One morning I received a call from a very upset homebuilder. He told me he was building a $2 million home on the west coast of Florida where they had installed several white marble vanities. Over the weekend one of the faucets broke in a bathroom and completely flooded the top. Once the water had been vacuumed up, they began to assess the damages.
In addition to warped wood, soaked drywall and an irate homeowner, the marble top seemed fine, except for some minor water spotting. After several weeks, however, the white marble began turning yellow. At first the builder thought it might be some type of residue, so he tried cleaning the marble with bleach and water, but the yellowing remained. The homeowner was getting more and more irate and threatened a lawsuit. The builder asked if I could get down there right away and make a suggestion of how to solve the problem.
This is a frequent occurrence when white marble is exposed to moisture. The burning question is, "Can the yellowing be removed from the countertop, or does it need to be replaced?"
Why Does White Marble Turn Yellow?
Although flooding is a common cause for yellowing, there are other reasons such a color change might occur:
1. Improper Maintenance. As marble wears, the highly polished surface begins to disappear. A worn surface becomes rough and is a magnet for dirt. If improper cleaners are used, this dirt begins to accumulate in the pores of the stone and will turn yellow. It is surprising how often I have seen this condition on marble.
Cure: If you suspect yellowing due to improper maintenance, the marble will have to be cleaned with an alkaline marble cleaner. I would suggest a heavy-duty stone cleaner. Be sure the stone cleaner you buy is alkaline and not an acid, since acid cleaners will dull the polish. Apply the cleaner to the marble and scrub with a soft brush. Be sure to rinse thoroughly. It may be necessary to repeat the procedure several times to remove all the imbedded dirt. If the marble is still dull after cleaning, I suggest re-polishing and an application of a good quality penetrating sealer (impregnator). If after several cleanings the yellowing is still not removed, proceed to #2.
2. Wax Build-up Or Coatings. Many marble tops are coated with waxes, acrylics, urethane and other coatings. Many of these coatings are not specifically designed for use on marble. Some of them are of poor quality and will begin to yellow. It is also not uncommon for them to be applied in multiple coats. As the coatings build up they soften, and dirt is easily embedded in this soft layer. These coatings require frequent stripping, which is often neglected.
Cure: The marble will need to stripped with a commercial wax stripper. I strongly suggest using a stripper manufactured by the same company as the wax or coating. This will help avoid incompatibility problems. Follow the directions on the stripper's label and be sure to rinse thoroughly. These strippers often require the use of abrasive pads, which can scratch and damage the marble surface. Before undertaking the entire project, perform a small test on an inconspicuous area to determine results.
3. Re-Crystallization. Another process used for polishing marble is known as re-crystallization. If this is applied to a white marble that contains moisture it will turn the marble yellow. Thus, it is important for the marble to be dry if it is to be re-crystallized.