Ideally speaking, marble surfaces such as floors or kitchen counters must be kept clean all the time so that it never truly turns dirty or soiled. Under these conditions, all that would be needed would be a casual washing with nothing but clean water and clean rags.
However, this apparently won't suffice if the marble has gone badly soiled and stained through years of neglect. In this event, a more thorough cleaning will be required to bring back its natural color and luster. Begin by wetting the surface thoroughly, then scrub up with a mild, nonabrasive detergent, with a clean fiber brush. Rinse by flooding with plenty of clean, hot water and repeat the washing if needed. The final rinse will remove all traces of the detergent, after which the surface must be wiped dry with a clean, lintless cloth to avoid streaking.
Stains on marble are a real problem, since they'll rarely come out with a mere washing. Most stains happen since spilled liquids are not mopped up right away. This permits them to eat their way into the surface. The longer the stain is left there to dry, the harder it would be to remove, so for the finest results, tackle it as speedily as possible.
Marble stains normally fall into three categories: rust stains, organic stains or oil stains. Each needs its own separate treatment.
Organic Stains. These typically vary in color and rapidly spread out in an irregular shape similar to a staining object. This type of stain is caused by such agents as tea, coffee, soft drinks, fruit juices, iodine, ink and tobacco.
Organic marble stains can normally be removed by bleaching out with 17- to 20-volume hydrogen peroxide hair bleach. This should be mixed with powdered whiting (available at all paint stores) so as to form a thick paste. Spread this generously over the stained area, then add a couple of drops of household ammonia to start the reaction. Maintain the paste damp by covering with a sheet of lightweight plastic and leave this to stand for many hours. Then take out the poultice by wetting. If needed, apply a 2nd or even a 3rd application till the stain is gone. Then rinse off the surface thoroughly with a lot of clean, hot water and dry at once.
Rust Stains. This type of marble stain is made by metallic objects, like lamp bases, ash trays or bolts, that are left in contact with the marble for quite a while where moisture is present. It will be orange to brown in color and will take the shape of the staining object. If discovered immediately, it can normally be removed by rubbing thoroughly with a clean, dry cloth. Otherwise, rust stains must be treated with a special reducer which is sold in a lot of hardware stores specifically for this purpose. Reducing agents of this type also can be bought from most chemical supply houses, and they must be applied following the manufacturer's directions.
Oil Stains. These are typically darker in the center and they scatter out in a circular shape. Oil marble stains can be made by all sorts of greasy household substances and are perhaps the hardest of all marble stains to remove.
Begin by first washing the marble surface with ammonia and then rinsing with plenty of clean, hot water. The stain should then be treated with a special solvent that can be bought from hardware stores and marble dealers. You can also create your own by mixing amyl acetate (ready at all chemical supply houses) with an equal part of acetone (available also at most drugstores). This solvent is utilized over the stain as a poultice which is melded with whiting. Allow it to dry thoroughly, then rinse with plenty of hot water and repeat if necessary. If the discoloration remains even after numerous applications, you can try bleaching with hydrogen peroxide as described above.