“Whoa, look at those legs!”

Yes, wine geeks are apt to swoon more about the legs in their glass than the shapely ones strutting the street.

Does all the hoopla about “slow legs” really merit our attention as wine drinkers? To check out the legs on your wine: Swirl a stemmed glass filled with two or three ounces of wine (any more than that and your neighbor will be wearing a wine hat) so that it rises up in the glass towards the rim, and then stop. Watch the thin coating of wine that’s left on the glass form liquid rivulets that slowly slide back down into the bowl. You are now looking at the “legs,” or what the French poetically call “tears.” Are they fast, slow, thick, or thin? Do slow legs mean delicious wine? Wine aficionados are oft found to be preoccupied with this sort of navel-gazing.

If you try swirling with only water in your glass, you will note the complete absence of legs. The amalgam of wine that is foremost water and alcohol with the addition of small amounts of acids, tannin, and sugars interact in the glass in a very specific way. The results of which are these much-speculated-about curious droplets.

Wine legs' shadow

Chemistry provides our investigation with its first clue: Alcohol evaporates faster than water. The thin coating of wine that remains on the glass after swirling is rich in water. The wine at the bottom of the glass actually has a higher alcohol content than the legs dripping down the sides. (Hmm, perhaps I could drink more if I weren’t such a lazy swirler?) Furthermore, if you cover the top of a glass of wine with your hand, stifling evaporation, the tears will not flow. And so the mystery of wine rivulets is at least in part due to the evaporation of alcohol.

The evaporation of alcohol may not alter your buzz but it does affect the surface tension of liquid to glass. Alcohol has a lower surface tension than water. You may see this for yourself in a quick home experiment. Place a few drops of alcohol in a puddle of water on a flat surface and watch the water race away from the alcohol.

As one swirls, the alcohol portion in this thin patch of wine pushes the water content up the sides of the glass. In the end, gravity wins the day and the water slides back down, dizzy with alcohol withdrawal. As to the arched shape of the tears, this is because alcohol does not evaporate at the same rate in all areas of the glass. The tears are dramatic outlines of these varying areas of resistance.

Back in 1855, British physicist James Thomson observed what he called “tears of strong wine.” However, Thomson’s research was not widely recognized and the discovery is popularly credited to the Italian physicist Carlo Maragoni, who published his doctoral thesis on the topic in 1871. Thereafter, the legs of wine were said to be a manifestation of the Maragoni effect. Not at all an indicator of wine quality, “nice legs” point to the presence of alcohol.

At this juncture, many a trade professional is more than content to happily depart from physics and return to sniffing and sipping. I leave them to their cups! For to seriously debunk the myth that slow legs equates with wines of superior quality, I must persist. High alcohol is not the complete answer to this mystery. If you have ever enjoyed a German or Canadian ice wine, which at six to eight percent is about half the alcohol of table wine, you would again be dumfounded by the appearance of slow, thick tears.

To cut to the chase, wine, unlike water, is a complex substance. The varying surface tension of liquid to glass is due to evaporation rates, alcohol level, residual sugar and the friction of the glass itself. High residual sugar in ice wine may produce legs as pronounced as a fortified tawny port. That said, neither the presence of high alcohol nor residual sugar point to the quality of a wine. For example, cool climate Oregon Pinot Noir or Bourgogne rouge with moderately low alcohol (12 to 13 percent) will paint thin, almost transparent legs and yet the taste and its ageability may be extraordinary.

Romance aside, wine is first of all a science. If you must embellish, then think of the legs of wine as is implied by the French name—“tears,” big, droopy tears, lamenting the loss of their beloved ethanol on the treacherous slopes of Riedel crystal.

Paula Paradise is a freelance wine writer and educator.