sparkling winemaking, making sparkling wines, most obviously involves the accumulation of gas under pressure in what was initially a still ‘base wine’ or, ideally, blend of base wines. The most common methods of achieving this are discussed below but these are matters of technique rather than substance. Almost all of them depend on initiating a second fermentation, which inevitably produces carbon dioxide, and most of them incorporate some way of keeping that gas dissolved under pressure in the wine (see fizziness), while separating it from the inconvenient by-product of fermentation, the lees. What matters most to the quality of a sparkling wine, however, is the quality and character of the blended base wines.
