Sanding Between Coats of Polyurethane: Flawless Wood Finishes (220–400 Grit Guide)

Applying polyurethane without sanding between coats often leaves bumps, dust nibs, or brush marks. Sanding between coats ensures each layer bonds properly and creates a silky-smooth, professional finish. This guide explains the grit sequence, tools, and steps needed for perfect results.

Why Sand Between Coats?

Each coat of polyurethane raises the wood grain slightly and traps tiny dust particles. Light sanding removes these imperfections and provides a surface that the next coat can grip. The result is a durable, glassy finish that enhances the natural beauty of the wood.

Best Tools for Polyurethane Sanding

• 9x11 in silicon carbide wet/dry sandpaper sheets
• Sanding block or flexible pad
• Tack cloth or microfiber rag
• Vacuum with brush attachment
• Respirator or dust mask

Recommended Grit Sequence

• 220 grit: First sanding after the initial coat.
• 320 grit: Intermediate sanding for smoothing out bumps.
• 400 grit: Final sanding before the last coat.

Step-by-Step: Sanding Between Coats

1. Let coat dry fully. Wait at least 24 hours or follow product instructions.
2. First sanding with 220 grit. Lightly smooth raised grain and imperfections. Use 220 Grit (25-pack).
3. Wipe clean. Remove dust with a tack cloth or vacuum.
4. Second sanding with 320 grit. After applying and drying another coat, smooth again with 320 Grit (50-pack).
5. Final sanding with 400 grit. Before the last coat, refine the surface to near perfection. Stock up on 400 Grit (100-pack).
6. Apply final coat. Brush or wipe on the last layer of polyurethane smoothly and evenly.
7. Optional polishing. After curing, buff with ultra-fine sandpaper or polishing compound for a mirror finish.

Special Cases

For water-based polyurethane, sanding dust can gum up easily. Use wet sanding with fine grits (320–400) to keep the paper from clogging.

Pro Tips

• Don’t sand too aggressively—light pressure is enough.
• Always sand with the grain, never across it.
• Replace sheets frequently; dull paper scratches instead of smoothing.
• Work in a dust-free environment to minimize imperfections.

Aftercare

• Allow final coat to cure for at least a week before heavy use.
• Clean surfaces with mild soap and water, avoiding harsh chemicals.
• Maintain gloss by applying paste wax periodically.

FAQs

• Do I need to sand after the final coat? No, unless you want a high-gloss polish—then use 600+ grit lightly.
• Can I use steel wool instead of sandpaper? Fine steel wool (0000) can be used, but sandpaper is more consistent.
• What happens if I skip sanding? Coats may not adhere properly, leading to peeling or rough finishes.

Watch & Learn

For the smoothest polyurethane finish, explore our full range in the Fine Sandpaper Collection.