Put your finger through a thin soap film and it’ll pop out of existence in the blink of an eye. Physicists have recorded exactly how this behaviour occurs using high-speed cameras to see how the soap film retracts when it is punctured.
How far can this technique be pushed? Is it possible, for example, to release one edge of a flat soap film and record how it retracts?
The conventional view is that this kind of experiment is impractical because edge effects make a perfectly straight rupture impossible.
Today, Hans Mayer and Rouslan Krechetnikov at the University of California, Santa Barbara, put the community straight on this matter by performing exactly this experiment on film.
Their technique is straightforward. They make a metal frame in the shape of, say, a square and dip it in water mixed with glycerol and water, 4% glycerol and sodium dodecyl sulfate–a standard soap bubble mix.
They then pass a current through one side of the metal frame which rapidly heats up and boils the liquid in contact with it. This releases one edge of the film, allowing it to retract.
But the really cool work comes from passing a current around the entire metal frame, thereby releasing all the edges and creating a “free” soap film for the first time.
Mayer and Krechetnikov publish their results in the form of high and low resolution videos for the APS Gallery of Fluid Motion (yep, it’s that time of year again). And they make for fascinating viewing