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

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... ng 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 high-speed 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.