The science behind the stickiness of ice

Q: Why is ice sticky? A: Ice is sticky, but only to certain kinds of surfaces at certain temperatures. What really happens is that conditions are just right for a shared ice layer to form between the two surfaces and link them.

A warm, damp tongue or slightly sweaty finger can stick readily to an ice cube as the warmth temporarily melts ice at its surface; once the warmth has dissipated, the water quickly refreezes, creating an icy link. If a cold, dry object touches the same ice cube, there is no melting and no adhesion.

Most of the time, however, ice is slippery, as ice skaters and Antarctic penguins demonstrate. The slipperiness of ice has a more complex explanation or combination of explanations.

It was long believed that pressure melting and frictional heating in some combination released liquid water at the surface of the ice, so that sharp or even smooth objects could glide across.

More recent research has also focused on the idea that a permanent liquid-like layer lies atop the ice, even at temperatures far below the freezing point.

And 2014 research published in the journal PCCP, Physical Chemistry Chemical Physics, suggests that a common supersolid skin, elastic and temperature stable, covers water and ice, and is responsible for its slipperiness.