Ring shells obtained from pure water drops evaporating on a soluble substrate

When a pure water drop evaporates on soluble substrate, the final ring deposit takes form of an inclined wall for small and flat drops hollow rim other geometries. We report here experiments evaporation salty salt single crystals inert substrates, which permit to define precisely experimental conditions necessary obtain such structured deposits. Their growth is not consequence particular thermal or chemical but peculiar geometry experiments. Beside advection solute toward edge by coffee-stain effect induced pinning drop, role nucleation site played substrate condition appear. These have also shown extent dryout microstructure reminiscent crystallography. Finally, these demonstrate potentiality phenomenon surface-patterning.