Supplementary material from "Drying paint: from micro-scale dynamics to mechanical instabilities"

During drying, an initially liquid dispersion of such particles is slowly concentrated into a solid, displaying a range of mechanical instabilities in response to highly variable internal pressures. Here we summarize the current appreciation of this process by pairing an advection-diffusion model of particle motion with a Poisson–Boltzmann cell model of inter-particle interactions, to predict the concentration gradients around a drying colloidal film.

We then test these predictions with osmotic compression experiments on colloidal silica, and small-angle X-ray scattering experiments on silica dispersions drying in Hele–Shaw cells. Finally, we use the details of the microscopic physics at play in these dispersions to explore how two macroscopic mechanical instabilities—shear-banding and fracture—can be controlled.