VCL Vintners



Maturing whisky in the cask

Maturing whisky in the cask

When the whisky runs down the stills, what you get is a clear liquid called new make. When you taste new make, it’s difficult to enjoy for the average scotch lover, it usually has a flavour profile that consists of fresh apples, pears, cereals, mint and citrus fruits. Doesn’t sound too bad, but it’s all pretty harsh. When it’s a peated malt, there’s of course notes like smoke and sulphur. New make is drinkable, but not something you sit back and relax with..

So whisky has to mature to make it the drink we all love. There’s a strict rule that maturation has to be at least 3 years and in oak casks. Why oak? Oak is very easy to come by and work with. It perfectly softens the harsh taste of new make and results in more depth and the flavours that people want to taste in whisky. How long a whisky matures and which types of oak casks are used, have an enormous impact on the taste. The longer the better is not ways true, although you can definitely tell the difference. So years and years of maturation is sometimes for the better, and sometimes for worse. It all depends on the initial spirit and the interplay between it and the casks.

These casks can be used multiple times and they often held other types of spirits before. There are also different sizes. The larger the cask, the slower the effect on the taste. But slower maturation also means more depth and elegance. A master distiller has to have a fine feeling for many aspects, and he sort of has to look into the future. Even casks of the same type can also have a very different effect throughout maturation, but that’s where the blending of casks comes in. Let’s keep it brief, you get the idea: there’s lots of factors that play a role when it comes to maturation.

Bourbon casks

Since bourbon has the strict rule to mature on fresh oak casks, it was a no-brainer for the early Scottish distillers to buy their used casks to mature their whisky in. And so scotch traditionally matures on ex-bourbon casks. Also, the Scottish climate is too cold for new oak to give the very best results, so it’s a huge win, both economically and flavour wise.

Ex-bourbon casks give whisky their typical vanilla taste, they also tend to enhance tropical flavours like pineapple and coconut. While virgin oak often leaves the whisky with an oaky and harsh character, ex-bourbon makes whisky creamy and smooth. It works very well with peat and is also a good base for a second maturation or finish in a later stadium. 


Virgin Oak Casks

You’ve probably heard from whisky that has matured on virgin oak casks and as the name already reveals, this spirit matured on a new cask that isn’t affected by any other liquid before. If this particular whisky doesn’t have a finish on a different cask, you’ll get the chance to taste the true character of the whisky, and the influence the new oak has on the new make. It is an interesting thing to see how the whisky develops with only new oak to mature on. Free from all the restraint or interference of other casks it needs to find a way to create a rich and complex palate and be as pure as possible at the same time.

Virgin oak casks are adding a new dimension to whiskies of all kinds, due to the freshness of the wood, spicy and peppery notes are shining through. Vanilla and of course oak flavours are richly presented. It depends largely on the character of the spirit how well the whisky turns out. Some might need a different finish to get that extra rich palate. And due to the cold Scottish climate, virgin oak doesn’t always have the preferable effect, which is why bourbon casks are mostly the cask type of choice for more impact on flavour in less time.


Sherry Casks

Sherry casks are probably one of the best-known to mature and/or finish whisky in. It pairs extremely well with all sorts of whisky and were of course present in sufficient numbers. Nowadays the demand for sherry casks for maturing or finishing whisky on is way bigger than people who actually drink sherry. They’ll even have to throw away sherry just to sell the casks to the distilleries, can you imagine?

Now, there are different types of sherry (casks) which are used in the whisky-industry, we’ll talk you through the most important ones.

Oloroso – Dry and rich, with walnuts, oak, tobacco and truffles. Autumn leaves and leather are in there as well. The finish is elegant and dry.

Pedro Ximénez (PX) – A sweet and syrupy sherry. Beautiful fruity notes such as raisins, figs and dates. Accompanied by honey, grapes and candied fruit. On the other side are coffee and dark chocolate. A sweet and long finish.

Amontillado – Aromatic and spicy, complex with hazelnuts, dark tobacco and coffee. Very intriguing finish with hazelnuts and oak spices. 

Palo Cortado – Complex and delicate, some sort of combination between Oloroso and Amontillado. Palo Cortado is the rarest of all varieties. Rich and allround, with orange zest, butter and grapefruit. Walnuts, toffees and tobacco. Briny notes and butterscotch in the end. 

Listed above are the most common used sherry casks in the whisky-industry, Oloroso and PX casks are probably best known to everyone. We believe a whisky with a sherry maturation of finish is a must have in your collection because of the rich palate it provides. Glendronach, Glengoyne and Tomatin are examples where the sherry influence has married beautifully.


Wine Casks

We think it is a fine line between hit or miss when it comes to whisky matured or finished on wine casks. Just because there are so many different types of wines in the world, and some do pair with particular whiskies, and others just don’t in our opinion. It is an impossible task to talk about all sorts of wine in this article, so we’ll talk you through a few that are used in the wonderful world of whisky.

Red Wine – There is a lot of red wine matured or finished whisky available on the market, so it is hard to choose which to buy and which to ignore. A lot of whisky hasn’t stated on the label which red wine (In terms of grape and/or region) it has aged on. The most common tasting notes you’ll get are those typical oak spices, plums, black fruit, chocolate and tobacco. A Cabernet-Sauvignon works best with non-peated whisky and a Merlot with peated drams, in our eyes. It is definitely worth trying if you are a wine-lover yourself!

White Wine – Which white wine the whisky has aged on, is often said on the label, contrary to red wine. Here also applies that not every whisky pairs well with the wine flavours chipped from the casks. Typical white wine notes are white grapes (obviously), floral and sweet. Fruits like pineapple, dried apricot and passion fruit. In the end you might encounter some forest soil flavours with autumn leaves and fungus. Chardonnay, Moscatel and Sauternes (Muscadelle, Sauvignon Blanc, Sémillon) do work incredibly well with whisky.

As said before, it is very hard to choose which whisky x maturation/finish will make a great pair, but once you know the tasting notes of both the whisky and the wine you’ll be able to some sort of predict how well it is going to work.


Port Casks

Many distillers aren’t shy of putting port casks into the mix. Whisky that has matured or finished on casks which held the well known fortified Portuguese drink, is part of many core or special release. The casks are better affordable than the beloved sherry casks, so why not?

Just as with wine casks, port is typically hit or miss. The whisky gets spicier, wooden notes are more noticeable, especially with ruby port. And sometimes a lovely and typical candy-like sweetness gives away that there was a port cask involved. Tawny tends to be more like sherry with nuts and dried fruits. So when the type of port is specified on the box or label, be sure to go for the one which has the flavour profile you prefer.


Rum Casks

A more exotic and lesser used method of maturing whisky, is with the use of rum barrels. Mostly just as a finish, because rum casks give a lot of flavour. You might expect a sweet and funky character, and when the sprit and casks are well-considered, this is very true. But definitely not always! 

When done right, you’ll get a tropical boost of bananas, cane sugar, pears, fresh leaves, warming spices and a splash of coconut. Peated whiskies make it even more funky and daring.  But when the spirit is weak and/or the used casks don’t match, there’s the danger of becoming something that more resembles cardboard and gunny bags. 

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