How to Sand Between Coats of Polyurethane for a Smooth Finish

Applying polyurethane is one of the best ways to protect wood surfaces, but if you want a truly professional finish, sanding between coats is essential. This process levels imperfections, removes dust nibs, and ensures that each layer bonds smoothly to the next.

Why Sand Between Coats?

Even in a clean workspace, tiny particles of dust and raised wood fibers can settle into wet polyurethane. Once dry, these create a rough or bumpy feel. Sanding lightly between coats solves this problem, resulting in a silky smooth surface.

Tools You’ll Need

• Orbital sander or sanding block
• Vacuum with brush attachment
• Tack cloth or microfiber rag
• High-quality silicon carbide wet/dry sandpaper sheets

Best Grits for Sanding Between Polyurethane Coats

• 320 grit: Light sanding to knock down dust nibs and imperfections.
• 400 grit: Final leveling for a super smooth finish.

Step-by-Step: Sanding Between Coats

1. Let the coat dry fully. Wait at least 24 hours or until polyurethane feels hard and no longer tacky.
2. Start with 320 grit. Use 320 grit (25-pack) to lightly sand the entire surface. Apply minimal pressure.
3. Move to 400 grit. Refine with 400 grit (50-pack) for the smoothest finish before the next coat.
4. Clean thoroughly. Vacuum dust and wipe with a tack cloth to ensure perfect adhesion.
5. Apply next coat. Brush or wipe on polyurethane smoothly and evenly, following wood grain.

Special Cases

For high-gloss finishes, some pros go up to 600 grit before the final coat. On softer woods, keep sanding pressure very light to avoid cutting through the finish.

Pro Tips

• Always sand with the grain, not against it.
• Don’t over-sand—your goal is leveling, not removing the finish.
• Use wet sanding with 400 grit for an ultra-smooth result.

Aftercare

• Allow the final coat to cure for at least 72 hours before heavy use.
• Clean sandpaper regularly to avoid clogging.
• Store unused sheets in a dry, flat container.

FAQs

• Can I skip sanding between coats? Not recommended—your finish will feel rough and may not adhere properly.
• Do I need to sand after the final coat? Only if you want to buff with polishing compound for a mirror finish.

Watch & Learn

Sanding between coats is the secret to silky, professional-looking finishes. Get the right sheets from our finishing sandpaper collection to perfect your next wood project.