Abstract: An electrographic copier/duplicator has a development station with a sump for holding a supply of two-component developer material. A magnetic brush applies the developer material to a photoconductor moved past the magnetic brush. The developer material may comprise carriers of hard, magnetic material. A ribbon blender mixes the developer material in the sump. The blender includes first and second ribbons with each ribbon having a first, relatively large diameter helical end portion and a second relatively small diameter helical end portion. The second end portion of each ribbon is located substantially within the first end portion of the other ribbon. Because the two end portions of the ribbon are connected, there is good axial mixing of developer material in the area between the two portions of each ribbon, and the level of the developer material tends to remain level throughout the length of the ribbon blender.