Polishing Scratched Acrylic Cases
A technical procedure for eliminating surface abrasions and restoring museum-grade transparency.
Acrylic (PMMA) is favored for display cases due to its optical clarity, yet it is significantly more prone to scratching than glass. Restoration involves a controlled, subtractive process: leveling the surface through progressive abrasion and then refining it with polishing compounds. For collectors, the goal is to remove the “cloudiness” while maintaining the flat, distortion-free surface of the case.
1. Surface Preparation and Diagnosis
Before beginning, the surface must be decontaminated using distilled water and a mild non-detergent soap. Avoid ammonia-based glass cleaners (e.g., Windex), as they cause “crazing”—micro-cracks that permanently weaken the acrylic structure. Use a 100% cotton cloth to identify if a scratch is Surface-Level (not felt with a fingernail) or Deep (catches the nail).
2. The Grit Progression: Wet Sanding
For deep scratches, wet sanding is mandatory. Start with the highest grit possible to avoid removing unnecessary material.
| Grit Tier | Target Surface | Application Method |
|---|---|---|
| 800 Grit | Deep gouges only. | Horizontal motion with heavy lubrication. |
| 1500 Grit | Moderate scuffs. | Vertical motion (perpendicular to previous). |
| 3000 Grit | Sanding haziness. | Circular motion until surface is smooth. |
| 8000+ Grit | Final refinement. | Produces a “frosted” but uniform finish. |
3. Mechanical Polishing: The Novus System
The industry standard for diecast display restoration is the Novus 3-Step System. Using this in the correct sequence ensures a professional-grade finish.
- Novus #3 (Heavy): Used after 1500-grit sanding to pull out deep abrasions.
- Novus #2 (Fine): Removes #3 residue and restores original gloss. Available at [Displays And Holders](https://www.displaysandholders.com/product/novus-8oz-5075.html) for around $8.
- Novus #1 (Clean): An anti-static, anti-fog liquid that seals the surface. Kits are available at [Home Depot](https://www.homedepot.com/p/NOVUS-2-0-oz-Kit-Plastic-Cleaner-Polish-and-Scratch-Remover-81770241/315400634) for approx. $14.
Technical FAQ
In an emergency, yes. White (non-gel) toothpaste is a mild abrasive roughly equivalent to Novus #3. However, it is inconsistent and often leads to more “hazing” than a professional liquid compound.
Internal scratches are often caused by the model’s mirrors or spoilers. These require hand-polishing with a cotton bud to avoid damaging the seams of the case. Do not use power tools inside the case structure.