Topping up: given that wood is a porous material, part of the wine in the barrels can evaporate.

As the environment is deliberately kept humid this phenomenon is limited, but does occur.

If the level of the wine drops even by a little, then a contact surface is created that may bring about alterations such as oxidation.

Continuous checking is therefore carried out, intervening by periodically topping up with wine in order to keep the barrels full where necessary.