Dip coating with colloids and evaporation

We investigate the coating of a glass plate with silica colloids by a dip coating method in presence of evaporation. We show experimentally that the deposed quantity plotted versus plate velocity V exhibits a minimum, in agreement with a simple argument developed by us in a previous, theoretical paper. This minimum corresponds to a crossover between the well-known Landau-Levich regime observed at higher plate velocity and a less well-known regime at lower plate velocity where the deposit is formed directly at the contact line. This very general result is consistent with experiments and calculations made by other teams with different compounds or under different drying geometries. Modifying our initial argument by taking into account the particle density gradient, we show that a simple modeling of each regime in terms of scaling laws is possible, the deposed mean thickness scaling respectively as V-1 and V-2/3 in the lower and higher velocity limits. (C) 2012 Elsevier B.V. All rights reserved.