Fortified wine casks introduced the concept of special finishes, with spirits such as calvados, cognac and rum following, but the range of wine cask finishes has become the most extensive.This includes grape varieties including chardonnay and chenin blanc, styles of wine such as Bordeaux, Sauternes and Tokaji, and even individual estates such as Chateau Margaux.Regulations stipulate that special finishes must comply with the ‘traditional casks’ principle, which includes “still wine (of whatever type or origin).” This may sound liberal but there’s an important proviso.“Even if the cask used for maturation or finishing of Scotch whisky is of a type which has traditionally been used for maturation of Scotch whisky, if as a result of that maturation the spirit ceases to have the taste and aroma and colour generally found in Scotch whisky, it will no longer qualify as Scotch whisky.” Going too far is one consideration, but not going far enough is another.“The spirit should have been matured for long enough in the ‘finishing’ cask to affect the organoleptic character of the spirit. How long that period of time should be will be a question of fact in each case, depending on the development of the spirit in the cask.” Meanwhile, what’s the rationale of a special finish for distillers?“You’re aiming to show a different side of a particular malt, which consumers can compare to the original. The finishing period needs to be long enough to allow for integration, although the house style of the malt needs to remain evident, and not be overpowered by the finish,” says Gordon & MacPhail’s Ewen Mackintosh.As the ‘finishing influence’ must stem from the cask rather than the contents, it’s thoroughly drained of any remaining liquid. Residual liquid absorbed by the cask staves is of course exempt, though it plays a significant role.Being a ‘wood extractive’ liquid rather than simply wine, it also includes flavour compounds derived from the oak. Consequently, casks for special finishes need to be a first fill, and as fresh as possible to retain maximum levels of residual liquid (the sooner casks reach Scotland the less ‘dehydrated’ they are).“There could be a few litres worth in a 220- 230 litre wine barrel, though how much residual liquid will be complexed with wood extractives is a difficult question,” says Glemorangie’s Dr Bill Lumsden.“I believe the flavour coming into the finishing cask from the wine has a more significant impact than the wood extractives.I’d say two-thirds is a direct result of the wine itself, and one-third is down to further woodderived chemistry.” The freshness of the cask also affects the level of “indrink,” meaning the amount of malt absorbed by staves when the cask is filled. This is typically two to three per cent, though drier casks could achieve up to eight per cent. As the indrink mingles with the wood extractive liquid within the staves and then leaches back into the malt, it instigates the beginning of various changes.One significant change is the volume of whisky in the cask.“Indrink sees the surface level go down, creating more air space and so promotes oxidation more immediately,” says Dr Bill Lumsden.Another factor is the filling strength.“We fill finishing casks with whiskies that could be in the mid-40s or up to 60% ABV. The higher strengths will have a more solvent effect and leach more extractives out of the wood,” adds Dr Bill Lumsden. “You may get a slightly different profile of extractives with different filling strengths, but how noticeable this will be is a moot point.” Selecting casks for a special finish involves various considerations.“You have to be imaginative and wait and see whether it will work sympathetically with your brand. We have the advantage that Glenmorangie is a soft, unpeated malt so it is complemented by a lot more flavours,” says Dr Bill Lumsden.Isle of Arran’s Douglas Davidson adds: “We do a lot of homework before we visit anyone, and once in the cellars I taste from barrel to barrel. Arran is a fairly delicate spirit so we avoid tannic or heavily resonated wines which would dominate it, so we’re staying away from more flinty wines like chablis for example.” One of Isle of Arran’s latest releases exemplifies how the house style can interact with a finishing cask.“The Chateau Margaux finish adds another layer of fresh summer fruit, including strawberries and cream, to the classic Isle of Arran orchard character of apples and pears.There’s also an extra layer of sweetness from the wine character,” says Isle of Arran’s Euan Mitchell.Another example is an 18 year old Benromach aged in first and refill sherry casks, that was finished in five puttonyos Tokaji casks (a renowned Hungarian dessert wine, with a scale of one to six puttonyos indicating the level of sweetness).“The sweetness is what we really needed, so we had to be at four, five or six puttonyos to get the sweetness coming through. In the first couple of weeks there was a hit from the actual wine itself, with the Tokaji giving a soft sweetness on the nose and palate, with a syrupy, treacley note, and the colour started to darken. At first they were separate layers of wine and whisky and not much marriage,” says Ewen Mackintosh.“In the middle, transitional period, the wine and whisky began to knit together finding common bonds. The sweetness of the Tokaji latched onto the sherry, creating a rich, creamy sherry note. You need some symmetry between the original wine and the character of the malt once it’s been finished.” Gordon & MacPhail have also shown how differently malts can interact with the same type of cask, by finishing a 10 year old Imperial and Caol Ila for two years in Bordeaux casks.“We chose those two malts to give a contrast between a Speyside and an Islay,” says Ewen Mackintosh.“With Imperial the wine influence came to the fore very quickly, and contributed to the flavour in a layered manner, on top of the Imperial. With Caol Ila the wine influence was very much intertwined, the Islay character led then the softer, fruity elements came through, so it’s very subtle and harder to pull out the wine finish.” Another aspect of cask provenance is whether the oak is European or American.“The nature of the oak is the second most important factor after the wine influence,” says Dr Bill Lumsden.Ewen Mackintosh adds: “The casks for our Bordeaux finishes were European oak, used for three to five years, so the tannic, resinous notes had been leached out by the wines, but they still had a resinous influence on the whisky.” European oak’s looser, more open and porous grain, compared to American oak’s straighter, tighter grain, enables the malt to penetrate the surface more readily. This heightens the release of wood extractive liquid, while European oak’s higher tannin levels also promote astringency, balance and structure. Consequently, European oak can offer a more immediate impact when used for finishing.An innovation is the use of oak from the Argonne forest in France, a traditional source for Champagne casks. When Isle of Arran decided to celebrate their 10th anniversary, a Champagne cask finish seemed the most appropriate. Eight year old Isle of Arran was filled into Argonne oak casks, sourced from the premier cru Champagne house Claude Giraud.“With the Champagne cask finish, it’s more the oak character coming through, with a distinct oakey, creamy, toffee character, and honeyed, syrupy sweetness. Citrus notes could be from the Champagne, though citrus also appears in Arran. The Champagne character is much more integrated, rather than adding another layer,” says Euan Mitchell.With no time limit on a special finish, the obvious question is when does a special finish become a case of secondary maturation?Springbank, for example, is bottling a 10 year old Longrow which spent six years in refill bourbon casks, followed by four years secondary maturation in Tokaji casks.“With Longrow the peat is more in the taste than the nose, and the Tokaji has given it a sweet, honey flavour, which combines with the peat to give a lovely, peaty sweetness,” says Springbank’s Frank McHardy.As the category continues to evolve, there’s a considerable incentive for distillers to keep launching concepts that are yet another ‘first,’ and as consumers we also play a part in prompting innovation.“There’s an element of people wanting to try something new and slightly different, and there’s a need on the marketing side to keep up interest. Everyone is coming out with new products,” says Bowmore’s Glen Moore.So, what are the parameters for the future, to ensure that special finishes remain special, and don’t descend into ubiquity or novelty?“The challenge is to ensure that wood finishes have an integrity and distinct point of difference from the on-going standard products that distilleries release,” says Glen Moore. “If a finishing cask is from a recognised chateau for example then all the better, but the difference the cask has made to the quality of the final product is paramount.”