A glass of wine

Did you notice how good quality wine flows down the sides of a glass? It trickles in dense streams and flows down slowly. Do you know why? Can you wash up a glass properly? Water flows down easily and there are no drops when the glass is really clean.

The two phenomena are explained by so called surface tension: the forces that interact between water particles and between water particles and container walls. The same surface tension forces a dew drop into a form of a sphere (however flattened a little thanks to gravity). This surface tension makes water climb the walls of a drinking trough for canaries.

And the surface tension of wine is half the tension of water. Wine, especially sweet wine, flows wide down the walls of a glass. While grease on the walls does not allow water to flow easily and some drops stick to it. If you don't drink wine, try water with some juice. Sugar, similarly to alcohol, lowers the surface tension of water.