The base wine is put into pressurized tanks for the prise de mousse; here it ferments for 18 - 20 days, with the aid of selected yeasts, at a controlled temperature of between 15 and 18 °C (59 – 64 °F). Once the desired pressure has been obtained (around 6 bar), the wine is chilled to -4 °C (25 °F) in order to block the fermentation and favor stabilization. It is then maintained at a controlled temperature for at least a month, so as to favor its natural maturation in contact with the lees. This is followed by filtering and isobaric bottling.