When the champagne cork is pulled out, why is it mushroom-shaped, with the bottom swollen and difficult to plug back in? Winemakers answer this question.
The champagne stopper becomes mushroom-shaped because of the carbon dioxide in the bottle—a bottle of sparkling wine carries 6-8 atmospheres of pressure, which is the biggest difference from a still bottle.
The cork used for sparkling wine is structurally composed of several cork chips at the bottom and granules at the top. The cork piece at the bottom is more elastic than the top half of the cork. Therefore, when the cork is subjected to the pressure of carbon dioxide, the wood chips below expand to a greater extent than the top half of the pellets. So, when we pulled the cork out of the bottle, the bottom half popped open to form a mushroom shape.
But if you put still wine in a champagne bottle, the champagne stopper doesn’t take that shape.
This phenomenon has very practical implications when we store sparkling wine. To get the most out of the mushroom stopper, bottles of champagne and other types of sparkling wine should stand vertically.