Painting with ice and light

New Scientist:

The image, (above), is a frizion, and it was created by NASA scientist and artist Peter Wasilewski. Rather than painting on canvas like most artists, he creates his images with polarised light and ice.

To do this, Wasilewski takes a Petri dish of ice in the process of freezing, sandwiches it between two polarising filters and passes white light through. The first filter polarises the light, causing all the rays to vibrate in the same plane. Ice crystals split polarised light into two rays which travel at different velocities through the ice, so when the rays are recombined at the second polarising filter there is a phase difference between them. This causes interference, creating the startling colours in the image. The colours are determined not only by the lattice structure of the ice, but also by its thickness. By controlling the thickness, for example by varying the temperature of the surrounding water, Wasilewski produces a wide variety of different patterns.

See this photo gallery to find out more about how Wasilewski creates them.