Peated whisky is made by using barley that has been dried with peat smoke during the malting process. Peat is organic plant matter, particularly moss, that has partially decomposed and been compressed over thousands of years in the boggy terrain so abundant in Scotland and Ireland. 

The smoky flavour in your whisky comes from organic compounds in the peat smoke called phenols. When peat smoke is used in the malting process to dry the wet barley, some of the smoke’s phenols adhere to the outer skin (husk) of the barley grains. These phenols remain in the peated barley throughout the rest of the journey as it is fermented and distilled into whisky, although some of the whisky’s phenolicity is lost naturally during the distillation and ageing process. 

The strength of the phenolic peaty flavour in malted barley and whisky is measured in parts per million (ppm). Phenols are so potent in flavour that even low phenolic intensities of only a few parts per million can be detected and recognised as peatiness by our noses and palates. A batch of barley that is peated to 25ppm may produce a whisky with around 8-15ppm depending on distillation and maturation factors, and still taste incredibly smoky and peaty to us. 

Peated whisky is most closely associated with Islay, the Western Hebridean island home of world famous distilleries such as Laphroaig, Lagavulin and Ardbeg. These three distilleries (and the revived Port Ellen distillery) are all located on Islay’s south coast and have historically produced the island’s smokiest, peatiest whiskies. While other Islay distilleries such as Bunnahabhain and Bruichladdich traditionally produced unpeated or very lightly peated whisky, nowadays the demand for peated whisky is so high that all of Islay’s distilleries produce at least some peated or heavily peated single malt whisky each year.

Phenols are complex organic compounds, and the flavours produced in whisky from peated barley can differ widely depending on a range of factors in the whisky-making process. Some of these factors include how much of the barley’s husk is retained when it is milled before mashing, the length of fermentation, the distillation speed and the length of maturation.

When peat is burned to dry barley, it is burned slowly to maximise the amount of smoke. As a result, this smoke imparts different phenols carrying both earthy, mossy flavours from the partially burnt peat, and smoky, ashy flavours from the fully carbonised peat. The flavours in whisky caused by these different phenols are manifold and can be broken down and subdivided in various ways ad infinitum, but broadly speaking peated whisky flavours can be classified into three types: Earthy, Smoky and Medicinal. 

Some typical Earthy phenolic aromas and flavours include soil, moss, heather, seashells, bacon, smoked fish, turf and wet peat. Common aromas and flavours in the Smoky type include ash, bonfires, tar, bitumen, burnt cereals, woodsmoke and the like. In between these two main groups are the Medicinal flavours like TCP, iodine, creosote, carbolic soap, bandages and so on.

Peated whisky doesn’t just come from Islay, of course. In the old days before industrialisation and commercial maltings, most if not all of Scotland’s malted barley for whisky production would have been dried with peat, and the tradition remains in many of Scotland’s distilleries. Arran, Jura, Tobermory, Raasay, Highland Park, Talisker and Torabhaig distilleries all make peated single malt whisky too, and that’s just the Island distilleries. 

On the mainland, Ardmore, Benriach, Brora/Clynelish and Springbank are probably the most famous of the mainland distilleries that have made medium or heavily-peated malt whisky for decades, but peat is present to a lesser degree in the malt recipes of most Scottish distilleries - it’s not always obvious, but peated barley has a part to play in the complexity of many great Highland and Speyside drams from Longmorn and Glen Keith to Ben Nevis and Loch Lomond.

This is all a far cry from the dark days of the 1980s and early 1990s when peated, smoky whisky was out of fashion and distilleries like Bruichladdich and Ardbeg were faced with extinction. The turnaround was remarkable: in the mid to late 1990s, perhaps fuelled by memorable Port Ellen and Brora whiskies released in the Rare Malts series and Glenmorangie’s revival of Ardbeg, suddenly peated whisky came back into favour with a vengeance. 

By the early years of this century popular peated malts like Lagavulin 16-year-old were having to be strictly allocated at whisky retailers as there simply wasn’t enough stock following the cutbacks of the previous twenty years. And the peated whisky revival didn’t stop there - soon distilleries outside Scotland were getting in on the act too.

The Cooley distillery in Ireland was always a step outside the mainstream. Founded in 1988 as the only independent Irish distillery of the era, Cooley’s owners the Teeling family were able to call the shots for themselves, and decided to practise double distillation instead of triple distillation - and to launch what was at the time Ireland’s only peated single malt whiskey, Connemara, in the late 1990s at the height of the new craze for peated whiskies. Cooley’s Irish whiskey innovations caught the mood of the moment with adventurous whiskey fans eager to experiment and thirsty for all things peaty, opening the floodgates for peated whiskies made outside of Scotland. 

Meanwhile, over in Japan the Yoichi and Hakushu distilleries had begun making peated single malt whisky even earlier. Japanese whisky is dominated by the duopoly of Suntory and Nikka, who don’t follow the Scottish practice of swapping whisky with each other for blending purposes. This means that if they need smoky whisky for their blended whiskies they have to make it themselves - and that was exactly what was happening at Hakushu and Yoichi, whose long-aged peated whiskies from the 1980s and ‘90s are now highly prized, and change hands for prices that would have been unthinkable only ten years ago.

Today, the list of distilleries from all around the world that are making peated whisk(e)y is far too long to list here, but peated single malts are being made in countries including Sweden, Wales, Denmark, India, USA, and New Zealand just to name a few. From the doldrums of the 1980s, peated whisky is now more popular than ever - and long may it continue.