To achieve glass-smooth surfaces, many timbers need to be filled with a high-solids material, wood filler, before you apply your finish. Where it might take a dozen coats of wood finish to create a smooth surface, Bartley's paste wood filler does the job in one or two applications. It's a traditional spirits-based material ready to use straight from the can, going on smoothly and allowing easy removal of excess after 3-5 minutes. Natural is suited for light woods such as birch and oak. Light is Cherry/Mahogany color, and Dark is for Walnut, Rosewood and other very dark species. Any color wood filler can be custom tinted with UTCs.