Whitening yellowed plastic

cat320 wrote: »

Anyone any ideas on how to whiten yellowed plastic? Im restoring a chainsaw its a stihl, the plastic parts (white) like the petrol tank etc have aged and yellowed a bit. Its not discoloured right through because i scratched a bit underneath and it came up white so its just the surface. I dont think bleaching will work. Any ideas? TIA..

You could try:
Kitchen sponge, the yellow and green ones usually, but i think lidl/aldi have green and pink ones, or yellow and white ones (not too abrasive but a bit of scrub in them), and Cif/Jif/cream cleaner. Shouldn't leave any scuff marks and will get most of it clean hopefully.

For smaller areas, nooks and crannies, you could use an old toothbrush to get into them.

If you're finding the yellowing won't lift, try a bit of white vinegar and fairy liquid in warm water to repeat the process, or verry dilute Milton/sterilising fluid and fairy liquid after. Careful on any metal areas, but if well diluted it shouldn't pose any problems.

Wipe down with a dampened cloth (just water) to remove any cleaning products after you're done.

cat320 wrote: »

Anyone any ideas on how to whiten yellowed plastic? Im restoring a chainsaw its a stihl, the plastic parts (white) like the petrol tank etc have aged and yellowed a bit. Its not discoloured right through because i scratched a bit underneath and it came up white so its just the surface. I dont think bleaching will work. Any ideas? TIA..

I used a method like this before on minor scratches on my car and it worked. Just make sure you use the right toothpaste with mild abrasives in it. https://www.hunker.com/12446529/how-to-use-toothpaste-to-clean-plastic

Cosmo fein or 123 Pvc cleaner either should work the Cosmo will be slightly harsher on the plastic but should leave it spotless.

There's a technique that's quite popular among Lego Collectors and Retro PC Collectors called the "Retr0brite method" that involves leaving the parts in a Hydrogen Peroxide / Oxiclean mixture in sunlight. I've used it myself on an old Lego set that had yellowed badly. You can read about it here: https://en.wikipedia.org/wiki/Retr0bright



The effects won't last forever as it's essentially a flaw in the plastic but the lego set above is still looking good 2 years on!

Cif won't do anything if it's the same scenario as the lego above - the plastic has chemically altered and cif wouldn't be a strong enough grinding agent to remove the affected layer of plastic (at least not by hand, maybe with a polishing mop?)