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Behind the wood used in cask maturation

Behind the wood used in cask maturation

Take a sip of whisky and you’ll be met with myriad flavours, the tasting notes of which will be exalted by whisky experts, aficionados and makers globally.

The flavour of a whisky develops over many years and, especially in Scotland, even decades. And while a large proportion of those flavours will come from the production process – from barley strains used, to fermentation times, still shapes and sizes – an even more important part is of course the humble cask it will be matured in. 

Using oak casks for maturation of a minimum of three years is a legality in Scotland if a producer wants to call the final product Scotch whisky, and every country has its own regulations around this. In the United States, for instance, in order for something to be called Bourbon, it must be matured in brand new– or virgin – oak casks. Over the years, many in the whisky trade and those who enjoy its products have said that the strict regulations imparted by the Scotch Whisky Association have stymied the creativity in its production. There can be no use of more exotic woods such as Chestnut or Pine, even if just for the fun of it. Others have argued that this strict regulation has kept a high quality in Scotch whisky, ensuring its regard is held up globally. 

However, a major rule change in 2019 shifted the dial ever so slightly for Scotch whisky producers, with the Scotch Whisky Association officially allowing the use of ‘non-traditional’ casks, including ex-wine, beer, ale and spirits casks. It may not sound like a big difference but if you think about the wide world of spirits, it gave whisky producers confirmation that there would be no issue with delving outside of ‘traditional’ casks such as those which previously held Port, Sherry, Madeira or Bourbon, in favour of casks which held Tequila, Mezcal, Genever, Brandy, Calvados or Real Ale. Whilst the regulations still stipulate that the ‘resulting spirit must have the traditional colour, taste and aroma characteristics of Scotch whisky’, and whilst it was never technically illegal to use them before (more a strongly worded suggestion) it felt like a big opportunity regardless for those itching to try out different casks and know they had the full support of the main regulation body in Scotland. 

But how did oak come to be such an important part of that process? 

Casks have been used as transportation vessels for alcohol for millennia. The Greeks and Romans both used casks held together by hoops to ship and store their wines, which they are said to have discovered during their invasions to these lands. The word cooper – the name of the trade for which a person trains when making and repairing barrels – is said to derive from the Latin Cupa, which meant vessel. 

Whisky, it is said, was put into casks as far back as the early 1800s when distillers began recognising the fact the cask had an impact on the maturing spirit. Oak is an excellent vessel as it can be made watertight by skilled coopers, but is porous, allowing for the interchange of spirit and wood tannins, which help to add and build flavour during the maturation period. 

Time will tell whether the Scotch whisky regulations will relax further to allow for use of woods other than oak, but the latest shift at least seems to be inspiring producers new and old to trial out interesting cask finishes to entice a wider range of whisky drinker

However, when it comes to regulations around the use of casks in maturation, these only came into effect in Scotland during the First World War. It was then that the government – led by teetotal David Lloyd George – made it the law to mature spirit in casks for a minimum of first two years, in 1915, and then a minimum of three years from 1916, before it could be called whisky. This was implemented as a way to stymie the flow of harsh, new make spirit into the hands of punters who were otherwise required to do things like fight in the war. By locking up the whisky in bond, less of it flooded onto the market and into the hands of those desperate for a distraction from the goings-on of the time – thought to be especially important by non-drinking George who famously said: ‘Drink is doing more damage in the war than all of the German submarines put together.’

Up until the end of Prohibition the most common type of cask used for maturation were those from Europe which previously held Sherry, Port and Madeira, all of which were extremely popular amongst the British public. These barrels would be sent to the UK filled with the respective tipple, and bottled upon arrival on these shores – something which later became illegal. Once emptied, the barrels would be sold or given to Scotch whisky producers for reuse. The whisky would be filled into these casks to be transported in bulk to other countries overseas, thereby closing the cycle.

But in the 1930s, new legislation in the US helped to push Scotch whisky distillers into using American oak barrels more frequently. In 1935, in a bid to support the lumber trade in the United States post-the Great Depression – and due to strong labour union of the Coopers – a law was put in place which stipulated that Bourbon could only be matured in brand new, virgin oak casks. This paved the way for a surplus of barrels – suddenly all those distilleries which had survived Prohibition could only use barrels once. To recoup some of their costs, they began selling them onto the biggest whisky producer of the time – Scotland – whose distilleries happily lapped up said barrels at a big discount. This was further enforced a few decades later when, in 1981, the Sherry industry outlawed the bulk shipment of its products to other countries, in favour of bottling in the country of origin, meaning barrels were no longer automatically making their way to Britain.  

Today, the vast majority of casks used in the Scotch whisky industry come from that Bourbon trade, with the casks originating from the Sherry industry tending towards being purpose built for the Scotch whisky industry. The lessening sales of Sherry over the decades has meant that the industry could never fulfil the demands of the whisky industry without being commissioned to make them. It is something which has helped keep many Sherry producers in operation over years of a dwindling interest in their products, despite their high quality. Today, most Scotch whisky producers have a couple of Sherry houses with which they work to specifically make casks to order, either seasoning American oak casks with Sherry, or more traditional European oak casks with Sherry for 1-2 years before shipping them to Scotland for use there. 

But with the updated legislation alteration comes the possibility that more distilleries in Scotland will push the boundaries out into new arenas of experimentation. 

One of the first to do so was Dewar’s with the launch of Illegal Smooth, an eight year old blended Scotch finished in ex-Mezcal casks. Launched just after the new regulations officially came into play, the whisky was created out of a curiosity to see how the sweet agave and vegetal notes of Illegal Mezcal would work with the honey and fruit character of Dewar’s, according to Fraser Campbell, global brand ambassador for Dewar’s. 

Campbell says they loved the initial trials done by their master blender, Stephanie MacLeod, and when they reached out to the team at Illegal Mezcal, their team sent over some Reposado casks for Macleod to do more trials with. It’s allowed for the opening of a ‘large can of curiosity for people’, says Campbell, who helped launch the brand globally. 

“For those who are familiar with Scotch whisky, they’re sitting there thinking; ‘how the hell does Mezcal play with whisky?’ which drives them to find out for themselves. The same goes for Mezcal fans in the reverse! It brings two cultures together,” he explains.

As for the impact on the world of Scotch whisky, Campbell says it’s a “signpost that we have really entered a realm of innovation where we can explore and experiment with a more unique variety of casks. It’s rewarding to be able to build bridges to spirit makers around the world to create some forward-thinking collaborations with our whisky, which are interesting, amazing value and damn tasty.”

It’s something that players in other countries have known for a while. In Ireland, where the laws are not as strict as in Scotland, producers such as Teeling and Midleton have been pushing the boat for many years. Campbell says that Teeling is actually one of his go-to whiskies of interest when it comes to trying out new things, such as whiskies matured in casks which previously held ginger beer, pineapple rum and various wines, with his top pick being their Sommelier Selection Margaux Cask. Midleton, meanwhile, has played around outside of the world of oak, choosing to test out whiskies finished in French chestnut wood and a very limited run done in Mulberry wood for its Method and Madness series. 

Meanwhile, in England, smaller producers which are at the forefront of the English whisky distillery revival, have also trialled out more interesting cask maturations to help give them a differentiation on the whisky stage. At the Cotswolds Distillery, founder Daniel Szor looked to his love of France to inspire some of the choices for maturation used on his small batch releases, choosing the Pineau des Charentes cask as one of the company’s latest creations. 

“We work with a great cooper in France who specialises in rejuvenating ex-wine casks and infusing them with a variety of really interesting wines.  One of these was Pineau des Charentes, one of my all-time favourite aperitifs, made from a mix of fresh pressed grape juice and cognac which has been aged in oak casks.   The thought of spicy French oak and this wonderful and very unctuous wine seemed a natural fit for our spirit, and – as is the case with all our caskings – we allowed our whisky to mature in these casks over its full term,” he says. 

While Szor is still using oak casks in the main, he very much intends to trial out different wood such as chestnut, acacia and cherry casks for the brand’s experimental collection. 

However, even with the ability to have slightly more freedom than his compatriots north of the border, Szor is keen to emphasise that the focus will always remain on staying true to the DNA of the spirit which flows from the stills in the English countryside. 

“I think it’s important to describe the effect of these ‘exotic’ casks on whisky as being exactly what it is – flavouring – and as such they can be successful in drawing in new consumers who might be looking for sweeter or more novel flavours.  Our goal, however, is to ensure that just below the surface of each cask expression of our whisky, the new make spirit – the ‘DNA’ of our whisky – can be clearly discerned.  We have no interest in flavours which completely overwhelm our distillery character, nor do we wish to allow too much wood into the spirit.  Balance is, for us, the ultimate goal – along with big and fun flavours.”

Time will tell whether the Scotch whisky regulations will relax further to allow for use of woods other than oak, but the latest shift at least seems to be inspiring producers new and old to trial out interesting cask finishes to entice a wider range of whisky drinker. And while oak will likely remain king due to its affordability and efficiency in maturation, the continuous desire for innovation in the Scotch world, and the proliferation of distilleries in other countries which have fewer regulations, will likely continue to push this shift into new realms for the future.  

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