During the third phase, the new wine is clarified and stabilized. Winemakers clarify wine by fining, racking and filtration. These materials must be removed to prevent them from precipitating out of the wine later. In the fourth phase of winemaking, the winemaker ages the wine. Most high quality wines are aged in bulk and then for an additional time in the bottle.
Winemakers have an active role throughout the lengthy bulk aging process.
Wines are smelled, tasted and measured every few weeks, and any needed adjustments are made promptly. Except for the first phase, the other three winemaking phases overlap each other. New wine starts to clarify toward the end of the fermentation period. Some tartrates precipitate out during primary fermentation, and the wine becomes more stable. Of course, wine is aging throughout the winemaking process.