WATCO® Exterior Wood is a unique penetrating oil that hardens in the wood, not on the wood. New, old, or pressure treated wood becomes water repellent, provides UV and mildew protection, and resists warping and swelling caused by changes in weather. Durable and easy to use, WATCO® Exterior Wood Finish is great for decks, siding, fences and more. Please read product labels for additional directions and precautions before using