Most exterior letters, signs and plaques will require some maintenance to retain their original luster and shine. We recommend that you clean all plastic and metal letters with a good dishwashing soap and water, using a very very light brush like a soft toothbrush 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 affect 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.