The role of the wood cask in whisky maturation is critical. The interaction between the new make spirit and the wooden vessel is critical to the changes that occur to give us Scotch. Legally Scotch after just 3 years in an oak barrel. The extent that the wood influences the flavour of the whisky is hotly debated; 75% is often banded about as a benchmark figure. Sometimes, higher percentages have been chosen by those whisky people involved in the supercharging of whisky with flavours imparted by sherry casks.
In reality the influence will depend on the cask, the style of whisky being developed, the length of time in the barrel, and the barrel’s previous contents. I’ve had some whiskies where the cask influence was at least as low as 25%, with the new make character very forward and barely tempered. Those inactive barrels can have spirit in them for 20+ years and whilst it mellows, develops, and oxidises over time the wood itself has perhaps 35% influence on the total, with a strong spirit forward whisky remaining. I’m thinking here of some fantastic indie bottlings of Jura from a time when hogsheads were reused on site for 50 or 60 years without any rejuvenation.
At the other end of the spectrum we have extremely wet sherry casks used as finishing vessels, which all but obliterate the original whisky character and perhaps have 90% overall influence on flavour. I know that casks are shipped wet but have heard that, if less than four 70cl bottles of sherry are in the bottom, it’s a disappointment. You might speculate that leaving a little of the transport sherry in the bottom to supercharge the flavour would be tempting. For this style I think of the Cadenhead’s Tomatin PX Sherry Finish.
Casks were originally used for all sorts of liquids and goods before whisky was conceived in Scotland. These casks were strong, relatively easy to produce, efficient to pack and stack, and easy to move around by rolling them. Over time, oak was found to leak less than other woods. For a long time, the reuse of transport casks was extremely common. Reciprocal trading resulted in an abundance of sherry and rum casks; no doubt barrels from wine and other fortified drinks, too, floated around. Initially, the availability of casks drove the spirit profile. The decline of sherry consumption in the UK over 100 years ago put a strain on cask availability and Prohibition (of all things!) created a transatlantic trade that resulted in an abundance of bourbon barrels available to the industry.
The public still enjoyed the sherried style, and seasoning of casks with paxarette became common practice. This was only outlawed fully by the Scotch Whisky Association in 1993. These days, seasoning continues with sherry made specially for the practice; this can be a single variety or indeed special blends of different sherry types. These American oak seasoned sherry casks now account for 80% of all sherry casks used in Scotch. Alyssa did a great review of the requirements of “proper” sherry casks. It’s worth noting that non-certified casks are seasoned with sherry in places like France and Scotland too where Diageo has their own bodega.
Until very recently, all whisky that went into a cask remained in that cask for a full maturation before being disgorged and bottled. The only exception was occasional re-racking of a leaking cask into another cask.
In the early eighties David Stewart of Balvenie began to take American oak matured whisky and put into European oak sherry butts for a period of finishing, or a “second maturation,” as it is often described. The practice spread rapidly over the last 30 years, and now all sorts of finishes are applied by almost all of the Scottish whisky producers and independent bottlers.
Many producers have now finessed and honed the second maturation – or cask finish – into a reliable and repeatable way to charge the slightly bland American oak-matured whisky usually held in reused casks with a burst of flavour suitable for the consumer’s current palate.
Further innovation in cask maturation was led by the late Dr. Jim Swan, a whisky consultant who became the go-to guy for new distilleries bringing their young, fresh, three-year-old whisky to market. Dr Swan championed the STR (shaved, toasted, and recharred) approach. Using wine casks in which the wine – and the rejuvenation of the surface of the casks by shaving and recharring – in conjunction with the development of wood sugars through the toasting process allowed for the supercharging of flavour into very young spirit.
The technique, often used alongside some sherry casks and bourbon casks (such as in the Lindores Abbey Distillery inaugural releases) has been fairly successful with young spirit. STR casks have been used also by the Scotch Malt Whisky Society for older aged whiskies, to mixed reviews. Ardbeg have also experimented with cask preparation and rejuvenation for a number of their committee releases, including the heavily charred Ardbeg Alligator, named after the resemblance of the deep charring of the staves to the crocodilian skin.
Recent relaxation of the SWA’s rules in relation to new cask types further adds to the flavour options available to distillers and bottlers. Permissible types now include tequila casks and beer casks, amongst others.
One area of great confusion to consumers is the lack of labelling and details on casks in the secondary market. Often bills of sale will only state “hogshead,” without reference to the previous cask contents. This is most often bourbon, but remarkably frequently can be something else, such as refill sherry and even fresh sherry. Independent bottlers are restricted in labelling bottles, with no additional information beyond the bill of sale. As such, it pays to check website descriptions or discuss with sales personnel, who may have a better idea of what kind of previous liquid was inside the “hogshead.”
Most recently, I have been hearing more about the application of STR on sherry casks, instead of wine casks. This has the effect of boosting the influence of the cask in a shorter period of time to mellow young spirit. I came across two five-year-old whiskies which seemed to be good examples of the practice from indie bottler Skene Scotch Whisky.
Five years is a reasonable maturation; it is similar to some of the non-age-statement entry level spirits found in the supermarkets. I reached out for some further information from Andrew Skene, who stated that the casks come from a supplier in the South of France who seasons them. So, how do these shape up?
Skene Tomatin 2015 – Review
Aged 5 years in an STR Oloroso seasoned cask (2015-2020). 50% ABV. £36.95
Colour: Rich caramel.
On the nose: Distinctly Tomatin; generic Oloroso, then developing with sliced white bread, citrus peel, golden raisins, coffee grounds, fresh bright juicy spirit with muted tropical fruits including passion fruit.
In the mouth: Fragrant and juicy fruit followed by toasted oats, raw dough, praline, blackberry, dry, dusty, with a little oak spice on the finish, which again is full Tomatin character
Young Tomatin is a hard whisky for indie bottlers to approach, as the Tomatin Legacy (43%) is so well priced and great quality coming in around £24. The same can be said of the Tomatin 12 year old (43%) at £34. But here, Skene Whisky have bottled a single cask at 50% which has quite a bit going on, and is keenly priced. Overall, I think the cask has aggressively done its job and delivered depth and complexity beyond the five-year age. It’s of the modern style that will appeal to many. I’ve added one extra point for price.
Skene Blair Athol 2015 – Review
Aged 5 years in an STR Oloroso seasoned cask (2015-2020). 48% ABV. £37.95
Colour: Rich caramel.
On the nose: Vanilla fudge, toasted sugar, orange marmalade, roasted plum, Maltesers, dark caramel, boiled sugar, with time more of the spirit comes through, a little fresh apple, drying on the end.
In the mouth: Dried fruit and toffee, oily with umami, buttered toast, milk chocolate covered honeycomb, dried ginger and cracked black pepper, toasted coconut, ground coffee, drying.
Definitely more cask at play here, with all the heavy STR processes somewhat overpowering the Blair Athol a little. Some of the burnt sugar notes are creeping in, which I have found off-putting in the past. Perhaps I’m closer to tracing the source of this flavour to France; it’s certainly not enough to be off-putting in this case, I should add. It’s richer and more direct than the Tomatin but lacking the balance. As such I’ve declined to boost the score, despite also being keenly priced.
For more information on the 10 point scoring scale, my scoring grid can be found here.