Dynamic contact angles. Part 7.—Impact spreading of water drops in air and aqueous solutions of surface active agents in vapour on smooth paraffin wax surfaces

Abstract

A drop of pure water impacting on a horizontal solid surface passes through a series of characteristic shapes which are, within specific limits, independent of the height of fall, size of the drop, ambient temperature, and the addition of surface active agents. The dynamic contact angles are independent of the height of fall and size of the drop but are affected by temperature changes and surface active agents. The pattern of contact angle changes is reproducible despite spreading velocities up to 10⁵ mm min^–1.