While granite is extremely dense, it still contains tiny pores. Some natural stone needs to be sealed to prevent stains. Marble and limestone are more porous than granite, so they are more susceptible to staining. Renaissance initially seals your stone countertops with a liquid silicon impregnator to help resist staining. Your granite will need to be re-sealed from time to time. A good indication that your granite needs to be re-sealed is when water takes longer to evaporate from the stone.