Field Notes #2—Can Champagne Go Flat...Without Bubbles?

APPLIED FIZZICS Field Notes · Edition #2

Looking at the universe through a glass of Champagne.

Missed Edition #1? Browse the Field Notes archive or browse the Recent Posts.

The night I saw a glass that didn’t bubble

Years ago, I actually saw a glass that didn't bubble.

I had just finished demonstrating one of the very first Perlage prototypes to the U.S. brand manager of Krug in Manhattan in 2005. The meeting went well, so that evening we celebrated with a bottle of Krug Champagne at a nearby restaurant.

The owner himself poured the Champagne.

I picked up my glass. I held it up to the light.

Something was wrong.

Not. One. Bubble.

The Champagne looked like apple juice.

I dipped my finger into the glass.

Instantly, tiny streams of bubbles raced upward from my fingertip.

The Champagne wasn't flat.

The glass was simply too clean.

I called the owner over and pointed towards my glass.

"Oh my goodness, Sir," he said. "I'm terribly sorry! I'll get you another bottle immediately."

He reached for my glass.

"No!" I said. "This is a miracle! I've never seen this happen before!"

I demonstrated the bubbles again by dipping my finger into the wine, then launched into an enthusiastic explanation of nucleation sites.

Finally, I asked if I could keep the glass.

He looked completely bewildered. Then he found me a zip-lock plastic bag.

I suspect he thought giving me the glass was the only way to shut me up!

The bubbles are not the main event

So if a perfectly clean glass doesn't bubble, why wouldn't the Champagne stay fizzy forever?

Here's another surprise.

Most people assume Champagne loses its carbonation only through the bubbles they can see.

It doesn't.

The bubbles are the spectacular part, but they aren't the main event.

Roughly 80% of the dissolved carbon dioxide quietly escapes by diffusing directly across the surface of the wine into the surrounding air. This happens one molecule at a time, and is completely invisible to the naked eye.

Only about 20% leaves inside the bubbles themselves.

In other words, even if you could magically eliminate every visible bubble in your glass, the Champagne would still go flat.

Just a little more quietly.

I find that astonishing. The bubbles are what make Champagne seem alive, yet they're responsible for only a small fraction of the carbon dioxide that actually escapes.

Why doesn’t the bottle bubble like the glass?

That leads to an even more interesting question.

We now know that bubbles need microscopic gas pockets to get started.

So why doesn't a freshly opened bottle of Champagne immediately begin bubbling from the glass walls, like a freshly poured glass of bubbly does?

After all, the inside of the bottle surely has those same tiny scratches and cellulose fibers that a fresh glass would have.

The answer lies in something called wetting.

You've seen this a million times. Maybe you're washing dishes, and you dunk a glass into the water and pull it out.

Notice how the water forms a perfectly smooth, continuous film over the glass.

Water naturally wants to spread across clean glass.

Physicists say the glass is wetted.

In the last edition of Field Notes, we talked about water wanting to stick to itself, and that's certainly true. Water molecules are polar, so they strongly attract one another through hydrogen bonding.

But water is also attracted to clean glass. Glass carries oxygen atoms on its surface that water molecules are attracted to. In fact, the attraction is so strong that the water prefers to spread across the glass rather than bead up into droplets. The water forms an extremely thin film over the surface because, energetically, that's the state it "likes" best.

But "likes" doesn't mean "completely." Water has an unusually high surface tension, which acts almost like an invisible elastic skin stretched over the surface of the liquid. Last time I compared surface tension to the skin of a balloon, and that analogy turns out to be surprisingly good.

That analogy is actually almost literally true. Imagine stuffing a small water balloon into a glass. Because of the rubber balloon around the water, the water simply cannot get into every nook and cranny of the glass. The glass wouldn't be wetted at all.

So it is with Champagne poured into a glass: the surface tension of the liquid acts like an invisible skin that prevents the liquid from flowing into every little scratch and crevice.

What happens inside the bottle?

So what is going on in a bottle of Champagne that has been under a cork for years?

When the wine was first bottled and corked, the glass almost certainly contained thousands of tiny pockets of trapped air, clinging to scratches, cellulose fibers, and other microscopic imperfections.

But remember: Air is soluble in water too. We know this, because that's how fish breathe underwater.

Over the next hours or days, all the nitrogen and oxygen in every little trapped bubble of air diffuses into the wine, just as water evaporates from the sidewalk on a summer day. All the little bubbles of trapped air simply "evaporate." Molecule by molecule, the oxygen and nitrogen diffuse away into the wine until the bubbles disappear entirely.

Those potential nucleation sites disappear.

So when you open a bottle of Champagne, assuming you do not agitate it—oh, don't worry; we'll get to that—the bottle does not vigorously fizz like a freshly poured glass. That's because, over time, the glass bottle has become essentially completely wetted, and there are simply no pockets of trapped gas left to create nucleation sites.

So a freshly opened bottle of Champagne behaves like the perfectly clean glass I got that one night in Manhattan.

Then someone shakes the bottle

But what if, instead of waiting for those tiny gas pockets to form naturally in a glass, you shake the bottle?

Now you've created tens of thousands of tiny air bubbles simply from the agitation. In fact, this has nothing uniquely to do with carbonation—you can create thousands of tiny bubbles by vigorously shaking an ordinary bottle of tap water. Try it. Fill a clear water bottle half full, put the cap on, and shake vigorously. Millions of tiny bubbles form just from the mechanical agitation of the water—it has almost nothing to do with dissolved gasses.

But if the liquid you're shaking is highly carbonated Champagne, every one of those tiny air bubbles suddenly becomes a potential nucleation site for carbon dioxide.

Now you don't have one or two places for bubbles to grow.

You have tens of thousands.

Within a fraction of a second, each tiny air bubble begins inflating with carbon dioxide, as CO₂ diffuses from the Champagne, where the concentration of CO₂ is high, into the bubbles, where the concentration of CO₂ is low.

Suddenly, you have millions of rapidly growing bubbles.

Suddenly, you have a Game 7 locker-room celebration.

We'll pick up there next time.

Now we finally have enough information to answer one of the oldest debates in Champagne: Which glass is best—a flute, a coupe...or something else?

I'll give you a hint.

It depends.

Stay tuned for Edition #3 of Field Notes where I'll give you what I think is the definitive answer to the question.