused in the next batch.

The resulting sugar solution is then cooled in a cooler, and is now known as wort. And don’t worry, all of that leftover isn’t wasted, it’s sent off to be used in the production of animal feed!

fermentation illustration

3. Fermentation

With the wort now cooled, it’s added to the washbacks along with yeast to ferment. This process can take anywhere from two days to four days – the length of fermentation is yet another huge factor in the final whisky’s characteristics. During this time, the yeast will convert the sugar into alcohol. Once done, we’re left with what the Scots call wash that has an alcohol content of around 9%. Time to bolster that number… Significantly!

distillation illustration

4. Distillation

Single Malt Whisky is always double distilled at least, with a handful of producers using triple distilling (most notably in cases such as Irish whiskey). This is done with two copper stills, the first and larger of the two is called the wash still, and the second, smaller one is called the spirit still. The distillation process occurs when the stills are filled, heated, and the alcohol within evaporates. The evaporated alcohol travels up the neck of the still, and into the condenser where it becomes liquid once more. During this process, the shape of the still has a major impact on the final whisky’s characteristic – the general rule of thumb is that short, fat stills produce richer and heavier palates; whereas tall, slender stills produce lighter and more gentle palates.

Once the wash has entered and gone through the wash still, it reaches an ABV of around 20-25% and is called low wines. The low wines is then sent directly to the spirit still, at which point it becomes one of three things:

  1. The first small liquid that runs through the spirit still is called the foreshot, which can contain poisonous methanol (modern yeast strains don’t produce this so we’re safer now!)
  2. The most important part, the middle cut, is what will actually be extracted from the spirit still; and
  3. The feints, which are heavy in fusel oils, are then cut off and sent back through the spirit still during the next batch. Fusel oils are in fact the main contributor to getting headaches, so it’s cut off very early, thankfully. The timings of this process are controlled by the stillmen using samples that go through the spirit safe, this is an integral step in the process that’s not only manually done, but will ruin the batch if done poorly.

5. Maturation

The new make whisky is completely clear at this point, like pure spring water, and it will gain its trademark colour from maturing in barrels. These barrels can vary greatly, from wood type, size, and even what it was previously used for. For it to be whisky by law, it must remain in barrels for at least 3 years prior to bottling, though of course many releases spend a lot more time than that.

maturation illustration

The barrels are traditionally stored in earth floored, dark warehouses, and are traditionally stacked horizontally in 3 to 6 rows, known as dunnage. During the maturation process, a lot happens inside the barrel, with a few more notable points:

  • The outside air gets into the whisky, and can in fact impart new flavours and aromas
  • The alcohol in the whisky slowly evaporates, and then escapes through the pores of the barrel, meaning each barrel lowers in volume and in alcohol content each year! This loss is known as the Angel’s Share.
  • The whisky extracts element from the wood of the barrel, taking on characteristics of the wood used, as well as some lingering flavours from the barrel’s previous occupant.
  • The charred insides of the barrel provide charcoal that acts as a filter to get rid of undesirable particles in the whisky.

6. Bottling

Once the maturation process has completed the desired length of time, all of the chosen barrels (and yes, people do get paid to taste each and every barrel, the lucky dogs!) are then blended together prior to being bottled. Of course, if the whisky you’re enjoying states that it’s a single barrel/cask release, then it was bottled directly from the barrel, without being blended with its brothers and sisters first.


bottling illustration