Vanishing spirits and surfactants in an oak barrel or the end of the silly season

Here is the recipe: 1) Leave a few drops of vodka in your glass. 2) Let evaporate overnight. 3) Inspect. There is nothing to be seen.

Here is the recipe: 1) Leave a few drops of vodka in your glass. 2) Let evaporate overnight. 3) Inspect. There is nothing to be seen.
Now repeat but using whiskey. All kind of patterns will be left on the bottom of the glass. Why? That was a question serious enough to merit an article in Physical Review Letters. But before you go there you may first want to read the introduction on the subject in the New York Times.