The science of whiskey-residue art

New York Times : Ernie Button, a photographer in Phoenix, Arizona, saw the fine lines in the filmy residue of a glass of Scotch and turned it into art by shining colored lights through the films and taking pictures. Over time, he began detecting patterns and similarities between different types of whiskeys and other alcohols. So he reached out to Peter J. Yunker, who had published a paper explaining the uneven formation of coffee rings , but Yunker was unable to help him. Button then found Howard Stone of Princeton University by doing a Google search of “fluid mechanics” and “art.” Stone and his colleagues began testing different liquors and their own alcohol mixes. They found that the patterns formed because of the different evaporation rates of ethyl alcohol and water. As the alcohol evaporates, the surface tension of the water left behind changes, which in turn affects the way the water flows and the particulate residue gets distributed. They also believe that whiskey contains a surfactant and polymers that their artificial water and alcohol mixes did not. The surfactant changes the surface tension of the water, and the polymers adhere to the glass, all of which affects the resulting patterns. Stone thinks that the work has practical applications, such as improved printer inks.