1. Champagne collar and bubbles

Champagne's brand image relies heavily on visual perceptions of foam, effervescence and the collar. These are the ephemeral foam generated by pouring, then the bubbles that rise from the nucleation sites and, reaching the surface, form an opalescent white cordon that outlines the periphery of the flute. As much as the foam generated by the pouring process is a constant feature of champagne, professionals are looking for a collar a few millimeters wide that lasts for the duration of the tasting: usually 5 to 10 minutes, rarely more.

Foams and bubbles are inherently unstable objects. Physicists call them "thermodynamically unstable". They can, however, be stabilized...