Whisky is rarely made using virgin casks. Instead, casks that have previously held other alcohols are used. The benefit of this is that the alcohol held previously is absorbed into the wood of the cask which - when used a second time – transfers its flavours to the whisky. Whisky produced from bourbon barrels has a sweet taste with vanilla and caramel tones.
There are two methods for burning a cask: charring and toasting. Charring causes the wood sugars in the interior of the cask to caramelize. The whisky absorbs flavours from the caramelized lining giving it a sweet taste. Toasted casks are heated gently; because of this, the wood sugars have less time to caramelize resulting in a sharper tasting whisky.
Scotch lovers: Know your barrels
Sherry casks work the same way as bourbon casks but with different results for flavour. In the cask’s first use, the sherry is absorbed into the oak and then absorbed into the whisky. The result of whisky matured in sherry casks are wine and raisin flavours.
BIG VS. SMALL CASK
When it comes to casks, size matters. Whisky develops its flavour by absorbing different elements from the wooden cask it’s contained in. The smaller the cask the more contact the alcohol has with the wood, and the greater the impact of the flavours. Correspondingly, bigger casks holding larger volumes of liquid result in a subtle extraction of flavours and a more understated taste.