just set it out in the sun for a few hours and thats all. the more it bakes in the sun the less yellowed it is. 😵

Tricias Brother wrote:

Hello! As user Tricia McMillan is gone, i'm taking her place...

I got an old laptop with a siver laquered plastic case and a light gray keyboard (pure plastic, i guess ABS). Both have become a yellowish tint over the years, so i'm looking for the best cleaner/detergent. I tried with "window shine" = alcohol and lighter fuel with little success. I won't try acetone (nail varnish remover) as this makes the plastic melt. Some abrasive cleaner (used for pots or cerane cookers) probably leaves scatches. I've read about hydrogene peroxide, a gel or foam that people use to bleach ther hair, but i think that's only good for PVC, and "learning by doing" seems too risky...

What do you use?

For actual cleaning (ie removing baked-in dust or greasy dirt) - use plastic cleaner detergent and IPA although make sure it won't harm any stickers etc. You can also use melamine sponge (magic sponge) for really hard to remove dirt, but it may hurt the plastic as it's slightly abbrasive.

For de-yellowing use hydrogen peroxide in gel (12%) - hair bleaching product or water hydrogen peroxide solution (you can buy 30% hydrogen peroxide).

Deyellowing in sun can also be somewhat effective but don't expect it will be fast or results will be as good as the 'chemical' solution. In my many tries leaving some parts for 5-7 days in the full sun is around 30-50% as effective as 2-3 hours of using hydrogen peroxide method. But it's much safer (chemical method may lead to uneven discoloration (marble effect) or overdoing it).

Also google "retrobright" for more info on the subject.

Wow, thank you for advice! I shall get the hydrogene peroxide and try it out... Flash: In the worst case i end up with a single-big-key-keyboard - computing the easy way...

Opinions on the best way to bleach differ, but here's my opinion:

The safest way (again, IMO) is with common liquid hydrogen peroxide from the supermarket. You will want a tub large enough to completely submerge the item in liquid peroxide. Optionally, cover the top with kitchen plastic cling wrap (Saran Wrap or similar) because heat seems to help, and it will keep the liquid from evaporating as fast. Set it out in the sun and make sure to expose as much of the affected area as possible. You may need to move it with the sun, and keep it from floating above the liquid peroxide. Leave it out for a few hours, check on it, if it's still yellow, put it back in.

Liquid peroxide is a little less powerful than most of the creams, which makes it harder to overdo it. Also, the creams are harder to spread completely evenly, which (IMO!) could lead to the "marbling" effect, where the color is uneven after treatment. (Just a theory, though. I could be wrong.)

I am skeptical about the "leave it out in the sun" technique, as that leaves it in ultraviolet light for a long period of time, and it seems probably to me that this would cause the plastic to become more dry and brittle than using chemicals to accelerate the process. Again, I might be off base, it's just a theory.

leaving it in the sun is the least destructive thing you can do, and it absolutely does work. using chemicals is the most dangerous thing to do and should only be done if the sun wont work.

OK, thanks, i shall be careful. I'm going to buy the hydrogene peroxide anyway for this DIY-off-topic reason: I got a shower with glass doors. It has plastic sealings, 2m long stripes (rims?) of PVC that were transparent when new. Now (after 5 years or so) they look ugly, like nicotine-yellow. (Bah!) The parts closer to the window, which get more direct sunlight, look worse than the less exposed ones...

You need to weight things so they don't float in the peroxide bath. I suggest taping nickels to the bottom. A lot of stuff will dissolve in peroxide.

Depending on the type of plastic and the condition, you may need a couple of weeks (at 3%) to get where you are going.

My advice - it's hard to tell when it's done, but do not push it to "make it perfect." That just ruins stuff. Carefully compare surfaces you are treating to those you aren't (the behind or sides which have the original color). Again, if you see some improvement, stop it there, you can reuse the solution on other parts if you like. Don't try to make it better.

And for heaven's sake don't leave stuff out dry in the sun and expect that to improve your devices...

Yes, understood! I got an old mobile (= trash) with the same silver-laquered plastic cover, i shall experiment with this first... Thanks once more!

SirNickity wrote:

I am skeptical about the "leave it out in the sun" technique, as that leaves it in ultraviolet light for a long period of time, and it seems probably to me that this would cause the plastic to become more dry and brittle than using chemicals to accelerate the process. Again, I might be off base, it's just a theory.

Not really. In regards to making plastic brittle it's safer than hydrogen peroxide... Check this out: https://www.youtube.com/watch?v=8P1OVj0IcqY - there's a good explanation of the sun retrobright technique and science behind it.

So much plastic! One more thing: When i look around in my kitchen, there are plastic parts that become yellowish when exposed to the sun and remain good when in darkness, examples: The white extension cable of my computer, the cable of my rice-paper-lamp, the front / back of my coffee-machine. Conclusion: Different plastics behave different...

GooGone does a great job of removing the yellowing from plastic. Apply and let it sit for a few minutes, then wipe off with a damp cloth.

precaud wrote:

GooGone does a great job of removing the yellowing from plastic. Apply and let it sit for a few minutes, then wipe off with a damp cloth.

googone also melts can dissolve plastic and rubber.

Tricias Brother wrote:

When i look around in my kitchen, there are plastic parts that become yellowish when exposed to the sun and remain good when in darkness

A big part of what causes yellowing is the leaching of bromine -- an element used in making fire-retardant chemical treatment for plastics. Materials not exposed to UV will still yellow as the polymer continues to ... what's the technical explanation of this ... gas off? But there is certainly sufficient evidence to suggest that heat and UV exposure accelerates the process.

UV light is also well known to fade and age many materials, dyes, etc. As I understand the "sun theory," leaving something exposed to UV long enough causes bleaching, which can undo some of the yellowing, but it seems to me that the negative processes associated with UV exposure wouldn't just stop or reverse course. Even mild peroxide treatments appear to speed up the effects considerably, meaning less time in the sun.

I'm watching this with interest though. I'm skeptical of sun-only, but not opposed to new evidence. I wish the Pediatric Guy video had a little more from the materials scientists. I feel like their input wasn't much more than "try this" and "hey, could be this'll help..." Not exactly conclusive. What is actually happening? Is the plastic's dye getting bleached, leading to less color despite the bromine that has migrated? Is the bromine evaporating? Migrating further in?

it's thought that some chemicals that cause yellowing in some plastics, yellow in the absence of sunlight, and that its not sunlight that causes the yellowing its artificial light and the chemicals are light sensitive.