Droplet evolution
Figure 4. A plot showing the diameter of the drop on the surface as a function of time. The red curve corresponds to a pure water drop and the dashed curve shows what happens to the part of the drop that has rebounded from the surface. Drops that stay on the surface follow the behaviour indicated by the purple curve. Often the diameter of the drop oscillates as it comes to rest on the surface. The speed with which the drop retracts after it has spread to its maximum diameter, Dmax, determines whether or not the drop sticks to the surface.