# The Steve Mould Effect

Simon has been dreaming to try creating the Steve Mould effect, or the chain fountain phenomenon, also known as the self-siphoning beads. It’s a counterintuitive physical phenomenon, almost a magic trick, that occurs when you place a chain of beads inside a beaker and pull on one end of the chain, allowing it to fall to the floor beneath. This establishes a self-sustaining flow of the chain of beads which rises up from the jar into an arch ascending into the air over and above the edge of the jar with a noticeable gap (the higher the distance between the floor and the beaker, the higher the arch), as if being sucked out of the jar by an invisible siphon.

According to the Wikipedia page about the chain fountain phenomenon, a ball chain (or anything with rigid links) produces the best results. Indeed, we had beautiful results with a 50m long nickel ball chain, but a 1m long pearl necklace also worked, even though the links it had weren’t that rigid (just knots of cotton thread)! Anything for science, I’m a young scientist’s mom.

Simon was delighted to learn that this phenomenon has actually been officially named after one of his favourite science presenters on YouTube, Steve Mould. Mould’s YouTube video, in which he demonstrated the phenomenon of self-siphoning beads and proposed an explanation, brought the problem to the attention of academics John Biggins and Mark Warner at Cambridge University! They published their findings in Proceedings of the Royal Society A.

So what’s the scientific explanation? According to Wikipedia, the chain fountain effect is driven by upward forces which originate inside the jar. The origin of the upward force is related to the stiffness of the chain links, and the bending restrictions of each chain joint. When a link of chain is pulled upward from the jar, it rotates like a stiff rod being picked up from one end. This rotation produces a downward force on the opposite end of the link, which in turn generates an upward reactive force. It is this upward reactive force that has been shown to drive the chain fountain phenomenon. A similar effect is observed when pouring viscous fluids from a beaker, Steve Mould pointed out.

We should warn anyone who’s about to buy ball chain, however, that it’s not only the joy of watching the chain fountains flow, but the tears of spending hours of untangling the wretched thing!