As a wine professional it never fails to make me giggle when I see people out and about in wine bars and restaurants swirling their wine in the glass, holding it up to the light and announcing to their friends "it's got good legs'. Most of them have no clue what 'having good legs' actually means apart from it's something they think will make them appear to know about wine. Well, I get a laugh out of it but I thought it time to explain what the legs actually are and what they mean.
It's a sign of good quality wine?
No, it's not. You cannot tell the quality of wine simply by looking at the pretty dribbles on the side of the glass.
Legs are basically an indication of viscosity, how thick something is. Water, for example, has almost no viscosity whereas golden syrup is really sticky and viscous. The more viscous a liquid is, the more it will stick to your glass and the more gloopy, creepy and slow the legs will be. If you tilt your glass and then straighten it up you may see the curve where the wine sticks to the glass, from this curve you may then see small drops that look like teardrops creeping down the glass. These are the legs and obviously the thicker, slower and creepier they are the more viscous the wine is. This is what we would refer to as 'good legs'.
So, what causes legs in wine?
Lots of things add viscosity to wine but the two main things are sugar or alcohol. You tend to find red wine displays more legs than white because red grapes contain more sugar. They are generally left on the vine for longer than white grapes to ensure ripeness and to develop the colour in the skins. Therefore the sugars are more pronounced, more can be turned to alcohol and so legs are more obvious.
If you have a white wine then and it is dry to taste but has good legs, you can assume it is the alcohol that gives it the viscosity. An oaked wine may have more legs than an unoaked wine as the sugars from the barrels integrate into the wine and add depth.
So, there you have it. 'Good legs' generally indicate a wine that has higher levels of sugar, higher levels of alcohol or perhaps both. They are something to be aware of but there's no need to put too much stock into them, they are nice to look at but are no indication of quality.