Since stone surfaces are quite porous they will absorb liquids, which may result in discoloring and staining. Although there are many commercial grade products available on the market that may bring the stone back to its original luster, taking simple precautions and regular maintenance can save a lot of trouble and cost. All granite and marble countertops are sealed during fabrication. This impregnating substance penetrates the stone clogging most of its pores making it quite impervious to alcohol, juices, soft drinks, cosmetics, cleaners, coffee, food and even oils. Over time, depending on how heavily the tops are used, this sealer may wear off. It is recommended that your marble should be sealed at least once every six months and your granite should be sealed at least once a year. If the countertops are heavily used, it is recommended to seal them twice a year.