The bubbles in champagne are pure carbon dioxide gas, made naturally by yeast as it ferments the grape juice. Champagne ferments twice - once in a tank, then again inside the sealed bottle. The second time, the gas has nowhere to go, so it dissolves into the liquid under enormous pressure.
A typical champagne bottle holds about 6 bar of pressure - roughly three times what’s inside a car tyre. That’s why the glass is unusually thick and the cork is wrapped in a little wire cage. Without the cage, that pressure could pop the cork right out on its own.
When you do release the cork, it can blast out at over 80 kilometres per hour - faster than a car in a school zone. Each year people lose teeth, eyes, and parts of ceilings to flying champagne corks, which is why bartenders are taught to twist the bottle slowly, keep their thumb over the cork, and aim away from faces.
