Sanding Between Coats of Polyurethane: Smooth, Durable Finishes

Polyurethane is one of the most popular finishes for wood, offering protection and enhancing natural beauty. But the secret to a silky-smooth, professional result lies in sanding between coats. This process removes dust nibs, levels the surface, and ensures proper adhesion for the next layer.

Why Sand Between Coats?

Even in the cleanest shop, airborne dust settles into wet polyurethane. Sanding between coats removes these imperfections and gives each new layer something to grip. Skipping this step risks uneven sheen, bubbles, or peeling.

Tools You’ll Need

• Wet/dry silicon carbide sandpaper sheets
• Sanding block or foam pad
• Vacuum and tack cloth
• Polyurethane (oil- or water-based)
• Clean brushes or applicator pads

Best Grits for Polyurethane Sanding

• 220 grit: Standard between coats for leveling (220 Grit (25-pack)).
• 320 grit: For ultra-smooth finishes before final coat.
• 400 grit: Optional for polishing the last coat (400 Grit (100-pack)).

Step-by-Step: Sanding Between Coats

1. Apply first coat. Brush or wipe on polyurethane evenly. Let it dry completely (check product instructions).
2. Sand with 220 grit. Lightly sand the surface until smooth, using minimal pressure. The goal is to dull the sheen, not remove the finish.
3. Clean thoroughly. Vacuum and wipe with tack cloth to remove sanding dust.
4. Apply second coat. Lay down a fresh, even layer of polyurethane.
5. Repeat as needed. For 3–4 coats, sand with 220 or 320 grit between each layer.
6. Final polish (optional). After the last coat cures, buff with 400 grit and polish for a silky sheen.

Special Cases

Water-based polyurethane dries faster and usually requires lighter sanding with finer grits (320+). Oil-based polyurethane may need longer drying times between coats.

Pro Tips

• Use a sanding block to keep pressure even.
• Don’t sand too aggressively—you only need to scuff the surface.
• Work in a dust-free environment for best results.

Aftercare

• Allow the final coat to cure fully before heavy use (typically 7 days).
• Clean finished surfaces with mild, wood-safe cleaners.
• Reapply polyurethane every few years to maintain protection.

FAQs

• Do I always need to sand between coats? Yes, except for products labeled “no-sand recoat.”
• What if I oversand? Simply apply another coat—polyurethane is forgiving.
• How many coats are best? Three coats are typical for durability, though tabletops may need four or more.

Watch & Learn

For flawless wood finishes, sanding between coats is essential. Explore the full range of fine grit sandpapers for professional woodworking results.