The Kaye effect occurs when a thin stream of shampoo is poured onto a surface. Though most of the time it just clusters in a pile, the surprising effect occasionally fires off an arcing streamer! The phenomenon ends when the ‘dancing’ jet hits the primary jet and suddenly collapses.
These streamers of fluid can actually fly quite far — the ones in my initial experiment were traveling up to 8 inches, leaving the bowl entirely and almost hit my camera. This is named after its first observer A. Kaye, who could offer no explanation for this behavior.
So how does this work? It has been long known that liquid soap and shampoo are thinning fluids: this means that, under stress, the fluid flows better and becomes more “liquid-like.”
Most of the time, the soap just forms a heap on the bottom of the surface. Occasionally, however, a dimple forms at the top of the pile. Then a thin layer of thinned fluid forms in the dimple, making a slippery barrier between the heap and the descending stream, preventing their merging. The stream is deflected and launches from the dimple like a ski jumper.
The reason you have probably never noticed this so-called Kaye effect is that it is generally over in an instant. The whole process, from the emergence of the jet to its merging with the incoming stream, typically takes about 300 milliseconds, “It’s usually so short that you don’t see it with the naked eye.” all my video is in slow motion.