break out the bubbly

"Come quickly, brothers, I am drinking stars!"
    — Dom Perignon, 17th century monk

Popular legend has it that the 17th century monk Dom Perignon invented champagne — hence the classic brand that bears his name. That's not entirely correct. The monk was indeed cellar master at the Abbey of Hautvillers, charged with getting rid of the bubbles in the bottled wine because the bottles occasionally exploded from the internal pressure. This being 17th century France, the explosions were considered to be the devil's handiwork. Because only Satan would be so unequivocally evil as to ruin a batch of perfectly good wine. French monks weren't big on the teetolling. The truth is, nobody is entirely sure who invented champagne. The first mention of a commercial sparkling wine pops up around 1535 in Languedoc. From there, it gradually spread around the world.

Dom Perignon did come up with lots of improvements to making the bubbly beverage. The basic process is fairly simple. Champagne grapes are generally picked earlier, when the fruit's sugar levels are lower, with higher acid levels. Like every wine, the grapes are pressed and sealed in containers to ferment, converting the natural sugars into alcohol. In this stage, the carbon dioxide byproduct is allowed to escape. The result is a base wine from which winemakers produce a tasty blend. To turn it into champagne, there must be a second fermentation, and this time the carbon dioxide trapped in the bottle, and stays dissolved in the wine.

For this part of the process, the blended wine is poured into sturdy bottles with yeast and a small amount of sugar (a concoction known as the liqueur de tirage). How much pressure is in the bottle depends on how much sugar is added during the second fermentation. For those who care about such details, 6 bars (or atmospheres) of pressure inside the bottle is the standard value, and this requires 18 grams of sugar.  The European Commission regulates the amount of yeast: 0.3 grams per bottle. Controlling the carbonation level can be tough; for every bottle of perfectly effervescent champagne, there are bottles that fail to be sparkly at all, and those that explode from the build-up of too much pressure. Hence the need for precise amounts — even to the point of official regulations.

Champagne adheres to "Henry's law" (sorry, couldn't find out much about who this "Henry" fellow was — but perhaps a commenter can help). The amount of gas dissolved in a fluid is proportional to the pressure of the gas with which it is in equilibrium. And that's what makes champagne bubble, gives it "effervescence" — which in turn gives rise to the tingly sensation on one's tongue that Dom Perignon likened to "drinking stars."  When the bottle is still corked, the carbon dioxide gas dissolved in the wine is in equilibrium with gas trapped in the space between the cork and the liquid. When you uncork the bottle and release that trapped gas — no more equilibrium. So the carbon dioxide is emitted from the wine through bubbles to re-establish that equilibrium.

As much as we've learned about perfecting the manufacturing process, champagne still retains some of its mysteries — for the time being. Over the last five years or so, scientists have gleaned several new insights into the dynamics of champagne bubbles, and leading the pack is an associate professor of physical sciences at the University of Reims Champagne-Ardenne named Gerard Liger-Belair, author of Uncorked: The Science of Champagne, and a consultant for Moet and Chandon. Jen-Luc Piquant considers him the Champagne King, a much more elegant moniker than, say, "Dr. Bubbles." (One should not confuse Liger-Belair — a serious scientist — with "Champagne Charlie," a 19th century famous entertainer named George Leybourne, who may have made the first celebrity endorsements — on behalf of Moet. The drink soon became associated in the public mind with Leybourne's highly sophisticated image.)

Ask any champagne connoisseur and s/he will tell you that the mark of a fine bottle of the bubbly depends on the size of the bubbles. Less is more: the smaller the bubbles, the better the champagne. LaPlace's Law states that the smaller the bubble, the higher the pressure. Fine bottled champagne has an internal pressure of about 6 atmospheres, so the resulting bubbles would measure around 0.4 microns (microns, people!) in diameter. Why should this have an impact on flavor? According to Liger-Belair, if the bubbles are smaller, there are more of them to release flavor and aroma.

Unfortunately, champagne makers have yet to figure out how to control bubble size, which is why scientists like Liger-Belair are avidly researching the physics of effervescence. He believes that a greater understanding of the various chemicals dispersed in the wine could hold keys to controlling bubble formation. A couple of years ago, he showed that even though champagne and more low-brow sparkling wines have bubbles of different sizes, they nonetheless have identical diffusion co-efficients, which lends credence to his theory. Liger-Belair wrote a recent article for Europhysics News about his latest work in this area. (For a more general article on the physics of fizz by Peter Weiss, go here.) And his work has implications beyond the bubbly: bubble formation resulting from gases dissolved in a liquid is one of the sticky points of fluid dynamics, so a better understanding of the underlying physics could yield insight into the nitrogen bubbles that form in the blood vessels of surfacing divers, causing "the bends," or in extreme cases, death.

How/why do the bubbles form in the first place? Scientists used to think that minuscule rough spots on the surface of the glass trapped pockets of air, forming bubbles. Liger-Belair found otherwise. There are impurities stuck to the glass wall, in the form of hollow cellulose fibers shaped like cylinders, and these serve as "bubble nurseries." When the champagne is poured into the glass, the liquid can't penetrate to the inside of the follow fiber, forming bubbles, because the carbon dioxide molecules have a high enough pressure to force their way into the fibers. Once they get big enough, they break free and rise to the surface, but there is still a carbon-dioxide-rich bubble trapped in the hollow fiber, so the bubbles keep generating. Liger-Belair says that these bubble nurseries can produce 30 bubbles per second, compared to 10 bubbles per second in beer, which has much less carbon dioxide content.

Champagne has become the mainstay of New Year's Eve celebrations but most of us become quite bewildered when faced with the task of choosing a good bottle. Do we stick with our friendly 17th century monk, Dom Perignon? Indulge in the fictional Lord Peter Wimsey's favored Veuve Cliquot? Or honor the spirit of "Champagne Charlie" by imbibing some Moet and Chandon?  For those (like me) who could use some help, we highly recommend a delightful blog called The Naked Vine — a guide to affordable good wines written by a guy in Kentucky named Mike. Mike has saved us from completely humiliating ourselves in wine stores on more than one occasion. And his most recent entry is a guide to good champagnes.

I celebrated the New Year with dinner at Lebanese Taverna with Future Spouse and Mondo Bob, toasting the changeover to 2007 with a rather young but tasty zinfandel; its fruitiness blended nicely with the spicier Lebanese fare. Kudos to Future Spouse for the selection. So I was the picture of holiday respectability (yawn — bored now). Jen-Luc Piquant, however, frolicked in Cyberspace into the wee hours, and indulged in quite a bit of Internet bubbly, judging by her the extent of her virtual hangover this morning.

Maybe it's the hangover talking, but Jen-Luc insists she impressed her fellow avatars by demonstrating her favorite bottle-opening technique: sabrage. The fact that the term shares a root with "sabre" isn't coincidence; the technique became hugely popular during the days of Napoleon's empire building, when every red-blooded male was swaggering around with a handy sabre at his side, ready to make quick work of any menacing champagne bottles in the vicinity.

One who uses sabrage slides the sabre along the body of the bottle toward toward the neck; it's not for slicing purposes, however. Rather, the force of the blade hitting the lip separates it from the neck of the bottle, and cork and lip fly away together in a pretty trajectory that could probably be easily calculated using Newton's laws. There's a handy real-world physics problem to assign students in the classroom; I guarantee 100% attendance the day of the in-class demonstration. Weaponry and the prospect of potential blood-spillage never fails to draw a crowd.

There are other hazards associated with champagne that have nothing to do with its alcoholic content. Here's a random bit of historical champagne trivia: there are tunnels under the Thames River in London, and the earliest of these was built using airlocks to maintain massive pressures inside the tunnel to keep the water from flooding in during construction. The day the two shafts from either side of the river met in the middle, local politicians gathered in the tunnel to celebrate with a dinner. I couldn't find any record of the quality of the food — I'm just impressed they found a caterer willing to venture into a tunnel under the Thames — but the champagne, alas, was disappointingly flat. That's because the high pressure in the tunnel kept the dissolved carbon dioxide from escaping into the air as bubbles — there was no need to re-establish equilibrium. The politicos drank it anyway, because wine should never go to waste. Unfortunately, when they left the confines of the tunnel, the ambient pressure dropped rapidly, and "the wine popped in their stomachs, distended their vests, all but frothed from their ears." Apart from intense gastric pain, the politicians were ultimately unharmed.

We also learned yesterday — courtesy of the molecular gastronomy blog Khymos — that a Swedish physicist named Hans-Uno Bengtsson has precisely calculated how far you can shoot a champagne cork (using the more traditional uncorking method). He's even written a book about it with a sommelier named Mischa Billing. According to Bengtsson, the initial cork velocity would be about 20 meters per second, or 70 kilometers per hour. If you ignore air resistance (as physics teachers almost always do for simplicity's sake), the cork should travel some 40 meters. The folks at Khymos have a whole bunch more fascinating fun facts about champagne which you can check out here.

Or you can just sit back and enjoy the first day of 2007 with no pressure to achieve much of anything.  Perhaps even pop open a leftover bottle of champagne, if you're feeling especially indulgent. It goes nicely with standard brunch fare. And oh yes — Happy New Year, everyone!