he process of making sparkling wine in sealed tanks in Italy is generally known as metodo charmat normally, refermentation on the lees lasts from two to four weeks.
In recent times, a method known as charmat lungo has been devised, mainly for sparkling wines from Chardonnay and Pinot. This "long" process leaves the wine in contact with the lees in the tank for three months to a year to duplicate some of the effects of the classic method. Both variations are based on the following procedures:
Refermentation
The base wines blended with selected yeasts and sugar are placed in large, stainless-steel tanks known as autoclavi,where refermentation takes place at cool temperatures under pressure of about 7 to 8 atmospheres.
Isobaric filtration
When refermentation is complete, the wine is separated from the lees by passing through a filter into another tank under equal (isobaric) pressure.
