All,

Would appreciate input on what’s causing this problem. Please see attached picture. This floor were just installed and grouted. The problem is the red stains on the edge of the tiles. What is causing the problem? My thoughts are that the moisture from the grout is oxidizing minerals in the stone. If that is the case, would applying a sealer before grout stop this from happening? They have already laid 600 sq.ft. of the tile, any suggestions on removing the red spots?  I my thoughts is to try to see if it is iron that is oxidizing and taking the appropriate steps. Or trying poultice with a hydrogen peroxide.

Thanks in advance for your help.

Roger Konarski