« Champagne »… « Champignon »… Almost the same word in French! But there’s no relation at all between cork’s shape and its etymology!
The role of the cork is essential; it’s the guardian of the quality of the wine. The corking must ensure the perfect sealing of the bottle’s content. The cork is elaborated from the slow-growing oak cork, and the syndicate of champagne corkers points out that the best quality of cork is obtained when the tree is 35 years old and over. The cork is not compulsory, but it is still used in Champagne except for some small exceptions.
Before being installed on bottles, the cork of sparkling wines, and therefore Champagne, have a perfectly cylindrical shape, alike the cork of wine’s bottles. Nevertheless, it is elaborated from a harder natural cork in order to prevent the gas to escape. This kind of cork is called « thin ». It has a strong density, allowing to resist to the pressure released by the champagne bottle. In order to ensure a proper resistance, their initial diameter must be 31 mm, 13 mm more than the diameter of the internal neck of a bottle of champagne.
Nowadays, the champagne cork is composed of 2 parts:
They are then softened so that they can be compressed and pressed into the neck of the bottle over half their length with the bottling machine. Last step: it is crushed in the shape of a mushroom to receive the muselet and to resist to the pressure. It is said that the cork cap petticoats!