What varnish is
Varnish is a clear or lightly tinted protective coating that dries to a hard film on the surface of wood. Traditional varnish combines resin, oil and solvent. The term is also used loosely for related clear coatings, including some polyurethane products, so it helps to check what is actually in the can.
No single product is the best varnish for every job. The right choice depends on where the wood will be used, how much wear it will see, and the look you want. This article gives you criteria rather than a ranking, because formulas change and brand performance varies by conditions.
Types of varnish
- Oil-based (alkyd) varnish. A traditional, durable film that typically adds a warm amber tone. Slower drying, stronger odor.
- Spar or marine varnish. Formulated to stay flexible and include UV absorbers so it can handle sun and movement outdoors. Often used on exterior doors, outdoor furniture and boats. Many such coatings still need periodic maintenance.
- Water-based varnish. Lower odor, faster drying, easier cleanup and typically clearer. See whether water-based polyurethane darkens wood for a related question about color.
- Polyurethane varnish. A tough, abrasion-resistant film often chosen for floors and tabletops. Interior formulas are generally not designed for sun exposure.
Best varnish by situation
- Indoor furniture and tables: oil-based or water-based polyurethane varnish, chosen by the tone you want and the wear it will get.
- Floors: products labeled for floors, because they are made to resist scuffing. See types of hardwood finishes.
- Exterior wood: a spar or exterior-rated varnish with UV protection, applied according to the label. Wood Magazine and others note that clear exterior finishes generally need regular upkeep, so expect to refresh them. For doors specifically, see the best clear finish for an exterior door.
- Marine use: use products specifically labeled for marine use.
- Wood that will touch food: many varnishes are not intended for direct food contact; check the label and consider food-safe finishes for cutting boards and bowls.
What to look for on the label
- Interior or exterior rating
- UV absorbers (for sun exposure)
- Sheen options (see the sheen guide)
- Dry time and recoat window
- Whether it is compatible with your stain or sealer; see wood sealer vs stain
- Required thinner or cleanup solvent
- Safety data and ventilation instructions
Should you varnish wood?
Not always. Varnish is useful where you want a durable, wipeable surface or exterior protection. Some woodworkers prefer oil or wax for a natural feel, or leave certain pieces bare. Varnish can be harder to repair than oil because damaged film often needs sanding and recoating. For a broader decision framework, see why wood finishes matter.
Varnish vs polyurethane vs polish
Wood polish and varnish are not the same. Polish (including wax and cleaner-polish products) is generally a maintenance product that adds shine and a light surface layer, while varnish is a protective film that cures hard. Polyurethane is a type of synthetic resin finish that is closely related to varnish and often treated as a varnish alternative.
How to apply varnish
- Sand to the grit the manufacturer recommends and remove all dust.
- Stir gently rather than shaking, to limit bubbles.
- Apply thin, even coats with a quality brush or applicator in the direction of the grain.
- Allow full drying between coats and scuff-sand lightly if the label says to.
- Apply the number of coats the label suggests; exterior pieces typically need more coats.
- Allow the finish to cure fully before heavy use.
Work at temperatures and humidity within the label range, and test on a scrap first.
Maintaining outdoor varnish
Inspect annually for dulling, cracking or peeling. Light sanding and a fresh coat before the film fails is usually easier than stripping after it breaks down. Keep end grain and horizontal surfaces especially well coated, since they take in the most moisture. Our guide on how to waterproof wood covers other protective options outdoors.
Safety
- Work with strong cross-ventilation, especially for oil-based and solvent-based varnishes.
- Use an organic-vapor respirator or other type specified on the label; a dust mask does not filter vapors.
- Solvents and varnish are flammable. Keep sparks, flames and pilot lights away.
- Rags soaked with oil-based varnish can self-heat as the product cures and may ignite. Lay them flat outdoors to dry, or store them in a sealed metal container with water, and follow local disposal rules.
- Use gloves and eye protection, and wear a dust respirator when sanding between coats.
Frequently asked questions
Are wood polish and varnish the same?
No. Polish mainly adds shine and surface care, while varnish is a durable protective film.
What are the types of wood finishes?
Commonly listed types include varnish, polyurethane, shellac, lacquer, oil and wax. See types of hardwood finishes.
What is the best clear coat for outdoor wood?
A spar or exterior-rated varnish with UV protection is a common choice, though all clear coats need regular maintenance outdoors. Penetrating exterior finishes are another option.
Should you varnish wood?
Varnish suits surfaces that need a hard, wipeable film. For a more natural, repairable surface, an oil finish may suit you better.