I've done some experimenting myself. Judge for yourself.

Day 0: Yellow keyboard plastic, white keys. Sickly yellow case front panel.

Day 1: After one full day of lightbrighting, the keyboard's plastic appears to be bleaching, the change in the case is subtle.

Day 1 End: After second full day of lightbrighting the keyboard and keys are all the same nice white color. The case front is starting to bleach, the contrast between where the stickers were and the rest of the front is starting to decrease.

It certainly works, and I will keep bleaching this case to see how far it goes. I will also start bleaching my K6 case soon as well.

I've been trying it with one cd drive cover from a case, but these past few weeks have been horribly rainy and overcast,
there were a few hours of sun at least, I think it had an effect, but it's very slow, I'll report back once I can get a good week of sunny days....

I have a lot of horribly yellowed stuff, it would be nice if this worked well.

oh man I am tempted to try that but I am afraid after some time the yellowing will return worse than ever
sun is no issue here 😁

It all depends on how strong the sun is on a given day. At least that is my theory. I tested with an old C64 breadbin keyboard. It did not make any noticeable differnce. On the other hand. It might have been, that the keys are those brown with white letters, and not completely white plastic.

Who knows.....

keropi wrote:

oh man I am tempted to try that but I am afraid after some time the yellowing will return worse than ever
sun is no issue here 😁

On the plus side.... You do not use any strong chemicals at all.
At least, it is not like plastic will get cancer or sunburn or anything like that.

brostenen wrote:

At least, it is not like plastic will get cancer or sunburn or anything like that.

Yes but it can degrade it and cause it to become weaker - this is something I've heard mentioned a couple of times since this 'under the sun' method has been doing the rounds and it does worry me; plastic outdoor furniture fades and crumbles after too much time in the sun and that's designed to handle it.

badmojo wrote:

brostenen wrote:

At least, it is not like plastic will get cancer or sunburn or anything like that.

Yes but it can degrade it and cause it to become weaker - this is something I've heard mentioned a couple of times since this 'under the sun' method has been doing the rounds and it does worry me; plastic outdoor furniture fades and crumbles after too much time in the sun and that's designed to handle it.

Yup, higher energy radiation can break polymer chains, degrading the plastic.

1 week of sun will not destroy your plastic, don't overthink it 😀

In a few months or weeks, I'm going to try it on a Commodore PC which is heavily yellowed. Curious for the result.

appiah4 wrote:

1 week of sun will not destroy your plastic, don't overthink it 😀

Sure, just don't think it's like whitening your teeth where you can safely do it all the time.

gdjacobs wrote:

appiah4 wrote:

1 week of sun will not destroy your plastic, don't overthink it 😀

Sure, just don't think it's like whitening your teeth where you can safely do it all the time.

Obviously, but now that you mention it I can't help but wonder whether the sun would bleach my teeth or not..

appiah4 wrote:

Obviously, but now that you mention it I can't help but wonder whether the sun would bleach my teeth or not..

Try it and report back - pics or it didn't happen 🤣

As the "sunbrighting" is becoming popular, the same happens for posts expressing concerns
https://www.reddit.com/r/retrobattlestations/ … ngsunbrighting/
https://imgur.com/gallery/0SdpDJ6 (image from the reddit post shared here for convenience, not mine)

TL;DR version: yellowing comes back very soon, reacts worse to subsequent treatment and causes brittling.

Ozzuneoj wrote:

appiah4 wrote:

jheronimus wrote:

One thing that I didn't understand: can I keep stuff behind a window under a direct sunlight, or does it only work outdoors?

I don't have a garden/pool area, I only have a windowed balcony.

Depends on whether your window glass has UV filtering or not, and whether the room is air conditioned or not. If No to the former and Yes to the latter, it ought to work.

Also, flourescent lighting seems to cause yellowing, while LED lighting can potentially reverse or stop it, according to the video linked above. So, switching to less "yellowing" types of lighting in your home or at least in the room where your retro gear will be used is probably also helpful.

Normal glass blocks UV to some degree, mainly the UV B and C ranges. Near-blue UV-A light (350+nm) is not blocked much.

Fluorescent lamps have normal glass, and so emit some part UV-A.
This might be an explanation if this observation is correct.
And it might also explain why yellowing occurs if sunlight is filtered through glass.

So I guess maybe the de-yellowing effect is due to the much more energetic UV-B and UV-C, which are both present in sunlight.
But the atmospheric filtering is dependent on the angle, too. So, for example in Greece, there will be far more energetic UV than in Scandinavia.

Does anybody of you have an UV-C bulb or burner?
Like an old eprom eraser which could test using some old scrap of yellowed plastic?

konc wrote:

As the "sunbrighting" is becoming popular, the same happens for posts expressing concerns https://www.reddit.com/r/retrobattlest […]
Show full quote

As the "sunbrighting" is becoming popular, the same happens for posts expressing concerns
https://www.reddit.com/r/retrobattlestations/ … ngsunbrighting/
https://imgur.com/gallery/0SdpDJ6 (image from the reddit post shared here for convenience, not mine)

TL;DR version: yellowing comes back very soon, reacts worse to subsequent treatment and causes brittling.

very interesting, my fear of that made me only test with the cd drive cover, and today it had a good amount of sun, and the effect is very clear, it's much whiter than before, still a little far from what it was originally, but...
I think I''ll keep doing it to this pice and see how it goes after a year, but I'm not going to try it with anything else if there is a high risk of damage.

I wonder if there would be a way to prevent/minimize the damage, with some sort of protection, leaving it under water while it's exposed under the sun? oh well, perhaps this is no the magic solution to our yellowed plastic.

that description on reddit....
it reminds me of my Compaq cds 524 which was saved from my house when it burned down, it suffered with the heat on the next room I suppose (pretty much nothing was left on the other room) but the PC was OK, it was cleaned and used normally, around 10 years later the plastic started to crack everywhere and like he described "started to break everywhere like potato chips , the plastic just lost it's normal strength completely, I never had any other plastic equipment of the same age going that badly.

so there is a new retrobright that you just need sun, thats all, and leave it for 4 or more days at sun.
there is a lot of videos from this week from people trying it out and showing the results. It is not as effective as Hydrogen peroxide but maybe it harms less the plastic.

now the question is...will it last after 5 or 6 months? or after 6 months it will look worse or equal than before

This summer I'm going to retrobrite some drive bay covers and cover half of them with clear laquer and stick em back out in the sun. I find retrobrite works differently depending on the case - I've had a 286 yellow out in less than 6 months, whereas my 486DLC is holding out very well.

90skidJohnny wrote:

I love perifractic's videos. It is borderline ASMR 🤣 but he's great.

The issues with "retrobrite" is sometimes it can leave streaks or whatever. I saw this video when he released it and im def gonna give it a try with some keyboards I Have. He has alot of neat stuff too 😀

I've retrobrited something like 40 computers so far and have not had any marbling. Smooth out the saran wrap and don't have pockets of air or large accumulations of the peroxide material and you'll be OK.

A sloppy application will cause most issues such as marbling/streaking. Just like painting a car, the prep work is 90% of the result.

konc wrote:

As the "sunbrighting" is becoming popular, the same happens for posts expressing concerns https://www.reddit.com/r/retrobattlest […]
Show full quote

As the "sunbrighting" is becoming popular, the same happens for posts expressing concerns
https://www.reddit.com/r/retrobattlestations/ … ngsunbrighting/
https://imgur.com/gallery/0SdpDJ6 (image from the reddit post shared here for convenience, not mine)

TL;DR version: yellowing comes back very soon, reacts worse to subsequent treatment and causes brittling.

damn not good at all
then salon cream is also bad because it returns after some months

the only real hope would be like a paint, a white mixed with ash paint but its difficult to find such paint that imitates real plastic from the 80s

With either method the yellow eventually comes back and temperature and humidity are the causes in my experience.