In the lighting industry annually more than 100,000 tons of lead glass are being produced for electric lamps. Because of the hazardous and volatile properties of lead, Philips Lighting has developed a lead free stem glass which is more acceptable for the environment. The lead is mainly replaced by barium which is much less volatile and practically harmless. In addition the mixed alkali effect of three alkali oxides has been used to realize a high electric resistivity and a low softening point. The properties of the new glass resembles the lead glass to a great extent. There are differences however, with respect to viscosity and surface tension. The performance of lamps made with the new glass is comparable or even better than that of lamps made with lead glass.
