Abstract

Painters often acquire a deep empirical knowledge of the way in which dyes and inks behave. Through experimentation and practice, they can control these fluids to create textures and images. David Alfaro Siquieros, a famed Mexican muralist, during an experimental painting workshop in New York in 1936, invented a technique to create explosive-like textures. He called this technique `accidental painting´: by pouring layers of paint of different colors on a horizontal surface, the paints ‘infiltrated’ into each other `creating the most magical fantasies that the human mind can imagine´. In this investigation, we reproduce the technique described by Siqueiros in a controlled manner. We analyze the patterns created by this process from a fluid dynamics point of view. We found that the viscous gravity current that is formed is unstable: for the correct color combination, if the top layer is denser that the lower one, the array undergoes a Rayleigh-Taylor instability. We analyze how these spotted textures form as a result of the mixing process of the plumes and bubbles of the unstable viscous layer. An analysis of the time and length scales of the problem is conducted. We have also identified other flows that share some similarities with the accidental painting technique: the formation of lava domes and the cooking of the crepes.