You’ve seen them as you’ve walked through any warehouse. Elephantine, hulking, they dwarf the tiny Yankees, look down on the hoggies. “Sherry casks,” you say to your guide. Some of you, knowing a little about whisky, may even murmur, “Ah... European oak casks” because you’ve been taught that it is the oak which matters.
Of course oak matters. It holds the whisky, matures it, gives it flavour and colour and grip, and these casks are integral to the creation of flavours which we recognise in ‘sherried’ whiskies: dried fruits, walnut, clove incense, tannic grip, that reddish hue from first fill.
Yet that term, ‘European’ is pretty confusing. What’s the difference between French oak and European oak? France is in Europe is it not? The species of oak which the whisky trade refers to as ‘European’ is Quercus robur, aka pendunculate oak and it grows across Europe, from northern Spain to Norway, from Ireland to the Urals, and yes it does grow in France where it is called Limousin oak. In general, it prefers soils which are slightly more fertile than those preferred by “French” oak, aka Q.sessiliflora/Q.petraea, (which also grows Europe-wide by the way).
From a whisky point of view, it is the trees which grow in the forests of northern parts of Spain, which are coopered into 500 litre casks, seasoned with sherry and then shipped to Scotland and Ireland.
There’s a simple reason why the whisky trade uses sherry casks. Scotland and Ireland drank a lot of sherry and it was shipped there in wood - usually in 500 litre butts. It was these casks which, when emptied, were then pressed into service by distillers.
The sherry makers used American oak (Q.alba) for the aging of their wines in solera and because they didn’t want oak in their wines they used inert wood. The shipping casks were, to some extent, disposable and tended to be made from a cheaper wood, Q.robur. They were also fresh, with lots of extractives still in the timber. Unlike solera casks, these gave big flavour.
"These flavours were easy enough to maintain when there was a constant stream of fresh shipping casks coming into the system. When however the law changed requiring sherry to be bottled at source, distillers had to find new ways of guaranteeing supply"
“They would go back and forward two or three times and end up on the docks of Bristol or Leith and tight-fisted Scotsmen would snap them up.” So says George Espie, managing director of Clyde Cooperage who, as the man in charge of Edrington’s casks, controls more Q.robur than anyone else in the global whisky industry.
As Espie recounts, the uptake in trade in ex-sherry casks started in the 1850s, but by the 1860s whisky firms were sourcing directly from the bodegas. The pioneer of this was W.P. Lowrie who as well as being a whisky broker and blender was the agent for Gonzalez-Byass sherries. By working with the bodegas he could guarantee supply.
The days of shipping casks are long gone, but Q.robur, ex-sherry casks are still used, due to the nature of the wood. It has a wider grain than Q.alba which means more tannin and colour; you’ll get a darker hue and more grippy mouthfeel. Although it has high levels of vanillin, Q.robur is also rich in a compound called eugenol, which gives a distinctive aroma of clove.
These flavours were easy enough to maintain when there was a constant stream of fresh shipping casks coming into the system. When however the law changed requiring sherry to be bottled at source, distillers had to find new ways of guaranteeing supply. They also had to maintain quality, which meant going the extra mile in terms of controlling wood.
"In Jerez, they go to the cooperage for a seven to nine month final period of air drying. They are then made into casks and seasoned with sherry for up to two years. The whole process from felling to arriving in Scotland takes 74 months"
The sherry industry wasn’t building casks, they didn’t need them for solera aging, neither was it making shipping casks, so if the whisky trade wanted Q.robur they would have to go and get it themselves. Enter the bespoke sherry cask, the modern replication of those old shipping casks.
Espie took me through how they are made for Edrington. “The wood is sourced in Galicia, Asturias and Cantabria,” he explains. “The trees are felled in autumn and winter and the timber is partially air dried, machined into staves, dried again and then shipped south to Jerez. That period from felling to arriving at the cooperage in Andalucia takes 12 months.
“In Jerez, they go to the cooperage for a seven to nine month final period of air drying. They are then made into casks and seasoned with sherry for up to two years. The whole process from felling to arriving in Scotland takes 74 months. We could speed up the drying by kilning the timber, but there has been research done on comparing kilning to air drying and the latter simply gives a better product.”
Does the sherry type matter in terms of seasoning? “We can’t have the casks sitting empty, so if a batch coincides with the harvest it will get fermenting must which is racked off in February/March and then the cask is refilled with oloroso. Casks made at other times of the year are filled with oloroso.”
"A similar attention to detail takes place at Irish Distillers which has operated a bespoke cask-building strategy since the late 1970s. The firm lays down 4,000 new casks a year and only ships them during the winter months to avoid any bacterial spoilage and the necessity to treat them with sulphur"
Why oloroso? “Tradition mainly. It was the original style of shipped sherry. We’ve done work on fino and amontillado, but oloroso gives us the best replication. My own view is that oloroso seasoning takes away unwanted elements from the oak (aggressive tannins and bitterness) as well as giving a contribution to the wood and then the whisky.”
But we do see whiskies with fino cask on the label? “Well, these won’t have been Q.robur. Anything which says ‘fino cask’ would probably have been an exhausted ex-solera cask. From Edrington’s point of view, it wouldn’t deliver what we call ‘sherry cask’.”
A similar attention to detail takes place at Irish Distillers which has operated a bespoke cask-building strategy since the late 1970s. The firm lays down 4,000 new casks a year and only ships them during the winter months to avoid any bacterial spoilage and the necessity to treat them with sulphur.
All of this comes at a high cost. “Each butt costs £650 to £700,” says Espie, “and we’re buying 20,000 a year.” I do a quick calculation. That’s up to £14m just in wood. It seems a high number, not just in cash but in fresh wood coming into the system which speaks both of an increase in production, as seen by Macallan’s new aircraft hangers in Speyside, and a strict rotation policy.
“We dispose of 10,000 casks year,” says Espie blithely. “We have to for quality reasons. Our firm belief is that 60 per cent of the whisky’s quality is coming from the wood so we operate a strict policy of nosing prior to emptying. If the cask won’t be able to provide the quality for another fill it is either rejuvenated and refilled with grain whisky, or malt for our blends, or disposed of.
“What we call ‘sherry cask” is first fill. After that it is ‘refill’ and we’d average three or four fills. Neither are they used for finishing. When I see ‘finish’ on a label it says to me there was something wrong with the whisky in the first place. It was unfinished.”
Edrington also makes a percentage of its sherry casks from Q.alba. “My predecessors would have been buying from cooperages and their order would have been for Q.robur and ex-bodega casks. They probably believed that the latter were also Spanish oak, but they were Q.alba ex-solera casks. We need to maintain a consistency of flavour in a malt such as Macallan, therefore we’ve always had to have that Q.alba element.”
£14m is a huge outlay however, especially if the financial climate is less than clement. “There’s always been the argument that we could save that money and put it behind a brand,” says Espie.
“My line has always been, ‘Ok, have the money back, but before you do put together a bottling without that wood and let me see you try to sell it.” No-one has dared try to take up Espie’s challenge.
"Why then are fewer using it? “Because of the cost. It’s more than twice the price of Q.alba. It was cost which drove the change away from ex-sherry casks in the first place and yes there has been a fundamental change in whisky flavour since then"
What though of people who say the old sherried whiskies were better? “If you are sitting with a glass of Macallan 12 today, my job is deliver wood which will deliver the same flavour in 12 years time, so we don’t have people saying ‘it’s not like it used to be’.” What of those who do? “They might have had a variant like Gran Reserva which was heavy Q.robur, or they might have had whisky from casks bought in the ‘50s or ‘60s when there was greater variability with shipping casks, sweet sherry casks and ex-solera casks in the system.” In other words, there’s more consistency these days.
Q.robur is the junior player these days. Today’s whisky industry seems to be skewed towards the vanillic hit of Q.alba. Are we now at a point where Q.robur is only suited for a small number of distilleries? “I’d say it’s suited to all distilleries,” says Espie. “There are only a few doing approaching it to the same extent as we are, but I’d say every distillery would benefit with a little Q.robur in its wood mix.”
Why then are fewer using it? “Because of the cost. It’s more than twice the price of Q.alba. It was cost which drove the change away from ex-sherry casks in the first place and yes there has been a fundamental change in whisky flavour since then. Could we though see a revival in ex-sherry casks as palates change? “It is slowly becoming the criteria of quality,” he says enigmatically. “So, yes.”
Bigger, richer, sweeter. Look at the hot markets in Asia and you can see that the boom is being led by whiskies with a hefty Q.robur component. Maybe the pendulum is swinging back once more.
Whisky and wine
It is hard to talk about the realm of casks and experimenting with different wood types without mentioning one of its first pioneers: Glenmorangie’s whisky creator Dr Bill Lumsden.
In the 1980s Glenmorangie pioneered the original concept of extra-maturation using a variety of exclusive ex-wine casks. The whisky creation team, headed by Bill, is still the leading experts in this field as it painstakingly explores the most distinguished vineyards of Europe in the search for exceptional casks. These casks will provide rich, intriguing and compelling layers of flavours and tastes to the original character of Glenmorangie’s spirit.
For his latest release, Bill has partnered with a group of select Italian wine makers to use Super Tuscan wine casks to create Glenmorangie Artein.
The rugged Tuscan coastal hills, built on stony foundations, are a seemingly improbable area for vineyards. However, the stony terroir plays an important role in the development of these fine wines. The vines are forced to delve deep into the soil seeking nourishment; as a result the grapes claim intense flavour from this unique environment.
Bill comments: “Wine is one of my huge passions and I was fascinated by the role stony ground played in cultivating the vines –therefore influencing the flavour profile of the famed ‘Super-Tuscan’ wines. I was inspired to experiment with extra maturing Glenmorangie in these wine casks and was thrilled with the result – a rich, outstandingly fragrant whisky – born of stone.”
The ‘finishing’ technique follows the same school as other whiskies from the Glenmorangie stable. The spirit matures for at least 10 years in American white oak ex-Bourbon casks, before being transferred to high quality wine casks for a further two years.