We've all seen it, the Ugly White film on Your Tile & Grout you describe that most often reforms again after you brush it away. This is called efflorescence; which is simply white salt deposits. These salts remain on the grout joints when the salts in water solution are wicked to the surface. The water then evaporates, leaving these salts in powder form.
What Causes Efflorescence?
Efflorescence is caused by water seeking out the porous grout joints because it cannot travel through glazed tile. Because it is difficult to say exactly where efflorescence comes from, it is just as difficult to say when it will stop appearing. These salts can originate in the grout, the mortar bed, the concrete slab beneath the mortar bed or even in the ground under the slab. They have also been traced to unwashed sand containing soluble salts, free alkali's in cement and occasionally to chemical concrete admixtures. More recently they have also been traced to high alkaline floor cleaners which absorb into the joints and reappear as efflorescence. That is the reason they call your substrate, (ex. slab) "the hidden floor below." It can even be caused by a failure to install a moisture barrier between the source of the moisture (the ground) and the grout joints. Frequently the efflorescence problem will reduce to a low level as the underlying moisture evaporates away. The bottom line, it is excessive moisture (more than normal) wicking through the porous grout joint.
How to Eliminate an Efflorescence Problem
The first step to eliminate the efflorescence problem is to let the installation dry out and the cement cure. During this process, merely brush off the white powder which will leave a stain, but do not address the stain until the wicking (moisture transmission) stops. For the final cleaning and to remove the stain, agitate the grout joint with a brush and, if necessary, utilize a neutral cleaner such as Aqua Mix's 'Tile & Grout Cleaner.' If this fails to remove all of the residue, it may be necessary to use sulfuric or phosphoric acid.
Sulfuric would be the acid of preference and three things are mandatory for either acid:
- It must be diluted a minimum of 5:1 to 7:1.
- The surface must be wet prior to administering the acid.
- Be sure and wash thoroughly to remove all the residue of acid.
Allow this to dry and if no more efflorescence appears, seal the grout joint with a grout sealer. NOTE: If by circumstance it is a fast track commercial job, the same process would be followed, except you may not be able to allow it to dry out as much as possible.
If you still need help and are in Palm Beach county. You can Contact Ceramic Solutions to come evaluate the situation!