After fermentation, the white wine is distilled into ‘eau-de-vie.’ To become Cognac, this involves a double distillation, for which only the heart, or middle portion of the second distillation is retained. The heads, too high in alcohol, and the tails, lacking harmony, are carefully removed and distilled over again to perfection.
For its first distillation, the unfiltered wine is brought to boil in the copper pot. Since alcohol evaporates faster than water, alcoholic vapors can be collected in the onion dome shaped cowl and in the swan neck, which slows the rectification process of the flavors, before passing into the long serpentine condenser coil. Vapors condense to the contact of the cooler and turn into a liquid known as ‘brouilli,’ with an alcoholic content of 27 to 30% vol. This is distilled a second time in a process called the ‘bonne chauffe’. The distiller’s key task is then to choose the moment when to isolate the ‘heart’ of this second distillation, extracting the ‘head’ and the ‘tail’ in the process.
This distillation process is a delicate and slow one. It lasts for approximately twenty four hours and requires the constant care of the distiller. It usually begins in November and is conducted day and night for several months. The rule binds it to stop at the latest at the end of March. Distillation is a key factor that gives Cognac its distinctive character. Its secrets are handed over from generation to generation.