Tears of Strong Wine

Give your wine a swirl round the glass.

See those gorgeous, syrupy looking drops of wine trickling down the sides of the glass like sleepy little raindrops? Those are tears.

Also known as legs:

Sorry, legs:

The phenomenon was first explored fully in 1855 (a big year for wine, right?) by a British physicist by the name of James Thomson. His work outlined a series of molecular relationships in wine that allow it to not only cling to the glass in gravity-defying wonder but also slink back down again like little blobs of honey.

Basically, liquids are held together by attractive forces between molecules - known as surface tension (essentially what makes it a liquid and not a gas). The same attractive forces exist between the liquid and the surface of a solid substance like glass - known as interfacial tension. With wine and indeed most everyday liquids, the forces of interfacial tension between the liquid and glass are slightly stronger than those of the surface tension, so the liquid will appear to stick to the glass (this is why you can see raindrops on your window for example).   

So even with water in a glass, look closely and you will see the liquid appear to climb up the glass a little around the edges, where the interfacial tension pulls water molecules towards the glass.

But where are the tears?

Well with wine, we have a solution of alcohol and water.

As the thin film of wine clings to the edges of the glass, the alcohol evaporates quicker than the water and the composition of the liquid changes. This is a process slow enough to see happening and as the concentration of water in the liquid increases, so does its surface tension, meaning it forms a nice little round blob.

Eventually, as the surface tension increases and more liquid is drawn to it, the blob becomes so heavy that its interfacial tension can no longer hold it fast, and so it trickles back down the glass - slowly, as the last of the alcohol evaporates and the blob of wine becomes both stickier and heavier. 

In the wine trade they are called tears or legs.

No wine geek worth their salt would not mention them if they were apparent. In fact their observation is a requirement in the WSET curriculum. But my favourite part is that they convey almost no information whatsoever about the wine you are about to drink.

Their presence signifies nothing, except - at most - the presence of alcohol.

Legs. 

Who needs them?