In thermal ink jets a complete understanding of the physical processes in ink-jet firing chambers still requires research. The experimental investigation of these high-speed dynamic processes is difficult due to the extremely short durations of the different phenomena in the ink chamber. For example, the bubble lifetime is approximately 15 μs. A new experimental setup is presented to record phenomena of very short durations, like bubble nucleation, bubble growth, bubble collapse, and the beginning of droplet ejection. This setup allows realcinematographic visualization of such processes with a spatial resolution of less than 1 μm and a time resolution of 10 ns. The apparatus also offers the possibility of studying transient processes such as droplet ejection at high printing frequencies. The essential part of the setup is a new highspeed camera. With an exact evaluation of the digitized images the locus, velocity, and acceleration distributions of the phase interface from liquid to vapor/air can be measured. In addition to experimental work simulation results of a dynamic numerical model with realistic geometric data of the firing chamber and the nozzle of a commercially available printhead are presented. A comparison of experiment and simulation leads to conclusions for pressure propagation in the vapor bubble.