Ernie Button, a photographer from Phoenix, USA, found that whiskey drops dry into fascinating colorful films. Different whiskeys produce different images.

Howard A. Stone, Hyoungsoo Kim, and colleagues, Princeton University, USA, investigated this effect in binary-mixture droplets using Particle Image Velocimetry. The ethyl alcohol in the droplet evaporates more quickly than the water. As the fraction of water increases, the surface tension of the droplet changes. This effect is called Marangoni effect. It generates complex circulating flow patterns that deposit various solid compounds inside the whiskey with a peculiar pattern.
Moreover, whiskey contains a natural surfactant and polymers. These attach to the glass and provide a template for the stripe patterns seen in the colorful pictures.

• Presented at the American Physical Society’s Division of Fluid Dynamics in San Francisco, CA, USA.
• Ernie Button: Vanishing Spirits – The Dried Remains of Single Malt Scotch