Gas discharge in high-pressure discharge lamps is a highly critical process requiring exactly the right conditions for activation and continued running. Switching alone takes quite a long time (2 -10 min.) before the full luminous flux needed for stable operation is reached.
Restrike after switching off is only possible after a cool-down period lasting several minutes because ignition voltage for a hot discharge lamp is higher than supply voltage or the voltage surge from the igniter. In the case of metal halide lamps, high-pressure mercury lamps and high-pressure sodium lamps it takes a few minutes before the lamp can be ignited again. The run-up period for restriking is shorter than at first ignition.