Follow the steps
1.Rub the grout haze with a dry cheesecloth. Shake out the cheesecloth as you work to remove grout dust.
2.Scrub the glass tile with a nylon bristle brush and warm water if cheesecloth doesn't work. Wipe away the loosened grout haze with a sponge as you work. Avoid using the nylon bristle brush in the grout lines of recent tile installations, as the stiff bristles may loosen or cause damage to the grout.
3.Mix a solution of 1 cup of white vinegar to 1 gallon warm water if haze remains on your tile. Scrub the grout haze with a nylon bristle brush dipped in the solution, wiping away the loosened grout haze as you work. Continued use of vinegar can weaken grout, so only use this method to remove haze and not for regular cleaning of glass tile surfaces.
4.Apply a commercial tile cleaner to the glass tile if the previous methods fail. Scrub the haze gently with a nylon scrubbing pad, letting the cleaner do most of the work. Rinse off the tile cleaner with clean water. Use a tile cleaner that is labeled for use on glass tile.
5.Remove the grout haze with a tile cleaner containing phosphoric acid or sulfamic acid as a final resort. These acids are safe to use on glass tile and are highly effective for removing grout haze. Avoid using phosphoric acid on colored grout, as the acid may cause bleaching or discoloration. Read the labels of these products carefully before using, and follow all manufacturer's safety precautions. http://www.regalotiles.com/productinfo/details/terrazzo-terrasso-polishing/17