Definition: Evaporation

The transformation of a liquid into vapour without boiling. The lower the humidity in a cellar, the greater the loss through evaporation from vats and barrels. The loss of liquid, known as 'consume', must be regularly compensated for by 'ouillage', a method of combating oxidation. In the production of brandy, this loss is known as 'the angels' share'. The average evaporation loss in a barrel cellar is estimated at 5% per year. Port producers in the Douro region have specifically chosen to store their wine in the cellars of Villa Nova de Gaia near Porto because it rains as much there as it does in Birmingham. This considerably reduces evaporation loss over years of storage.