Volume conservation endows soap bubbles distinctive roll-off characteristics

Soap bubbles bring joy to children and can be seen floating in our baths and during dishwashing. We investigate the thinning and breaking of soap bubble necks when subjected to stretching, providing a contrast to the more extensively studied films with open boundaries. Our analysis reveals the difference in the evolution of the profile between film and bubble during the initial non-equilibrium state, known as the roll-off regime. Furthermore, we observe that the scaled profile of the bubble is primarily determined by the ratio V/R3, where V and R represent the air volume and the cap size. The former implies that successive profiles at different times can be mapped onto a master curve by appropriately scaling them with the time until pinch-off occurs, τ. Additionally, the significance of the latter lies in the fact that akin to the insensitivity of films to R during the final pinch-off regime. The process of memory erasure commences earlier in bubbles while maintaining a fixed value of V/R 3 . Moreover, we discover that the minimum radius which remains independent of both V and pulling speed deviates from the previous prediction of～τ 2/3 for the film. It is important to note that our discussion is limited by the short duration of the roll-off regime, spanning from 10 -2 to 10 -3 seconds.