What’s the best way to clean grout off a newly installed marble floor without dulling the marble? All grout cleaners seem to contain acid.

Several excellent grout cleaners are available from your stone care supplier that will not dull polished marble. Try a mild solution of bleach ; use a soft tooth brush to apply the solution to the grout joints and scrub lightly.

TIP If the grout is very dirty it may be impossible to clean. It is best to remove a thin layer of grout and replace with new grout.