developer mixtures comprising finely - divided toner particles electrostatically clinging to the surface of carrier particles . the toner particles comprise a colorant and at least about 60 percent by weight , based on the weight of the toner particles , of a resin mixture comprising between about 40 and about 90 parts by weight of a styrene resin and from about 10 to about 60 parts by weight of an epoxy resin . electrostatographic imaging processes employing said developer mixtures are also disclosed .