Until now, I didn’t know the technical term for the phenomenon that made my prized Hypercolor sweatshirt so special in the 1980’s. This cool clock by Che-Wei Wang and Taylor Levy uses that same concept—thermochromism—to tell time:

Thermochromic Clock is a 4-digit 7-segment timepiece. Each segment in the display is made with a length of nichrome wire and then covered by a thick layer of black thermochromic paint. Time is displayed by applying voltage to the nichrome wire. As the wire sustains an electric current, it heats up the surrounding thermochromic paint, causing it to become transparent.

[via Creative Applications]