TRANSLUCENT ALUMINA Alumina ceramics are usually opaque because of the reflection of the light on their residual microporosity. But through hydrogen sintering of submicronic and ultrapure alumina powders, the mobility of the grain joints is reduced, the growth of the grains is inhibited by the presence of MgO, the porosity can be practically eliminated and the remaining pores do not exceed 1 µm. Translucent alumina ceramic tubes are commonly used in High Pressure Sodium lamps (HPS) :    · HPS lamps are the first choice in outdoor lighting. 80 % of all HPS tubes in the world are made from Baikowski's ultrapure alumina powders. · Baikowski also contributes to the development of new ceramic Metal Halide lamp tubes for indoor lighting.