Courtesy University of Louisville.

It's possible to tell the difference between an American whiskey and other whiskeys just by studying the residual patterns left behind by the American variety as it evaporates, according to a new paper in Physical Review Fluids. Liquors like Scotch whisky, moonshine, and Irish whiskeys don't leave these telltale patterns, or "whiskey webs," when they evaporate.

As any connoisseur could tell you, the difference between Scotch whisky and American whiskey is more than just a single letter. "Scotch whisky typically acquires its flavor while it ages in mature—often recycled—barrels, while American whiskey, such as bourbon, is aged in new, charred-oak barrels," Matteo Rini wrote at APS Physics. "Understanding what this means at the chemical level could help with spotting illegal counterfeits and suggest faster alternatives to traditional aging." (Corn whiskey is an exception among the American varieties; it does not require wood aging at all.)

Co-author Stuart Williams, a professor of mechanical engineering at the University of Louisville in Kentucky, noticed one day that if he diluted a drop of bourbon and let it evaporate under carefully controlled conditions, it formed what he terms a "whiskey web": thin strands that form various lattice-like patterns, akin to networks of blood vessels. Intrigued, he decided to investigate further with different types of whiskey—plus a bottle of Glenlivet Scotch whisky for comparison. It was the perfect project for his sabbatical leave to study colloids (suspended particles in a medium, like Jell-O, whipped cream, tea, wine, and whiskey) at North Carolina State University.

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