Every once in a while, you will see someone swirl their glass of wine, raise it towards the light, and watch with bated breath for the wine's legs to appear. These legs, or "tears" as the French refer to them, are the streaks of wine forming on the side of the wine glass.
The legs were once thought to be associated with a wine's quality: the more legs, the higher the quality. However, the legs have more to do with physics, the wine's surface tension, and alcohol content, than perceived quality.
The Science Behind Wine Legs
Wine is a mixture of alcohol and water. These two elements are responsible for a wine's legs when they are exposed to air.
Alcohol has a faster evaporation rate and a lower surface tension than water, effectively forcing the alcohol to evaporate at a faster rate. This dynamic allows the water's surface tension and concentration to increase, pushing the legs up the glass until the surface tension drives the water into beads. Finally, gravity wins the battle and forces the liquid to tear down the glass in a defeated streak.
A simple at-home experiment will prove that it is physics—not wine quality—that drives this phenomenon. Try covering your next glass of wine and see if the legs that are present dramatically decrease when covered compared to when the glass is left open to the air. You will also notice that no legs are present if you shake a closed bottle of wine.
When wine is not exposed to air, there is no evaporation happening. Without evaporation, no legs will form.
What Do Wine Legs Indicate?
Wine legs do not provide any indication of the wine's quality. Instead, the legs are a scientific phenomenon that can provide some information on the level of alcohol in the wine.
- Wines with higher alcohol levels will collect a higher density of wine droplets on the sides of the glass than lower alcohol wines.
- The viscosity of sweeter wines is much higher. The tears, or legs, will flow more slowly down the sides of a glass with a sweeter wine.
- Both the temperature and humidity of a room will greatly affect the rate at which wine legs form. If you were to examine the legs of the same wine in different seasons, you should be able to see a difference.
How to Examine Wine Legs
You can become familiar with observing wine legs at home by simply pouring yourself a glass of wine.
- Hold your wine glass at an angle.
- Let the wine flow up one side of the glass and then level the glass.
- Examine how the wine flows. This flow (or viscosity) will help indicate the sweetness of the wine. A slower flow indicates a sweeter wine.
- Examine the density of the legs that form. A lot of legs indicate that the wine is higher in alcohol content.
Other Names for Wine Legs
Wine legs can also be referred to by a few different names:
- Tears of wine
- Church or monastery windows
- Gibbs-Marangoni Effect: This effect refers to a scientific phenomenon that is the result of fluid surface tension caused by the evaporation of alcohol.