How to Clean CMU Grout Haze

Concrete masonry unit, or CMU, grout haze is simply a film of grout powder residue left on tile once the grout has been filled into the joints. It is a common occurrence when laying any type of tile, including stone, ceramic and porcelain. Though its removal may be a simple-sounding procedure, it is an arduous and tedious task because it takes time to completely remove grout haze from tile before sealing.

Things You'll Need

• White vinegar or trisodium phosphate
• Buckets
• Spatula or paint stirrer
• Grout sponge

Instructions

1. Wait for the grout to dry completely. If you introduce moisture to unset grout, it could produce more film or haze on the tiles while cleaning them.

2. Mix together 1 qt. of warm water with 2 cups of white vinegar or trisodium phosphate in a bucket. Stir with a spatula or paint stirrer until well-blended.

3. Put a grout sponge into the mixture and soak up some solution. The sponge should be very moist to spread the most solution possible.

4. Scrub over the tile to remove the grout haze. Squeeze the sponge into another bucket to avoid contaminating the vinegar or TSP solution. Remember the grout haze is simply a film of grout, and reintroducing it into the mixture will only serve to worsen the problem.

5. Repeat the process of mixing warm water with white vinegar or TSP after rinsing the bucket clean until all the grout haze has been cleaned off the tiles. It may take several attempts and several mixes to successfully clean the grout haze.

Tips & Warnings

• You must remove grout haze prior to sealing the tile or the haze will be "locked" onto the tile.

References

• "Setting Tile"; Michael Byrne; 1995
• "Black & Decker The Complete Guide to Ceramic Tile"; Carter Glass; 2010