Curious Bubbles: collecting research data on bubble blowing from the public

Although street artists can blow soap bubbles over one meter in length, bubble width is determined by the size of the wand used. These bubbles detach from an elongated soap cylinder created in a high air speed “jetting” regime and have diameters double that of the wand. In recent work we demonstrated that much larger bubbles, relative to the wand size, can be blown using slower air speeds. In this “dripping” regime, each bubble is inflated more slowly before detaching from the wand. In laboratory measurements our bubble sizes were well described by a simple predictive law with the largest bubbles blown at the slowest speeds. To see whether these idealised findings translate to the real world, we designed an outreach activity to record bubble-blowing data from the public. We ran the experiment on several occasions through the Curious Rebels outreach initiative, and noticed that unlike in the controlled experiments, nearly all volunteers naturally varied the speed at which they were blowing, reacting in real time to the growth of the bubble. We collected data on the variable air speed and bubble size, again showing good agreement with the simple model. The experiment also provided an excellent opportunity to discuss the surprisingly complex science of soap bubbles with the public.