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Peat
The decayed vegetation of bog land anaerobically decomposed over thousands of years and partially carbonised by chemical changes to a sort of precursor to coal.

The vegetation includes mosses, bog myrtle, bog cotton, heather, sedges and grasses. For it to develop, the climate must be cold and wet, the drainage must be poor and the ground poorly aerated. The result is an acidic bog. There are environmental concerns about destroying peat bogs. The whisky industry however uses a small amount and it is therefore not so environmentally damaging. Some peat bogs are 10,000 years old, the layer of peat being as deep as nine metres, sitting like a sponge on top of the bedrock.

In the traditional hand cutting method, the growing sward is removed, and replaced where the previously dug peats have been taken, ensuring that the sward continues to grow – albeit a metre lower down than before. The peats from under the surface (the ‘top’) are crumbly, rooty and oily, which is what the maltsters want for kilning. The deeper peats, the ‘second’, are darker and burn hotter, and the deepest of all (the ‘third’ ) about four to five feet below the surface, dry hard and black, almost like coal. These are the best domestic peats.

The peat is then sliced with a cow-horn topped peat spade, a fal in Gaelic, making an evocative ripping, tearing sound, as the roots are cut. A wet, slippery, spongy black rectangle is removed (a one foot peat represents about 3 thousand years of time) and is placed on the sward. The individual peats are then spread out to dry, where they shrink by two thirds in size as they dry over the summer months.

Mechanical cutting is now more efficient, with a plough-like device towed behind a tractor.

The smoke produced by peat is highly aromatic and oily, and if malt is dried over it, these aromas – called ‘phenols’ by chemists – stick to the grains (coal smoke does not) and ultimately flavours the whisky made from them.