Bubble Periodicity: these bubble timer tubes exhibit amazing regularity in the formation of a train of bubbles- so evenly spaced and similar in size! The physics of surface tension, viscosity, and buoyancy combine to produce this phenomenon. An inverted tube will release 30 bubbles and each bubble takes about 60 seconds to get from bottom to top. Note the bubbles in the blue tube seem to rise slightly faster than those in the green tube. ➡️ Follow the link in my profile for info on where ti get