How do you remove grout haze from natural stone mosaics. tried an acid cleaner from tile shop,it was useless?

Had you sealed it prior?Or did you seal it after it was grouted and not clean? If you hadn t then you may not be able if the acidic cleaner they sold you didn t have any effect. And if you did it before it was clean you may have sealed it right in . You might have stained it completely. GL