The effect of two spray modifier adjuvants, NalcoTrol ® and Nalco-Trol ® II, on physicochemical properties, spray atomization and deposition patterns was studied in a laboratory chamber. Six spray mixtures were selected with and without the two adjuvants in glyphosate formulation and water. These were atomized using spinning disc, twin fluid and hydraulic nozzles to study the droplet size spectra and deposit levels on Kromekote card/glass plate units. Physicochemical properties such as relative 235 236 SPARKS ET AL. viscosity, surface tension, viscosity-shear rate relationship, volatility, pH, conductance, electrophoretic mobility and zeta potential of the spray mixtures were measured to determine what properties would contribute to differences in atomization and deposition patterns of the spray mixtures with and without the two adjuvants. The data indicated that the two adjuvants significantly increased the proportion of large droplets in the spray clouds produced by all three atomizers. However, the effect was more pronounced with the twin fluid and hydraulic nozzles than with the spinning disc nozzles. Among the physicochemical properties studied, surface tension, electrophoretic mobility and zeta potential could play important roles, since all other properties were very similar for the spray mixtures with and without the two adjuvants.