• The neck of a bottle of champagne behaves like the nozzle of a rocket reactor, according to our partner The Conversation.

  • This “explosion” could be observed and studied using ultrafast cameras.

  • This analysis was conducted by Gérard Liger-Belair, professor of physics at the oenology laboratory of the University of Reims Champagne-Ardenne (URCA).

Rapid imaging has seen dizzying advances in recent years, particularly with the advent of digital sensors and the miniaturization of electronic circuits.

Today there are ultra-fast cameras capable of revealing extremely fleeting phenomena to us.

We used a camera of this type to examine the detail of the mechanisms at work when uncorking a bottle of champagne.

The uncorking of a bottle of champagne kept at 20°C, observed using an ultra-fast camera © Gérard Liger-Belair / The Conversation

During their second fermentation (called prize de mousse), Champagne wines produce carbon dioxide (CO2) – the equivalent of almost 5 liters for a single 75 cl bottle – which remains trapped under pressure in the closed bottle. .

The pressure that reigns in a still corked bottle varies greatly with its temperature.

Thus, at 20°C, the pressure reaches almost 8 bars, the equivalent of 8 times the atmospheric pressure, i.e. the pressure which reigns 70 m under the sea!

The video sequence in the image above illustrates the phenomena that occur in the wake of the cork which springs out of a bottle under an initial pressure of 8 bars.

When the cork pops, the volume of carbon dioxide under pressure in the neck of the bottle suddenly expands.

Its pressure then goes from 8 bar to an ambient pressure of 1 bar.

This is accompanied by a drop in its temperature: physicists speak of an adiabatic expansion.

However, depending on its temperature and its pressure, a pure substance is likely to exist in three phases: gaseous, liquid and solid.

Thus, under a pressure of 1 bar, water is liquid at 20°C, turns into ice below 0°C and boils to turn into vapor at 100°C.

But what about CO2?

Under a pressure of 1 bar, CO2 remains in a gaseous state above a temperature of -78.5°C;

below this critical temperature, it exists in its solid form: dry ice.

Uncorking a bottle at room temperature, be careful of the pressure!

© Effervescence Team / CNRS / University of Reims

​At unclogging, dry ice and shock wave

For this bottle under an initial pressure of 8 bars, the temperature of the carbon dioxide which suddenly expands drops to almost -90°C.

The CO2 vapors then turn into tiny crystals of dry ice, which can scatter ambient light.

The azure blue color of the plume is a sign of the very small size of these crystals.

Indeed, the particles or molecules having a size lower than the wavelengths of the spectrum of the ambient light (centered around approximately 0.6 µm) diffuse much more effectively the small wavelengths of the spectrum (blue, in particular) than long wavelengths (such as red): we speak of Rayleigh scattering.

It is the same phenomenon that explains why the sky appears blue to us:

Our "CHAMPAGNE" file

Did you notice the small horizontal line that crosses the blue plume?

This is a characteristic shock wave of supersonic jets, known as Mach disks.

It appears approximately 500 µs after unblocking, progresses in the wake of the blockage before fading out some 500 µs later.

We find similar shock waves in the supersonic plume blown by the nozzles of the reactors of a fighter plane or a rocket.

During the very first millisecond following the expulsion of the cork, the neck of a bottle of champagne therefore behaves a little like the nozzle of a rocket reactor.

Who would've believed that !

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This analysis was written by Gérard Liger-Belair, professor of physics at the oenology laboratory of the University of Reims Champagne-Ardenne (URCA).


The original article was published on The Conversation website.

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Declaration of interests

Gérard Liger-Belair has received funding from the CNRS and the Grand-Est Region

  • Physical

  • Wine

  • Gas

  • Chemistry

  • The Conversation

  • Science

  • Video

  • Champagne

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