No, it is not necessary to seal stone, however, we do it to most natural stone countertops because the sealer provides great benefit at little cost. In 99% of the cases if you clean up after meals you will never have a stain. Mineral surfaces like granite are generally not porous, but some stones can absorb minor amounts of liquids, which rarely result in minor discoloration and staining. Although there are many good sealers on the market, taking simple precautions and performing regular cleaning can save trouble and cost. All marble and granite tops are sealed twice in our shop before they are installed. The impregnating substance penetrates the stone deep below the surface, making it quite impervious to alcohol, juices, soft drinks, cosmetics, cleaners, coffee, food, and even oil. Over the course of time, and everyday use, the sealer wears out (10 to 15 years inside the home).
Quartz and Slate do not require sealing. Granite is also a very low porous stone and doesn’t require sealing after purchase and installation. Quartzite is similar to granite and should not require re-sealing before the 10-15 year timeframe. Travertine should be re-sealed on an annual basis. Sandstone and LImestone also require annual re-sealing but these materials are typically not used for countertops.