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Friday, September 19, 2014

Question

An employee spilled acid bowl cleaner on a marble floor. The marble does not have a smooth hi-gloss factory finish. It is a more natural finish with veins and natural pitting. Any ideas on how to remove the stain, or at least lighten it, without having to grind the stone?


Answer

The hydrochloric acid in the bowl cleaner etched the marble by reacting with the calcium carbonate in the stone. I would suggest cleaning the area with an alkaline detergent solution to completely neutralize the acid (although it probably is spent by now), rinse well and dry the area. Once it's dry, try gently sanding a small test area of the damaged spot with very fine sandpaper (800 grit) to see if the damage is less noticeable, if this work, cautiously continue the process and blend the damaged area onto the rest of the area around the damaged spot. If this works, there would be no reason to hone or grind the floor unless the etching is deep or a high gloss must be restored. If this doesn't work, you'll need to bring in a stone restoration professional that can fix and blend in the damaged area.
Lynn E. Krafft, ICAN/ATEX Associate Editor
lekrafft@juno.com