Contractor Member Question


The photo attached shows a stain in the marble, my client used stone poultice to pull out the stain, then sealed the tile. Everything was fine until she took a shower for the first time, and the stain reappeared. What are your thoughts?









Mark’s Response

Thank you for contacting the National Tile Contractors Association.
It appears to me the stain (or darkening) may possibly be caused by water pooling beneath the tile in a potential low spot formed in that section of the shower pan.  Do you know if the darkening of the stone lightens with time / as it dries out?  It may or may not be a possibility that the initial removing of the “stain” by application of a poultice may have been coincidental to the stone simply drying out (i.e. from mortar curing under the stone).
I have attached a copy of the NTCA’s Mesh Backed Stone and Tile white paper.  This may shed some more light on the issue with this installation.
Many sealers protect the molecular structure of the tile from staining but do not keep water from passing into the stone and potentially darkening it. To learn more about how sealers work, here is a link to a complete listing of NTCA’s archived webinars.
Please view the webinars I’ve listed below for more information on how sealers work and other relevant information:
I hope this helps.
Mark Heinlein
Technical Training Director