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. (Some houses have automatic riddling machines.)
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.
