How can I clean the Grey Limestone Pebbles to remove the Brown Stain from Grouting?


We just had a new bathroom remodeled to a grey and white color scheme. The grey limestone pebbles all turned brown after being grouted except one sheet. What can we do? It looks awful!


ANSWER - There are different types of limestone.  The low density limestones are porous and more susceptible to staining.  Medium density limestones are less porous, and high density limestones are even less porous.   All of the limestones can potential stain, but some have a greater propensity to stain.

Assuming you used a cementitious grout, they have pigments that can be absorbed by more porous stones.   If there is a risk of staining, normally the tile installer will seal the stones first using a stone sealer as a grout release to prevent staining.

Once the stone is stained you have to experiment to determine how to remove the stain.  You might need to use a stone poultice to remove the stain.  It would be best to have a professional stone restoration company to restore the stone if possible, since they have the experience of dealing with similar issues.

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