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.