There are many "urban myths" regarding the legs or tears of a wine. Some say it’s a sign of quality, and others say no… who’s correct?
Sorry to disappoint if you’re on the offending side, but those who say no are correct. Wine legs refer to the way wine swirled in a glass runs down the inside surface. Some wines having been swirled, may flow down in a fairly even sheet, while others may pull into more concentrated rivulets; these rivulets are what are referred to as legs, or sometimes tears.
Some people believe the presence and thickness of legs relates to the sweetness, viscosity or quality of wine…and none of these is correct. Legs form because of the alcohol content of the wine and the effects of surface tension, adhesion and evaporation.
The alcohol, because it has a lower surface tension, tends to crawl up the glass; at the same time, it evaporates faster than the water in the wine because of its lower boiling point. As more alcohol evaporates, the water concentration increases; the greater surface tension of the water causes the wine to pull together into a teardrop that then runs down the inside of the glass.
Finally, because a wine’s “body” is affected by the alcohol content, there is some relationship between legs and body, but there are so many other factors involved that legs alone are a poor indicator of quality.
Cheers!