How to Remove Copper Stains on Limestone
Q. I am making some improvements to an 87 yr old building with limestone floors. There are some copper stains on the limestone, caused by some moisture and the copper lights bleeding. Please tell me how to clean up this stain.
A. Use a soft brush and a solution of 50% water and 50% ammonia to clean the stains. If this does not work, try cleaning with rust remover. If the stain remains, mix rust remover and poultice powder or diatomaceous earth to create a poultice paste. For instructions on poultice application, including a How-To video, visit our Stain Management Application. If none of these stain removal methods work, your professional stone restoration contractor can try using hydrofluoric acid to remove the stains. Hydrofluoric acid is extremely corrosive. It will easily destroy skin tissue and bones, including lung and eye tissues from improper ventilation, resulting in serious injury or death. You should not attempt to use this substance. If your stone restoration contractor is able to remove the stain, your limestone may need to be honed or polished to remove the acid etching caused by the hydrofluoric acid. If you do not have a professional stone restoration contractor, you can find a vetted, reputable contractor close to you by clicking on Find a PRO and then choosing the stone restoration category.