How to Apply Polyurethane to Wood
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Polyurethane wood finish is used to coat surfaces, protecting them from scratches and helping to resist water damage. Learning how to apply polyurethane can give wood furniture and flooring a glossy, smooth finish while improving its durability. Read on for steps on how to apply polyurethane to furniture, plus tips for getting professional results.
Oil-Based vs. Water-Based Polyurethane
The two basic types of polyurethane are oil-based and water-based. Both have different pros and cons.
- Water-based polyurethaneis clear, low-odor and has a quick drying time. It is recommended for surfaces that see little exposure to heat or the elements. Water-based polyurethane works well for projects like desks, bookcases and end tables. It may require more coats.
- Oil-based polyurethane has more durability than water-based. It withstands heat better so it’s a good choice for projects such as kitchen tables or countertops. Oil-based does develop an amber tint over time. It also tends to have a stronger aroma and a slower drying time.
Different formulations of polyurethane create different levels of luster or sheen, so choose based on your preference.
- Flat or matte polyurethane leaves the least shiny coating and conveys the look of natural, unfinished wood.
- Satin polyurethane has a low to medium sheen that helps conceal dirt and scratches, making it popular for flooring.
- Semi-gloss polyurethane and gloss polyurethane have a higher level of sheen and reflectivity.
Remove Old Finish and Sand
You’ll get the best results from your polyurethane topcoat if you remove any old paint, varnish or other finishes before polyurethane application. For a smooth coating, you’ll want the surface to be as smooth as possible.
- Prepare the wood by sanding it with a sanding block or orbital sander.
- Start with 120-grit sandpaper on refinished pieces and 80-grit on new wood.
- After sanding the entire surface thoroughly, wipe off the dust and all loose sandpaper grit with a clean cloth.
- Then, sand with 180-grit until you've removed all the marks left by the 120-grit, and the surface appears level.
Vacuum or Wipe Away Dust
If dust or other particles settle on wet polyurethane, they can create a rough surface. This defeats the goal of a smooth topcoat.
- After sanding, dust and vacuum the surface and room as thoroughly as possible.
- Wipe the surface with a damp, lint-free cloth or sponge.
- If you’re going to apply water-based polyurethane, dampen the cloth with water.
- If using oil-based, dampen the cloth with mineral spirits.
Apply the First Coat
You can use a brush, rag or spray for your project. The best way to apply polyurethane will depend on the surface of the wood project.
- Brushes are best for flat surfaces such as tables or some chairs. Brushing a rounded, contoured or vertical surface is more likely to create drips. Apply a thin coat following the grain with a tapered, bristle brush.
- Rags or cloths are ideal for contoured surfaces. When applying polyurethane, use a clean microfiber towel. Apply each coat with the grain.
- An aerosol spray is good for hard to reach areas or surfaces with intricate designs like chair rails. Apply by holding the can 8 to 12 inches from the surface in a well-ventilated area.
Sand Between Coats
Make sure to sand the polyurethane between coats. Sanding removes drips, bubbles and other uneven spots in each coat.
- Dry the first coat for a full 24 hours. If the coat feels tacky or sticky after that, let dry until it feels completely dry.
- Sand the topcoat with 180 to 220 grit sandpaper.
- Wipe off any residue after sanding.
- Repeat as needed.
Tips for Professional Results
- Apply 1 to 2 coats of stain when using a brush and 2 to 3 coats if you’re spraying the polyurethane.
- To keep outdoor dust and particles away from the surface, applying polyurethane should take place in a well-ventilated room indoors, with an open window or fan to circulate fresh air. This also helps clear the fumes of oil-based polyurethane.
- If sandpaper is inadequate to remove dried drips or other imperfections, shave them off with a razor.
- Before use, a can of polyurethane should be stirred, not shaken. Shaking can introduce air bubbles in the finish that could make an uneven coat.
- Minimize or eliminate brush marks. Choose a tapered brush, thin the varnish with mineral spirits and apply long strokes at a vertical angle.
Polyurethane wood finish offers durability and water resistance. This makes it a popular alternative to more traditional coatings such as shellac or lacquer. Learning how to apply polyurethane to wood can enhance the appearance of the stain. It will also protect the surface from scratches and more.
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