Sanding Between Coats of Varnish: Grit Guide for a Glass-Smooth Finish

Applying multiple coats of varnish adds depth and protection to wood, but without sanding between coats, the finish can look uneven or trap imperfections. This guide explains the grit sequence, tools, and techniques to achieve a flawless, glass-smooth varnish finish.

Why Sand Between Varnish Coats?

Each coat of varnish can leave behind dust nibs, brush marks, or bubbles. Sanding between coats levels the surface, improves adhesion, and ensures the final finish is perfectly smooth and durable.

Tools You’ll Need

• Wet/dry sandpaper sheets
• Sanding block or hand pad
• Tack cloth or microfiber rag
• Vacuum for dust removal
• Varnish (oil- or water-based)

Best Grit Sequence for Varnish Sanding

• 320 grit: First sanding after the initial coat.
• 400 grit: Smooths mid-coats for even build-up.
• 600 grit: Final sanding before the last coat for silky smoothness.

Step-by-Step: Sanding Between Varnish Coats

1. Allow full drying. Make sure the varnish coat has cured according to manufacturer’s instructions.
2. First sanding pass. Use 320 grit (25-pack) after the first coat to level raised grain.
3. Intermediate sanding. Apply 400 grit (50-pack) to refine the surface between mid-coats.
4. Final sanding. Before the last coat, use 600 grit (25-pack) for a silky, glass-like base.
5. Clean the surface. Vacuum dust and wipe with a tack cloth.
6. Apply next coat. Use smooth, even brush strokes or a sprayer for best results.

Special Cases

For water-based varnish, lighter sanding is recommended since coats are thinner. For oil-based varnish, sanding may require more passes to fully level the surface.

Pro Tips

• Always sand lightly—removing too much can cut through the coat.
• Wet sanding with fine grits reduces dust and provides an ultra-smooth finish.
• Inspect the surface under angled light to ensure imperfections are removed before recoating.

Aftercare

• Let the final coat cure fully before using the surface.
• Clean with a damp microfiber cloth—avoid harsh cleaners.
• Reapply varnish every few years to maintain protection and shine.

FAQs

• Do I need to sand after the final coat? No—only between coats. The last coat should remain untouched for a smooth finish.
• Can I skip sanding if the surface looks smooth? Skipping can reduce adhesion—always sand lightly for best results.
• What if I sand through the varnish? Reapply a thin coat to the affected area and blend it in.

Watch & Learn

Sanding between coats of varnish may take extra time, but it guarantees a smooth, professional finish. Stock up on 320 to 600 grit wet/dry sheets for your next refinishing project.