Barrel Aging BeyondAmerican Oak

Exploring alternative woods, aging techniques, and experimental cask programs 

Written By: Davin De Kergommeaux

Websites, social media, magazines, books, podcasts, masterclasses; no matter where you get your information, you learn very quickly there are only three ingredients in whisky: water, grain, and yeast. 

Yet, ask where the flavour comes from, and immediately, the topic turns to wood. Does better wood really make better whisky? What do you mean by better? And why are so many whisky makers experimenting with alternate woods?

If barrels are key to whisky flavour, then whisky makers must put a lot of thought into selecting just the right ones, right? Right. But sometimes, factors with no impact on flavour determine which barrels they choose. For example, exotic woods are trendy right now, and many producers are jumping on the bandwagon, not because they enjoy how these woods flavour whisky, but because they are afraid of being left behind.

In the late ‘90s and early 2000s, representatives from The Macallan routinely proclaimed that up to 80 per cent of the flavour of their incredible whisky (it really was amazingly flavourful) came from using Oloroso sherry casks. They would mention a Spey-fed freshwater spring and swore by Golden Promise barley, but the secret sauce that made Macallan the most collectable whisky in the world was Oloroso butts made from European oak.

By 2004, the brand needed to adjust. Sales were soaring, and there were not enough Oloroso casks to keep up with Macallan’s burgeoning needs. That was when the brand launched its Fine Oak series. Macallan had matured these new whiskies, for the most part, in ex-bourbon barrels, with just a sprinkling of sherry cask whisky blended in. They also let it be known that they now had sherry producers custom-seasoning new casks for them. If Macallan lovers were dismayed, collectors were horrified. Claimed to be comparatively thin and insipid – what more diplomatic pundits call “lean” – the whisky no longer showed much Macallan character at all.

Some prominent Macallan collectors stopped collecting. Others wrung their hands and sold or poured their collections. Amidst widespread outcry, management held firm in its belief that Macallan’s reputation was solid enough to sustain massive expansion, even without the famed Oloroso butts. In the end, they were proven right. The old Macallan was gone, new fans raved about the new Macallan, and sales continued to soar.

Ultimately, and somewhat ironically, The Macallan demonstrated that wood truly was the major contributor to the flavour of its whisky while also showing that with good promotion and the natural turnover of whisky drinkers, altering that wood had no negative impact on sales. Seasoned barrels were easier to work with, available in unlimited supply, and, as a side benefit, were less expensive than Oloroso casks. As a disenchanted older generation of Macallan drinkers was stripped for parts, a larger, younger cohort raced in. Wood, it seems, serves as a great talking point, but ultimately, people will learn to enjoy almost any well-made whisky. To a long list of professional wood experts –woodworkers, lumberjacks, architects, forestry scientists, engineers, sculptors, furniture makers, home builders, arborists – we can now safely add whisky makers. As in their glory days, Macallan is back to earnestly crooning that they are wood specialists. The whisky maker that built its reputation on real Oloroso butts has seen its sales and reputation grow even as it replaced those butts with seasoned sherry casks. The new whisky does not taste the same, but in Macallan’s skilled hands, the switch saved one of the world’s most revered whisky brands from extinction.

How Wood Works

First, about the words. What North Americans call barrels, Europeans call casks. A butt is a large (475-500 litre) cask used for maturing sherry. In the industry they all are often referred to simply as cooperage. There are two kinds of cooperage: loose and tight. Loose casks have thinner staves and are made from pretty much any type of wood. You can fill loose casks with almost anything except liquids. Tight casks, on the other hand, are nearly always made from oak, generally have thicker staves, and will hold liquids for extended periods without leaking. Why oak? Because, unlike the wood of almost all other trees, the pores in oak wood are filled with tiny, highly effective natural plugs called tyloses. These plugs prevent the cask from leaking. Whisky makers use tight cooperage exclusively.

A couple of hundred years ago, distillers flavoured newly distilled spirits with herbs, spices, tobacco juice, and various unmentionables. In Scotland, they called this gin; in the Netherlands, genever; and in America, it was whisky (a semi-literate bunch, they hadn’t fixated on spelling yet). Although cognac and brandy makers were using wine casks to mature their spirits, whisky making was still at the quick-sale stage. Somewhere along the line, though, whisky spirit began finding its way into barrels, and people soon noticed a considerable improvement in flavour, though no one had a clue why.

So, here's why: Once the spirit is in the cask, several things happen that change its flavour. Essentially, alcohol dissolves or washes flavourful wood components and the residues of previous barrel contents into the spirit. As well, the air inside the cask reacts with these components, creating new flavours. Finally, oxygen and alcohol slowly induce chemical changes in the wood, adding more flavourful compounds. This is how floral vanillas, oak caramels, and pulling tannins that seep into the spirit from charred virgin American oak barrels create the signature flavour of bourbon. It is also how seasoned barrels change the spirit’s flavour: the barrel soaks up the seasoning like a sponge. Then, it transfers it directly into the spirit without undergoing any maturation.

And, this is why seasoned sherry casks cannot compete with genuine Oloroso casks for flavour. When casks are used to mature sherry, they undergo changes just like barrels holding whisky spirit do. Except, sherry is more acidic than whisky spirit and less alcoholic, so it alters the wood in different ways and creates different flavours. There is a compensating benefit to using seasoned casks for high-volume brands, though. As there is less variation among them, it is easier to forecast the finished whisky’s taste profile. This means less time and money spent sampling casks, without compromising flavour consistency among batches.

Exotic Woods

While credit for introducing the concept of finishing barrels goes to Dr. Bill Lumsden for his work in the late 1990s with Glenmorangie, in North America, the practice remained relatively unknown until 2010 when Maker’s Mark 46 hit the market. The idea of finishing bourbon flies in the face of the regulation that bourbon must mature in charred virgin American oak. However, by inserting French oak staves inside traditional white oak bourbon barrels and then re-filling them with mature Maker’s Mark whisky, Bill Samuels Jr. matched Lumsden’s innovation without violating American bourbon law. The new spicy flavours added by the French oak, along with the novelty of the process, made Maker’s 46 a winner.

Around the same time, Odd Society Spirits in Vancouver was experimenting with placing pieces of exotic wood inside oak whisky barrels. This practice had begun among small distillers in the US, who bought staves of unusual woods from Black Swan Cooperage in Minnesota. Black Swan’s staves, featuring a matrix of small perforations, quickly added new flavours to the spirit when distillers inserted them into barrels. “Quickly” is the operative word here. Finished whisky seems to taste best when the finishing wood is used gently to add highlights. Overdoing it risks spoiling the ‘whiskiness’ of the finished product.

In North America, whisky usually matures in barrels made from American white oak, and since World War II, most Scotch whisky has followed suit. American bourbon makers use virgin barrels once before selling them to Scotland, Canada, and other whisky nations. More often than not, it is ex-bourbon barrels that Scottish distillers and others select to season with sherry. By tradition though, Scotch was matured in European Oak casks imported from France and Spain, and most of these, including those used for the old Macallans, had first spent decades maturing sherry.

In recent decades, European oak casks have found their way into North American distilleries, often imported and used first by winemakers. Unlike the brasher caramel, vanilla, and tannin tones of American oak, European oak exhibits spicier, nuttier, and fruitier flavours. European oak casks that were first used to mature sherry often go through three or more whisky refills before the sherry influence tapers off.

Asian Woods

About 20 years ago, when Japanese whiskies matured in Mizunara oak casks first arrived in the UK, connoisseurs went wild. Best known in Japan for its soft, incense-like aromas that some find similar to sandalwood, Mizunara reveals other typical Japanese scents of sweet sakura (cherry) blossoms, vanilla, and coconut macaroons. Despite its robust influence on the whisky, Mizunara complements without overpowering it. Mizunara is not the only oak that grows in Japan though. It’s a buyer-beware reality that not all Japanese oak imparts the glories of Mizunara to whisky—however, Japanese cedar might.

At Whisky Live in London, following the World Whiskies Awards, a new whisky maker called Kamiki was pouring whiskies finished in barrels made from Japanese cedar. Mild incense tones—similar to, but softer, than mizunara—explain why these barrels are popular for maturing sake. They’re not yet available in North America, but now that word is out, you can bet they will be soon. And by the way, unlike North American cedars, which can be fatal if consumed, Japanese cedar is not poisonous.

North American Woods

It wasn’t whisky makers but Spanish winemakers who first experimented with cherry casks. They found that cherrywood didn’t so much alter the flavour as it tightened the tannic backbone of flabby red wines. The barrels leaked badly—no tyloses—so they just used them briefly for finishing. Today, some whisky makers overcome that problem by inserting cherrywood staves into oak barrels. These tend to give a lovely soft tannic pull with hints of floral fruitiness.

If you have tasted nocino, the dark Italian liqueur, you have experienced walnut flavour. Traditionally, nocino is made from English or Carpathian walnuts. In North America, however, some distillers have begun (somewhat foolishly) to experiment with black walnut. A walnut is a walnut is a walnut, right? Wrong! The popular North American walnut species, known as black walnut, is quite familiar to farmers, gardeners, and, sadly, to veterinarians and doctors for producing juglone, an allelopath. That’s a big word for chemicals one plant uses to poison other plants. These keep the area around the black walnut tree free of weeds. Unfortunately, some animals, especially horses, and some people, react badly to juglone – badly meaning long-term difficulty breathing, swollen lips, and sometimes death.

Nocino tastes great, but the original does not use North American black walnut. Distillers tempted to try walnut wood for whisky are strongly cautioned to ensure they obtain a European variety that does not produce juglone. And if you feel the urge to place a piece of strange wood in your home mini barrel, check what Google says about the tree it came from. Some common woods are downright lethal.

In 2011, when Canadian Mist introduced a new upscale whisky called Collingwood, they did something most people had never heard of. Once the whisky was mature, they dumped it into stainless steel tanks and added maple staves that floated around in it. A solid, yet subtle influence, the maplewood seemed to add structure and fruitiness to the whisky without making it too woody. Like Maker’s Mark 46, Collingwood has built a solid following among whisky aficionados.

Brazilian Oak

Sometimes called Brazilian oak, although it is not related to common whisky oaks, amburana is one of those trendy woods used to quickly imbue whisky – primarily bourbon – with exotic, cinnamon-like spicy notes. Amburana flavours appear very quickly in the spirit, and a little goes a long way, so, unless your goal is to create the next Fireball, infusion coils inserted into American oak barrels are the most effective way to use it. In Brazil, distillers commonly mature Cachaça in amburana barrels.

Scraped, Toasted, Re-Charred (STR)

Rejuvenated casks are not new. Distillers learned long ago that with each use, flavourful components of the wood dissolved away, reducing the influence of the barrel in subsequent uses. One inexpensive solution was to scrape the char out of used barrels and then re-toast and re-char them. While they were not as rich in flavour as new barrels, they imparted more flavour than used barrels. With booming whisky sales at the turn of the century came a rush of new, cash-poor distilleries seeking ways to bring their whisky to market as quickly and inexpensively as possible.

Enter whisky consultant Jim Swan. He suggested that rejuvenating used red wine barrels by scraping, toasting, and re-charring them was a quick and cost-effective method to produce flavorful whisky – kind of like maturing and finishing at the same time. Some producers refer to it as rapid aging, as it produces an enjoyable dram in about five years. Enjoyable, yes, though, as Kavalan has demonstrated, these whiskies still benefit greatly from longer time in cask.

Without question, there are benefits to using woods other than oak for finishing. The unavailability of desired casks or, more frequently, a need to cut costs is often the deciding factor. Yes, you can taste the difference, but consumers quickly learn to enjoy new flavours, so nothing is fixed. Those who earned their whisky wings on the old Oloroso-matured whiskies may harbour little but disdain for today’s short-cut STRs. Still, a whole new generation of whisky lovers genuinely appreciate young STR whiskies.

And what about you? Well, a number of smallish European distillers, such as Zuidam/Millstone, still use the real old-style Oloroso casks, and if you get the chance to try them, don’t miss it. At the same time, don’t hesitate to enjoy various exotic finishes and woods. Every whisky has something to offer, and like it or not, each one expands your taste memories and vocabulary.