We have 2Vm+Va+Vwρwg = Vmρcρwg+Vwρwg where Vw is the volume occupied by water in the shell, Va is the volume occupied by air in the shell and Vm is the volume of the material in the shell. Vw = Vm(1−2ρc)+Va If ρc > 21, we get Vw < Va. If ρc < 21, we get Vw < Va.