An apparatus and process for electrostatically charging insulating toner particles (24) to either a positive or negative polarity, and an etectrostatographic imaging system containing such apparatus. The apparatus includes a transporting surface (12) and a charging surface (16) which are arranged so as to be in close proximity to one another in a charging zone (19), the transporting surface (12) being arranged to transport the particles through the charging zone (19) in contract with the charging surface (16), and said surfaces being electrically biased (20,18) to predetermined potentials. In one embodiment, the apparatus comprises a roller (12) containing a coating (13) thereon, a toner supply (14) containing therein uncharged insulating toner particles (24), a charge injecting means (16), a voltage source (18) for said charge injecting means, and a voltage source (20) for said roller, wherein charges are injected from said charge injecting means into the uncharged insulating toner particles deposited on said roller, said injection being accomplished in a charging zone (19) encompassed by said roller and said charge injecting means.