A.Bill Feist, a wood finishes expert in Middleton, Wisc., responds: Semitransparent stains are most effective on roughsawn and weathered wood because more finish can be applied. The best exterior house stains are usually described as semitransparent, penetrating, and oil- or alkyd-based (solvent-borne). The better alkyd-based penetrating stains contain a fungicide (preservative or mildewcide), an ultraviolet light stabilizer, or a water repellent. Check the label for these important ingredients.
The alkyd-based solvent-borne stains actually penetrate the wood surface to a degree, and do not form a surface film like paint does. Thus, they don’t totally hide the wood grain and will leave a soft, flat appearance. They will not trap moisture that may encourage decay. Since they penetrate and don’t form a film like paint does, the stains...
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