Changes

"Mushrooming" is the actual or perceived compression of the top part of the cork that protrudes out of the bottle, and is often preferred for the aesthetic appearance. The practical benefits of mushrooming are debatable, as is the cause of mushrooming when no effort is made by the brewer to manually compress the top portion of the cork. Some people believe that this compression happens naturally after packaging over time and is due to high carbonation in the bottle pushing the cork out of the bottle, which is held in by the cage. However, in many cases this might be just an illusion of appearance and the cork may not actually be compressed at all, but just appears to be compressed by the cage due to the much thinner "leg" of the cork which is compressed by the lip of the bottle (see [http://www.notcot.com/images/2009/09/gatinoismain.jpg this image] for an example). A more likely explanation is that the lip of the bottle compresses the "leg" of the cork, making the top portion look like a mushroom, but this top portion of the cork may not actually be compressed at all. Some people claim that manual mushrooming makes removing the cork easier and allows for more "pop" noise, while others say that mushrooming does not serve any functional purpose and is not necessary. See [https://www.facebook.com/groups/MilkTheFunk/permalink/1920123874682484/ this MTF thread] for more opinions from various brewers.