Remove Mill Glaze on New Siding: 80?120 Grit Guide

Fresh cedar, pine, and other exterior siding often ships with a shiny, slightly burnished surface known as mill glaze. It looks smooth, but that sheen can block stain and sealer from soaking in. The fix isn’t ultra-fine sanding—it’s a short, disciplined cut that breaks the glaze without fuzzing the grain. This guide shows you how to prep new siding with an 80 ? 120 sequence so stain wets evenly, color stays consistent, and early maintenance is a breeze.

Why Sanding Matters

Planer knives, high feed rates, and heat compress the surface cells and smear resins. That polished “glaze” reduces absorption and causes premature peel, uneven color, or early gray. A light sanding pass creates a microscopic profile that finishes can key into—not scratchy, but open and receptive. Going too fine too soon can re-burnish soft earlywood and trap oils at the surface. That’s why a quick 80 cut followed by 120 is the sweet spot for most siding species and stains.

Tools You’ll Need

• Random-orbit (RO) sander with dust extraction and a firm pad (flatness control)
• Long, hard sanding block for edges and narrow trim
• 9×11 in silicon carbide or aluminum oxide sheets: 80 and 120 (optional 150)
• Pencil for guide-coat and a bright raking/side light
• Vacuum with brush head, microfiber cloths, and tack cloth
• Exterior stain or penetrating oil/sealer, brushes/pads, and masking
• PPE: respirator (P100), eye and hearing protection

Recommended Grit Sequence

• 80 grit — Quick, light cut to break glaze and level planer knife traces.
• 120 grit — Refine 80’s scratch and set a uniform, receptive surface.
• Optional 150 grit — Only on dense hardwood siding or trim under clear coats.

Step-by-Step: Even Color, Long-Lasting Stain

1. Map and test. Under raking light, look for shiny tracks and burnished areas. Do a small test board: sand half with 80 ? 120, leave half unsanded, and wipe with your stain. You’ll see instantly how mill glaze blocks color.
2. Break the glaze at 80. On field faces, make overlapping passes with an RO sander and a firm pad using 80 grit (25-pack). Keep pressure light—you’re not trying to remove stock, just cut the polish. On narrow edges, use a long, hard block to avoid scallops.
3. Refine at 120. Re-map with a light pencil crosshatch and step to 120 grit (50-pack). Sand only until every 80-grit line is gone and the surface is uniformly matte. Stop before the wood feels “slick”—over-polishing reduces stain uptake.
4. Optional 150 for clears. If you’re using a clear or very light semi-transparent on dense species, give a brief pass with 150 grit (100-pack) on trim for a tighter scratch. Skip this on softwoods destined for penetrating stains.
5. Dust control & wipe. Vacuum thoroughly (tongues, grooves, lap gaps), then tack. A clean, dust-free surface prevents blotches and gives truer color.
6. Coat promptly. Apply stain/sealer soon after sanding, ideally the same day. Sun can re-harden resins; rain raises grain. Work in the shade, maintain a wet edge, and back-brush to drive finish into pores.

Special Cases

Cedar & redwood: Their soft earlywood bruises easily. Keep pressure feather-light, run fresh paper, and stop at 120 for stain.
Pine & spruce: More resin pockets = more glaze. 80 ? 120 is ideal. If pitch smears, pause and swap sheets; don’t push hard.
Engineered/primed siding: Follow the manufacturer: often a quick 120 scuff on glossy primer is plenty. Avoid cutting through factory primer on edges.
Shiplap & bevel siding: Use a hard block on the thin edge to prevent round-overs that show as dark “lines” after stain.

Pro Tips

• Pencil + raking light. Map between grits so you only sand as much as needed.
• Firm pad for flats. Reserve soft interface pads for gentle blends; they round edges and can re-burnish glaze if overused.
• Fresh paper wins. Dull paper polishes instead of cutting and leaves streaky stain uptake.
• With-grain finish strokes. Even with an RO, finish each board with a few hand passes along the grain to hide arcs on narrow stock.
• Seal end-grain. After sanding, flood finish onto end-grain cuts to prevent dark halos and early checking.

Aftercare

• Respect recoat/maintenance intervals—UV and rain beat up siding fast.
• Clean gently; avoid strong detergents that strip oils and leave the surface dry.
• Touch-ups: light 120 scuff, wipe clean, then spot-apply finish. Keep a labeled offcut sanded to the same final grit for color tests.
• Keep landscaping off the wall so boards dry quickly after storms.

FAQs

• Is 220 better before stain? Usually not on softwood siding—220 can burnish and reduce penetration. 120 leaves the right micro-profile.
• Can I skip 80 and start at 120? If the glaze is mild, yes. But where you see shiny tracks or planer marks, a quick 80 pass saves time and gives more even color.
• Why does my stain look blotchy? Inconsistent sanding or residue on the surface. Re-scuff the light areas at 120, clean, and re-coat.
• Do I need to sand factory-primed boards? Often a light 120 scuff is enough to de-gloss. Don’t break through primer on edges and laps.
• What about T&G interiors? Similar idea—run 120 only (skip 80) to avoid fuzzing; then finish per product.

Video: Mill Glaze Removal Pass

Closing: Mill glaze is a finish barrier, not a finish. Break it quickly with 80, refine with 120, keep dust down, and coat the same day. The payoff is richer color, better adhesion, and siding that weathers evenly instead of peeling in patches.