How is Scotch whisky aged?

One of the most important parts of whisky production is a component that is hardly overlooked. In fact, most bottles mention it proudly right on the label. We’re talking, of course, about the type of barrel used in the aging process. The raw spirit produced in the distillation process is colourless and lacks the rich taste the wood in the barrels will provide after years of maturation. The barrels play a huge role in giving the final product its flavour and appearance. So what are the various types of barrels used? Well, Scotch is aged in oak casks. American or European oak to be precise. But that’s not all, there’s much more to it than just the cask. What these casks previously held before the raw spirit was placed in them for aging is even more interesting in terms of what the final product will taste like.

Most whisky, as any trip to the SAQ or local liquor store will confirm, is made from barrels previously holding bourbon. Bourbon casks are only used once, so it makes for a great relationship between the two industries. The casks, once used, are shipped across the Atlantic to Scotland to find a second life as ex-bourbon whisky casks. Bourbon casks are charred on the inside, and provide a distinct range of flavours. Many Scotches are produced using casks previously having held sherry. Again, different flavour profiles can be achieved though these ex-sherry casks. The remainder can be all kinds, the bottle of the whisky you are purchasing will normally indicate what you’re looking at. In some of my tastings, I have noted that the Scotch is principally aged in one type of cask and finished in another. This is clever play on tastes and differentiating one product from another, even within the distiller’s own line.

Of import is also how many times the cask is used for aging. The first time the barrel is used for whisky imparts more flavour, the more a cask is used, the less of its features will be transferred to the final product. Again, this can be used to modify the final product depending on what the distiller is hoping to achieve. A strong product using first fill ex-bourbon? A weaker bourbon cask mixed with a strong first fill ex-sherry to pull some more sherry and limit the effects of the charred oak cask? All kinds of possibilities are available to a master distiller.

Sherry casks come in many different types, the one I see the most on labels happens to be Oloroso. Sherry being a type of fortified wine, the grapes end up impacting the flavour of the final product.

I spoke about the size of the cask and its potential impact in my Laphroaig Quarter Cask review and won’t go into it further here. However, other conditions, such as allowing the whisky to age near the sea and let the salt water permeate the barrels, also plays a role in the final flavouring. The type of cask, ex-bourbon or ex-sherry, also plays a part in the colour of the whisky. Ex-sherry casks will give off a deeper amber while ex-bourbon is typically in the gold hues range. Some whiskies are even finished in a barrel holding another type of alcohol altogether, such as rum. Fascinating stuff really and only limited by the distiller’s imagination.

By law, Scotch must be aged at least three years to be called such. Most, of course, is aged longer. Longer does not necessarily mean better. As you can see, several factors play into the final product and everyone has a different definition of a good whisky.

Hope that helps, I’ll add more as I learn more about this subject and notify when I update this space.



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