Cleaning and polishing a granite countertop is as easy as using warm water, a small amount of soap and a wet sponge or soft cloth to clean the surface and keep it shiny. If the countertop near the stove or sink is still dull, wipe the area with a soft cloth dampened with acetone to dissolve the grease, oil or soap scum residues.
Granite is an igneous rock that is naturally porous. If the countertop is not sealed properly before installation, the stone may become etched and dull over time. Resealing the granite may help solve the problem. Use a high-quality granite sealer product designed to resist water and oil stains. While some granite countertops must only be resealed once a year to keep them in good condition, some need to be resealed more often. Test if the countertop requires resealing by pouring droplets of water on the countertop. If the water beads up, the sealant is still in good condition, but if the water seeps through, it is time for resealing..
If the countertop is in poor condition and is faded beyond repair, a grinder or stone polisher may be able to restore it to its old glory. This is an arduous task requiring the skills of a professional granite or stone restorer. Contact the handyman that installed the countertop or have a professional repolishing service company handle the job.