Crown splashing, produced by high speed impact of a droplet on a rough or
wet wall, is physically very complicated. It is impossible to determine
the size of secoundary ejected droplets by literally solving the full
set of nonlinear Navier-Stokes equations supplemented by complex initial
and boundary conditions. In order to get useful impact laws and, most
importantly, to propose a genearl concept of deriving useful results
without going through the complex mathematical details, we propose a
backward formalism in which we determine the size of the secoundary
ejected droplets by tracking the past event whenever it is required and
just what is required. This procedure allows us to discard those complex
details of negligible importance. Such a formalism, conceptually very
simple and possibly meaningful for other complex problems, leads to a
reasonably correct formula for the most probable diameter of secondary
ejected droplets, compared to know experimental data.