Legs in wine, also known as tears of wine, are the droplets of wine that form on the inside of a wine glass. They are caused by the Gibbs-Marangoni Effect, a phenomenon that is the result of fluid surface tension caused by the evaporation of alcohol. When the surface of the wine meets the side of the glass, capillary action makes the liquid climb the side of the glass. As it does so, both alcohol and water evaporate from the rising film, but the alcohol evaporates faster, due to its higher vapor pressure. The resulting decrease in the concentration of alcohol causes the surface tension of the liquid to increase, and this causes more liquid to be drawn up from the bulk of the wine, which has a lower surface tension because of its higher alcohol content. The wine moves up the side of the glass and forms droplets that fall back under their own weight.

The intensity of the phenomenon depends only on alcohol content, and it can be eliminated completely by covering the wine glass (which stops the evaporation of the alcohol) . More “legs” or droplets can indicate either high alcohol content and/or high sugar content in wine. However, wine legs are not an indication of the quality of wine.