The purpose of distillation is to separate the alcohol from the remaining substance generated in the fermentation tanks. Its principle is simple: the alcohol turns from liquid into gas at a temperature of 78.4°C, while water turns into vapour at 100°C.
The distillation room is also called the "salle du Palais", since it contains the most impressive machinery in the distillery. There are three distillation columns, ,three wine heaters, five coolers, and two alembics. It is also the quietest room, since distillation is done under the protection of the statue of Saint Mary Magdalene, the patron saint of the distillers and of the sinners.
By gravity, the fermented malt is poured in the transfer tank located between the fermentation room and the distillation room; then it is pumped by means of four twin pumps towards one of the three brass wine heaters.
The wine heater fills from the bottom with fermented malt; by overflow, the malt arrives at the top of the distillation column. Each brass column is of 1880 and consists of 17 plates with 7 holes with caps and of one single chimney to allow the alcohol to rise. The plates are crossed in order to slow down the descent of the substance in the column.
The distillation column is heated from the bottom with live steam to reach a temperature of 99.5°C below. The malt, fed into the top of the column descends from one plate to the other to the bottom of the column. As the descent proceeds, the liquid alcohol turns into gas and rises gain in the column, whereas the water still liquid and the remainders of the solid substance are released at the bottom; they form swill.
The alcohol vapours, after arriving at the top of the column pass through a spiral tube in the wine heater. By means of heat exchange, the malt coming from the fermentation room is pre-heated by the spiral tube, which contains the alcohol vapours that are pre-cooled due to loss of calories.
The alcoholic vapours descend through a spiral tube in the cooler to reach 20°C. The alcohol gas is cooled and becomes liquid: it contains 35% of alcohol volume; it is called flegme. That alcohol is not usable as such, since its taste is not refined enough. That alcohol was given to the soldiers who fought in the trenches during WW I. The flegme is pumped by one of the twin pumps towards the two raised transfer tanks to rest there for 48 to 72 hours.
The remainders of the distillation arrive at the bottom of the column with their alcohol contents completely removed, and they are then pumped to a sump tank. There will be separated the clairs (the liquid remainders of distillation) and the swills (solid). The clairs (30%) are pumped to the cooling building, called the "Plat bac", to be cooled gradually in the large surface tanks of hardly 30 cm high, in contact with the surrounding air.
The shallow tank, located on a kind of Eiffel Tower, is a well-ventilated building. The clairs will be reused during the cooling and yeasting stages.
The swills, more solid (70%), are given to the cattle breeders in the neighbouring villages and constitute for the cattle high-quality food, natural, and much richer than the imported soy cakes.
After being deposited in the raised resting tanks, the flegmes are emptied in one of both alembics to undergo a "distillation by slow evaporation". The purpose of that second distillation is to produce consumption alcohol, which is perfumed by the juniper berries.
the brass alembic of the "Charentais" vapour heated alcohol is infused, and 900 g of juniper berries are suspended in a basket. The alcohol, with its property of absorbing perfumed gas, fills itself with the perfume of the juniper berries. As such, a jenever is obtained, which bears the juniper perfume. That second distillation enables to remove the "heads", to keep only "heart of the distilled substance" which will produce the alcohol needed for the jenever, and to remove the "tails" that contain the fat alcohol.
The alcohol comes out from the swan neck of the alembic, passes through a cooling substance and has a 63-65% volume at a temperature of 20°C. after an imperative passage through an official meter that registers the quantities of jenever produced, the jenever passes into glazed tanks in order to be quantified again.
Animated and commented scheme of the production process (Flash)