When you start a blowtorch, for example to caramelize a crème brûlée just before serving the dessert, you can hear the gas flowing, a little click and after the ignition of the gas, the flame glows blue. With Schlieren imaging and CAVILUX laser illumination you can see the whole process literally in a new light. Small ripples characterize the gas flow before ignition. A shockwave that is visible reveals the ignition spark which you hear as the click. Once the gas starts burning the gas flow pattern changes.
Read more about CAVILUX laser illumination.
Read more about Schlieren imaging.