Cleaning Cast Stone
After installing a Cast Stone mantel it should be cleaned with Muriatic Acid. This should be done after the mantel’s grout has had time to dry. This process is best left to the mason who is accustomed to using Muriatic Acid. Gloves should be worn as it can cause skin irritation. We recommend using two spray or mister bottles. One should be filled with water and the other filled with a mixture of 1 part Muriatic Acid and 7 parts water. If the wall and floors are already finished you should protect them by taping down plastic drop cloths. Begin by thoroughly wetting the stone area to be cleaned with plain water by misting. You should start at the highest point on the mantel and working downward. Do not attempt to clean the entire mantel at one time. While wet, spray on the Muriatic Acid, taking care to cover the entire area being cleaned. You will notice a slight foaming action. A light scrubbing (with a small nylon bristle brush) while the acid is working will ensure a more even cleaning. Do not leave the acid solution more than 30 seconds to one minute to avoid "etching" the stone. You stop the action of the acid by spraying more water on the area until clear of acid. Continue this process until entire mantel as been acid washed. This process may be repeated for stubborn stains.

Acid washing helps remove the whitish film that is a normal result of the masonry process known as efflorescence. It also helps clean up excess mortar and the leaching of the mortar onto the stone. It also exposes some of the silica and gives the stone a beautiful luster. The washing process does leave the stone wet and should be allowed to thoroughly dry before sealing.