Siquieros accidental painting technique: a fluid mechanics point of view

This is an entry for the Gallery of Fluid Motion of the 65th Annual Meeting of the APS-DFD (fluid dynamics video). This video shows an analysis of the 'accidental painting' technique developed by D.A. Siqueiros, a famous Mexican muralist. We reproduced the technique that he used: pouring layers of paint of different colors on top of each other. We found that the layers mix, creating aesthetically pleasing patterns, as a result of a Rayleigh-Taylor instability. Due to the pigments used to give paints their color, they can have different densities. When poured on top of each other, if the top layer is denser than the lower one, the viscous gravity current undergoes unstable as it spread radially. We photograph the process and produced slowed-down video to visualize the process.