Before a cork is installed in a bottle, it is in cylindrical form (and not in the shape of a mushroom, as it appears when you look at a cork) with a diameter slightly lesser than the neck of the bottle.
Uncorking a champagne bottle is more than the simple act of removing a bottle cap; it’s actually a tradition that has a symbolic significance. The custom has existed in western culture for many years, and is becoming increasingly popular among the masses across the rest of the world. Whether it is a sports ceremony, a corporate celebration or a social get-together, it is fairly commonplace to see the host uncorking a champagne bottle to mark an important event.
If you’ve ever been (physically) present when a champagne bottle was being uncorked, you would have definitely noticed that the cork comes out of the bottle with an impressive pop; sometimes, it even flies out with great force and can potentially harm someone in its rapid flight path. The question is, why does the cork pop out? And more importantly, how do they cork the bottle in the first place?
Why Do Champagne Corks Pop?
You may already know that champagne/sparkling wine bottles are under a significant amount of pressure, which makes the cork pop out once you loosen it or remove the wire frame keeping it in place. However, where does this pressure come from? As you may suspect, it has everything to do with the contents of the bottle. Fermentation keeps the carbon dioxide produced by yeasts trapped inside the bottle in the form of bubbles. Since these are special yeasts that are highly tolerant to alcohol, they continue to make more and more carbon dioxide. Having no outlet for release, the pressure inside the bottle keeps on building.
This is why when you uncork the bottle, the pressure is released with tremendous force, making that iconic popping sound. Now that you know what makes the cork pop, can you guess why vigorous shaking of the bottle makes it fizz even more? (Check out the answer here: Why Does Shaking A Soda Bottle Make It Fizz Even More?).
How do they get the cork in the champagne bottle in the first place?
As you saw, there is a tremendous pressure built up within the bottle ready to blast past anything that tries to hinder its outburst; so how do they cork the bottle with that much force working against them? Also, you have surely observed that the corks in regular wine bottles appear to be larger than the holes they fill. So how do they get in there?
The corks of champagne bottles are known for their elasticity and compressibility. Typically, corks are made out of the bark of a tree, Quercus suber (or the cork oak), which is known for having rugged bark and being very large in size. At the cellular level, corks can be easily compressed upon insertion into a bottle; as soon as they are pushed into place, they expand, forming a tight seal.
Now, you may be wondering how they get a cork with a bigger diameter inside the opening of a bottle that has a much smaller diameter. Well, before a champagne cork is inserted into a bottle, it is in a cylindrical form (and not in the shape of a mushroom, as it appears when you look at a cork once it’s been removed) with a diameter that is slightly less than the neck of the bottle. At that point, there’s no problem putting the cork inside, thanks to its ability to be easily compressed when an external force is applied.
Once in place, the cork expands and seals the opening of the bottle shut. This is the reason why champagne corks appear mushroom-shaped when you take them out; the curvature of the cork entirely depends on the shape of the bottle in which it’s installed.
Since uncorking a bottle releases a tremendous amount of pressure, it’s best to point the bottle away from everyone present (including yourself, obviously!). Otherwise, the result may not be something to celebrate.