How to Remove White Build-up on Marble
Q. I have an (intentionally) distressed marble seat in my shower. After years of use, there is a build up of white on top of it. How do I get ride of it? Thanks.
A. White residue on the top of stone can be attributed to several things. Ask these questions. Is the substance powdery? Does the substance scrape easily with a fingernail?
If the substance is powdery and the bench is closed (not open underneath where it gets airflow), then I would go to the second step for checking whether the substance could be efflorescence (soluble salts), which might indicate a water issue behind the stone. This is not too likely, but if the stone was improperly installed on block and mortar and if there were water getting to the substrate, then it could happen.
The next test tells us whether the substance is likely to be dried soap products or hard water. If it is soap, it will build up and can be scraped off carefully with hard plastic. If it is hard, it may be hard water build up. There are two ways to remove hard water, agitation with a compatible abrasive or chemically. Either option is pretty tricky. My best advice is to try a white scotch brite pad or a dobie pad and see if you can remove it. Don't try it dry. In addition, it would be best to try it after the shower has been going so that the water can soften the substance. If using gentle pressure doesn't work, it may be best to call a stone care professional. Calcium-based stones will etch using anything acidic and it is not recommended to try removing it chemically. That is better left to the pros.
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