Polyurethane Application

Polyurethane: The Durable Choice

Polyurethane is the most common protective finish for wood due to its excellent durability, water resistance, and availability. Understanding the differences between oil-based and water-based formulations helps you choose the right product and apply it successfully.

Oil-Based vs. Water-Based Polyurethane

Surface Preparation

Proper preparation prevents most polyurethane problems:

• Sand to 180 grit for stained surfaces, 220 grit for natural wood.
• Remove all dust with vacuum and tack cloth.
• If using water-based poly, wet the surface first to raise the grain, let dry, then sand smooth.
• Apply dewaxed shellac as a sealer over problem woods like pine to prevent blotching.

Application Technique

1. Thin the first coat: Mix 10-20% mineral spirits (oil-based) or water (water-based) for better penetration.
2. Apply with brush or foam applicator: Work in the direction of the grain. Avoid overworking the finish.
3. Remove bubbles: Lightly tip off the surface with just the brush tips.
4. Sand between coats: Use 220-320 grit after each coat is fully dry. Remove all sanding dust.
5. Apply 3-4 coats: More coats for high-wear surfaces like tabletops and floors.

Troubleshooting

• Bubbles: Don’t shake the can—stir gently. Apply thinner coats.
• Brush marks: Use a quality brush, apply thinner coats, and tip off properly.
• Dust nibs: Work in a dust-free environment, sand between coats.
• Cloudy finish: Usually moisture-related. Ensure low humidity and dry wood.