IRA FLATOW: This is Science Friday. I’m Ira Flatow. Coming up this hour, we’re going to revisit some of our favorite stories of the year, including Riley Black’s look back at the last days of the dinosaurs. And that rodent biologist who had to, let’s say, warm up to the subjects she studies.

But first, as we head into the weekend’s festivities, a dip into our archives for a classic sci-fi story about when science meets champagne.

[CORK POP]

[FIZZING]

Ahh. We’ve got some scientific advice on how to get the most bang out of your bubbly. Hmm, taste good. Up next, we’re poring over the science of bubbles. Here are some facts to whet your appetite. Lipstick and champagne, they clash chemically. Frosted beer mugs? A no-no for flavor. And if you want to keep that open champagne fizzy, corking is not the answer. What is the answer? Well, here to explain is Bubble Master Dr. Richard Zare. He is Professor of Chemistry at Stanford University in Palo Alto, California. Welcome back to Science Friday. Happy New Year.

RICHARD ZARE: Well, thank you, Ira. Same to you.

IRA FLATOW: Thank you very much. Let’s go through some of this bubbleology tips for us. Do you have any tips for getting the most flavor and fizz out of champagne?

RICHARD ZARE: Well, it turns out that as it warms up you get more volatiles that come off when it evaporates. And that’s, of course, very enjoyable because most of our taste comes from smell, not actually from inside our mouth.

IRA FLATOW: So let it warm up a little bit before you drink that icy stuff.

RICHARD ZARE: That’s right. This also actually applies to beer, Ira. Let me mention some things. Many people drink beer just from the bottle. And while I understand how quickly that is, to take in the beer that way, because as I mentioned to you, smell is involved, you just don’t get much smell when you put a bottle to your mouth. Much better is to drink beer from a glass.

IRA FLATOW: Mm-hmm.

RICHARD ZARE: Now what type of glass? Well, many bars serve frosted glasses. They think that’s quite fancy and wonderful. But actually, I think that’s a bad idea, as does my friend Norman Metzger in Washington, DC, who pointed this out to me.

It turns out that if you cool liquids that contain gases, they really– the liquids dissolve the gases better. And they– it is the gas coming off the liquid which is part of the aroma, which makes, again, beer be so enjoyable to many of us.

Now I understand that on a very hot day, nothing like a really cold beer, but in terms of taste, sipping from a glass that’s cool is really quite wonderful.

IRA FLATOW: Mmm. Now I understand, as I said before, I understand that as for lipstick, lipstick will kill the bubbles?

RICHARD ZARE: Well, the bubbles are held together by this sort of membrane of various things that surround the carbon dioxide that’s making the bubble. And when you add something like too much detergent, somebody doesn’t really wash out the glass well, or some people even rub their nose and then put their finger down, and this kills bubbles.

And the oils– any type of oil, including Chapstick, Vaseline, et cetera, will actually cause the bubbles to burst. It really just destroys the surface tension and makes it uneven and the bubbles burst this way.

IRA FLATOW: You’ve now opened our bottle of champagne. You want to save a little bit for the morning after. What’s the best way to save it? I know you have done experiments about the best way to keep the bubbles in a bottle of champagne fizzy till the next morning.

RICHARD ZARE: Well, actually, Harold McGee and I, he’s the Curious Cook who wrote a column for The New York Times for that subtitle, I think, looked into this. And the truth is that the best way to keep gas dissolved in your liquid is to keep the liquid cold. Anybody who’s played around with water knows as you start to heat it up, it really drives the gases off, and hot water is much flatter. And so is any hot– any liquid, and it releases gas that way.

So you really– to keep your champagne effervescent, you want to keep it cold. So returning it to the refrigerator or keeping it in an ice bucket is just the right thing to do.

IRA FLATOW: You don’t have to put the cork back in it or anything–

RICHARD ZARE: You actually do not. There’s enough carbon dioxide in the champagne to go on for many days. We’ve seen that.

IRA FLATOW: I’ll bet–

RICHARD ZARE: There’s something else that’s interesting that happens. If you leave the champagne uncorked, just like with wine, you get a change in its taste due to some oxidation from the air. And that actually can be quite pleasant, too.

IRA FLATOW: I’ll bet you have spent many hours verifying–

RICHARD ZARE: Oh, it requires it. All in the name of science, Ira.

IRA FLATOW: Of course.

[LAUGHTER]

But what about that trick of sticking a spoon down the neck of the champagne? Is that all just an old wives tale?

RICHARD ZARE: Well, from what I can tell, the only effect the spoon has, like a silver spoon is, if it helps cool the bottle down when you put it back in the refrigerator. Otherwise, I don’t think it works. Now

IRA FLATOW: Let’s talk about the bubbles in your glass of champagne or your glass of wine, because there’s a whole bunch of physics going on there, isn’t there? Let me start with–

RICHARD ZARE: Well, a lot a lot of chemistry, too.

IRA FLATOW: Of course, you’re a chemist, you would be saying that.

RICHARD ZARE: Well, let’s consider how the bubbles get there in the first place or what goes on in champagne. I think it all starts with this Frenchman by the name of Dom Perignon who lived about 1639 to 1715 and developed this thing called the méthode champenoise where you take some type of wine and you bottle it again with sugar and yeast that cause a second fermentation.

And this yeast converts the sugar into carbon dioxide and ethanol, the alcohol we enjoy drinking. And you also, of course, have other things that are left over from this. You get a couple grams per liter of different other materials like glycerol and tartaric acid and lactic acid. And it turns out that champagne’s actually acidic, has a pH of about 3.

IRA FLATOW: Wow.

RICHARD ZARE: But if you look at the amount of carbon dioxide that’s in the champagne, it’s immense. At sea level, the pressure of the air is 1 atmosphere. The amount of carbon dioxide in the bottle of champagne when you opened it is something like 7 atmospheres. It’s loaded. It’s supersaturated. It wants to come out.

And here’s the problem. How do you get bubbles to come out? It’s one of the same questions about, how do you get clouds to rain? You need some form of nucleation, something to happen. And now I need to tell you that most of champagne is actually just water.

And water loves water. Water loves water so much that it crushes little bubbles. And you don’t see bubbles ever form in the middle of a glass of champagne the same way you don’t see bubbles form when you boil a pot of water and you look at it, the bubbles do not form in the center of the liquid.

Instead, they form on the walls, on the sides. Why? Because they need to hide and grow to a critical size. And they tend to actually form on various forms of, well, shall I call it dirt, fibers, a dust, scratches in the glass, places to hide and build up to be a big enough bubble so it can escape and not be crushed by the water.

IRA FLATOW: So that’s why you see them forming in lines or maybe lining up in a crack in the glass or they’re coming off the sides? And I guess you can revise– or revive a stale glass of beer by nucleating it or something.

RICHARD ZARE: Well, one of the simplest ways, but I don’t recommend it, of seeing this effect is to dump in a tablespoon of either sugar or salt into a carbonated beverage. You’ll see a great deal of foam being formed.

IRA FLATOW: Wow.

RICHARD ZARE: Sand will work, too. I don’t recommend any of those three.

IRA FLATOW: Well, does that explain why– and in soft drinks like root beer, which has a lot of fizz inside of it, when you make a root beer float and you pour it on the ice cream, it just explodes with foam, because the ice cream has all those little nooks and crannies in it?

RICHARD ZARE: Yes. And ice cubes, too. Let me talk about ice cubes for a moment.

IRA FLATOW: Please.

RICHARD ZARE: Have you ever noticed that when you pour any carbonated beverage on ice cubes for the first time, lots of foam.

IRA FLATOW: Right.

RICHARD ZARE: You drink it, then you say, I want a refill. The next time people pour on the ice– the same ice cubes, right?

IRA FLATOW: Right.

RICHARD ZARE: Much less foam. It’s not that the bottle is gone flat, it’s that all the sharp spots on the ice, the disparities on the ice have melted away. And without these little nooks and crannies, again, the carbon dioxide doesn’t know how to escape. It wants to escape, it wants to go to 1 atmosphere, it just doesn’t know how.

IRA FLATOW: That would explain why I’ve heard about bartenders sprinkling some salt in your beer to make it foam up again.

RICHARD ZARE: It does. [LAUGHS] Try it. It works in champagne and beer, but I don’t think that– for the purpose of taste, it’s the thing to do.

IRA FLATOW: Not at all. Now let’s talk about one of– I once saw a video that you created about bubbles in a glass of beer that they don’t always go up, the bubbles seem to be going down, and you tried this with what?

RICHARD ZARE: It was actually with Guinness Beer.

IRA FLATOW: Guinness? Famous for all those bubbles in there?

RICHARD ZARE: [LAUGHS] And it’s, at first, quite a puzzle, and you wonder, people reported that the bubbles on the sides of Guinness– glass of Guinness beer were going down. How could bubbles be going down? Is it that they just had too much beer to drink? What’s happening here?

What’s actually happening is that everywhere it’s bubbling, but the bubbles in the center of glass actually have less drag, less friction on them, and they rise more rapidly, more easily than the ones on the side. And the result is they set up a circulation of the liquid. And bubbles are very slowly moving in beer.

IRA FLATOW: Hmm.

RICHARD ZARE: In fact, if you’ll notice, champagne has much more rapid-moving bubbles than beer bubbles, and we could discuss why that is in a moment. But anyways, the result is that because of the liquid circulation, the bubbles go down initially–

IRA FLATOW: Wow.

RICHARD ZARE: –in a glass of Guinness or some of the other very highly carbonated beers.

IRA FLATOW: Well, one last quick question for you, Dr. Zare. Why are some bubbles bigger than others? Depending on the beverage, is that what it is?

RICHARD ZARE: [LAUGHS] Oh, I wish I understood all this. Part of it has to do with the size of the crack or crevice that you have. And it’s been a mystery to me as to what controls totally the size of the bubbles.

IRA FLATOW: All right, well–

RICHARD ZARE: I don’t know the answer to that.

IRA FLATOW: Well, we hope you enjoy finding out.

RICHARD ZARE: More to learn.

IRA FLATOW: Boy, always–

RICHARD ZARE: I should study this.

IRA FLATOW: Please do that, and maybe next year we’ll come back and talk to you again.

Dr. Richard Zare is Professor of Chemistry at Stanford University in Palo Alto, California. That conversation was from 2012, and we have indeed had him back over the years. Please enjoy your New Year’s holiday responsibly.

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