There are two main methods of making sparkling wine: the champenoise method of bottle fermentation, known as the metodo classico or tradizionale in Italian, and the sealed tank fermentation method, often referred to as metodo charmat. A detailed description of the former starts with the following paragraph, while the latter is the subject of this section's next and last chapter.
Assembling the base wine White Chardonnay and dark Pinot Nero grapes (as well as Pinot Meunier and sometimes other varieties) are picked before they are fully ripe to retain high acidity. After alcoholic fermentation, the wines are blended by each producer into an individual cuvee, which may include different vintages.
The tirage The base wine is then put into the same bottle in which it will eventually be sold and the liqueur de tirage - a syrupy solution that includes cane sugar and special strains of yeast - is added.
The refermentation After being sealed with metal caps, bottles are stacked horizontally in a cool cellar where the wines undergo a second fermentation. The yeasts gradually transform the sugar into another 1 or 2 degrees of alcohol as carbon dioxide builds up to a pressure of 5-6 atmospheres. This process, known as the presa di spuma in Italian, forms the fine bubbles known as perlage.
Aging on the lees The wine is now sparkling but is by no means ready for sale. It must now age on the lees for about two years as the yeast cells break down in a process known as autolysis. Bottles are periodically restacked to control breakage and shaken violently to keep the yeasts suspended. The wine develops a faint yeasty flavor, though freshness and fruitiness are maintained by the formation of esters that also enhance aromas. The absence of oxygen consumed in the refermentation allows the wine to develop natural stability.
Riddling Once aging is complete, the spent yeasts must be removed from the bottle to leave the wine bright and clear. The first step is riddling, or remuage, in which bottles are placed top down at 45-degree angles in the slots of hinged A-frame racks known as pupitres. Over the next few weeks, riddlers deftly agitate and twist each bottle an eighth of a turn a day to work the sediment down to the neck. The bottles are gradually declined in the pupitres until they are directly upended and the deposit rests against the cap.
Removing the sediment The next step is to remove the sediment from the bottle. This degorgement, or sboccatura in Italian, was difficult when done by hand, but it is now accomplished quickly and cleanly by machine. The neck of the inverted bottle is inserted into a chilled saline solution, freezing the deposit. Then the bottle is placed upright and the cap removed as the wine's pressure expels the plug of ice.
Topping up After removal of the sediment, the bottle must be topped up immediately and sealed with a cork. Most types of spumante classico receive a dosage, or rabboccatura in Italian, of the so-called liqueur d'expedition, a solution of aged wine and cane sugar. (Chiedere a Majolini)
But the driest type, known as pas dose', is topped up with the same wine. The dose of liqueur varies according to types, which are classified as follows, according to degrees of residual sugar:
Brut, or pas dose' (no more than 15 grams per liter of residual sugar)
Extra dry (from 12 to 20 grams per liter)
Secco (from 17 to 35 grams per liter)
Semisecco (from 33 to 50 grams per liter)
Dolce (more than 50 grams per liter)
Bottles are then sealed with corks, which acquire the familiar mushroom shape with time. Corks are anchored with wire baling, to insure that the pressure within the bottle won't force them out, and bottles are stored for a time so that the liqueur becomes amalgamated with the wine.
On average, a fine, bottle-fermented spumante requires about three years of processing before it is sold.
