Whiskey Drops Inspire Coatings Technology


Whiskey may unlock the secret to improving uniformity in films and coatings, according to Princeton University researchers.

Inspired by a set of photographs showing whiskey residue left behind in glasses, a group of Princeton surface engineers began studying whiskey evaporation. Specifically, the team measured the fluid motion within evaporating droplets of the liquor.

The engineers found that a combination of molecules—surfactants and polymers—help route the deposition process in whiskey resulting in a spatially uniform deposition, according to a synopsis of the research.

Results of the study have recently been published in the journal Physical Review Letters.

Photos Inspire Spirited Study

Many solutions produce uneven stains when they dry on a surface, called the “coffee-ring effect,” because edges of the drops evaporate at a faster pace than those at the center.

Previously, researchers have discovered that mixing solvents, such as water and alcohol, reduces the coffee-ring effect but only for submillimeter drops, according to the engineers.

Large drops of whiskey, however, appear to produce uniform stains, as revealed by photographer Ernie Button, of Phoenix. The photographs examine residues left behind by whiskey in a clear drinking glass when lit from below with various colors.

Ernie Button
© Ernie Button / used with permission

Photographer Ernie Button's Vanishing Spirits: The Dried Remains of Singlemalt  Scotch inspired the research. An image from the collection appears above.

Button’s images prompted the Princeton team to use florescent markers to track the motion of fluid in whiskey drops. They reportedly observed inward flow that partly countered the outward flow from differential evaporation, the synopsis explains.

How it Works

The team reasoned that the presence of fat-like molecules lowered the surface tension.

“As a drop evaporates, the surfactants collect on the edge, creating a tension gradient that pulls liquid inward (the so-called ‘Marangoni effect’),” the synopsis indicates.

Additionally, the team found that plant-derived polymers stick to the glass, helping to guide particles to the substrate where they adhere.

To confirm their findings, the researchers showed that whiskey-like liquids lacking either polymers or surfactants did not produce the same uniform stains.

As for applications, the team says the research could lead to new coatings or 3D printing technologies.


Tagged categories: Coating chemistry; Coatings Technology; Coatings technology; North America; Quality control; Research and development; Surface profile

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