Yeah, I watched the video. I already posted my thoughts in the comments:

You are spot on! And this has actually been scientifically researched before, and actually published, as you can find in this ar […]
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You are spot on! And this has actually been scientifically researched before, and actually published, as you can find in this article: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4320144/

"Exposure to ultraviolet, UV, radiation may cause the significant degradation of many materials. Damage by UV radiation is commonly the main reason for the discoloration of dyes and pigments, weathering, yellowing of plastics, loss of gloss and mechanical properties (cracking), sun burnt skin, skin cancer, and other problems associated with UV light."

Also of interest is this article: http://read.nxtbook.com/wiley/plasticsenginee … antscorner.html

Basically, there are multiple ways that plastic can degrade. The yellowing is a result of oxidation; this can happen in multiple ways, two of which are thermal oxidation and photo-oxidation.

So let's talk about photo oxidation for a minute: 1. The UV component in sunlight is known to cause yellowing of plastic through photo-oxidation. This is a chemically proven fact, your plastic will yellow because of sunlight. 2. As paradoxic as it may sound, the UV light sans other contributing negative factors (heat and moisture which cause thermo-oxidation and are probably the cause of yellowing to occur or return in my stored electronics in a poorly vantilated storage) also causes photodegradation of the yellow pigment hence a return to a more neutral look.

Hence, if your plastic is exposed to sunlight in the presence of thermo-oxidizing conditions, the sunlight causes more yellowing than bleaching. If your plastic is exposed to the sun in the absence of thermo-oxidizing conditions, the bleaching process cures the yellowing.

Now that the science of the process is somewhat established, here's another experiment for you to try. Bake those yellowed plastics under a very strong UV Light indoors, in an air conditioned room. For giggles, do it in a room where the Ozone generator is also running. Compare.

I'm confident it will work.

Add a bath of hydrogen peroxide, heat and sun and it happens even faster

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 😀

Yes, that seems to work. I left an old yellowed desktop case from the cellar outside for about two weeks, exposed to sun, wind and rain.
After that time, the yellowed parts, especially the front covers (for the drive bays, plastic) faded to gray/white.
Anyway, I'm a bit worried about the health of the plastic now. I hope it stays the way it is and doesn't become brittle.

I've got a very very badly yellowed Commodore Amiga case that I had written off . . . if/when the sunny season next reaches the UK I shall try it.

Yes I’m looking forward to trying this out - I’d long since given up on the retobrite process due to the variable results and the nasty chemicals involved. I liked his idea of putting the item on a little turntable to ensure even coverage!

I'm having great results with the no soaking way to bleach.
Takes way less (liquid) Hydrogen Peroxide to do it.
Tho you need a semi sealed container to do it.

1H in the sun gave a noticable effect, tho not perfect.
But zero chance of streaking, and no need to fiddle with it during the process.

It depends on the climate - much easier to see an effect in the Australian sun, than other locales 😀 I only retrobrite in summer, in a peroxide/oxy crystal bath in direct sun - a day of it works wonders.

I can't wait to try this! I have a few things that I'd love to de-yellow a bit.

It sounds like the ideal situation is a lot of sun with a mild or cool temperature, correct? As long as I can catch a day that isn't raining, I should be able to try this out. I'm very hopeful! 😀

I have been trying this out and can confirm it works. It might take longer to achieve what you'd get with using peroxide but I'm pretty pleased.

It's slower, and might only take the yellowing back a few shades, but much less risk.

Wikipedia says a few words about solarization (physics).

Please notice that UV-C below 200nm is being used in industry to cure/oxidize plastics, and could be potential contributor to yellowing.

I wonder if Wood lamps could help, as their spectrum does not go below 250nm.

Ehh Not that I have the resources to do it, but I think we need a solid, well-documented and well-replicated set of tests including multiple options, chemistry before and after, brittleness, even more replication, as many different plastics as possible...

Unfortunately almost everyone (including me) is working with samples that are way too small.

I tend to avoid UV just because of random pseudo-statistical experience with UV and plastics. And the light's at kind of the wrong angle here.

I think eventually someone will settle on a per-plastic technique with testing and maybe a stabilizing coating, then storage in the dark as much as possible. Wild guess.

I have read something similiar about 7 or 8 months ago on thinkpad forum where someone wanted to tell everyone that his original IBM mouse was getting whiter just by using sun.

Sure Its easier than bleaching it with peroxide since you can do whole computer without dismantling it first, but Iam quite skeptical about using only sun, since every plastic part I have left outside is more prone to cracking.

I have done experiment in the past with using plastic drive bay covers from same case,in peroxide it took about 6 hours to be white again and It took 7,80 kilograms to break it in half using weights, on the other side the second cover took about 1 week of direct sunlight and it wasn't as white as first one and it whitstanded only 6.7 kilograms to break it in half. It might be in margin of error or different plastic of each cover.

Anyway its better be safe than sorry. 😊

It works!

Before

After

Before

After

It was about 55F to 65F and sunny (not a cloud in the sky) all day, so I figured it'd be perfect for this experiment. These components were out in the sun from about noon until 7PM. I moved them a couple times so that the angle was more direct and so that shadows didn't get in the way as the day went on.

Here is the super technical method I used:

Some things changed more than others, and of course some things I forgot to take good "before" pictures of. The old 3-button mouse was very dark on one side, but has since blended out to be much more evenly colored. The front bezel of that AT tower didn't seem much different, but it was incredibly bad. I intend to do this again the next time we actually have sun, but if the forecast is even remotely accurate it could be a while.

All in all, I think this was a success. The old Kensington power switch was so terribly dark before and it is noticeably better. I'm really hoping that another couple of treatments will get it closer to the original beige color of my IBM 5150 and 5153, since that's what I use it for. I will get more pictures of the other items as I do more sun bleaching treatments.

Thank you so much for posting about this! I bought a cheap ozone generator and have been contemplating other (messier, more expensive) methods for a while now, but we just don't have the climate for the ones that require many many hours of intense heat and sunlight. This I can probably do at any time of the year other than the hottest months of summer. 😀

Interesting!

I guess the brittleness issue Apple experienced with some of their PowerMacs could be a result of incorrect UV plastics curing.
Too sad they had and have mouths closed about the causes, and apparently everybody who received a replacement Mac because of overly-brittle plastics seems to have got it only under the condition of signing a NDA.

Does anybody of you have access to irradiation facility services?
I'd be really curious about the discoloration and brittleness-influencing effect of intense gamma irradiation, short- and long-term. A potential advantage would be the radiations' penetration through plastics, avoiding shadowed parts.

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.

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.

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.