The charmat method is a fairly new method of producing sparkling wines, dating back less than 100 years. The more traditional method is that of conducting the second fermentation in the individual bottles in which the wine is later sold.
Champagne has been made in this way for approximately 300 years and, according to French law, can be made in no other way. Many other French sparkling wines are made in the same way, as are the best sparkling wines from Spain, California, and other countries.
The technique of conducting the second fermentation in the bottle is called the classic or traditional method in Europe; in the U.S., it's called the champagne method or méthode champenoise.
Bottle fermentation (or, more correctly, second fermentation in the bottle) is an elaborate process in which every single bottle becomes an individual fermentation tank, so to speak. This process requires a minimum of one year and usually takes three years or more. Invariably, sparkling wines made in this way are more expensive than those made by tank fermentation.
The elements of bottle fermentation are:
• Each bottle is filled with a mixture of base wine and a sugar-and-yeast solution, closed securely, and laid to rest in a cool, dark cellar.
• Inside each bottle, the second fermentation occurs, producing carbon dioxide and leaving its fermentation lees inside the bottle.
• As the bottles continue to lie in the cellar, the wine gradually undergoes changes through interaction of the lees and the wine.
• Eventually - nine months to several years after the second fermentation - the bottles are put through a process of shaking and turning so that the solid lees fall to the neck of each upside-down bottle.
• The lees are flash frozen in the neck of each bottle and expelled from each bottle as a frozen plug, leaving clear sparkling wine behind.
• A sweetening solution (called a dosage) is added to adjust the flavor of the wine, and the bottles are corked and labeled for sale.
The classic method as practiced in Champagne involves several steps that occur before the second fermentation. For example, the pressing to extract the juice for the first fermentation must be conducted with meticulous care to prevent the grapeskins' bitter flavors — and their color, in the case of black grapes — from passing into the juice. Another step crucially important to the quality of the sparkling wine is the production of the base wine for the second fermentation.
Following the first fermentation, the wines of different grape varieties and different vineyards are kept separate. To create the base wine, or cuvée, the winemaker blends these separate wines in varying proportions, often adding some reserve wine (older wine purposely held back from previous vintages). From 100 to 200 different wines may go into a single base wine, each bringing its own special character to the blend. What's particularly tricky about blending the base wine - besides the sheer volume of components in the blend - is that the winemaker has to see into the future and create a blend not for its flavor today but for how it will taste in several years, after it has been transformed into a sparkling wine. The men and women who blend sparkling wines are the artists of the wine world.