What To Do About White Marble Floor Turning Yellow

Q. We just recently had a white marble installed on our bathroom floor and just noticed the section that is getting no sun from our window (it is being blocked from our tub deck) is yellow. It does have a heating system installed under it. Do you have any thoughts as to why the shaded tiles are yellowing? Thanks so much!

 A. Thank you for the question. Unfortunately, this problem is not uncommon.

Your white marble is most likely turning yellow because of iron. The shaded area stays wetter longer, creating the perfect conditions for oxidation. 

The first step is to determine the source of the iron. It could be your water or the stone – or both. 

Have your water tested to determine the levels of iron present. Inexpensive test kits are available at home stores. If your water has a high iron content, have a whole house iron filter installed that uses an oxidizing carbon/sediment filter. 

You should also have the stone tested. Bring a spare piece to a testing lab to see if the marble does contain iron. If oxidation in the stone is indeed your issue, preparing and applying a poultice solution can rid the yellowing from the marble. 

A qualified stone restoration contractor can perform the poulticing for you, but you can also do it yourself by mixing your own poultice or purchasing a poulticing kit.

To mix your own poultice to remove the iron staining, prepare a poultice solution using water and Sodium Hydro Sulfite and Sodium Metabisulfite, chemicals available in a product called Iron-Out. Your poultice should be the consistency of peanut butter. Apply the poultice to the affected tile. Allow it to soak into the tile and keep wet for several hours. Do not allow the solution to dry. After several hours pick up excess solution with a wet vacuum and rinse thoroughly with water and a chelating agent such as EDTA. 

Since these chemicals in the poultice can cause etching, you may need to have your marble honed and/or polished to restore the finish. A qualified stone restoration contractor can perform this service for you. Should you need the assistance of a Certified SurpHaces PRO Partner, contact us to find one in your area.