Explaining the phenomenon relating to my cup of tea I'm sitting in front of my computer and just made myself of cup of tea ("Brasilianische Limette") and see the water on the top evaporating into the room. But what caught my eye was a small rotating veil. Sometimes the veil tries to move to the center but gets pushed back by a turbulence. Sometimes parts or regions of the veil suddenly disappear.
Why does the veil sometimes disappear instantly? Please explain for someone who has basic physics knowledge ;)
 A: Probably what you saw is the effect explained in this physics arXiv blog : The Mysteries Of White Mist On The Surface of Black Coffee
The effect was first reported by the Japanese physicist Terada in the 1920s.  
The arXiv paper, also from a Japanese team, is dated January 2015. They report that the white mist is a cloud of tiny water droplets, about $10~ \mathrm{\mu m}$ in diameter, levitating $10-100~ \mathrm{\mu m}$ above the surface of hot tea or coffee - or indeed any hot-water-based beverage. Since it is a white mist, it is seen more easily against black tea or coffee. I suspect also that after the addition of milk the liquid is not hot enough for the mist to levitate.
The mist is thought to originate from vapour condensing in cooler air above the hot beverage and falling down like rain onto the surface. It floats on rising hot air/vapour from the hot drink and forms a triangular lattice, suggesting that the droplets are charged. 
The mist can vanish in about 1/30 of a second, at the same speed as capillary waves - which suggests that it is being swamped by a surface capillary wave. The trigger for such events is one droplet touching the surface, presumably after being hit by a cosmic ray and changing its charge. Other effects include "whiffling" as though wafted by a gentle breeze, a splitting of the lattice by a $1~\mathrm{mm}$ wide rift, and the formation of complex patterns.
