ABSTRACT
30 vacuum fired [Vita] porcelain discs [10 mm. In diameter were prepared under identical conditions. All the specimens were finished to smooth surface and divided into three groups no. one glazed with natural glaze, the second with low fusing glazing paste, and the third glazezd with diamond polishing paste. Comparisons were evaluated by means of [surtronic] tracer. The mean surface roughness, obtained by the diamond poliching paste, was less than natural glaze. The difference was not significant at 5% level. The mean surface roughness, obtained by the diamond poliching paste, was less than the low fusing glazng paste, the difference was significant at 5% level. From this study, it is concluded that: 1- Glazing of vacuum fired porcelain can be achieved by polishing paste. 2- After spot grinding of porcelain, resmoothing and reglazing the surface can be achieved without exposing the porcelain and the underlying metal to a more further firing. Agreement with Barghi et al [1976][3] who found that the vacuum fired porcelain is less porous than air fired porcelain