How to Apply Polyurethane Varnish

By Anna Roberts

Applying a coat of polyurethane varnish to wood can revitalize an old piece of furniture or give a beautiful finish to a new project. Different stain colors, including clear, give you flexibility to choose your desired look while protecting the wood from damage. This do-it-yourself project is easy enough for anyone to accomplish with very good results, as long as some basic techniques and recommendations are followed. Polyurethane varnish is available in oil-based and water-based forms, but the application process is essentially the same.

Preparation

Step 1

Thoroughly sand, clean and dry the piece that you are going to finish before beginning. The smoother the wood, the smoother the finish will be.

Step 2

Set up a clean work area. You do not want dust, dirt, lint or other particles getting into the finish before it dries.

Step 3

Work in a well-ventilated area. If you are inside, open all windows and doors. Wear a respirator if you don't have excellent ventilation.

Step 4

Wear work clothes that you don't mind getting stained or dirty, just in case.

Step 5

Use a natural-bristle brush. A synthetic brush may promote air bubbles.

Sealing the Surface

Step 1

Read the label to see if your polyurethane product is self-sealing. Some are and some are not. If your product is self-sealing, skip this section and start with Section 3.

Step 2

Mix 1 part mineral spirits to 2 parts polyurethane in a glass jar to make the sealant.

Step 3

Stir the mineral spirits and polyurethane gently with a flat paint stick until it is completely mixed. Don't stir too vigorously because you want to avoid introducing air bubbles into the polyurethane.

Step 4

Dip your brush 1-inch into the polyurethane/mineral spirits to load it.

Step 5

Apply the sealant with long, even brush strokes. Try to travel from one end of the piece you are working on all the way to the other end with each stroke. Overlap slightly with each pass.

Step 6

Catch any drips with your brush and smooth them out.

Applying the Finish Coat

Step 1

Apply an even coat of pure varnish within 24 hours of applying the sealant coat, if you used it. Use long, even strokes to cover the entire surface. If you are getting a lot of drips, you may be using too much. You only need enough to cover the surface.

Step 2

Go over the surface with the brush once the varnish has been applied, using even strokes from edge to edge along the wood grain to even out the finish to a uniform coat.

Step 3

Let it dry for 24 hours.

Removing Blemishes

Step 1

Use fine sandpaper to remove any imperfections, like dust bumps or drips that you may have missed when applying the coat of varnish. Dip a sheet of 400-grit sandpaper in water and wrap it around a sanding block.

Step 2

Wet-sand in a circular motion. It is important to have a clean work area so you won't have too many contaminants sticking to the varnish. Be very careful not to sand to much or you will go through the finish to the wood. Try to keep it as even as possible.

Step 3

Wipe off the residue after sanding and dry it with a clean cloth.

Applying a Final Coat

Step 1

Apply one more coat of polyurethane finish within 48 hours as the previous coat, using the same technique as before.

Step 2

If there are still blemishes in your work, use the same wet-sanding technique as before to smooth them away. If you do have to sand now, you will also have to polish it to smooth it out again so it is best to be very careful as you work to make sure that the final coat goes on smoothly.

Step 3

Let the finish dry for at least 24 hours, or according to the instructions on the can. If polishing is necessary, wait several days until the finish has cured first.

Step 4

Polish the surface in a circular motion with a rag and some rubbing compound if needed.

Step 5

Let it dry. Then buff the item with a clean rag until it shines.

About the Author

{{}}