Exterior 450 Topcoat a clear-drying finish suitable for vertical exterior surfaces, such as fences, patio furniture, garage doors and entrance doors. It is not recommended as a deck finish. Exterior 450 is fortified with UV absorbers to stabilize and protect the integrity the finish*, and built-in mildewcides to slow mold and mildew growth. It performs well as a clear coat or as an optional topcoat over darker colors General Finishes Milk Paint. Do not use over light or white paints as yellowing may occur.