Asked on Jul 28, 2013

Problem with new grout. Additional question asked.

Gail lichtsinnKMS WoodworksLynn C.


Two months ago my shower was redone completely because of a leak. The tiler used the Bostic Neverseal Commercial Grade Pre Mixed Grout. We noticed that there are areas where the white grout now looks gray and we have some joints where the grout has black in it. We used this expensive grout because it was touted by This Old House and it never has to be sealed, no color fading ,shading, crack resistant, stain proof,colors won't darken or yellow, has antimicrobial get the idea. Any ideas what is going on. The shower has white subway tile. Could this mean it was not properly mixed in the beginning? I appreciate any help.
To add to above. This grout already contains a sealer, that is why you never have to seal. If the grout was not stirred properly or not at all when opened, could that affect the sealing properties in the mix?
4 answers
  • KMS Woodworks
    on Jul 29, 2013

    Its my guess that this "darkness" is the start of some mold and mildew issues. A way to test this would be to scrub the area with a 1:4 mixture of bleach and water. You can check out this article I wrote for some other tips

  • Lynn C.
    on Jul 29, 2013

    Thanks for your suggestion. I already use the product 'Clean Shower' after each use. This grout is not suppose to have problems with mold or mildew. It does contain an antimicrobial also. Over and above that, it is only two months since it was completed.

  • KMS Woodworks
    on Jul 30, 2013

    Most antimicrobial products don't do diddly squat in terms of reducing pathogens. The manufacturers sell this "hype" to uninformed and paranoid consumers. The bostic site states the grout needs to cure for a full 7 days before being subject to water, use or cleaners. The use of enzymatic cleaners will void all warranties, and the use of vinegar or acid cleaners is not recommended. As far as the "Clean Shower" product the active ingredients, and MSDS data is elusive. I'm still thinking it is a early mildew / mold issue. Can you post some detail photos of the affected area compared to other non-affected areas? I did find a MSDS that lists the pH at 4 to 5 which is 100 to 1000 times more acidic than basic water. (Since pH is a log function)

  • Gail lichtsinn
    on Jul 31, 2013

    you need to contact the person who installed the tile and have him come look at it..He should be able to tell you whats wrong and if this is common problem..Or call a tile store and ask them..I would almost guess theres a few places where the gout does not meet the edge of the tile and water is getting behind it and wetting the grout..Might have a fungicide mixed in it also..Since you know the name of the product call the company who makes it and tell them whats going on

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