Ultimate Guide to Sanding Between Coats of Polyurethane on Wood (320–1000 Grit)

Sanding between coats of polyurethane is essential for a flawless, glass-smooth finish. This process removes dust nibs, evens out minor imperfections, and improves adhesion for subsequent coats. Here’s how to choose the right grits and technique for perfect results.

Why Sand Between Coats?

Even in controlled environments, airborne dust and small bubbles can settle into wet polyurethane. Light sanding levels these imperfections, ensuring your final coat looks professional and feels silky smooth.

Tools & Materials

• Vacuum and tack cloth
• Sanding block or foam pad
• 320 Grit (25-pack) for first coat leveling
• 400 Grit (50-pack) for second coat smoothing
• 600 Grit (100-pack) for fine finishing
• 1000 Grit (10-pack) for final polishing prep

Best Grit Sequence for Polyurethane

• 320 grit — First sanding pass after initial coat dries.
• 400 grit — Smooths second coat for improved clarity.
• 600 grit — Prepares surface for the final coat.
• 1000 grit — Optional polishing stage for ultra-gloss finishes.

Step-by-Step: Sanding Between Coats

1. Wait for full cure. Let polyurethane dry according to manufacturer’s directions (usually 24 hours) before sanding.
2. Sand with 320 grit. Use light pressure and sand with the grain to knock down dust nibs and bubbles.
3. Clean the surface. Vacuum and wipe with a tack cloth before re-coating.
4. After the second coat, use 400 grit. Smooth out any imperfections before applying the final layer.
5. For a high-gloss finish, wet sand with 600–1000 grit. Keep the surface damp and use circular motions, then buff after drying.

Special Cases

For water-based polyurethane, sanding can be lighter as these finishes tend to build up fewer imperfections. Oil-based finishes may require more attention between coats.

Pro Tips

• Always sand lightly—too much pressure can cut through the finish.
• Use a sanding block to maintain even contact with flat surfaces.
• Allow extra curing time in humid conditions.

Aftercare

• Protect finished surfaces with coasters and pads under furniture.
• Clean with a soft, damp cloth—avoid abrasive cleaners.
• Recoat every few years to maintain appearance and protection.

FAQs

• Can I skip sanding between coats? Not if you want a smooth, professional finish—each coat needs a clean, keyed surface to bond.
• Should I use steel wool instead? While fine steel wool can work, sandpaper provides more consistent results and avoids residue issues.

Watch & Learn

By following this grit sequence, your polyurethane finishes will look flawless and feel luxurious. Stock up on 320 Grit (25-pack), 400 Grit (50-pack), 600 Grit (100-pack), and 1000 Grit (10-pack) to achieve a perfect finish every time.