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APPLIED FIZZICS Field Notes · Edition #3
Looking at the universe through a glass of Champagne.
Missed an earlier edition? Browse the complete Applied Fizzics Field Notes archive.
Previously in Field Notes
In the last Field Notes, I ended with a quiz:
Suppose you pour two identical glasses of Champagne. Glass A is producing beautiful streams of bubbles. Glass B has almost no visible bubbles.
Which one will lose its carbonation first?
- A) Glass A
- B) Glass B
- C) Nearly the same rate
The best answer is probably A.
Glass A is losing dissolved CO₂ in two ways: through the visible bubbles rising through the wine, and by invisible diffusion directly across the liquid-air surface.
Glass B is losing CO₂ mainly through diffusion at the surface.
If my claim from the last Field Notes is correct—that roughly 80% of the CO₂ escapes through the surface and 20% through visible bubbles—then we might expect Glass A to go flat about 25% faster.
But after the last Field Notes, I received an interesting response from a reader named Artie, who has been drinking Diet Pepsi almost exclusively since 1971.
Artie insists that Pepsi tastes fizzier in a cheap plastic cup than in a glass.
And he may be right.
But here's the strange part:
The plastic cup may seem fizzier precisely because it's helping the Pepsi go flat faster.
A cheap plastic cup generally has a rougher microscopic surface than glass. More microscopic imperfections mean more nucleation sites. More nucleation sites mean more bubbles.
And more bubbles mean CO₂ is escaping faster.
But I don't think Artie is imagining the difference in taste. We drink with our eyes as well as our mouths, and all that extra bubble activity may genuinely change the sensory experience. A drink that is losing its carbonation faster may actually seem more carbonated while you're drinking it.
In this sense, a carbonated beverage is a little like a radioactive isotope (hang with me...I'm going to bring this analogy in for a landing!)
The faster a Geiger counter is clicking, the faster radioactive atoms are decaying—and the shorter the material's half-life.
With a carbonated beverage, the more bubbles you see, the faster CO₂ is escaping—and the shorter its carbonation half-life.
So Artie's cheap plastic cup may really make his Pepsi seem fizzier.
It just won't stay that way as long.
Missed an earlier edition? Browse the complete Applied Fizzics Field Notes archive.
So What Is the Best Champagne Flute?
Unexpectedly, the phenomenon that Artie brought up is exactly the tension at the heart of choosing the best Champagne glass.
Let's take two extremes of Champagne glassware: a tall, narrow flute, or a wide, short coupe. Champagne in a coupe will have a much larger liquid-air surface area than Champagne in a tall, narrow flute.
Remember, in Field Notes #2, we discussed the fact that roughly 80% of CO₂ loss is from molecular diffusion at the surface of the Champagne, and only 20% from visible bubbles. So if your goal in your choice of Champagne glassware is to conserve the amount of dissolved carbon dioxide to the greatest extent possible, the tall flute is the clear choice.
I did a quick measurement of glasses in my collection, and my shortest, widest coupe was about 4 inches in diameter at the top, while my tallest, narrowest flute was about 2 inches in diameter at the top. Recalling that the area of a circle is given by A = πR², where R is the radius of the glass, the Champagne in a coupe has four times the liquid-air surface area of the flute.
That's a much bigger escape hatch for the CO₂.
So, all else being equal, the coupe has four times as much surface area available for CO₂ to escape by diffusion. Since diffusion is the dominant loss mechanism, the tall flute is the clear choice for preserving effervescence.
But glass shape also affects bubble formation, bubble streams, aroma release, sensory perception, and the drinking experience.
A coupe has a larger surface area, so it loses CO₂ faster—but perhaps that's not always bad.
If you're trying to appreciate the Champagne's aroma rather than preserve its fizz, rapid CO₂ loss may actually be desirable. Every bubble that bursts at the surface releases a tremendous amount of energy for its tiny size, like a microscopic popping balloon. Counterintuitively, the smaller the bubble, the more energy it releases per unit volume—it's that old surface-area-to-volume ratio popping up again. These tiny explosions aerosolize the Champagne around them, throwing microscopic droplets into the air—right next to your nose as you take a sip.
So the bubbles aren't just something you see. They're actively delivering Champagne to your nose.
A wider glass can encourage aroma release—but the shape of the glass also determines whether those aromas are concentrated near your nose or simply allowed to escape into the room.
A tulip or wine glass offers another compromise: more room for aromas to collect and reach your nose, while retaining more carbonation than a broad, shallow coupe.
So it depends on what you mean by "best" Champagne glass.
Best CO₂ retention? Tall flute.
Most pleasing bubble display? Tall flute also, but that's just my opinion.
Best expression of a Champagne's aroma? Probably a red wine glass.
Most traditional—and maybe the most glamorous? Probably the coupe. One of the oldest styles of Champagne glassware, dating to the early 1800s, its design is sometimes rumored to have been inspired by the breast of 18th-century French Queen Marie-Antoinette. I have never been able to find definitive proof of this assertion; but absent any proof to the contrary, I shall continue to believe this story.
Physics Corner: A deeper dive for fellow science geeks
The two most important variables determining how much CO₂ dissolves in Champagne are pressure and temperature.
Increase the pressure of CO₂ above the liquid, and more CO₂ dissolves.
Decrease the pressure, and CO₂ escapes.
Lower the temperature, and the liquid can hold more CO₂.
Raise the temperature, and it can hold less.
This is why a bottle of Champagne behaves so differently before and after you pop the cork.
Inside an unopened bottle, the Champagne is in equilibrium with the pressurized CO₂ in the headspace above it. CO₂ molecules are constantly escaping from the liquid and entering the headspace. At the same time, other CO₂ molecules are leaving the headspace and diving back into the Champagne.
At equilibrium, the traffic hasn't stopped.
The traffic is simply flowing equally fast in both directions.
The amount of CO₂ dissolved in the Champagne remains roughly constant. The amount in the headspace remains roughly constant. And the pressure remains constant.
Not because nothing is happening.
Because two opposing processes are happening at the same average rate.
Then you pop the cork.
The pressure above the Champagne collapses almost instantly to atmospheric pressure. The equilibrium is shattered. Suddenly, CO₂ is leaving the Champagne much faster than it is returning.
That's when the bubbles begin.
Temperature changes the equilibrium too.
Warm a bottle of Champagne, and CO₂ becomes less soluble in the liquid. More CO₂ moves into the headspace, increasing the pressure inside the bottle.
Cool the bottle, and the opposite happens: more CO₂ can remain dissolved in the Champagne, and the pressure decreases.
The temperature dependence is profound: more than twice as much CO₂ can dissolve in ice-cold Champagne than at room temperature. See the graph below. At about 24 C (room temperature), water can hold 0.15 g of CO₂ per 100 ml of water. But at 0 C, it can hold 0.33 grams of CO₂.
But here's something else I find fascinating:
Shaking the bottle doesn't change where equilibrium ultimately ends up. It only changes how quickly you get there.
I know this from direct experience; I've measured it with a pressure gauge attached to the top of a Champagne bottle.
If I pressurize a half-full bottle of water with CO₂ and leave it sitting undisturbed, the gas may take 24 hours or more to diffuse through the few square inches of liquid surface and reach equilibrium.
But shake that same pressurized bottle vigorously, and I can reach equilibrium in about five seconds.
Five seconds instead of 24 hours.
Why?
Because shaking creates enormous numbers of tiny bubbles throughout the liquid, vastly increasing the surface area across which CO₂ can diffuse.
If that entire 17,000-fold increase in speed came from increased surface area alone, it would correspond to nearly 80 square meters—more than 800 square feet—of effective gas-liquid interface inside a single bottle.
In reality, vigorous shaking also constantly mixes the liquid and accelerates mass transfer, so the actual bubble surface area is probably smaller.
Either way, the increase is extraordinary.
And this brings us back to Champagne.
The amount of CO₂ that remains dissolved in a sealed bottle at equilibrium is determined primarily by pressure and temperature.
But how quickly CO₂ moves between the liquid and the gas above it depends enormously on surface area and agitation.
Same molecules.
Same physics.
Whether it's a bottle of Champagne quietly resting in a cellar or a bottle of water being violently shaken under pressure, the molecules are always trying to find their way toward equilibrium.
If you want to play with these concepts in greater detail, check out our molecular simulator, where you can see how pressure, temperature, and equilibrium play out at a molecular level. You can find it here at Applied Fizzics Molecular Simulator. Add CO₂ molecules to a liquid, for example, then change the temperature interactively to see how it affects equilibrium.
Today's Pop Quiz
Here's a practical question about Champagne—and one that might save you from a very unpleasant surprise.
You leave an unopened bottle of Champagne in a hot car on a summer day. As the bottle gets hotter, what happens?
- A) Nothing. The bottle is sealed, so the pressure stays the same.
- B) The pressure rises because CO₂ becomes less soluble in the warm Champagne and moves into the headspace.
- C) The pressure falls because the gas expands as it gets warmer.
- D) The amount of CO₂ increases, creating additional pressure inside the bottle.
I'd love to hear what you think. You can leave your answer directly in the Comments below.
I'll reveal the answer in Edition #4.
And perhaps the more important question:
Could a bottle of Champagne actually explode if you left it in a hot car?
We'll talk about that next time.
Until next time...
Stay curious.
Cheers,
Evan Wallace
President, Applied Fizzics Inc.
Makers of The Perlage System®
Want more Champagne science, carbonation experiments, and behind-the-scenes product stories? Visit the Applied Fizzics Field Notes archive.
I’m going to go with B. As the CO2 moves to the headspace, pressure increases since the liquid in the bottle is unable to compress.