Sand Between Polyurethane Coats: 220?320 Grit

Polyurethane builds durable, glossy protection on wood, but each coat can leave dust nibs or raised grain. To achieve a flawless finish, sand lightly between coats using 220 ? 320 grit. This smooths imperfections and ensures strong adhesion for the next layer.

Why Sand Between Coats

Without sanding, new coats may not bond properly. Dust particles get trapped, leaving bumps. Light sanding removes these defects and levels the surface for a professional, glassy finish.

Tools & Materials

• 9×11 in sandpaper sheets: 220, 320 grit
• Sanding block or sponge
• Vacuum and tack cloth
• Polyurethane (oil- or water-based)
• Foam brush or applicator
• PPE: respirator, gloves, eye protection

Recommended Grit Sequence

• 220 grit — First sanding between coats, removes bumps.
• 320 grit — Final leveling for ultra-smooth topcoat.

Step-by-Step: Sanding Between Coats

1. Apply first coat. Brush or wipe polyurethane onto clean wood.
2. Let dry fully. Oil-based requires 8–12 hrs; water-based 2–4 hrs.
3. Sand with 220 grit. Use 220 grit (25-pack) lightly to knock down dust nibs.
4. Clean surface. Vacuum thoroughly and wipe with tack cloth.
5. Apply next coat. Smooth strokes along grain for even coverage.
6. Sand with 320 grit. Before final coat, use 320 grit (50-pack) for a silky base.
7. Finish with topcoat. Apply last layer of polyurethane for durable gloss.

Special Cases

Dusty shops: Wipe surface multiple times between coats.
High-gloss finishes: 320 grit is critical for mirror reflection.
Matte finishes: Stop at 220 grit—extra fine sanding not necessary.

Pro Tips

• Sand lightly—only remove surface imperfections, not full coat.
• Always sand with the grain for invisible scratches.
• Don’t rush drying time—soft polyurethane gums sandpaper.
• Use fresh, sharp sheets—dull paper polishes instead of cutting.
• Vacuum first, then tack cloth—dust ruins final finish.

Aftercare

• Wait full cure (7 days oil, 3 days water) before heavy use.
• Clean surfaces with mild soap, not harsh chemicals.
• Refresh topcoat every few years by light sanding and recoating.

FAQs

• Can I skip sanding? Not recommended—coats may peel or look uneven.
• Why 320 grit for final sanding? It leaves ultra-smooth base without blocking adhesion.
• Do I need to sand bare wood first? Yes—prep with 120?180 before first coat.
• Can I wet sand polyurethane? Yes—use 400–600 grit for ultra-gloss after final coat.

Video: Sanding Between Poly Coats

Closing: Smooth, professional polyurethane comes from careful prep. With 220 ? 320 grit sanding between coats, you’ll achieve durable finishes with a glass-like surface.