The yeasted malt is pumped to the fermentation tanks. The fermentation room contains 10 tanks of 5000 l each. To fill one of those tanks, two yeasting containers of about 2500 l are needed. That stage occurs naturally due to the yeast and does not require water to be added.
The substance will rest for 48 hours at a temperature of 28°C. during that period, fermentation will take place. The sugar obtained during the saccharification stage will be converted by the yeast, alcohol, and CO2, evacuated through the holes of the mounted floor; the room is ventilated by means of open windows.
To be noticed is the fact that fermentation actually begins after 4 hours of rest. A 'hat' is formed, which stays at the surface due to the yeast rising for the 'high' fermentation. After 24 hours, temperature rises to 33°C, stabilises, and then gradually decreases. Yeast sinks then again in the tank. After between 48 and 72 hours, we obtain a "petite bière" with 4 to 5% alcohol volume.
Animated and commented scheme of the production process (Flash)