Avoid Burnishing Softwoods: Stop Sanding at 220 Grit

Softwoods like pine, fir, and spruce are budget-friendly and widely used—but they’re prone to blotching under stain if sanded too fine. The culprit is burnishing: polishing the dense latewood smooth so stain can’t penetrate, while soft earlywood still drinks deeply. The fix is simple: stop sanding at 220 grit (or coarser for stain) and condition the surface before finishing. This guide explains why over-sanding hurts and how to prep softwoods for consistent, even color.

What is Burnishing?

Burnishing happens when fine sanding (240–400+) compresses and polishes the harder bands of softwood. Under finish, those slick areas resist absorption, leaving blotchy dark/light contrast. Instead of a rich, even tone, you get zebra stripes and dull spots.

Tools & Materials

• 9×11 in sandpaper sheets: 120, 150, 180, 220
• Random-orbit sander with firm pad
• Hand sanding block for rails, edges, and profiles
• Pencil for guide-coat, raking light
• Vacuum and microfiber cloth
• Pre-stain conditioner for softwoods

Safe Grit Sequence for Softwoods

• 120 grit — Removes mill marks and planer tracks.
• 150 grit — Refines scratch pattern.
• 180 grit — Pre-stain sweet spot for most softwoods.
• 220 grit — Maximum before burnishing risk rises.

Step-by-Step: Stain-Ready Softwood Prep

1. Inspect the surface. Under raking light, highlight scratches and shiny glaze. Mark with pencil to confirm full sanding coverage.
2. Level at 120. With 120 grit (25-pack), sand flat panels and rails. Keep the sander moving; use a block for edges.
3. Refine at 150. Step to 150 grit (50-pack). Erase 120’s scratch field and prepare for the next grit.
4. Finish at 180–220. For most stains, stop at 180 grit (100-pack). For clear coats or paint, you can go to 220—but stop there. Beyond 220, risk of blotching rises quickly.
5. Clean thoroughly. Vacuum, then wipe with a microfiber cloth to remove all dust before conditioning or staining.
6. Condition before stain. Apply pre-stain conditioner to equalize absorption across earlywood and latewood.

Special Cases

Knotty pine: Knots are resinous and resist absorption—don’t oversand; rely on conditioner.
Clear finishes: If not staining, you can stop at 220 for a smoother film, but avoid going higher.
Painted projects: You can sand finer if blotching isn’t a concern—but don’t waste time beyond 220 unless required.

Pro Tips

• Mark with pencil and use raking light—don’t oversand just to chase a shine.
• Replace dull paper early; dull sheets polish instead of cutting.
• Finish by hand with the grain to hide swirl marks from RO sanders.
• Always test stain on a scrap sanded to the same grit as your project.
• Conditioner is non-negotiable on softwoods—use it every time.

Aftercare

• Expect to scuff lightly with 220 between coats of clear finishes.
• Wipe spills quickly—water raises grain and can highlight blotches.
• Touch-ups: lightly scuff with 180–220 and reapply conditioner + stain.

FAQs

• Why not sand pine to 320? Because it polishes dense bands, making stain blotch badly.
• Can I stop at 150? Yes—stain will be darker. Stop at 180 for balance of smoothness and absorption.
• What about gel stains? They reduce blotching but sanding past 220 still risks uneven color.
• Is water-popping useful? Yes—especially on maple or birch. It opens grain evenly before final grit sanding.

Video: Burnishing Explained

Closing: Softwoods reward restraint. Stop at 180–220, condition, and stain. Sanding finer risks burnishing and blotching, leaving finishes uneven. Follow the safe grit ladder and your pine, fir, or spruce will show warm, even color with no ugly stripes.