Sanding Cypress Siding Before Stain: Mill Glaze Removal Without Fuzz

Cypress siding is popular for its durability and warm, natural look, but it comes with one hidden challenge: mill glaze. This thin, shiny layer left from the milling process can prevent stain from penetrating evenly, leading to blotches or premature finish failure. The key is learning how to sand cypress siding effectively—removing mill glaze without fuzzing the surface fibers.

Why Sanding Cypress Siding Matters

Unlike softer woods, cypress has natural oils and resin that make it resistant to rot, but when milled, the heat and compression seal the surface. This mill glaze acts like a barrier, blocking stain and water-based finishes. Sanding breaks that barrier, opening pores for deep, uniform absorption.

Tools You’ll Need

• Orbital sander or pole sander with dust extraction
• 9x11 in wet/dry silicon carbide sandpaper sheets
• Vacuum with brush attachment
• Painter’s tape and drop cloths
• Safety gear: respirator, safety glasses, gloves

Best Grit Sequence for Cypress Siding

• 80 grit: Cuts through mill glaze and rough saw marks.
• 120 grit: Smooths the surface and evens out scratches.
• 220 grit: Creates the perfect profile for stain absorption.

Step-by-Step Guide

1. Prep the area. Mask off trim, windows, and landscaping. Set up dust control with a vacuum attachment.
2. Break mill glaze with 80 grit. Use steady passes with an orbital sander. For hand-sanding tight areas, wrap 80 grit (25-pack) sheets around a sanding block. This grit removes the shiny surface without digging deep.
3. Smooth with 120 grit. Transition to 120 grit (50-pack) sheets to erase swirl marks and level fibers. Always sand with the grain to prevent cross-scratches.
4. Finish with 220 grit. For stain-grade siding, polish with 220 grit (100-pack). This fine step ensures consistent stain penetration and reduces fuzzing.
5. Clean thoroughly. Vacuum dust, then wipe with a damp cloth. Don’t leave residue that can interfere with stain adhesion.
6. Stain application. Apply an oil-based or penetrating stain within 24 hours of sanding for best absorption.

Special Cases

On older siding, check for weathered gray fibers. If present, add an initial pass with coarse grit before moving to the 80–220 sequence. For freshly milled cypress, often just one round with 120 and 220 grits is enough.

Pro Tips

• Work in shade when possible—direct sunlight dries stain too quickly.
• Replace sandpaper as soon as it clogs with resin; dull paper will burnish instead of cutting.
• Don’t skip directly from 80 to 220 grit—you’ll leave faint swirl shadows visible under stain.

Aftercare

• Inspect annually—touch up faded spots with light sanding and recoat.
• Keep siding clean with gentle washing to extend finish life.
• Store leftover sandpaper flat and dry to avoid curling.

FAQs

• Can I pressure wash instead of sanding? No—washing won’t remove mill glaze and may raise fibers.
• Do I need to sand between stain coats? Only if more than 48 hours pass before recoating—use 220 grit for a light scuff.
• What if the siding starts to fuzz? Back up one grit level (120) to knock fibers down, then refine with 220.

Watch & Learn

By following this sanding sequence, you’ll unlock the natural beauty of cypress and ensure your stain lasts. With just the right grits and proper prep, your siding will take on rich, even color and remain protected for years.