Processes for the generation of glossiness on ground granites and ceramics

The present investigation was undertaken to explain the mechanisms for the generation of glossiness on diamond ground granites and ceramics by following their topographic features at each separated stage ranging from rough grinding to fine polishing. The topographic features of the ground granite and ceramic surfaces were quantitatively evaluated in terms of surface roughness and gloss readings in addition to SEM and AFM observations. Temperature responses at the workpiece-tool contact zone were in-process monitored by using a pair of grindable thermocouple. It is found that the gloss readings increase with a decreasing surface roughness in an exponential curve, which provides an important basis for more efficiently generating a better gloss finish on granite surfaces. The surface roughness, and hence glossiness, were found to go through a gradually changing process, during which the material removal mechanism changes gradually from brittle fracture to ductile flow with a reducing diamond grit size. Temperatures generated during the grinding of granites were found to be not high enough to cause chemical reactions and phase transformation on the granite surfaces. Therefore, the reduction in surface roughness, and hence the increase in surface glossiness, are mainly dependent on the mechanical interactions between the diamond grits and granites, rather than thermally induced chemical reactions.