Before you touch it, work out whether you have scratches or crazing - because scratches polish out and crazing never does. Scratches sit on the surface and catch the light as lines. Crazing is a network of fine cracks within the material, caused by ammonia cleaners or solvents, and no amount of polishing removes it. Polishing crazed acrylic just thins the panel.
Run a fingernail lightly across the mark. A scratch you can feel is a real scratch. If you feel nothing but see a spidery web when you tilt it to the light, that is crazing, and the honest answer is to live with it or replace the panel.
Most "scratches" are actually haze
The usual complaint is not one deep line - it is that the case has gone slightly cloudy and lost its clarity. That haze is thousands of very fine scratches accumulated from cleaning, and it has one dominant cause: wiping a dry, dusty surface, usually with paper towel.
Paper towel is wood fibre, which is harder than acrylic. Every dry pass grinds the dust already sitting there across the panel. Haze responds very well to polishing, which is the good news - and it comes straight back if the cleaning habit does not change. Fix the habit first: how to clean a display case covers the flood-then-wipe order that prevents it.
Work out how deep it is
| What you see | Fingernail test | Fix |
|---|---|---|
| Overall cloudiness, no distinct lines | Feels smooth | Plastic polish only |
| Fine lines visible at an angle | Barely catches | Fine abrasive, then polish |
| A line you can clearly feel | Catches firmly | Wet-sanding sequence, then polish |
| Spidery web of tiny cracks | Feels smooth | Crazing - not repairable |
| Deep gouge, catches your nail hard | Stops the nail | Usually not worth it - replace the panel |
Be realistic about the last row. Removing a deep gouge means sanding the surrounding area down to its depth, and on a thin display panel that leaves a visible optical dip - a distortion that is often more noticeable than the original scratch.
Light haze: polish only
- Clean first. Lukewarm water, a drop of mild dish soap, rinse. Any grit left on the surface becomes an abrasive under your cloth.
- Dry with a clean microfibre.
- Apply a plastic polish made for acrylic or plexiglass - a pea-sized amount on a fresh microfibre.
- Work in straight passes, light pressure. Not circles. Circular marks catch light from every viewing angle; straight ones only from one.
- Buff off with a second dry cloth and check at an angle under a light before repeating.
Two or three light passes beat one hard one. Heat is the enemy - if the panel feels warm under your hand, stop and let it cool.
Deeper scratches: the grit sequence
This works, and it is also where people ruin panels by starting too coarse. Start with the finest grit that makes any progress at all, not the one that removes it fastest.
- Wet-sand with fine wet-and-dry paper, kept genuinely wet throughout. Typical progression is around 800, then 1500, then 2000, then 3000 grit - but skip straight to the finer grades if the scratch is shallow.
- Change direction 90 degrees with each grade. This is how you know the previous grade's marks are fully removed - keep going until you see no lines running the old way.
- Keep the area larger than the scratch and feather outward, so you do not create a dish.
- Finish with plastic polish as above to bring back clarity. Sanding leaves the panel matte; the polish is what makes it transparent again.
Practise on the back or a hidden edge first. And remember which face you are working on - the inside face of a display case is easier to reach on a removable panel, but scratches on the inside are usually not what you are seeing.
What not to use
- Toothpaste. The common internet advice. It is an uncontrolled abrasive of unknown grit, and it will haze a larger area than the scratch it removes.
- Metal polish or car cutting compound unless it is specifically rated for plastics - most are far too aggressive.
- Ammonia-based glass cleaner, acetone, alcohol. These cause the crazing you cannot fix in the first place.
- Heat guns or flame polishing on an assembled case. Flame polishing is a real technique for cut edges; used on a display panel it warps it.
- Power tools on a first attempt. A buffing wheel builds heat faster than you will notice.
Prevention, since it recurs
Polishing is a repair for a habit. Three changes stop it coming back:
- Never wipe dry. Wet the surface so grit floats free before the cloth touches it.
- Microfibre only, and a cloth that has not been used on other surfaces.
- Deal with the static. Acrylic holds a charge that pulls dust to it, and dry-wiping recharges it - which is why a damp cloth is doing two jobs at once.
If a case is scratched badly enough to need sanding more than once, it is worth asking whether the case is the problem. Cases where the front is a separate panel can often be replaced far more cheaply than the whole unit.
Related
- How to clean a display case - the habit that prevents this
- Acrylic vs glass display cases
- How to protect diecast cars from dust
FAQ
Can you remove scratches from acrylic?
Yes - surface scratches and haze polish out with a plastic polish, and deeper ones respond to a wet-sanding sequence finished with polish. Crazing, which is a network of fine cracks inside the material caused by ammonia or solvents, cannot be removed at all.
How do I tell a scratch from crazing?
Run a fingernail lightly over it. A scratch catches; crazing feels perfectly smooth but shows a spidery web when you tilt the panel to the light. Polishing crazing achieves nothing except thinning the panel.
Does toothpaste remove scratches from acrylic?
Not reliably. Toothpaste is an uncontrolled abrasive of unknown grit, so it tends to haze a wider area than the scratch it removes. Use a polish formulated for acrylic or plexiglass instead.
What grit should I use on acrylic?
Start with the finest grade that makes any progress - often 1500 or 2000 - rather than the coarsest that works fastest. Wet-sand throughout, and turn 90 degrees with each grade so you can see when the previous grade's marks are gone.
Why does my acrylic case keep getting scratched?
Almost always from wiping it dry, especially with paper towel, which is harder than acrylic and drags existing dust across the surface. Wet the panel first so the grit floats free, and use microfibre only.