The base wine is put into pressurized tanks for the prise de mousse. There it ferments for 18-20 days, with the aid of selected yeasts, at a controlled temperature between 14 and 16Á C (57 _ 61Á F). When the desired pressure has been obtained (around 6 bars), the wine is chilled to _ 4Á C in order to arrest the fermentation and encourage stabilization. The sparkling wine is then kept at a controlled temperature for at least a month, in order to favor its natural maturation in contact with the yeasts that have deposited on the bottom of the pressurized tank. At the end of this phase, filtration and isobaric bottling is carried out.