Further laboratory studies have been made of the charge transferred when ice crystals collide and then separate from an ice target. Previous results indicated increased charge transfer when cloud droplets were present. The new data show that the size distribution of the droplets is important. When the cloud droplets are too small to collide with the growing target, it charges negatively; for the same liquid water content but with larger droplets that hit the target, it charges positively. The results suggest that the relative growth rate and the surface states of both the interacting bodies may be important in controlling the sign of the charge transfer. It is suggested that these results may explain the observation of negative charge centers in thunderstorms at temperatures warmer than -20¿C.