WHISKY IN CASKS

Whisky is made in the cask. To put it simply, the young spirit that goes into the cask emerges transformed into complex, multi-layered whisky. In Scotland the whisky must by law spend three years maturing in cask to be legally labelled as Scotch, while in Japan any whisky classified as Japanese Whisky must be cask aged for a minimum of two years. So, what exactly goes on inside the cask and how does it affect the flavour of the whisky?

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What Happens In The Cask?

Once inside the cask the young spirit gradually begins to change in character thanks to evaporation. Oak is used to make whisky casks since it is porous and allows a small quantity of liquid to evaporate. Alcohol is more volatile than water, meaning that a greater proportion of alcohol is lost compared with water and other components of the whisky. The result is that over several years the whisky becomes smoother and rounder, and also absorbs flavours from the oak itself.

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Size Matters

Another key factor to consider is the size of the cask. Smaller casks mature more quickly since there is greater contact between the whisky and the side of the barrel which facilitates a faster rate of evaporation and thus maturation. In larger casks there is also less extraction of flavours from the oak due to the reduced surface contact per litre of whisky. This is why Scotch must be made in a cask that is no larger than 700 litres and made of oak to ensure consistency.

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Maturation Length

As mentioned earlier, Scotch must be matured for at least three years in the cask, but many highly-prized whiskies are aged for decades in the cask before being bottled and released. Single malts are usually aged for at least 12-21 years. It is important to bear in mind that the whisky only continues to evolve and develop inside the cask. When it is bottled the flavour profile will not continue to improve.

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Sherry & Bourbon Casks

Once inside the cask the young spirit gradually begins to change in character thanks to evaporation. Oak is used to make whisky casks since it is porous and allows a small quantity of liquid to evaporate. Alcohol is more volatile than water, meaning that a greater proportion of alcohol is lost compared with water and other components of the whisky. The result is that over several years the whisky becomes smoother and rounder, and also absorbs flavours from the oak itself.