There is something deceptively simple about whisky. At first glance, whisky seems to be made from just three basic ingredients: grain, yeast, and water.
Yet, this simple story is immediately complicated by the use of wooden casks (usually oak, and in the case of Scotch, only oak) and the time required to age the spirit in those casks. Conservative estimates suggest that around 60% of the flavour of a whisky will come from the casks, as the chemical constituents of the wood leach into the liquid inside. Could casks count as a kind of additional ingredient?
Then, there’s the potential use of peat to dry the germinating grains, where the rich smoke that’s produced by the peat fire and full of phenolic compounds is absorbed by the grains. Is that an additional ingredient? Then there’s also the focus of this article: the fact that many of the casks used to age whisky have already been used by other industries. Often, residual traces of whatever those casks previously held can remain in the wooden staves, and remnants of the previous contents can leach into the whisky that’s placed in the cask as it matures over the years. Would any remaining vestiges of wine in an ex-wine cask count as an additional ingredient?
Whisky finishing – where whisky is transferred from one cask to a second, different type of cask for a shorter period of time – is a relatively recent phenomenon. Although these kinds of experiments occurred earlier, the practice really began in earnest in the 1980s when Balvenie experimented by moving some of their whisky from ex-bourbon casks into ex-sherry casks. They wanted to see if there would be a noticeable difference in flavour compared to simply marrying together whisky that had been aged separately in ex-bourbon and ex-sherry casks – and they decided there was.
Nowadays, most distilleries experiment with different cask finishes to produce whisky with unique flavours and characteristics. In addition to sherry cask finishes, some common finishes include rum casks, port casks, craft beer casks, a variety of wine casks, and tequila casks. There are also quite a few whiskies on the market that are being finished in ex-Islay casks – a region known for smoky whisky – in order to impart a subtle smokiness to the whisky. Yet, whisky can also be finished in virgin oak casks (casks that have never held any liquid before) or in casks of different sizes (like quarter casks).
There have also been some truly unusual cask finishes. Westland’s “Inferno” was a single malt from the USA finished in tabasco barrels. In 2007, an independent bottler got their hands on a single cask from Bruichladdich and experimented with finishing the whisky in barrels that previously contained herring, calling the result “Fishky.” Although this might seem extreme, it’s not actually as insane as it sounds, as it’s believed that early Scottish distillers occasionally made use of fish barrels (out of necessity). Reviews of “Fishky” were mixed, with a few saying it was actually quite nice, and others saying it was the worst whisky they’d ever tasted.
Whisky makers seem to be paying more attention than ever to the types of casks used, particularly as the trend of exotic whisky finishes continues to grow. As a consequence, the image some may have of whisky as a time-honoured, unchanging spirit is increasingly at odds with the growing experimentation within the industry today.
As noted above, the great thing about barrels is that they absorb some of the flavour characteristics of whatever liquid they previously held. This happens because, as the barrel breathes, the liquid soaks into the wood. Even after being emptied, dried out, and passed along for use in the whisky industry, the barrel can retain some of that liquid in its staves. This can leach out into the whisky placed in that barrel during the maturation process. As a result, the flavour profile of the previous contents can integrate with the whisky.
Reflecting on the growing number of whiskies finished in various types of casks, I began to wonder if this would raise any interesting questions about what counts as an additive in whisky production. While the rules vary slightly from country to country, one thing is clear for Scotch: you cannot add any flavourings to whisky. If you do, it’s no longer considered whisky. According to the Scotch Whisky Association (SWA), no additives are allowed, with the sole exception of caramel colouring (E150A). But what about any residual wine, for example, that is absorbed by the cask and then incorporated into the whisky that’s finished in said cask?
My understanding is that, officially, any influence a cask has on a whisky is considered part of the natural maturation process; any trace amounts of what that cask may previously have held is just viewed as part of the cask’s history. The flavour influence from the cask’s previous contents are taken to occur indirectly through the wood, so anything that seeps into the whisky is not regarded as an additive.
That said, the SWA does stipulate certain rules about which casks can and cannot be used for finishing whisky. Acceptable casks are those traditionally used in whisky making (such as ex-sherry and ex-bourbon casks – but a number of other types are also deemed acceptable). Unacceptable casks include those of “wine, beer/ale or spirit produced from, or made with, stone fruits”, or any cask used to age wine, beer/ale or spirit which have had any artificial sweeteners or flavourings added.
The whisky (if I can call it that?) from Glen Moray’s Cider Cask Project caused a stir in the whisky world, and it turns out that the use of cider casks has since been more clearly prohibited. Does this controversy mean that we ought to be concerned about the actual contents of the cask seeping into the whisky and… contaminating it? And if so, it’s hard not to wonder about ex-wine casks, or ex-rum casks, too, even if they are seen as acceptable.
The SWA goes on to state that a cask which meets their above criteria may still not be allowed for whisky finishing, because it’s also the case that “all casks used must still result in a spirit which has the taste, aroma and colour generally found in Scotch Whisky.” For those wondering about Inferno and Fishky: neither of those whiskies were Scotch. Still, this final stipulation strikes me as awfully vague. Given the enormous variety in whisky flavours, how do we determine what tastes and aromas are “generally found” in Scotch whisky?
To my mind, it remains unclear whether or not one can confidently say that someone is right or wrong when they say that they detect particular aromas or flavours when nosing or tasting a whisky. While we now know that certain aromas and flavours are associated with certain chemical compounds (vanilla and vanillin, say), we also vary genetically from one another, and so one person may simply be more sensitive to certain aromas or flavours than others. For example: Gary Beauchamp, one of the world’s most eminent sensory scientists, has noted that there is a hormone called androsterone that a third of all people simply cannot smell at all, while “one-third smell something like urine and one-third smell sandalwood.” I’m pretty sure sandalwood is an aroma some people have detected in whisky before. Moreover, individual life experiences also play a role in what aromas or flavours we detect. Someone who has encountered a particular flavour before may easily identify it in whisky, while someone unfamiliar with that flavour might struggle to identify it, or fail to notice it at all. Even those sympathetic to the SWA’s ruling would likely acknowledge that such considerations complicate things.
Since thinking more critically about whisky finishing, I’ve come across the existence of self-declared whisky purists who are sceptical about the practice. This is because a surprising amount of liquid – a few litres, in some cases – can remain in a cask’s staves, and this liquid could in theory be “sweated” out of the cask. At first, I was quite sympathetic to their view, but it’s difficult to hold when you consider that most Scotch is aged in ex-bourbon and ex-sherry casks. If one is concerned about the use of ex-wine or ex-rum casks etc., shouldn’t one also be concerned about the use of these well-established casks? Yet the use of these casks is not usually questioned. On the other hand, does the use of ex-tabasco and ex-herring barrels legitimately a step too far? (Although, as mentioned, Fishky does lay claim to some historical precedent!)
It’s hard to draw clear lines – how do we decide where to draw them? And why do we place so much emphasis on the lines we happen to have already drawn, especially when they seem somewhat arbitrary? The philosopher Julian Baggini writes, “behind almost every tradition is a myth, and behind all traditions is the biggest myth of them all: that this is what our people have always done.” It’s worth remembering that whisky today differs from what it was in the past.
At one point in time whisky wasn’t necessarily aged at all, and was often flavoured with herbs, heather, lavender, and honey to make it more palatable. Rules and regulations around whisky are continually being updated, amended, and refined. As such, there will always be tension between the pull of tradition and the push to innovate in the creation of great whisky. As new cask finishes expand the boundaries of what whisky can be, they also force us to confront important questions about how far these experiments can go before we believe whisky loses its identity.
