Disgorgement is specific process of removing the dead yeast lees (sediment) resulting from the secondary fermentation which occurred inside the bottles of Champagne and other quality 'Méthode Traditionnelle' Sparkling wines.

So how is this process done? - Once the bottle has been inverted (nearly upside down - after riddling), the next process is called disgorgement, disgorging (or 'degorgement' in French), the removal of lees (dead yeast cells) now collected in the neck of the bottle. The neck containing the sediment is snap frozen by immersing it in a solution of freezing brine solution at around -20ºC to -30ºC (or with liquid nitrogen).

 

Once this has occurred, the bottle is carefully moved to an upward angle of approximately 45º degrees - at this point, the bottle will be closed with a bottle crown-cap in most cases, some producers may still use a cork and clip closure. Then carefully opened and the ice plug of frozen wine (containing the deposit and a small amount of wine) is ejected by the carbon dioxide gas pressure inside the bottle, leaving behind a clear Champagne.
As the wine is now very cold, there is minimum gas pressure lost from solution during this process. The bottle is then topped up with the same wine and normally sweetened with 'liqueur d'expedition' to give it the desired balance and finished style. Even wines designated as 'Brut' are sweetened and contain 6-12 grams/litre of residual sugar.
The bottle then has the cork inserted and the wire (muselet) is applied. The sparkling wine can then rest for a period of time, and then dressed for the market and eventual enjoyment.

Until this process was invented - Champagne was cloudy, a style still seen occasionally today under the label 'Methode Ancestrale'. The removal process was a skilled manual process; modern disgorgement is now automated but still great care and attention is required to ensure the result is a clear, quality sparkling wine.