Abstract: A fluorescent lamp discharge tube has an electrostatically coated envelope. The coating comprises a mixture of 100 parts by weight of phosphor, 0.01 to 3 parts by weight of a fatty acid having a melting point greater than 40.degree. C. or the ammonium, aluminum alkaline earth salts thereof, and 0.05 to 5 parts by weight of finely divided aluminum oxide having a grain size smaller than 0.1 micron. The phosphor is applied to the tube by a venturi effect and results in a more uniformly applied coating than is provided using a suspension coating. Uniformity of the coating is measured by the disclosed optical densitometry test.

Abstract: A phosphor for use in fluorescent lamps which comprises calcium sulphate and, optionally, up to 50% of strontium sulphate together with cerium (0.5-10%), manganese (up to 10%), an alkali metal (0.001 to 3%) and boron and/or aluminium (0.001 to 8%). The phosphor may be produced by blending and then firing the individual components. Tubes for use in the lamps may be electrostatically coated with the phosphor.

Abstract: Synthetic willemite phosphor for use in fluorescent lamps in the form of particles coated with from 0.001% to 0.5% of an oxide of scandium, yttrium, lanthanum or a rare earth element. Fluorescent lamps comprising the phosphor which have improved aging qualities are also provided.