Raking Light: Spot Pre-Finish Scratches Before You Topcoat

Nothing ruins a beautiful finish faster than scratches you didn’t see until the first coat flashes off. The simplest way to catch them is with raking light—a low, glancing beam that skims across the surface and makes every ridge and swirl pop into view. In this guide you’ll learn a complete sanding workflow (grit map included), how to set up raking light correctly, and how to fix what you find so your stain, oil, or clear coat lays down silky and even.

Why Sanding (and Raking Light) Matter

Sanding creates the foundation your finish will either showcase—or expose. Even if the wood looks smooth in overhead lighting, cross-grain scratches, pigtails from a random orbit sander, and tiny swirl marks will telegraph once the finish wets the surface. Raking light exaggerates those defects before you commit to a topcoat, saving time, materials, and frustration. Combined with a disciplined grit sequence, you’ll produce a crisp, uniform surface that accepts dye evenly and levels under clear coats.

Recommended Tools

• Random-orbit sander (5–6 in.) with fresh hook-and-loop pad.
• Rigid sanding block and a soft foam interface pad.
• Silicon carbide wet/dry sheets (9×11 in.) for 150–320+ grits.
• Bright LED flashlight/headlamp or a 2–4 ft LED shop light on a movable stand.
• Pencil for scratch mapping, microfiber cloth, and tack cloth.
• Vacuum with brush attachment and a crepe block for de-loading abrasives.
• Optional: raking-light jig (adjustable arm or tripod) so your hands are free.

Baseline Grit Sequence (Most Hardwoods)

• 120–150 grit: Level mill marks and flatten panels; establish straight, with-grain scratch pattern.
• 180–220 grit: Refine and erase previous scratches; prepare for most film finishes and oil.
• 320 grit: Optional pre-finish pass for waterborne clears or when you need ultra-smooth feel.

Note: All eQualle silicon carbide sheets support wet or dry use. Dry sand for speed; switch to a light mist for final passes to keep paper cutting clean and minimize dust.

Step-by-Step: Train Your Eye with Raking Light

1. Set your raking angle. Kill the overheads. Place an LED light at 5–25° off the surface. Lower angles exaggerate defects; raise slightly if the glare overwhelms. Start with a large panel and position the light so the beam skims toward you.
2. Map the surface in pencil. Lightly scribble a fast crosshatch across the work. This is your leveling indicator: once the marks disappear uniformly, you’ve sanded that region evenly.
3. Level at 150 grit. Using a block on flats and the sander on broad fields, work with the grain until the pencil map fades evenly. If you need a reliable, pro-volume option, stock up on 150 Grit (25-pack) — aggressive enough to erase mill lines without digging deep cross-scratches. After each section, sweep the raking beam; any dull troughs or shiny ridges mean you’re not yet flat.
4. Vacuum and rotate your light. Turn the light 90° and sweep again. Changing the light direction reveals scratches that were hiding in the original orientation. Vacuum dust; touch stubborn low spots with a hard block.
5. Refine at 180–220 grit. Switch to 180 if the species is open-pored or you see heavy 150-grit lines, otherwise go straight to 220. Make a light, slow pass with even pressure and finish with three with-grain strokes. For consistent results across multiple pieces (doors, drawer fronts, case sides), it helps to keep bulk on hand like 220 Grit (50-pack) — a shop staple for pre-finish checks. Under the raking light, 220 should show a tight, uniform sheen with no visible crosshatch.
6. Optional water-pop, then 220 again. For blotch-prone woods (maple, cherry) or when chasing deep micro-swirls, lightly mist the surface to raise grain. Allow to dry, then make a short, controlled 220 pass. Inspect in raking light—raised whiskers should level instantly.
7. Pre-finish pass at 320 (select cases). For waterborne clears or silky touch on tabletops and rails, add a 320 grit pass. Keep pressure feather-light, and use a soft interface on edges to avoid burn-through. The goal is refinement, not removal. A contractor-friendly option: 320 Grit (100-pack) — ideal for consistent feel across a full kitchen set or stair package.
8. Edge and profile discipline. Switch to a soft block or a folded sheet on profiles. Glide the raking beam across coves and beads; if the highlight suddenly widens, you’ve flattened a curve—back up and re-establish the profile with lighter strokes.
9. Final solvent reveal. Wipe a small, inconspicuous area with mineral spirits or naphtha. Under raking light, this simulates finish wet-out. If swirls appear, backtrack one grit and re-finish with disciplined, with-grain strokes.
10. Dust control before finish. Vacuum, tack, and let the room settle for a few minutes. Hit the surface one last time with the raking beam; when the highlight glides smoothly with no sparkle or halos, you’re clear to coat.

Special Cases & Adjustments

Softwoods (pine, fir): Start at 120 to prevent deep scratches, then 150→180. Avoid over-sanding to 320 if you plan to stain; too fine a scratch pattern can reduce color take-up.

Ring-porous woods (oak, ash): After 150, consider a brief cross-grain leveling with a hard block, then finish with-grain at 180→220. Raking light will show latewood ridges—stop when they’re uniform rather than chasing full pore flatness.

Maple and cherry: These telegraph swirls. Keep your sander speed moderate, use fresh discs/sheets, and consider a water-pop step before your 220 finish.

End grain: Work 120→150→180 with a hard block. End grain drinks finish and reveals scratches; the raking beam should show a tight, even sparkle with no deep grooves.

Repairs and spot-sanding: Feather repairs by stepping down a grit in the repair zone and up a grit at the boundary. Raking light will show the blend line as a faint halo—erase it with two long, with-grain passes at the higher grit.

Pro Tips

• Time-on-grit discipline: Don’t rush jumps. If 150 marks remain, 220 won’t fix them efficiently. Stay until the raking beam says the field is uniform.
• Fresh, flat backers: A dead sander pad or a spongy block creates dips that only show after finish. Replace worn backers early.
• Light choreography: Sweep the beam from multiple directions—front-to-back, side-to-side, and diagonals—to reveal every scratch orientation.
• Dust = defects: Clogged paper cuts erratically. Tap sheets on a crepe block, vacuum often, and consider a brief wet pass at the end to keep scratches consistent.
• Pencil & solvent checks: Use them on each grit. They’re cheap insurance against do-overs.

Aftercare & Between-Coat Sanding

Once you’ve laid a first coat, switch to 320–400 for between-coat scuffing. Use a soft pad on profiles and keep raking light handy—dry films show scratch direction clearly. Vacuum thoroughly; any leftover nibs telegraph under the next coat. For the final sheen, remember that sanding sets the feel more than the finish does; the smoother and more uniform your substrate, the more professional your result.

FAQs

• What’s the ideal raking angle? Start around 10–15° off the surface. Too low can produce glare; too high hides defects. Adjust until scratches appear as crisp lines.
• Can I use a phone flashlight? Yes—great for small parts. For panels and doors, a brighter, wider bar light is easier to position and read.
• Do I always need 320 before finish? Not for oils and many solvent polys. For waterborne clears or ultra-silky tabletops, a quick 320 pass is worth it.
• Wet or dry? Dry for speed and bulk removal; finish with a light wet pass at your final grit if you want maximum uniformity and minimal dust. eQualle silicon carbide sheets are designed for both.

Watch: Raking Light in Action

Closing

Raking light turns invisible scratches into obvious, fixable lines. Pair it with a disciplined grit sequence—150 to level, 220 to refine, 320 when the finish calls for it—and you’ll stop holding your breath after that first coat. Build the habit now and every finish will look more professional, with less sanding overall.