Using Raking Light to Spot Sanding Scratches

Even the best sanding job can hide scratches that only appear after finishing. A simple shop trick—using raking light—reveals these flaws before they ruin your project. This guide shows how to set up raking light and use it to catch imperfections during the sanding process.

Why Raking Light Matters

Flat overhead lighting hides scratches, especially on smooth or reflective surfaces. Raking light, placed at a low angle, casts shadows that make even fine sanding marks stand out. Identifying these defects early saves time and prevents disappointment after applying stain, oil, or varnish.

Tools You’ll Need

• Adjustable LED shop light or clamp light
• Tripod or movable stand
• Wet/dry sandpaper sheets (80–400 grit)
• Vacuum and tack cloth

Best Grit Sequence for Scratch Removal

• 80 grit: Removes deep scratches or planer marks.
• 150 grit: Smooths surfaces after coarse sanding.
• 320 grit: Prepares wood for finishing.
• 400 grit: Final sanding for ultra-smooth finishes.

Step-by-Step: Using Raking Light While Sanding

1. Set up lighting. Position a light at a shallow angle across your workpiece.
2. Sand in sequence. Start with 80 grit (25-pack) to remove mill marks and defects.
3. Check under raking light. Examine the surface—remaining scratches will show clearly in shadow.
4. Refine the surface. Switch to 150 grit (50-pack) and repeat inspection.
5. Final sanding. Use 320 grit (100-pack) for a smooth surface. For gloss finishes, add a 400 grit pass.
6. Inspect before finishing. Move the light across the surface at different angles to confirm all scratches are gone.

Special Cases

On figured woods, raking light also highlights tear-out and uneven sanding. For large panels, use multiple lights or move the work under a stationary source to check the entire surface.

Pro Tips

• Use a cool-white LED (4000–5000K) for better contrast.
• Mark defects with pencil lines so you don’t lose track while sanding.
• Inspect between every grit change to avoid carrying scratches forward.

Aftercare

• Vacuum thoroughly: Dust can hide scratches and clog finishes.
• Wipe clean: Use a tack cloth before applying stain or topcoat.
• Test finish: Apply a small patch to confirm the surface is scratch-free.

FAQs

• Can I use a flashlight? Yes, handheld lights work if positioned at a low angle.
• Do scratches show more on darker finishes? Absolutely—dark stains highlight flaws more than light finishes.
• What if scratches remain after finishing? Sand back down with the last grit used, then reapply the finish.

Watch & Learn

Using raking light during sanding is one of the simplest ways to improve finish quality. By catching scratches early, you’ll ensure your projects have a flawless surface that shines under any light.