Beginner · A sunny afternoon (4–8 hours), mostly waiting
Retrobrighting: Reversing Yellowed Plastics
Why old Macs turn yellow, and how hydrogen peroxide and sunlight can bring back the platinum.
That yellow-brown tint on your Mac's case isn't dirt and it isn't age, exactly — it's chemistry. Vintage ABS plastic contains bromine-based flame retardants, and decades of UV exposure cause reactions in the plastic that shift its color toward yellow. The good news: the process is largely reversible. 'Retrobrighting' uses hydrogen peroxide plus UV light to reverse the discoloration, and a badly yellowed compact Mac can come back shockingly close to its original platinum in a single sunny day.
Two honest caveats before you start. First, results can regress — retrobrighted plastic can slowly re-yellow over months to years, especially with UV exposure, so treat this as maintenance, not surgery. Second, uneven application causes 'marbling' or streaks, which is the main failure mode. The technique below — the submersion method — is the most even and beginner-friendly.
The bench list
- Hydrogen peroxide: either 3% liquid (slower, gentler, cheap at any pharmacy) or 12% 'Volume 40' salon developer cream
- A clear plastic tub large enough to submerge your parts (for the liquid method)
- Plastic wrap (for the cream method)
- Nitrile gloves and eye protection
- Mild dish soap, soft brush, and microfiber cloths for pre-cleaning
- Sunshine, or a UV LED strip/lamp if your climate won't cooperate
- A Torx T15 driver (long shaft) if you're opening a compact Mac to treat the case halves separately — plus patience for the tube inside; see the safety note below
1Disassemble and clean first
Retrobright works on bare plastic, so strip the case: remove boards, shields, badges, and anything metal or rubber. On compact Macs, the case screws are Torx T15, with two hiding deep in the handle recess — a long-shaft driver is mandatory. If you're new to compact Macs, read our CRT safety note first: the tube holds a charge even unplugged, and you should treat the inside of the machine as off-limits until you've learned discharge procedure. For a first project, consider retrobrighting something tube-free, like a keyboard, mouse, or drive enclosure.
Wash every part with warm water and dish soap, scrubbing gently with a soft brush. Grime blocks the peroxide and guarantees uneven results. Dry completely. This is also the moment to decide what NOT to brighten: printed legends, badges, and textured areas can be affected, so mask or remove anything you want untouched.
2Choose your method: submersion or cream
Submersion (recommended): fill your tub with 3% peroxide until parts are fully covered. Weigh floating parts down with something glass or plastic. The liquid gives perfectly even coverage, which is why beginners should start here despite the higher peroxide volume needed. Loosely cover the tub with plastic wrap to slow evaporation — loosely; never airtight.
Cream method: for parts too big to submerge, paint a thin, even coat of 12% salon cream onto the plastic, then wrap tightly in plastic wrap, smoothing out air bubbles — the wrap keeps the cream from drying out and evening out is everything. The cream method is faster but streaks if applied unevenly, so keep coats thin and consistent and re-smooth the wrap periodically.
3Add UV and wait
Put the tub or wrapped parts in direct sunlight and rotate them every 30–60 minutes so every face gets equal exposure. Peroxide plus UV is the whole reaction; warmth speeds it up, but avoid extreme heat — hot cream dries fast (streaks) and hot ABS can warp. A bright day between 15–30°C is ideal.
Check progress hourly. Light yellowing can clear in 2–4 hours; a deeply bronzed SE might want a full day. Pull parts as they finish — over-processing can leave plastic slightly chalky or brittle over many repeated treatments, so stop when the color looks right, not when the clock says so.
4Rinse, dry, reassemble
Rinse every part thoroughly under running water, wash once more with dish soap to neutralize residue, and dry completely before reassembly — trapped moisture and vintage electronics are enemies.
Compare against a hidden original area (inside surfaces rarely yellow) and repeat a shorter session if a part needs another push. Store and display the machine out of direct sunlight from here on: UV caused this, and UV can bring it back.
A freshly retrobrighted compact Mac next to an untreated one is one of the hobby's most satisfying before/afters — the difference between 'old computer' and 'museum piece' is often just this one afternoon. Photograph your results in indirect light, and if you submit your machine to our Community Wing, we love a good before-and-after pair.