We found that at very low glycerol content (0.1-0.3 vol%) there was a very large impact on the stick-slip behavior (Figure , Figure ). In opposition to the single solvent viscosity study, an increase in viscosity provoked more marked stick-slip banding, with more interband particle deposition. Break-up happens for a large enough Marangoni number, a dimensionless parameter comparing the relative effects of surface tension and viscous forces. Thus, both surface tension and viscous forces will impact pinning and interband distance. In the case of the single solvents, increasing viscosity decreased the propensity for pinning leading to a more homogeneous coverage. In the co-solvent case, the viscosity increases much faster than the surface tension in the initial moments of pinning. But, the Marangoni number will increase rapidly as the alcohol evaporates, encouraging break-up. By 0.4 vol% glycerol content, the distance between banding dropped dramatically, as pinning and depinning became more frequent and more erratic. This behavior is consistent with Marangoni flows away from the contact line. By 0.5 vol% glycerol, the film pattern was completely chaotic. Increasing to 2 vol% glycerol content generated lacy patterns, as if beading were somehow occurring. By 5 vol% a mixture of mono-and multilayer regions is observed on a highly inhomogeneous surface. What is certain is that the quantity of particle deposition increases with increasing glycerol content, but at the expense of reproducibility, homogeneity, and an understanding of the deposition process. We find it impossible to tease out the contributions of surface tension and viscosity gradients across the meniscus in the co-solvent system. To better understand the stick-slip banding in a co-solvent system (poly(acrylic acid) in i-PrOH), anisotropic silica particles, in the form of long ribbons (0.5-1.0 μm in length, ~20 nm in width), were studied. The ribbons are semi-flexible, and thus can follow the flow pattern of the Marangoni currents, providing evidence for the currents upon drying. Based on our previous study, 1 the ribbons dispersed in poly(acrylic acid)/i-PrOH were deposited at three different temperatures to investigate the flow instabilities as a function of drying speed (Figure ). At room temperature, no evidence for flow instabilities was detected, the ribbons were aligned parallel to the meniscus and largely parallel to each other. Thus, it seems that break-up occurs before a significant gradient in surface tension establishes at ambient temperature. Both the leading and trailing edge were clean, attesting to classical stick-slip behavior. As the temperature in the chamber was increased to 35 and 55 °C, the leading edge remained clean and the trailing edge showed swirling patterns. The organization of the ribbons parallel to the swirling patterns reveals the direction of the Marangoni flow current. Pinning seems to occur regularly, creating a linear band at the leading edge. As in the co-solvent system for the spherical silica particles, a gradient in surface tension must be created before break-up, due to the evaporation of the alcohol. Marangoni flows in a sessile droplet, in the presence of 0.5 wt% PEG, have been studied by Seo et al., where they observed a delay of 10 s before a surface tension gradient generated, and the Marangoni flow began. Perhaps before break-up, as surface tension begins to increase at the trailing edge, a flow instability is created where the silica particles try to flow away from the drying line, rather than in the direction of convective flux. The co-solvent system clearly has several competing forces that make studying these systems rather complex.