The tendency of a light-colored stone to yellow can be caused by several reasons. First, many white marbles contain iron that oxidizes over time causing the yellow appearance. This type is difficult to repair and may require tile replacement. Most yellowing, however, is caused by dirt that is ground into the stone or by wax type coatings that turn yellow. This type can usually be remedied by stripping or deep cleaning with a suitable alkaline cleaner or wax stripper.
Many white marble tiles contain naturally occurring deposits of iron. If iron is present, it will begin to oxidize when exposed to water or other oxidizers such as acids and household bleach.
White marble tiles can last for years without yellowing, then over time may slowly turn yellow. This process of oxidation is similar to the rusting of metal. If you expose a brand new nail to water and air, it will turn brown and rust. The same process is occurring with the iron in the marble.
The process is difficult to reverse and replacement of the tile may be necessary. We suggest contacting a professional to take care of this stain removal process because you need to be sure the staining is from iron before attempting removal, and the stone will require additional restoration work to bring back its natural luster once the stain removal process is complete.
As marble wears, the highly polished surface begins to become scratched and worn. The wearing of this polish causes the surface to become rough and become a magnet for dirt. If improper cleaners are used, this dirt begins to accumulate in the pores of the stone and will turn yellow.
If you suspect yellowing due to improper maintenance, the marble tile will have to be cleaned with an alkaline marble cleaner. Apply the cleaner to the marble and scrub with a soft brush. Be sure to rinse the tile thoroughly. It may be necessary to repeat this procedure several times to remove all the embedded dirt. If after cleaning the marble is dull, call the experts at The Marble Restoration Company to professionally repolish and seal your stone.
Wax Coating and Crystallization
Many marble floors are coated with waxes, acrylics, urethane and other coatings. Most of these coatings are not specifically designed for use on marble. Some of these coatings are of poor quality and the coatings themselves will begin to yellow. It is common for a coating to be applied in multiple coats. As the coating builds up, it becomes soft and dirt is easily embedded in the soft layer. These coatings require frequent stripping which is often neglected.
To remove yellowing due to a wax or coating buildup, the marble will need to be stripped with a wax stripper. These strippers often require the use of abrasive pads which can scratch and damage the marble surface, so we suggest contacting a stone care expert for assistance.
Another possibility is a process sometimes used for polishing marble floors known as crystallization. If this process is applied to a white marble floor that contains moisture, it will turn the marble yellow.
If the marble tile has been crystallized, it will be necessary to remove the crystallized layer with a powder polish containing oxalic acid. It is strongly suggested that the polishing and honing procedure be performed by trained individuals.
Marble yellowing is a common problem in light-colored marble, but it is frequently able to be fixed. New installations should be sealed with a quality penetrating sealer, which will help prevent oxidation of the iron by eliminating moisture.
For additional care tips for your marble, granite, travertine, terrazzo or other natural stone and grout, please visit our Care Tips page! If you have additional questions or would like to schedule a free estimate with one of our stone care experts, please contact us today!