Earlier this year, scientists fired molecules of unaged malt into outer space in order to explore how whisky ages in a micro-gravity environment. While we wait for the results of that experiment back on Earth, I thought it would be a fitting moment to sip a dram of “Ardbeg Galileo,” a delightfully fruity new bottling from Islay, and ponder the wonder of wood ageing.
Up to 70 per cent of a whisky’s flavour comes from the cask it’s aged in. You can distil the finest spirit in Christendom, but if you age it in a lousy cask you’ll end up with lousy whisky. This is because the cask performs a variety of quasi-mystical feats, absorbing unpleasant sulphury notes and rounding off rough edges in the young spirit while, in turn, imparting colour, flavour and complexity as the whisky moves gently in and out of the wood’s pores.
Scotch whisky must, by law, be aged in oak (people have tried other woods but they simply don’t work as well). The two most common types are American oak, which is normally imported in the form of cast-off casks from the US bourbon industry (bourbon distillers are only legally allowed to use each cask once), and European oak in the form of ex-sherry casks (typically oloroso sherry, but occasionally fino or PX sherry).
If the whisky you’re drinking has big notes of vanilla, coconut or bananas, then it’s probably been aged at least partially in American oak—Glenmorangie are masters in this department and their Glenmorangie Astar is a massive, creamy bourbon cask bomb. European oak, by contrast, tends to contribute more dried fruit and spicy Christmas cake flavour, beautifully typified by Orkney’s Highland Park 18 year old.
Less common in whisky production, but a mainstay of cognac making, is French oak or Quercus Petraea. Pitched somewhere between US and European oak in terms of flavour, French oak has been skilfully employed by artisan whisky blending company Compass Box in their Spice Tree whisky, a bold blend of Highland malts full of fiery stem ginger in syrup, silky crème brûlée and a touch of soot.
The rise of Japanese whisky has also introduced Japanese oak, or mizunara, into whisky distilling. Expensive, difficult to cooper and prone to leaking, it’s a tricky wood to work with, but in the right hands it produces whiskies with an exotic, incense-filled note. The new limited edition Yamazaki Mizunara,…