You should never seal a thermal or rough finish on your granite, as it will compromise the texture, potentially making it slippery, and making it more difficult to keep clean. You can and should seal polished top Granite, as in a counter top application. Granite will weather beautifully over the years, and if set in a shady or damp spot, this process will be accelerated. Surface dirt can be removed with a stiff scrub brush and soapy water. If there is a grease or oil stain, do not try to clean it until you contact any Granite Works associate. They can guide you through the cleaning process, and avoid any greater damage.