Capacity determines the volume to surface ratio
The size of the casks determines the volume to surface ratio.
The greater the capacity, the higher the ratio, which at equal volumes leads to slower ageing with, in particular :
● less extraction of the wood’s compounds and
● fewer transfers (evaporation, oxidation, etc.).
The technique called “ullage,” which consists in topping up casks with eau-de-vie from the same source, is used to compensate for natural evaporation, in order to preserve the volume to surface ratio.
Ageing is faster in smaller containers
350 litre barrels are currently the most commonly used for ageing Cognac eaux-de-vie.