Title: Humidity-insensitive ferrite developer materials

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Abstract: Humidity-insensitive electrostatographic ferrite carrier materials having an average particle diameter from between about 30 to about 1,000 microns prepared by blending an essentially stoichiometric mixture of ferrite forming metal oxides, calcining the blended oxides to provide the blended oxides with a saturation magnetic moment of between about 6 to about 30 electromagnetic units per gram, milling the calcined oxides in a slurry to reduce their particle size, adding manganese oxide, copper oxide, sodium-free deflocculant, and water to the slurry to provide a slurry having about 80.0 percent by weight of solids, pumping the slurry to hold/feed tanks with continuous mixing while adding a binder material, spray-drying the slurry, screening the particles, firing the particles to provide them with a saturation magnetic moment of about 48 electromagnetic units per gram, deagglomerating the particles, and screening the particles to obtain ferrite particles characterized as having surface sodium in an amount of less than about 20 parts per million, surface zinc in an amount of less than about 5,000 parts per million, and a BET surface area of between about 170 cm.sup.2 /gram and about 500 cm.sup.2 /gram.


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