Post-PTSOS2 note: Leidenball video clips

This is the clip I showed of the very hot brass ball immersed in 75degC water. The envelope of water vapor around the ball is the result of the Leidenfrost effect. The poor thermal conductivity of the vapor allows the ball to remain hot for a surprisingly long time.


I shot this one in class with a highly vocal and somewhat roudy group of Advanced Placement Physics students. I didn't tell them what was going to happen beforehand, but you can hear one of them say, "Leidenfrost, eat your heart out." They had seen Jearl Walker's Leidenfrost effect video one calendar year earlier.


While trying to film the effect, I ran through several takes. Not all of them went according to plan.

Still, there's a lesson to be had here. How is it that the ball could sit in the flame for ten minutes only liberate itself from the rod stem seconds after being immersed in the water?

Here's the one I shot of demo discoverer, Paul Robinson, showing the Leidenball at the workshop.


Technical note to Mac OS X users hoping to upload clips to YouTube. If you upload QuickTime files to YouTube, the sound will lag behind the video by a second or two. Be sure to convert your clips to MP4 format for uploading to YouTube. Apple's QuickTime Pro ($29) will do this.