Question: “The travertine tile grout on the floor of the shower use to be a tan color, not it is turning white. How can I get it back to the original color?”
Answer: The grout isn’t actually turning white, but what’s happening is that you are getting efflorescence. This condition happens when water gets below the tiles and or sits in the pan. It has to go somewhere so as the water evaporates it pushes up salts from the setting bed. The grout lines are the path of least resistance so it ends up there.
Most likely your caulking around the change of plane joints at the base may be degraded and is allowing water into the pan. This condition is also related to the construction of the shower stall.
MB-3 or Klenzstone 3 could help remove it as well as using a light acid like vinegar.If your tiles are honed the vinegar should work fine-remember anything acidic will etch marble but if it is honed to a matte finish it should be fine.
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