Soap Film Hydrodynamics: In Color, and In Black and White

Iridescent colors of soap bubbles or films arise due to interference between light reflected from two surfactant-laden surfaces that are $\sim$ 100 nm - 10 micron apart. Sandwiched between these interfacial layers is a fluid that drains primarily under the influence of gravitational and capillary or interfacial forces, including disjoining pressure. Below 50 nm the thin films appear as black. We experimentally follow the drainage kinetics of soap films using imaging {\&} color science and UV-Visible spectroscopy. We find fascinating examples of two-dimensional hydrodynamics and unexplained, if not unprecedented, drainage kinetics.