How to Sand Between Coats of Polyurethane for a Glass-Smooth Finish (220–400 Grit Guide)

If you’ve applied polyurethane and noticed tiny bumps or a slightly rough texture, don’t worry—this is normal. Sanding between coats is the key to a flawless, glass-smooth finish that feels as good as it looks. This guide covers the grit sequence, techniques, and pro tips for perfect results.

Why Sand Between Coats?

Each layer of polyurethane can trap small dust particles or develop raised grain. Light sanding between coats levels these imperfections and creates microscopic scratches that help the next coat bond better.

Tools & Materials

• Orbital sander or sanding block
• Vacuum and tack cloth
• Protective mask and safety glasses
• Wet/dry sandpaper sheets

Recommended Grit Sequence

• 220 grit: Leveling imperfections after the first coat.
• 320 grit: Smoothing mid-coat surfaces.
• 400 grit: Final prep before the last coat for a silky finish.

Step-by-Step: Sanding Between Polyurethane Coats

1. Let the coat cure. Wait at least 24 hours or as directed by the manufacturer before sanding.
2. Start with 220 grit. Use 220 grit (50-pack) to remove dust nibs and smooth out high spots.
3. Move to 320 grit. For mid-process coats, sand lightly with 320 grit (25-pack) to refine the surface.
4. Finish with 400 grit. Before your final coat, polish with 400 grit (100-pack) for a professional, glass-like base.
5. Clean thoroughly. Vacuum and wipe with a tack cloth to ensure no dust remains.
6. Apply the next coat. Brush or spray evenly, following the grain for a uniform look.

Special Cases

For water-based polyurethane, sanding can be lighter because these coatings tend to level better than oil-based varieties.

Pro Tips

• Always sand by hand along the grain for the final prep before the last coat.
• Use wet sanding for the final 400 grit pass to reduce airborne dust.
• Avoid pressing too hard—let the abrasive do the work.

Aftercare

• Store leftover sandpaper flat to prevent curling.
• Clean tools immediately after use to prevent hardened finish buildup.

FAQs

• Do I always need to sand between coats? Yes, unless you apply the next coat within the manufacturer’s recoat window.
• Will sanding remove too much finish? Not if done lightly; you’re just leveling the surface.

Watch & Learn

For flawless polyurethane finishes, keep the right grits on hand. Shop all wet/dry sandpaper sheets today.