Grout Haze is a bit tougher to deal with unless you’ve just installed your tile and are in the tile cleanup phase. Let’s assume that this haze has been around for awhile and you’re finally getting around to cleaning it up.
1. First, determine if your problem is actually Grout Haze or Efflorescence. Efflorescence is the rising of the salts in grout to the surface and typically happens in new tile installations when too much water is used to cleanup the grout. If your tile installation is less than 10 days old, try using water or (water and vinegar) and then apply some elbow grease.
2. If it’s been longer than 30 days since the new tile installation, you can treat this problem with a mild acid solution (Phosphoric Acid Restroom cleaner), plenty of scrub pads, protective gloves, and plenty of elbow grease. Make sure to neutralize the acidic wash with a baking soda and water rinse.
3. When using a mild acid solution it’s usually a good idea to test an area first to see if there is any adverse reaction. To test your tile, follow the directions of the grout haze remover on a spare extra tile or a tile that’s not easily visible to traffic. After you have applied the solution and allowed it to dry, check for any damage such as pitting. If you apply the acid solution and things start fizzing the acid concentration is too strong and you’ll need to control the reaction by diluting the solution with more water.
Some slate tiles are known to be acid sensitive and it’s always a good idea to take your time to test before starting a project rather than forcing things for the sake of speed and ending up regretting yourself later. Remember that the grout haze most likely is a result from impatience in the first place and that fixing the problem with more impatience is likely going to result in some nice video footage for America’s Funniest Home Videos.