[Update: Aspects of the below article are considerably expanded upon and covered in more detail in our comprehensive feature piece, “The complete guide to oak and whisky maturation” which we suggest you head straight to now and read here. ]
Whisky maturation is a complex process. You’ve doubtless heard or read the oft-accepted mantra that the spirit’s contact with the wood during maturation contributes as much as 60-70% to the whisky’s final flavour.
When it comes to playing around with wood and cask experimentation, few do it better than Glenmorangie. Often credited with the innovation of “finishing” (although Balvenie may beg to differ), Glenmorangie was certainly the first to commercially release a range of whiskies where the whisky was matured primarily in one type of cask, and then given a second period of maturation in a different cask. The “Port Wood” expression was one of my early favourites, having spent 10 years or so in bourbon wood, before being finished for 6-12 months in port pipes.
20 years on, finishing is so common now, it’s passé. For some companies, it also makes economic sense: Not every distillery can afford to invest in expensive sherry casks for a 12 year maturation, but some impressive results can be had by re-racking the whisky in first-fill sherry butts for just 6-12 months. Not surprisingly, the results merge and marry the characteristics of the contributing parent casks, and any number of permutations and possibilities can be trialled. Tired or non-performing whiskies can also be rescued: For some distillers, finishing the spirit in a new or exotic cask can polish or breathe life into whisky that was flat or over-cooked. We won’t name names, but a number of resurrected distilleries have had to do this to rescue tired casks that were inherited when the distillery’s ownership changed hands.
Of course, that’s not to say that every combination or finishing exercise works. Or that putting good whisky into an unusual or exotic wine cask will evolve it into something better. Some result in drastic flavour clashes that serve only to confuse the whisky or destroy the spirit. Dr Bill Lumsden, Head of Distilling & Whisky Creation at Glenmorangie, has confided to me on several occasions that for every hit, there have been more than a few misses. Of course, The Scotch Malt Whisky Society can bear testament to this – the Society’s famous (infamous?) Hotscotch cooking whisky was the result of a failed attempt to mature whisky in casks that previously held Tobasco sauce!
But the main point to note here is that the industry is now trialling and experimenting with all sorts of cask types to develop new or improved flavours. The only limitation is that the casks must be made of oak – anything else, and the resulting drink cannot legally be called Scotch Whisky. But it is in the use of casks that previously held some other liquid that distilleries are now ploughing new fields.
The scientists at the Scotch Whisky Research Institute (yes, there is such a thing) tell us that 60-70% of the final flavour we taste in a freshly opened bottle of whisky can be attributed to the cask maturation. Or, in simple terms, most of the flavour comes from the wood! Little wonder, then, that distillers now focus closely on their wood regime and the quality of their casks.
It is now less common for casks to be re-filled a third or fourth time than it was a few decades ago. Many old or well-used casks now undergo a “de-char / re-char” exercise, where the exhausted inner surface of the cask is scraped back to expose fresh wood, and the cask is then re-charred or re-toasted. Charring aids the wood in removing sulphur compounds from the spirit, and also promotes fast lignin breakdown and caramellisation of hemicellulose, thus extracting considerably more guaiacols, isoeugenol and vanillin into the spirit. (In plain speak, it makes the whisky taste better!)
Not surprisingly, there are a lot of experiments going on right now with casks that previously held wines, and a trip through a distillery’s warehouse can reveal casks of all shapes, sizes and origins. Yes, sherry casks have long been in the picture, but I’ve walked through warehouses in Scotland and spotted burgundy barriques, port pipes, sauternes casks, tokay casks, pedro ximinez casks, madeira puncheons, rum casks, limousine oak, Spanish oak, quarter casks, bloodtubs, barrels, butts, and plenty of humble hogsheads.
Finished whiskies or whiskies matured in unusual, exotic casks are usually the domain of the OB’s or distillery bottlings. They’re rarely seen amongst the independent bottlers, although The Scotch Malt Whisky Society has bottled a few over the years. In addition to some sherry gordas, they’ve put out bottlings from re-fill port pipes, red wine barriques, port barriques, madeira hogsheads, white wine hoggies, limousine casks, and even a few virgin wood casks.
But let’s not lose perspective here…if finished or fancy casks aren’t your thing, you needn’t despair. 90% of all scotch whisky bought and sold today is still blended, and so single malt still only accounts for 10% of the market. And the vast, vast majority of this figure is made of the big brands’ flagship offerings that sell in huge quantities, e.g. Glenfiddich 12yo, Glenlivet 12yo, Glenmorangie “Original”, etc. There are a small handful of distilleries that seemingly release a higher component of exotic expressions (Bruichladdich, Benriach, and Edradour were particularly active in this regard), but their contribution to the big picture is still extremely small.
Ultimately, we should just be concerned with flavour. And if the cap fits…
Cheers,
AD
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