Maturing in oak casks is a delicate art that shapes and refines every nuance of whisky. The maturation process gives whisky its amber hues and complex aromas. Discover with us the subtleties of whisky maturation, where each year spent in cask weaves a new chapter of flavour, colour and character.
Due to its many essential qualities in barrel making, the main wood used in cooperages is oak. Other than its mechanical properties, it also has excellent thermal insulation and remarkable watertightness.
Oak growth depends on multiple factors, and consequently affects the grain size and chemical composition. Depending on the growth conditions, the heartwood of the three main oak species used in cooperages has a specific polymer structure and aromatic molecules, that will influence the quality and sensorial characteristics of whiskies.
The barrel making process in cooperages involves a series of steps that influence the oenological quality of the wood. As we have seen previously, the geographical origin determines the structure and the chemical composition of the wood.
Once the selection has been made and after the transformation of logs into rough staves, the last crucial step is drying the wood. Natural seasoning encourages wood maturation, reduces bitterness and astringency, and increases its aromatic properties. This evolution in the wood’s structure is decisive for its future transformation into barrels.
« Bousinage », or toasting, follows the bending step in the barrel’s production cycle. This process has a strong influence on the wood’s final quality, and therefore on the whisky.
Generally, a distinction is made between light, medium and heavy toasting. During this step, there is a thermal degradation of the wood’s macromolecules, generating the release and accumulation of new aromatic compounds. Therefore, depending on the desired sensory profile, it is possible to adjust the toasting level for a better integration of the wood’s properties into the whisky.
Charring is a key stage in the manufacturing and recycling of a cask. This process affects the interaction between the whisky and the wood on several levels. On the surface, large cracks are created by very high temperatures, allowing molecules to be released and enhancing whisky maturation. This active charcoal surface also improves the quality of the distillate by absorbing unpleasant odours.
Some casks are also recycled by scraping and then re-burning the surface, reactivating the wood. This regeneration releases certain compounds but does not give the whisky as much complexity as ageing in new casks.
