Cognac is the product of the double distillation of local white wine, which is acid and not high in alcohol, in a Charentais copper alambic, heated over and open fire. Of the “brouillis” thus redistilled only the “heart” is retained, the “head” and the “tail” being eliminated.
The clear and aromatic eau-de-vie which emerges from the alambic only becomes “Cognac” at the end of a long process of ageing in oak casks in the windowless winestores. The substantial amount of alcohol which evaporates during this ageing is called the “Angel’s Part”. This evaporated alcohol is responsible fot the black patina on the walls.