How to Sand Polycarbonate Plastic Without Fogging or Cracking

Polycarbonate (Lexan®) is one of the toughest clear plastics available—used for face shields, machine guards, and headlight covers. But its impact resistance comes with a challenge: it scratches easily and reacts to heat during sanding. This guide explains how to sand polycarbonate surfaces smoothly without fogging, warping, or creating stress cracks.

Why Polycarbonate Needs Gentle Sanding

Unlike acrylic, polycarbonate softens under frictional heat and can craze if over-sanded. The goal is to level and smooth scratches using very fine grits, constant lubrication, and controlled pressure. With proper wet-sanding, you can restore optical clarity or prep the surface for coatings without damaging the material.

Recommended Tools

• 9x11" wet/dry silicon carbide sandpaper sheets
• Soft foam or rubber sanding block
• Spray bottle with clean water and mild soap
• Microfiber towels and tack cloth
• Plastic polish or UV sealant (optional)

Ideal Grit Sequence

• 800 grit: Scratch leveling and surface restoration
• 1500 grit: Refine texture and remove micro-lines
• 2000 grit: Final prep before polishing or coating

Step-by-Step: Sanding Polycarbonate Smooth

1. Clean thoroughly. Remove all dust and debris from the surface. Even small particles can create deep scratches in soft polycarbonate.
2. Start with medium-fine grit. Wet-sand using 800 Grit (25-pack) silicon carbide paper. Keep the surface soaked and move in straight, overlapping passes. Avoid circular motion—it can generate heat and swirl marks.
3. Rinse and switch direction. Move to 1500 Grit (50-pack), sanding perpendicular to the previous direction to erase cross scratches. Maintain light, even pressure and plenty of water.
4. Finish fine. Use 2000 Grit (100-pack) paper for final smoothing. The surface should appear evenly matte with no visible lines or fog patches.
5. Polish for clarity. Apply plastic polish or fine compound using a microfiber cloth. Buff until the surface regains transparency and gloss.

Special Cases

If the polycarbonate is UV-coated, only sand within the damaged area—removing the coating entirely may reduce future durability. For heavily scratched or frosted surfaces, start at 600 grit cautiously, using very light pressure and continuous lubrication.

Pro Tips

• Always wet-sand—heat from dry sanding can deform or stress the surface.
• Use fresh, sharp sandpaper to prevent drag marks.
• Keep sanding strokes long and consistent; avoid concentrated pressure points.
• Inspect frequently under bright, angled light.
• Finish by sealing with UV protectant to extend clarity and prevent yellowing.

Aftercare

• Clean with mild soap and water only—avoid alcohol or ammonia-based cleaners.
• Apply UV sealant periodically to preserve transparency outdoors.
• Store polycarbonate parts in cool, shaded environments to prevent warping.

FAQs

• Can I use a power sander? Only at low speed with foam backing—manual sanding offers better control.
• What if the surface looks cloudy after sanding? Continue with finer grit and polish; cloudiness means incomplete refinement.
• How do I avoid heat buildup? Keep the surface wet at all times and sand in short intervals.

Watch & Learn

For flawless results, use precision wet/dry silicon carbide sheets from the super fine sandpaper collection. The 800–1500–2000 grit sequence keeps polycarbonate surfaces smooth, cool, and crystal clear.

Conclusion: Sanding polycarbonate takes finesse, not force. With gentle wet sanding, fine silicon carbide abrasives, and consistent water cooling, you can restore clarity and maintain durability—without fogging, cracking, or distorting the surface.