How to Remove White Powdery Substance On Coquina Tile

Q. I just bought a house with coquina tile that has not been cleaned in decades. We contracted a limestone expert (after interviewing 4 companies, 2 of which were not familiar with what coquina tile was) to clean them. They ground the floor and then used acid to remove dirt from pores. 

Some rooms look great and maintained the stone's natural cream/brownish color, but in the living room the tile is almost white, almost like a film of white powder is covering the tile. The whole floor has been sealed. Is there anything that can be done to fix this or is the stone damaged forever?

A.  Thank you for reaching out about your Coquina Tile issue. There are a number of possibilities for the appearance of the floor in your living room.  The technician may have left a residue on the surface of the tile. If you wet the tile, and it darkens, the floor needs to be re-cleaned to remove the residue. 

However, if it does not darken, that white powdery substance could be efflorescence, which will continue to appear after professional cleanings until all moisture escapes from the stone. Hopefully the contractor sealed the stone with a sealer that allows moisture to escape.

Another possibility is that too much acid, used during the cleaning process, may have caused a discoloration in the tile. If this is the case, try a color enhancer, which does a great job of bringing out the colors in the stone. 

We highly recommend finding a skilled and experienced stone restoration contractor to correctly diagnose and resolve the problem using one of the above-mentioned methods. 

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