Although most granite countertops don't need to be sealed, it does help the stone resist dirt and spills, which can cause etching and staining [source: Marble Institute of America].
By its nature, granite is moisture-resistant -- however, it's also porous. Sealants block liquids from seeping into the granite. A properly sealed countertop will cause liquids to bead on the surface.
Liquids with color -- like grape juice and red wine -- cooking oil and fat can all discolor the countertop. Pizza grease can be a culprit, too, when it soaks through the bottom of the pizza box and onto the countertop.
In small areas where the faucets, sinks and stovetops lie, you should apply sealer after the countertop is installed. This should be done before appliances are put in because you won't be able to reach these spots later on -- but seeping liquids can [source: Hart].
Generally, you should seal most kitchen granite countertops annually. Keep in mind that different pieces of granite have different porosities. Some countertop areas may need to be sealed more often than others. To determine if it's time to reseal a countertop, dribble some water onto the countertop. If it beads up, great. If the water soaks into the granite, it's time to reseal.
Sealing is straightforward. Get a good-quality granite countertop cleaner, a granite sealer that's designed to resist water and oil-based stains, and some clean rags. Follow the cleaner's directions first, making sure the granite is dry before you start sealing. Some sealers, such as those with a solvent base, are good for several years [source: Marble Institute of America].
When sealing, work in small areas, allowing the sealer to absorb for the recommended amount of time before applying the second application. Then move to another area. Follow the sealer's recommended amount of drying time (usually several hours or overnight) before using the countertops.
Before making the decision about granite countertops, it's important to know the benefits and costs. Read on to learn about the pros and cons of granite countertops.