These are essentially colorless, penetrating finishes that are commonly used for cedar siding. These natural finishes enhance the appearance and service-life of cedar siding. The water-repellent preservatives are preferable to the water-repellents because they contain a mildewcide and often other fungicides that help inhibit surface mildew growth. Many of these water-repellants contain ultraviolet light blockers or absorbers that help protect the Western Red Cedar from damaging sunlight. To date, the best of them are solvent-borne. The water repellent preservative finishes are very effective in stopping the absorption of liquid water thus reducing swelling and shrinking of the wood. Water-repellents should be used only on newly manufactured bare cedar, on restored bare cedar, or on cedar previously treated with the same type of product. When used as a natural finish, the service life of a water repellent is only one to two years depending on the wood and exposure conditions.