Sanding Between Coats of Paint or Polyurethane: Smooth Finish Guide (320–600 Grit)

When painting or finishing wood with polyurethane, sanding between coats is the secret to a silky smooth, professional look. Skipping this step often leaves behind brush marks, raised grain, or tiny bumps. This guide explains why, when, and how to sand between coats for flawless results.

Why Sand Between Coats?

Each coat of paint or polyurethane slightly raises the wood grain and traps dust particles. Sanding levels the surface, removes imperfections, and creates a micro-roughness that allows the next coat to bond better.

Tools You’ll Need

• Fine and super fine wet/dry sandpaper sheets (320–600 grit)
• Sanding block or soft pad
• Tack cloth or microfiber cloth
• Vacuum with soft brush attachment
• Respirator mask for dust safety

Recommended Grit Sequence

• 320 grit: First sanding after primer or first coat of polyurethane.
• 400 grit: Leveling mid-coats for smoothness.
• 600 grit: Final sanding before topcoat for a silky finish.

Step-by-Step Process

1. Allow coat to dry fully. Check manufacturer’s recommended drying time.
2. Start with 320 grit. Lightly sand using 320 grit (100-pack) sheets after primer or first coat to remove raised grain.
3. Smooth mid-coats. Use 400 grit (25-pack) sheets between paint or polyurethane coats to remove brush strokes and dust nibs.
4. Refine before final coat. Use 600 grit (50-pack) wet/dry sheets for the last sanding pass before the topcoat.
5. Clean thoroughly. Vacuum dust, then wipe with a tack cloth to ensure a clean surface.
6. Apply next coat. Brush or spray evenly, letting the sanded surface grip the new layer.

Special Cases

For high-gloss finishes, some professionals go beyond 600 grit and polish with 800–1000 grit before buffing. For matte finishes, 400 grit is typically sufficient.

Pro Tips

• Sand lightly—too much pressure can remove the previous coat entirely.
• Always sand with the grain of the wood.
• Use wet sanding for polyurethane to reduce dust and improve smoothness.
• Replace sheets often; clogged paper scratches the finish.

Aftercare

• Let the final coat cure fully before handling or placing objects on the surface.
• Maintain the finish by cleaning with a damp microfiber cloth only.
• For furniture, use protective pads under items to avoid scratches.

FAQs

• Do I always need to sand between coats? Yes—except for some specialty self-leveling finishes. Most paints and polys benefit from sanding.
• What if I forget to sand? The next coat may not adhere properly, and imperfections will show in the final finish.
• Should I sand after the final coat? No—only polish if needed for extra gloss.

Watch & Learn

Sanding between coats is a simple step that makes a big difference in finish quality. Stock up on fine sandpapers and super fine sheets to ensure your projects always look professional.