Spilled coffee develops a ring as the liquid evaporates, depositing solids alongside the edge of the puddle. This “coffee ring effect” has fascinated scientists for many years; however, now a group says they’ve uncovered the mechanism behind an even more striking, net-like sample that forms when drops of American whiskey dry up. The outcomes, reported in ACS Nano, suggest that these distinctive ‘whiskey webs’ may sometime be used to plan counterfeit spirits.
When a drop of the liquid evaporates, solids are left behind in a pattern that depends upon what the liquid is, what solids are in it, and the environmental conditions. Stuart Williams and colleagues beforehand found that drops of diluted American whiskeys—however not their Scotch or Canadian counterparts—formed webbed patterns when dried on a glass surface, and there have been hints that the sample was distinctive for different manufacturers of whiskey. In the study, the researchers wanted to see how the whiskey webs form in more detail, and whether they might serve as fingerprints of the spirits.
The crew used time-lapse microscopy to look at droplets of diluted American whiskey as the liquid evaporated. Non-volatile organic compounds, including phenols, aromatics, and esters, clustered collectively and have been pushed to the floor of the droplet, where they fashioned monolayers. As the floor area of the droplet decreased, the monolayers collapsed, creating strands of the web.
The researchers showed that different American whiskeys confirmed distinctive web patterns that might be correctly matched to unknown samples over 90% of the time. The distinctive webs arise from the distinctive combination of solutes in each whiskey, the researchers say.