3. There are also some new chemicals available containing ammonium thioglycolate, which look promising for removing iron oxidation. Check with your local stone maintenance supply company for more information.
Before attempting to remove iron staining, it is important the marble be dry. If water or moisture are still present, oxidation of iron may continue. The yellowing of white marble is a common problem. New installations should be sealed with a good quality penetrating sealer (impregnator), which will help prevent oxidation of the iron by eliminating moisture. The procedures described above also work for other stone types with iron staining problems.
About the Author: Frederick M Hueston columnist and author, is director of the National Training Center for the Stone & Masonry Trades (NTC) located in Asheville, N.C. NTC offers hands-on training to industry professionals on topics ranging from basic fabrication techniques to onsite repairs. NTC's website can be found at www.ntc-stone.com.