Rust-Oleum Marine Spar Varnish is a clear finish designed to provide maximum protection against sunlight, water, sea spray, and chemical resistance on exterior wood boat surfaces, including trim, railings, and wood furniture. Use above the waterline only. Marine Spar Varnish can be applied over varnished, stained, or lacquered surfaces. Surfaces must be free of grease, oil, silicone, and wax, and contaminants that may interfere with adhesion to the surface. Do not apply over shellac, fresh lacquer, fresh varnish, or lacquer sanding sealers. Not for use below the waterline or on galvanized surfaces.