How Much Does Cask Matter?
There are two main types of casks for maturing Scotch whisky. Ex-Bourbon casks, which make up around 90% of maturation casks in Scotland; and ex-Sherry casks, which make up around 7%. These two casks give very big differences in flavour.
Ex Bourbon casks tend to give sweeter flavours of vanilla, toffee, and coconut, along with lighter citrus notes of lemon, in both zesty and fleshy types. With some spirits, ex Bourbon casks can also give more tropical fruit flavours as well as stone fruit flavours.
Ex Sherry casks tend to give more spicy flavours, such as those found in Christmas cake or European pastries, including cinnamon, nutmeg, clove, and ginger. The citrus fruits tend to be more like marmalade and involve oranges and grapefruit. There can also be darker flavours of chocolate and coffee.
Another factor is the type of oak the casks are made from. In modern times most of the Ex Sherry casks used for maturing whisky are made from American oak. These casks give sweeter flavours which balance the spicy flavours well. Whisky that’s been matured in Ex Sherry casks made from Spanish (or European) Oak tend to be dryer on the palate with more discernible tannin.
The age of a cask before whisky is added impacts the flavour as well. The longer a cask has previously held another liquid, like Sherry, the more impact that cask will have on the whisky. Wine and spirits interact with oak in a different way, so even if the Sherry cask is very old, the higher abv whisky will still gain a great deal of flavour from it.
What is more important in terms of the age of a cask is how many times it’s been used and for how long. A cask can be used, let’s say four times if each time the whisky placed inside is only matured in it for three or four years each time. If a whisky has been maturing in a cask for many years, then it probably can only be used once more.
This doesn’t mean that old casks are of no use. If one wants to end up with a very old whisky of more than 30 or forty years, then placing that spirit into a cask which has never had whisky in it before will not be any good. The whisky will be overpowered by the wood too quickly. Rather, a cask which has been used before will be much better as the wood will not overpower the whisky. This whisky will probably not be any good after ten or twenty years, as the cask will have a very slow effect on the spirit, but over a very long period the spirit will penetrate deep into the wood picking up a great deal of complexity. In the past, the effect of oak on maturation was little known and in years gone by, in the 1950’s or 1960’s for example, spirit was filled into some very used casks, which after 50 or sixty years has created some of the most remarkable whiskies ever bottled.
Around 2-3% of casks used for maturing whisky are made from unusual ex wine or fortified wine casks. For example, ex Port pipes, Madeira barrels, ex Cabernet Sauvignon or Sauternes barrels can be used. These casks give a huge amount of flavour to whisky and must be used carefully if a full maturation of the spirit is intended. More often, these casks are used for what is called “finishing”, “extra” or “double maturation”.
A spirit might spend the first years of its life in an ex Bourbon cask, and then between two months and a few years in one of these other types of cask. This can create other flavours, for example ex Port pipes can give red fruit flavours, and Sauternes more honied flavours.
Ex whisky casks can also be used to give flavours not normally associated with a particular spirit. For example, a distillery not making peated whisky could use casks which previously held peated whisky to give a little of that flavour profile to their spirit. In recent years, with greater understanding of using different types of casks for maturation, there has been a great deal of experimentation. I once asked Diageo’s Master Blender Jim Beverage shortly before his retirement about what types of wood he was experimenting with. His answer was “If you’re asking the question, the answer is yes”.
In Scotch whisky maturation, size does matter but it depends on what you want. In general, like in wine, the larger the vessel, the longer the maturation will take. A quarter cask (50lt) will take much less time to mature a whisky than a barrel which is around 200lt, and a 500lt Sherry Butt will take even longer. The climate also needs to be considered.
In Scotch whisky maturation, size does matter but it depends on what you want. All in all, cask maturation is as much an art as it is a science. Being able to judge a cask and use it appropriately is a great skill. Size, wood type, previous liquid held, age of cask and where it is kept are all important. A quarter cask (50lt) will take much less time to mature a whisky than a barrel which is around 200lt, and a 500lt Sherry Butt will take even longer. The climate also needs to be considered.
ABOUT THE AUTHOR
Colin is a presenter on The Three Drinkers TV series on Amazon Prime, chairman of the Circle of Wine Writers and a Keeper of the Quaich . After starting his career at The Scotsman, he has worked at The Times and FT before becoming the founding editor of Whisky Quarterly. He is now the whisky editor for Club Oenologique magazine, and is an international wine and spirits judge, including judgi ng for the International Wine and Spirits Competition. Colin Is also a liveryman of the Worshipful Company of Distillers. Jennifer was thrilled for the opportunity to merge her communications background with her passion for wine in accepting a position as Acker’s Director of Marketing & Communications in 2021. Wine is intriguing to Jennifer in large part because there’s always something new to master, and she’s currently busy learning the auction side of the business as part of the team at Acker. When she’s not holding a wine glass, Jennifer is lifting a barbell or planning her next travel adventure.