Scientists have uncovered why whisky does not leave behind “coffee rings” when it dries, an advance that may lead to a new type of industrial coating or even ink for 3D printers.
When coffee is spilled and allowed to evaporate on a surface, it typically leaves behind a ring, which has come to be known logically enough, as the coffee ring effect.
Researchers at the Princeton University in US analysed various whiskies and other fluids and their results suggest the possibility for a new type of industrial coating.
Ernie Button, a photographer living in Arizona noticed that the residue left behind when whisky dried in a clear drinking glass, was starkly dramatic when lit from below with various colours.
He began photographing such residue and eventually noticed that not all whiskies left behind interesting patterns, ‘Phys.org’ reported.
The research team at Princeton found that those whiskies that did not leave behind a coffee ring type pattern when they evaporated, had two important features.
The first was fat-like molecules that lowered surface tension - as the liquid evaporated, they collected on the edges of the drying surface which created a tension gradient that pulled the liquid back inward.
The second feature was plant-derived polymers that caused a sticking effect, which helped channel particles in the liquid to the base material where they remained stuck.
The researchers created liquids that behaved in the same way as whisky. Removing either the polymers or surfactants prevented the liquid from leaving behind non-coffee ring characteristics.
Researchers noted that because of its even coating distribution characteristics, whisky-type liquids could be industrial coatings or even a type of ink for 3D printers.
The research was published in the journal Physical Review Letters.