When we are given a glass of wine, we give it a swirl.
Swirling a glass of wine is fun. I love watching the colors change as the light bounces off the rotating liquid. I’m sure you have done this as well.
We swirl for a couple of reasons. First, it adds a little air into the wine and releases the aromas so that our noses can better sense them. Second, we can observe the color, the body and the legs.
What are wine legs? When wine is swirled, some of it clings to the side of the glass. The wine then turns into rivulets of liquid, streaming down the sides. While these droplets have long been a source of fascination and speculation, their true significance is often misunderstood.
Wine legs are known by various names around the world. In France, they are called the “tears of wine,” and in Germany, they are known as “church windows.”
They scientific process behind them is called the Gibbs-Marangoni Effect, named after two scientists who researched the phenomenon in the late 1800s. When wine is swirled, a thin film coats the interior of the glass. As the alcohol evaporates, it alters the surface tension, causing the remaining liquid to form droplets that flow back into the glass. This effect is influenced by several factors, including wine’s alcohol content and sugar levels, the current temperature and humidity, and the glass itself.
Stepping out of the lab and into the tasting room, how can this science help you appreciate and understand wine better?
The first thing the science taught us is that the presence of wine legs does not mean the wine is of higher quality. The wine could taste absolutely awful, yet if it has enough alcohol and a thicker body, it could have beautiful-looking legs.
When I am evaluating wine in the glass, imagining what it might taste like, legs give me several clues, based on my experience of observing many thousands of glasses of wine. The first clue is the number of legs. More legs tell me the wine likely has an alcohol content above 15 percent. The second is the legs’ thickness. Thicker legs let me know the wine will have more body; it will feel more like 2 percent or whole milk in my mouth than water. In specific wines, the legs’ thickness is due to the wine’s sweetness. The more sugar content, the slower and thicker the legs.
If you want to see this effect for yourself, start with a clean glass. A wine glass that is dirty or has mineral buildup or scratches will distort the effect. A glass that has a wide mouth allows more air exposure, promoting faster alcohol evaporation and more pronounced wine legs than a narrow glass. The shape of the glass can also impact the temperature of the wine, which also affects the leg development. A wider bowl will make the wine warmer quicker, enhancing the legs.
After you have your clean glass, add just a couple of ounces of wine, and give it a gentle swirl to coat the interior of the glass. Now, hold the glass still, and watch the legs form. Pay attention to their density, the speed as they flow down the glass, and their thickness. Remember wine legs will look different here in Nevada’s high desert, with our low humidity, than they will in a more humid area.
The best reason to observe legs is because they can help you identify at a glance which wines you’re likely to prefer. Do you like wines better if they have thicker, slower legs? Have you noticed that light, white wines with thin, fast legs are refreshing on a warm summer day? Wine legs are just one more evaluation point when tasting a wine.
While definitely not a measure of quality, legs offer a fascinating glimpse into the physical properties of wine. They remind us of the complex interplay of elements in each glass and can provide useful hints about a wine’s structure. However, the true measure of a wine’s quality and enjoyment ultimately lies in its aroma, taste and the overall sensory experience it provides.