How to Apply Polyurethane Finish

When you need a smooth finish on a wood or outdoor project, a polyurethane finish is an excellent choice. It creates a smooth, finished look and protects the wood against the elements.

Apply Polyurethane Finish

Applying the finish properly will help avoid getting air bubbles or dirt in your project and make your work look like it was done by a professional.

  1. Clean the surface of the wood you are sealing. Mix together one part mineral spirits and two parts polyurethane in a jar and stir with a flat stick.

  2. Dip a natural bristled brush 1 inch into the mixture and brush onto the wood in long, even strokes. Cover the entire piece. Catch any drips before they dry and brush them back into the liquid.

  3. Allow the polyurethane to dry for 24 hours. Apply a second coat the same way, except use pure polyurethane instead of mixing it with mineral spirits.

  4. Allow this second coat to dry for 24 hours and add a final coat on top. Once it has dried completely, cut away any drips you missed with a razor blade.

  5. Dip a piece of sandpaper into water and use it to sand away any blemishes in your stain. Make sure to sand lightly and use lots of water as lubricant. Wipe off with a moist cloth and dry with a dust-free rag.

  6. Apply a last coat if you had to sand the board. Once dried, the board should be smoothly stained and free of bumps or blemishes.