Islay: The Island of Peat and the Source of Smoke

Key facts

Location

about 55.8°N, off south-west Scotland

Legal status

protected Scotch locality

Source of smoke

phenols from peat fire during kilning

ppm

measured in the malt, not the whisky

An island at 55.8°N

Islay is one of the Inner Hebrides, at about 55.8°N off the south-west coast of Scotland.

It takes the Atlantic weather head on: cool, wet and windy for most of the year. That wet climate is why so much of the island is peat bog.

Most of the island’s distilleries sit on the shore, because barley, fuel and casks once came and went by boat.

Under Scotch law Islay is a protected locality, so a label can say Islay only if the whisky was distilled on the island.

What peat is

Peat is partly decayed plant matter that has built up in waterlogged ground over thousands of years.

Where the ground stays wet and cold, dead plants rot very slowly and pile up in thick layers. Cut and dried, peat burns, and on a largely treeless island it was the household fuel for centuries.

Peat varies by place. Coastal island peat holds more mosses, heather and sea-influenced plant life, while mainland peat tends to carry more woody roots and shrubs.

Drying the malt over a peat fire

The smoke enters at the kiln, when the malt is dried, not in the cask.

After barley has been steeped and allowed to sprout, it is dried to stop growth. If peat is burned during the early, damp stage of drying, the smoke passes through the wet grain and its phenols stick to it.

Part of those phenols survives fermentation and distillation and ends up in the spirit. A charred cask can add some toasty or burnt notes, but it is not the source of peat smoke.

Today most distilleries take their malt from large commercial maltings, peated to the level each distillery specifies. Only a few still malt part of their own barley.

Not every distillery on the island is heavily peated

Islay does not automatically mean smoky, because the peating level is a choice each distillery makes, not a property of the island.

Some distilleries work mostly with heavily peated malt, some with light peating, and some make whisky with almost none. One distillery may also release both peated and unpeated whisky.

The reverse holds too: smoky whisky can be made in any region with peated malt. The word Islay gives you the location; for the smoke, look for the word peated or other detail on the label.

• ppm (parts per million) is the phenol level measured in the malt before fermentation
• It is not the phenol level of the whisky, since a share is lost in distillation and maturation
• Older whisky usually tastes less smoky than younger whisky made from malt of the same ppm

A ppm figure tells you whether the malt was lightly or heavily peated. It cannot rank two bottles against each other, because each distillery’s stills and casks change how much smoke survives.

Wind and sea

Islay whisky is often described as salty, briny or medicinal, but how much the sea itself contributes is still argued over.

Many distilleries sit on the shore, and some warehouses take the sea wind directly. One view is that years in damp, salty air leave a mark on the whisky in the cask.

Another is that coastal peat, with its sea-influenced plant life, gives the smoke a maritime edge at the kiln. Some Islay whisky is also matured off the island, so the coastal warehouse cannot be the whole explanation.

What is certain is that malt, stills and casks shape Islay whisky first; the sea is a secondary factor that is hard to measure.

Questions people ask