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Friday, April 18, 2014

Question

Our lobby has an unglazed blue ceramic tile. It has been down for about 15 years and no matter what we try to clean it with there are always foot prints left afterwards. It looks clean when wet, but as soon as it dries the footprints come back. The lobby is not heavily used, either. My employees say it has always looked that way. Could it possibly be from the walk-off mat? Would steam cleaning work, or should we try to deep scrub it?


Answer

I think you can rule out the matting, unless it is becoming tacky or disintegrating in some manner. Walking on a wet floor will often leave prints once the floor dries, so the simple solution is to not walk on the floor until after it dries.
Now, if the prints are just there and untouched by daily mopping, you have the problem of determining what they are from. Obviously, footware, but what was on the feet that left a mark that cannot easily be removed?
Test one print on one tile and see what is making them permanent. Are they tar? Try a petroleum distillate. How about tile grout that hardened on the surface? See if muriatic acid (careful!) will dissolve it. Try steam and try deep scrubbing. It all depends on the source of the print. Are these the same prints in the same places day after day or are they prints that show up after someone walks on the undried floor?
I suspect grout as a result of poor cleaning after tile installation, but 15 years is a long time to see something such as this and not correct it.

Lynn E. Krafft, ICAN/ATEX Associate Editor
lekrafft@juno.com