Abstract: A method for preconditioning an electrographic developer comprising an unconsolidated mass of discrete particles of a carrier and of a toner which carries a charge control agent of negative or positive polarity, said method comprising repeatedly passing a flowing stream of such developer through an electrostatic field between a positive or negative electrode and a grounded electrode of opposite polarity, and attracting part of said toner particles to the electrode of sign opposite the sign of said charge control agent. The grounded electrode has an inclined surface and the stream of developer slides down such surface under the other electrode, which is parallel to the grounded electrode. The apparatus includes mixing mechanism for mixing the developer, and conveying mechanism for carrying mixed developer from the bottom of the inclined grounded electrode back to the top for repeated passage through the electrostatic field.