How Casks Contribute to Scotch’s Flavor

Of course wood plays a huge part,” says Glenfarclas’s brand ambassador George Grant, “otherwise we would all be drinking clearic.”

That’s true, of course, but for many years past, the majority of the Scotch whisky industry has been content to employ bourbon casks to mature the majority of its new make spirit (or clearic). The casks are readily available, comparatively cheap, and add flavors that complement scotch, so everyone is happy. Again, speaking broadly, the relatively small amount of scotch matured in sherry casks can be used by the blender to add a touch of richness and depth to the final product. For all the ink spilled in blogs and magazines over single malts matured in sherry casks they make up a very small part of the market. While they excite enthusiasts and are the lifeblood of one or two brands, they can never account for more than a modest overall share, partly because there are simply fewer casks available and they are considerably more expensive to buy.

So that might seem to be that—and for a long time, it was. But over the past two decades, the whisky industry has been getting more and more curious about casks and the wood’s contribution to whisky flavor. Let’s look a little deeper.

Personnel at a Diageo Global Supply site in Clackmannshire, UK manage barrel inventory. (Photo by Martin Hunter)

Considering a Cask

When it comes to a cask, there are six things we should ideally consider: the wood it’s made of, its history, the shape and size of the barrel, the warehouse used for maturation (its type and, some would say, location), the practice of finishing, and then the treatment of casks that are to be filled once again with new make spirit. That’s way more than can be covered in one short article, so my purpose here, is to investigate some of the more innovative cask types now being explored in distilleries around Scotland, and a few of the whiskies that have already resulted. As blenders in particular have become more curious about casks, some curious casks have resulted.

But to begin at the beginning, I believe we should start at the finish! The very first documented ‘finish’ that is; which as far as I can determine was the 1982 release of Balvenie Classic. That was a Balvenie which had enjoyed an additional period of maturation in sherry butts to add extra depth and richness to the whisky. Balvenie’s malt master David Stewart did that simply because it made the whisky taste better; it improved the flavor and so ‘finishing’ was born, at least as a conscious and acknowledged practice. It may in fact have been happening for years prior without anyone making anything exceptional of it. Balvenie Classic which, as it happens, was eventually offered as a No Age Statement (NAS) version and an 18 year old expression, has long since been withdrawn, but has been succeeded by Balvenie Rose (finished in port), Balvenie PortWood, DoubleWood, TripleWood (now known as Triple Cask), and so on as cask finishing has become an established part of the brand’s style. Most of the latter expressions are readily available today.

But Balvenie Classic passed largely unnoticed by the industry for some years. It wasn’t until the release of the first Glenmorangie Port Wood Finish nearly a decade later that the finishing bandwagon began to pick up speed. That first release was something of a happy accident, not the carefully-planned strategic move that the distillery’s publicists would have you now believe, but they very soon realized that they were on to something and the release of a number of innovative finishes using unconventional casks such as Madeira and various other wines soon followed.

Today the Glenmorangie approach is rather more systematic. The latest release in their Private Edition series, Glenmorangie Milsean (it means “sweet things” in Gaelic) is a case in point. I spoke recently with Dr. Bill Lumsden, Glenmorangie’s head of distilling, whisky creation, and whisky stocks, who explained that he had turned the whisky-making process on its head to arrive at Milsean. Rather than using different barrels or using different raw materials, and waiting to see what the outcome was, the goal here was to target a particular flavor profile.

“I wanted to create a whisky with flavors that reminded me of an old-fashioned sweet shop,” said Lumsden, “so eventually, after much research and advice, we had some moist red wine barrels re-toasted such that the residue of the wine was caramelized onto the inside surface of the barrel. Finishing for 2 ½ years in these barriques gave the base Glenmorangie whisky all these lovely confectionery and candy flavors.”

Sandy Hyslop, Ballantine’s master blender, noses each barrel to select the best for resting Hard Fired.

Hard Firing

But experiments with the rapid re-toasting of casks are not unknown elsewhere. French cognac house Camus prepares casks for their Extra Dark and Intense expression using a similar technique. In scotch, Ballantine’s has used double charring for their most recent release, Ballantine’s Hard Fired. This went into test market late last year. The company envisages a global roll-out, so it should shortly be available in the U.S. 

But first: what is Ballantine’s Hard Fired? At its simplest, it’s a Ballantine blend, but with a twist, using a very different process to treat the barrels used to finish the whisky. The company refers to the “transformative power of fire” and explains that this bespoke process starts with the individual selection of bourbon barrels by the wood management team. The barrels are then sent to highly-skilled craftsmen at the cooperage to char them for a second time—a process known as “hard firing”—while judging the char length and intensity by sight. Finally, Ballantine’s master blender Sandy Hyslop noses each barrel and selects the best to be filled with a unique Ballantine’s blend which is then rested prior to bottling.

Drawing on his expertise as one of Scotland’s most highly-regarded blenders, Hyslop stated, “Hard Fired showcases the natural and unique results that American oak and fire produce on Scotch whisky. When charred, casks form a natural layer of caramelized wood sugars that react with whisky, and a double char understandably intensifies this effect. The result is a smooth, creamy, and subtly smoky Scotch whisky with tasting notes of sweet honey, soft red apples, and tangy licorice. This balanced flavor profile results in a premium whisky that sits well within the Ballantine’s family style while offering something new.”

The signature hard firing of the barrels, similar to the process behind Glenmorangie Milsean, unlocks vanilla notes, hints of smoke and spice, and provides a distinctive smoothness resulting in a characterful and uniquely balanced whisky. The hope is that this distinctive taste profile will, “appeal to whisky drinkers seeking authenticity and craftsmanship in new scotch styles,” stated Hysolp. But note the differing contribution of the casks’ original content—Portuguese red wine casks providing sweetness, where the Ballantine’s casks, which previously held bourbon and then maturing scotch, offer up more vanilla, smoke, and spice.

Ballantine’s is not alone in using innovative cask regimes for their blends. For some years Diageo has been running a program of experimental casks described as seeking, “to create a scientific frame of reference for mastering and marshaling the natural, organic process of maturing whisky in oak casks.” Beginning some 20 years or so ago, more than 800 different casks were the subject of an extremely detailed study, involving many different permutations of maturation and finishing processes through cask origins, construction, treatment (charred, toasted), and seasoning (fillings of port, sherry, bourbon, and others) to create numerous unusual flavor combinations—all carefully controlled and carried out by skilled coopers under the direction of Diageo’s blenders.

Dr. Matthew Crow is part of that team. “We are experimenting methodically with an output in mind, rather than doing something weird with wood for the sake of it,” he explained. “And this output is generally a newer or differentiated flavor profile. What our experiments have shown is that [it] is not simply about the cask. It’s very much matching an experimental cask with a particular whisky, and as we have fortunately over two dozen distillery characters to play with, we can deliver a very rich and varied palette of flavors—many more than could be achieved with one single distillery. This extensive work leads us finally to delivering liquids that consumers will enjoy.”

Dr. Matthew Crow, wood and cask science manager, is part of the team experimenting with casks and their effect on whisky at Diageo. (Photo by Martin Hunter)

Proof of Patience

And what might those liquids be? Well, already the experimental cask program has been a key part of releases such as the John Walker Private Collection. There, the casks used included fresh, never before used American oak, toasted to deliver dramatic and intense vanilla and caramel, and brand new European oak, seasoned with fortified wine prior to filling to provide a profound, dark and rich fruitiness in the final blend. As I can testify, having been fortunate enough to taste the 2014 Private Collection release, it is a superb whisky. However, it’s a $900 bottle, so not for everyday drinking.

At a less stratospheric level, Diageo has been using their work in whiskies such as Talisker Port Ruighe, Cardhu Amber Rock, and Johnnie Walker Select Casks Rye Cask Finish. This blend, more approachable at around $50, is based on Cardhu single malt with a number of grain whiskies that have been matured for 10 years in first-fill bourbon casks and then finished for up to 6 months in American rye casks. According to the distillers, “this combination imparts rich layers of flavor, with hints of spice and vanilla woven throughout.”

The extended duration of the Diageo work points to one simple challenge here: the company needs to have the patience to wait and see what works and what does not. As Richard Paterson, Whyte and Mackay master blender, was keen to emphasize, curiosity about casks is a long-term business, requiring, as he put it, “many, many years of experimentation—this is a highly-crafted area that takes years to master,” as the blender seeks to find a wood that, “gives a point of difference yet is true to the distillery character.”

Unlike some of his opposite numbers, Paterson was candid enough to admit that not everything works, recalling an experiment with calvados casks that after several years became clear was not going to work satisfactorily. For him, each cask, “must individually show enhancement. It’s a synergy; we’re looking for something where the whole is bigger than the sum of its parts.” This search is carried to its extreme with Paterson’s vatting for the Dalmore King Alexander III, which draws on casks that previously held Matusalem sherry, Cabernet Sauvignon and Cabernet Franc wines, Madeira, Marsala, Kentucky bourbon, and port. Yet at the end Paterson insists, “whatever you choose must be compatible with the spirit.”

For Glenfarclas, George Grant drove home the point. “We have always experimented with filling into different types of wood, never to finish it but for the entire maturation. Using different types of oak casks not only shows us how the spirit can mature differently, but also lets the consumer see how different casks can play their part. Ultimately though, it is the base spirit of Glenfarclas that wins through regardless of what was in the cask before.”

Perhaps the distillery most closely associated with unusual casks is Bruichladdich. As the distillery’s Carl Reavey explained, “The development of modern Bruichladdich has been closely connected to working with casks that are quite unusual, or not traditionally associated with mainstream Scotch whisky. We have also never made any secret of the fact that, back in 2001, we were not happy with a significant proportion of the ‘old’ stock at Bruichladdich. The spirit was very high quality, but it was being kept in tired wood and needed additional work to bring it to life.”

Today Bruichladdich has whisky maturing in casks from around 200 different sources. Octomore 07.4, which is a complex vatting based around virgin oak, has just been released and at the distillery one can find Octomore spirit maturing in Ribera del Duero casks. The next Port Charlotte release will feature European oak sourced from the cognac region, so there is clearly much for Bruichladdich fans to savor in the near future.

In fact, the same holds true for whisky enthusiasts in general. The industry’s curiosity of the last 20 years is now paying off, with a stream of innovative releases offering a cornucopia of flavors that will appeal and intrigue in equal measure.

More From Insights