Whisky

Whisky is distilled from a fermented grain mash and aged in wood. Barley, corn, rye and wheat in some combination; the mix is called the mash bill and it sets the character before it has aged even a single day.

The spelling gets fussed over more than it deserves. Scotland, Canada and Japan write whisky. Ireland and the United States write whiskey. The memory aid: countries with an E in the name tend to use the E. In Scotland the spelling is enforced: under the Scotch Whisky Regulations a bottle of Scotch has to say whisky, and whiskey on a Scotch label is illegal.

Malting is the first move: barley is soaked until it starts to germinate, then dried to stop it. Germination converts starch into fermentable sugar; drying halts the process before the grain uses that sugar to grow. If the drying is done over a peat fire, the smoke leaves compounds called phenols in the barley - they're what tastes of smoke and tar - and they stay there through fermentation, distillation and years of ageing. That's where Islay comes from.

• Malt whisky - from malted barley, pot-distilled. Richer and more cereal-tasting, and where most of the flavour is.
• Grain whisky - from unmalted grain, usually corn or wheat, with a little malt in the mash to supply the enzymes. Column-distilled, lighter and cheaper.
• Single pot still - the Irish style: malted and unmalted barley together, pot-distilled. The unmalted share gives it an oily, spicy texture.
• Single malt - malt whisky from one distillery. "Single" means one distillery, not one barrel and not one year.
• Blended - malt and grain mixed, usually across many distilleries. The blender's job is consistency: a bottle this year has to taste like a bottle last year.
• Single cask - one barrel, bottled on its own. Here "single" does mean one barrel.

A barrel holds around 200 litres, and roughly 2% of it evaporates every year. That loss is called the angels' share, and it compounds: a whisky sitting for twenty years has lost a serious fraction of the cask before anyone opens it. This is most of why old whisky is expensive. The rest is that the distiller has had money tied up in a warehouse for two decades. The cask earns it: the usual figure is that 60 to 80 per cent of what you taste comes from the wood rather than the spirit, which is why one distillate in two barrels makes two whiskies.

American whiskey must go into new charred oak, which is why bourbon is sweet, vanilla-heavy and quick to take colour. Bourbon has three other numbers attached to it, all of them limits rather than recipes: a mash of at least 51 percent corn, distilled to no more than 160 proof, and into the barrel at no more than 125 proof. No colouring is permitted. Scotch mostly goes into barrels that have already held something else - ex-bourbon casks, which the Americans can't legally reuse, and sherry butts, which give the dried-fruit character. Japanese producers also use mizunara, a native oak so porous and hard to coop that the staves need three years' drying and the casks still leak; what it gives - sandalwood, coconut, incense - takes fifteen years or more in the wood to show.