Our experience shows that most, if not all, stone installations should be sealed with a quality penetrating sealer designed specifically for natural stone. Although some materials are less porous than others (granite to marble, for example,) the application of a sealer is still necessary. Most penetrating sealers work by entering and filling the pores found in natural stone. By filling these pores, the sealer helps prevent the intrusion of liquids into the material.
Sealers are designed to help prevent staining by foreign substances. There is no foolproof, 100% protection to be had. However, a good quality sealer protects your stone investment by preventing the penetration of these substances into the stone, forcing them to remain on the surface long enough to be cleaned or mopped up using normal methods.
Sealers are subject to wear and chemical breakdown and require re-application periodically to maintain their efficacy. Lemon juice, wine, and other acidic liquids, as well as solvents of any kind, all take their toll on a sealer. A conscientiously applied maintenance program of sealing and cleaning with recommended methods will assure the longevity of your natural stone installation.
As a final word, it is critical that natural stone used in wet areas, or areas that are intermittently exposed to water be sealed and maintained well. The length of time between sealer applications will vary depending on the use, type of stone, and type of exposure the installation typically receives. A good rule of thumb is the water-beading test: water should bead on the surface for 5 minutes, and when wiped away, leave no water stain. If the water beads break down and leave a dark mark on the stone when blotted away, it’s time to reapply a sealer. A short trial period should give you an idea of a worthwhile maintenance schedule, but there is never any harm in reapplying a sealer when desired. Most sealers will “break themselves down” when applied over a previously sealed installation (assuming the same type of sealer), and excess sealer that doesn’t penetrate should simply be cleaned away. As always, prevention is the best protection.
