Most exterior letters, logos, and plaques will require some maintenance to retain their original luster and shine. We recommend all plastic and metal letters to be cleaned simply with a good dishwashing soap and water, and a very very light brushing like a soft toothbrush or the like, or even a towel. This will remove any dirt and pollutants gathered from the environment. Please do not use any harsh or other chemicals, as we can not guarantee the effect it will have on letter finishes. If the face of a metal letter gets scratched, the polyurethane coating can be refinished using a high quality car wax.