Nice Legs! But why is my wine crying?

When I first started drinking wine people would talk about the "legs," the streams of wine that fall down the side of the glass after you swirl it. People would say, "look at those legs," or "those are nice legs." Kind of dirty, no? In Spanish-speaking countries they call these lágrimas, or tears... so much more civilized and poetic. Anyway, as I learned more about wine I realized that legs can tell you a little bit about the wine's alcohol level or viscosity, but not all that definitively or importantly. Legs that move more slowly may indicate a wine with more alcohol or sugar, but they are not an indicator of quality or even taste, and legs are not a very relevant descriptor when talking about wine in general. People in the American wine trade find it passé to even mention the legs, but you can't help but be mesmerized by them when you swirl your glass if wine.

I recently came across an article and video explaining the science of the legs and what is really going on here. To preface, the reason the legs form is because when you swirl the glass and the wine sloshes on the sides, the alcohol in the wine evaporates more quickly than the water in the wine, affecting the equilibrium of the liquid and forcing it to pool together in a sort of dance along the sides of the glass. The video is intriguing.

If you want to be really geeky about it (or is that just me?) a couple pages in this free e-book explain the science even further.