Supplemental videos

Boiling heat-transfer experiments of a heated surface underwater. An insulating vapor film surrounds the surface. As the surface cools, the vapor film is destabilized until it collapses at the Leidenfrost point.We used phase-contrast X-ray imaging to observe the dynamic film collapse process. Images from a visible light camera, and thermoprobe temperature measurements were synchronized with the X-ray camera to observe when the vapor film collapsed.An algorithm was written in Python to identify the interface between the vapor film and ambient liquid. This allowed us to quantify the film thickness as a function of time.