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6 Types Of Whisky Casks And How They Impact Flavour

By: Shireen Jamooji

whisky casks

Have you ever wondered what makes a fine whisky truly unique? It’s likely that the first thought that comes to your mind is its age. After all, we all know that an aged whisky is more valuable than a new one. But it’s not simply the time frame which contributes to the unique profile of the alcohol, it's the container in which it's aged, otherwise known as whisky casks. 

Over the years, there have been many types of casks and processes used to treat them which help determine the final flavour of the whisky inside. The size and shape can also be significant factors with smaller casks imparting a more concentrated flavour which makes them more popular for finishing whiskies. Many distilleries also employ the use of casks that previously held other alcohols. For example, ex-bourbon casks can be used to mature whisky and impart sweeter vanilla and caramel notes. Sherry casks too are also popular with each variant of sherry lending its own profile to the final product. 

whisky

The number of times a cask is employed to mature whisky significantly affects the flavour of the dram. As a cask undergoes more refills, it imparts less flavour and colour. Consequently, many whiskies specify on the label whether the liquid matured in a first-fill or refill cask. But by far the most important factor to consider is the type of wood used to make the cask. Oaks are the go-to wood for whisky casks and each one goes through a toasting process that caramelises wood sugars to create the sweet flavours imparted into the dram. However, some whiskies mature in heavily charred casks, with the charring process lasting between 30 seconds and three minutes. The longer the charring, the more porous the wood surface, facilitating greater absorption of the spirit. 

Here are a few types of whisky casks you should know and how they affect the flavour of whisky.

6 Types Of Whisky Casks

Sherry Cask

This popular fortified wine from Spain is frequently employed in maturing whiskies and brings out a fruity, nutty, flavour with rich aftertones. The oak cask imparts a rich flavour, while the sherry contributes to a velvety texture. Whiskies aged in sherry casks typically exhibit a darker colour and an almost nutty flavour. If you're sampling a whisky aged in a sherry cask, you'll likely detect a subtle sweetness from the previous alcohol.

Bourbon Cask

American bourbon is legally only allowed to be called bourbon if it's aged in new oak casks, this means that there is always plenty to go around for the whisky industry. When aged in these charred oak casks, the whisky acquires a spicy, smoky flavour from the wood and toasting process as well as a slight sweetness with hints of vanilla.

Rum Cask

The pride of the Caribbean, barrels used to store and age rum often find their way into the whisky industry and impart a robust flavour and a touch of sweetness to the cask wood. Whiskies aged in rum casks often exhibit a caramel flavour thanks to the residual sugars in the rum, are rich and full-bodied, and are usually designed to be enjoyed neat or with a few ice cubes. 

Tawny Port Cask

Another variation on the wine cask Port, a wine from Portugal, is commonly used in maturing whiskies, providing a strong, woody flavour and an almost smoky taste. Whiskies aged in tawny port casks are typically rich, full-bodied, and enjoyed neat or with ice. Tasting a whisky from a tawny port cask, you may notice a slight sweetness attributed to the residual sugar in the cask.

whisky cask

Muscat Port Cask

Muscat port, a wine variety often used in whisky maturation, imparts a strong, woody flavour reminiscent of a smoky taste. Whiskies aged in Muscat port casks are rich and full-bodied, often enjoyed neat or with a few ice cubes. Tasting a whisky from a Muscat port cask, you're likely to discern a subtle sweetness from the residual sugar in the cask.

Mizunara Oak

A speciality variation on the common oak barrel comes from Japan and is highly sought after. These oaks need to be a minimum of 200 years old before they can be cut and used in casks and the huge demand has resulted in them being some of the most expensive casks around. They’re known for imparting flavours of sandalwood and coconut into the whisky.