Abstract: A method is disclosed for reproducibly producing manganese activated zinc silicate phosphor particles, which comprises dry blending a mixture of components consisting essentially of zinc oxide, silicic acid, a source of manganese, ammonium chloride, ammonium fluoride, tungstic oxide, and silica, wherein the Zu+Mn/Si mole ratio is from about 1.95 to about 2.02, wherein the silica is colloidal and has a surface area of from about 50 to about 410 m.sup.2 per gram, and wherein the colloidal silica makes up from about 0.01% to about 1.0% by weight of the mixture, and firing the resulting dry blend of components in a nitrogen atmosphere at a temperature of from about 1200.degree. C. to about 1300.degree. C. for a sufficient time to produce the phosphor wherein the phosphor exhibits reproducible brightness.