A magnetic mono-component development system for printers and copiers is comprised with silica particles on the surface of each toner. The silica particles are used as external additives to improve flow ability, to reduce toner aggregation and to modify the tribo-charge characteristics. In most cases, increasing the amount of positive additives to the positive toner result in the increasing of the positive tribo-charge, while sometimes the charge perform too high or too low and it makes toner tribo-charge unstable. Thus, the reverse charge additives are applied to stabilize the tribo-charge and image density in the printing. This study is about how the reverse-charge elements stabilize the image density in the printing.