Starting life as a relatively raw spirit, whisky takes its sweet time to develop the flavours, fragrances and smoothness that define its character. The spirit itself is vital, but the cask is also key. Whisky draws its taste and colour from it and, over time, mellows and grows in complexity.

INTO THE WOOD

At the heart of whisky’s flavour profile is oak. Spanish, French and American oak are the most widely used, as the tight grain of the wood is dense enough to prevent leakage but sufficiently porous to allow the spirit to draw upon its flavours.   

SEASONS CHANGE

It’s not just the physical time that whisky spends in the barrel that influences its character, but also changes in its environment. Fluctuations in seasonal temperatures cause the liquid to expand into and contract out of the wood, an essential exchange that helps develop flavour. Various climates contribute to a whisky’s character in distinct ways. Scotland’s mild temperature swings have a very different effect than Kentucky’s more dramatic changes between summer and winter. This more pronounced shift from hot to cold can ultimately speed the maturation process of bourbon in comparison to Scotch.

TIME AND SPACE

Even the characteristics of the warehouse play a part in developing taste, which is why distillers maintain such close control of the internal temperatures. The building’s structure and materials also have an influence — for example, it matters whether the cask is stored on the warmer upper or cooler lower racks in the warehouse.

SLOW FINISH

To tweak the final result, some whiskies will undergo a last stage known as “finishing,” during which they are transferred to a different cask — wine, sherry, port and Madeira casks are common — to add another level of complexity. Then it’s out of the barrel, into the bottle and, finally, into your glass.