Coefficient of restitution as a function of impact velocity for collisions of 1.5 cm (diameter) ice spheres with a target surface at 90° to the direction of travel (b/R = 0, shown by crosses), a target surface at 60° to the direction of travel (b/R = 0.5, shown by squares) and no target (both this data, shown by circles, and data previously reported by Heißelmann et al. 2010 shown by stars). The chemical composition of the spheres are indicated with colours (black for water, red for methanol, blue for formic acid and grey for the previous data). The rectangles (black for pure water, red for 5% methanol in water and blue for 5% formic acid in water) show the data encompassed by one standard deviation of the mean.