How does the cask affect the character of the whisky?

Malin Åberg

Maturing is the result of a complicated chemical interaction between the material in the cask, the oxygen in the air, and the fusel oils chosen to be kept in the new distillate during the distillation process. The whisky gets its colour and many flavours from the casks. The sweetness comes from the sugar, which comes from the wood as xylose, combined with the lignin, which also comes from the wood (the lignin acts as the glue that glues the tree’s cellulose and turns it into a hard material). When the inside of the cask is charred, the lignin and tree sugar is caramelised, bringing out greater sweetness and notes of vanilla. Oak contains different tannins, which gives a dry and bitter flavour. To bring out the tannins, we let the wood lie outside in the rain and wind before building the casks.

The more times a cask is used, the more its flavouring disappears. Hence, the quality of the cask if very important to the development of a whisky. Mackmyra therefore uses only casks of the highest quality. The American White oak (Quercus alba) is the most common tree to use for casks. We use it in our ex-Bourbon casks and ex-sherry casks. Our Swedish oak casks are built with the Swedish Forest Oak (Quercus robur), which has less tree sugar and lignin. The Swedish oak thus creates different flavours in the whisky compared with the American oak: less vanilla sweetness and a spicier ‘oakiness’.


Traditionally, whisky is aged on casks measuring 200 litres up to 700 litres (700 litres is the biggest size allowed). At Mackmyra and for Den Första Utgåvan (The First Edition) now Svensk Ek, we chose to use smaller casks of only 100 litres. What happens when we use smaller casks is that the maturation speeds up. This is down to the fact that a smaller cask has more wood in proportion to the liquor compared to a bigger cask.

What else can be said about whisky aged in small casks? First and foremost, it’s a new kind: a bolder whisky compared to the traditional. Compared to the traditional, it certainly comes from the cask with more intense flavours. There are more fresh toffee notes in the ex-bourbon casks, more sherry notes in the ex-sherry casks, and more spicy oak in the new Swedish oak casks.

Let me know in the comment field if you have more questions!

/ Malin Åberg, Marketing Coordinator