As a general rule, use exterior stains outside and interior stains indoors, but what's a rule if you can't break it? Exterior stains are formulated to make wood last longer in areas of high moisture and intense sunlight. If your kitchen is such an area, you might consider using an exterior stain on your cabinets, but choose the right one. You don't want mildewcides contaminating your kitchen, nor do you want a heavily pigmented stain peeling from your hardwood-faced plywood.
Exterior Stain Options
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Exterior stains differ in their base solvent -- which is either water or a volatile petroleum distillate -- the amount of pigment they contain and the mildew- and rot-killing additives they contain.
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Solvents
Like paints, stains can be formulated with water, which gives them good resistance to mildew, good color retention and makes them easy to clean up. Water doesn't promote the growth of mildew, so water-based stains are more likely to be free of the mildewcides that you don't want in your kitchen. Water-based stains tend to penetrate less deeply than oil-based ones, though. That isn't a major issue when staining softwood decking boards, but it can can be an issue when staining hardwood cabinets.
Pigmentation
One of the important functions of an exterior stain is to block ultraviolet sunlight, which deteriorates the surface cells of wood and turns the wood gray. Not all exterior stains are heavily pigmented, but those that are may not be the best choice for kitchen cabinets. Semi-transparent and solid stains are essentially thin paints, and while they might look attractive in a rough-sawn cedar fence, they might not spread evenly on an interior hardwood surface. In addition, they will probably peel if your cabinets already have a finish.
Exterior Stains in the Kitchen -- Pros and Cons
On the pro side, durability, water resistance and ease of application make exterior stains well-suited for the kitchen, but consider also the disadvantages -- hazardous additives, limited color choices and possible adhesion problems -- before choosing an exterior stain over an interior.
Pros
- Durability -- Semi-transparent and solid exterior stains are designed to cure to a washable, scratch-resistant that needs no clear coat. You'll need a clear-coat if you're using a transparent stain, but that's true whether the stain is an exterior or interior one.
- Water Resistance -- Standing up to rain and high humidity are what exterior stains are all about.
- Ease of Application -- In most cases, a single coat is all you need. Apply it with a brush; if it's semi-transparent or opaque, that's all you need to do. If the stain is transparent, wipe off the excess, just as you would do with an interior stain.
Cons
- Hazardous Additives -- If you're drawn to an oil-based product for its color and penetrability, check the container carefully for the list of mildewcides in the product. You're bound to find some, because the oil base actually promotes mold growth without it. That list may be enough to make you change your mind about using the product in your kitchen. Many water-based products also contain mildewcides.
- Color Choices -- Because of the differences in light conditions and surrounding scenery, the colors that look good outside don't always look good inside.
- Adhesion Problems -- The exterior stains that are safest for your kitchen are water-based, and they are formulated to cover highly porous decking, siding and fencing. If your cabinets are finished, you'll probably have to strip the finish to ensure adhesion, and even so, you may still have problems with maple or equally close-grained wood species.