In time for New Year's Eve, Science Friday examines the chemical reactions that transpire in fluted glassware. Ira Flatow and Richard Zare, a chemist at Stanford University, pore over the science of bubbles — from how to keep that open champagne fizzy (forget the cork) to why beer tastes better from a glass rather than a bottle.
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IRA FLATOW, HOST:
Don't clear the table just yet. We've got another helping of food science for you.
(SOUNDBITE OF CORK POPPING AND WINE POURING)
FLATOW: We've got some scientific advice on how to get the most bang out of your bubbly. Hmm. Tastes 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.
DR. RICHARD ZARE: Well, thank you, Ira. Same to you.
FLATOW: Thank you very much. Let's go through some of these bubbleology(ph) tips for us. Do you have any tips for getting the most flavor and fizz out of champagne?
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.
FLATOW: So let it warm up a little bit before you drink that icy stuff.
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. 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(ph) in Washington, D.C., 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.
FLATOW: Hmm. Now I understand, as I said before, I understand that as for lipstick, lipstick will kill the bubbles?
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.
ZARE: And this kills bubbles. And the oils - any type of oil, including the ChapStick, Vaseline, et cetera, will actually cause the bubbles to burst. It really destroys the surface tension - makes it uneven and the bubbles burst this way. So it's very interesting to see and it's very obvious on New Year's Eve, generally, women have less bubbles in their glass of champagne than men do for the obvious reason that women generally wear lipstick. On the other hand, this thing I just told you doesn't always work, because just like you can have second-hand smoke, Ira, you can have second-hand lipstick.
ZARE: So try it out.
FLATOW: I'll tell you. What a pick-up line for New Year's Eve. I am doing a scientific survey of the lipstick around here. Let me ask you a few questions about your lipstick and your champagne. There's an opening.
FLATOW: All right. Let's talk about having that open - 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 til the next morning.
ZARE: Well, actually, Hal McGee and I - he's the Curious Cook who wrote a column for the New York Times with that subtitle, I think - looked into this. And the truth is the best way 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.
FLATOW: You don't have to put the cork back in it or anything like it?
ZARE: You actually do not. There's enough carbon dioxide in the champagne to go on for many days. We've seen that. 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.
FLATOW: I bet you have spent many hours verifying that.
ZARE: Oh, it requires it. All in the name of science, Ira.
FLATOW: Of course.
FLATOW: But what about that trick of sticking a spoon down the neck of the champagne? Is that all just an old wives' tale?
ZARE: Well, from what I could 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.
FLATOW: Now, 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...
ZARE: Well, a lot of chemistry too.
FLATOW: Of course. You're a chemist. You would be saying that.
ZARE: 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 methode champenoise, where you take some type of wine and you bottle it again with sugar and yeast that causes second fermentation. And this yeast converts the sugar into carbon dioxide and ethanol - the alcohol we enjoy drinking. And he also, of course, have other things that are leftover from this. You get a couple of grams per liter of different other materials, like glycerol and tartaric acid and lactic acid, and it turns out that champagne is actually acidic. It has a PH of about three.
ZARE: But if you look at the amount of carbon dioxide that's in the champagne, it's immense. You know, at sea level, the pressure of the air is one atmosphere. The amount of carbon dioxide in the bottle of champagne when you opened it, is something like seven atmospheres. It's loaded. It's super saturated. It wants to come out. And here's the problem: How do you get bubbles that come out? One of the same questions about how do you get clouds to rain. You need some form of nucleation, something to happen. And 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 side. 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, dust, scratches in the glass, places to hide and build up to be a big enough bubble so we can escape and not be crushed by the water.
FLATOW: Hmm. Let me just interrupt for a second to remind everybody. I'm talking with Dr. Richard Zare on SCIENCE FRIDAY from NPR.
So that's why you see them forming in lines. They've been lining up in a crack on 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.
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.
ZARE: Sand will work too. I don't recommend any of those three.
FLATOW: Well, does that explain why - 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?
ZARE: Yes. And ice cubes too. Let me talk about ice cubes for a moment.
ZARE: Have you ever noticed that when you pour any carbonated beverage on ice cubes for the first time, lots of foam. You drink it, then you say, I want a refill. The next time people pour on the ice - the same ice cubes, right?
ZARE: Much less foam. It's not that the bottle has gone flat. It's that the - all the sharp spots on the ice, the asperities 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 one atmosphere. It just doesn't know how.
FLATOW: That would explain why I have heard about bartenders sprinkling some salt in your beer to make it foam up again.
ZARE: It does.
(SOUNDBITE OF LAUGHER)
ZARE: But try it. It works in champagne and beer. But I don't think that for purpose of taste is the thing to do.
FLATOW: Not at all. Now, let's talk about one of the - I once saw a video that you created about bubbles in a glass of beer that they don't always go up. The bubble seemed to be going down, and you tried this with what? And you...
ZARE: It was actually with Guinness beer.
FLATOW: Guinness? Famous for all those bubbles in there.
ZARE: That's right.
ZARE: And it's - at first, quite a puzzle and you wonder if 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?
ZARE: What's actually happening is that everywhere it's bubbling. But the bubbles in the center 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. In fact, if you'll notice, champagne has 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...
ZARE: ...in a glass of Guinness or some of the other very highly carbonated beers.
FLATOW: Well, one last quick question for you, Dr. Zare: Why are some bubbles bigger than others - depending on beverage? Is that what it is?
ZARE: Oh, I wish I understood all if 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 bubble. I don't know the answer to that.
FLATOW: Well, we hope you enjoy finding that.
ZARE: More to learn.
FLATOW: Boy, (unintelligible).
ZARE: I shall study this.
FLATOW: Please, do that and maybe next year, we'll come back and talk to you again. Dick, have a Happy New. Thanks for joining us.
ZARE: And, oh, I get no kick from champagne. Mere alcohol doesn't throw me at all. So tell me why should it be true, Ira, that I get a kick from you. Thanks so much.
FLATOW: Thank you very, very much. Dr. Richard Zare, who is, I guess, he has a day job, but he likes to do most is being a bubbleologist(ph). He's professor of chemistry at Stanford University in Palo Alto. Transcript provided by NPR, Copyright NPR.