Experimental Study of the Spreading of a Viscous Droplet on a Nonviscous Liquid

We describe experiments on the spreading of liquid droplets deposited on a (wettable) liquid substrate, when the friction in the droplet dominates. We find that the horizontal radius R increases with the spreading time t like t 0.26±0.02 in the capillary regime (R < κ-1, the interfacial capillary length), and like t 0.51±0.02 in the gravity regime. These results are in good agreement with a recent theory.