I installed 100 sq ft of mosaic tile on a floor without cleaning excess mortar as I went. Now I have what seems like 10,000 grout lines that all need to be cleaned. Any advice or suggestions on how to clean them? How clean do they need to be?

  • I didn't do mosaic, but I did do some 3x6 tiles in a herring bone pattern with narrow grout lines. Rather than using the traditional "mortar remover" with the triangle shaped head, I purchased a "backer board cutter" like this that has a sharp carbide blade. Worked good for the narrow lines.
    – JPhi1618
    Oct 1, 2015 at 19:35

1 Answer 1


Make a weak acid solution using Muriatic Acid (pool acid) and water in a 5 gal. plastic bucket, 1 cup:gallon. Using gauntlet type chem gloves and eye protection, scrub with acid. Use a grout sponge to rinse and wipe clean, using clean water and wringing frequently. Repeat until all excess mortar and haze is gone.

Note: above method is effective for removing dried smears and haze, solid clumps of dried mortar must be mechanically removed (scraped).

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