An experimental study on slow and fast bubbles in tap water

Gas bubbles rise in water at different velocities due to different physical states of the interface. While the actual state of any bubble is not traceable two limits can be distinguished which are the totally mobile and the totally immobile interface. It has been a general view that mobile interfaces may occur only in the strict absence of surface active substances. Everything else is partially or totally immobile. This work shows that both limits of the interface can be created in regular tap water. When the initial state is mobile it stays mobile and the bubble is fast. When it is immobile the bubble is slow. In this sense the key issue of the paper is the mechanism of the creation of the initial state.

► The rise velocities of gas bubbles in tap water are measured.
► A new experiment allows to generate bubbles in a well controlled way.
► Fast and slow bubbles are observed depending on generation.