It is a crystalline deposit of salt that can form when water is present in a stone surface. It usually presents when there is a water drainage issue (or lack thereof.) Efflorescence can be removed, which we have done many times. But if there is a drainage issue, perhaps a drain pitch problem, or an incorrectly constructed shower stall is to blame.
Another way to think of it, let’s pretend we are doing a cave tour. You enter the cave, and if you are in the cave where there is water that emits from the cave surfaces, well you may see some stalactites and stalagmites that have developed. The stalactites emit from the cave ceiling where water exits the stone, and drips down. And you get stalagmites that form from a cave floor, again where water pools or exits the floor surface.
In addition to there being discoloration, the salt deposit tends to be rough or crusty, and can be hurtful to feet if it develops on the shower floor (which we have been called out to remove as well.)
We advised the client we could remove it, but we could not guarantee that it wouldn’t come back. Asking him to keep an eye on it, if it returns he would need a plumber and tile repair person.
We used a series of diamond encrusted pads starting with a coarse grit and doing a 5-7 pass process before cleaning and powder polishing the stone. All in all it was a long, laborious day, akin to watching water boil or grass grow while holding and using a jackhammer. For the young at heart, and not for the seasoned “senior team,” they powered through it and got it done.
Well done. What a difference it makes. Grinding or essentially wet sanding is the solution for efflorescence and etching. Now if only the stone would behave once and for all.
Ps- this customer has reported the efflorescence is starting to return. We have advised him to have a plumber and tile guy in to assess the situation. It is our understanding that there is a drain pitch and or wall situation that needs attention to fix the problem. We have referred him some competent professionals who can help.