'Once the sediment is sitting securely behind the seal closure it is a simple process to release the cork or cap and thus allow the pressure built up within to push out the wine, complete with sediment. This process, the dégorgement a la volée, has however been largely superseded by the dégorgement a la glace, although there are a number of producers, largely small family firms, still using the former method. The added finesse with the a la glace technique is achieved by freezing the liquid - complete with sediment of course - in the neck of the bottle.'
(http://www.thewinedoctor.com/regionalguides/champagne4method...