If sanded grout were used, the installer would scratch the tile inside instillation process.
The first thing that handful of basic to do before one goes about regrouting shower tile is wash it. They include reinforced cast acrylic; porcelain enameled steel or porcelain cast iron. http://Nccproduction.com/wiki/ideas_ega_ding_how_to_initiate_g_out_and_tile_cleaning