Removing yellowing from Amigas with peroxide

[demolition]

Originally Posted by Methanoid

The sunlight is a cause AND a cure for yellowinG?

Well, perhaps there is a difference between being in full sunlight and being exposed to filtered sunlight or indirect sunlight. The light is quite different when shining through a window.

[ReadOnlyCat]

Originally Posted by demolition

Well, perhaps there is a difference between being in full sunlight and being exposed to filtered sunlight or indirect sunlight. The light is quite different when shining through a window.

UltraViolet (UV) rays are the most energetic of the sun electromagnetic radiation and are the most likely cause of chemical modifications induced by sunlight exposure.

I am skeptical about the claim that regular light would be enough to cause yellowing but UV light would not be, the contrary should be true: maximum chemical activity should occur as a consequence of UV exposure, not because of its absence.

As far as retro brighting is concerned, there is ample evidence that it works and its chemical underpinnings seem relatively well understood. Even if they are not rock solid, at least they offer a sensible and plausible explanation of the process.

The claim that yellowing is reversed without the use of peroxide is not consistent with these experiences and these currently accepted chemical models.

I would caution everyone to wait for a verifiable reproduction or to test that claim only on parts they do not care too much about before attempting "pure sunlight retrobrighting".

[demolition]

Originally Posted by ReadOnlyCat

I would caution everyone to wait for a verifiable reproduction or to test that claim only on parts they do not care too much about before attempting "pure sunlight retrobrighting".

Agree, and that is also what I have done. I started with one item which was very bad and at a point where I considered painting it, so I did not have a lot to lose in the color department. It turned out well, so I continue my experiments with this a few items at a time. I wouldn't just put my entire computer collection out in the sun for a month now.

UV exposure will speed up chemical reactions and so will heat and in this case we have both UV+heat so many things could happen. Not only could it cause a change in color (yellowing/deyellowing), but it could also cause the plastic to become brittle, or simply cause deformations due to the temperature (depends on where you live obviously but the sun is quite excessive over most of Europe atm.).

[mattsoft]

Originally Posted by demolition

Agree, and that is also what I have done. I started with one item which was very bad and at a point where I considered painting it, so I did not have a lot to lose in the color department. It turned out well, so I continue my experiments with this a few items at a time. I wouldn't just put my entire computer collection out in the sun for a month now.

UV exposure will speed up chemical reactions and so will heat and in this case we have both UV+heat so many things could happen. Not only could it cause a change in color (yellowing/deyellowing), but it could also cause the plastic to become brittle, or simply cause deformations due to the temperature (depends on where you live obviously but the sun is quite excessive over most of Europe atm.).

In the name of science, I have a sharp cheddar cheese yellow colored 128 that I'll leave out in the hot sun for the next few days without peroxide. It can't get any worse, really.

[ReadOnlyCat]

Originally Posted by mattsoft

In the name of science, I have a sharp cheddar cheese yellow colored 128 that I'll leave out in the hot sun for the next few days without peroxide. It can't get any worse, really.

Take before and after pictures please.

[mattsoft]

Before pic attached. It's sitting in direct sunlight for most of the day. We are expected to have full sun with 90F (32C) temps all week. Will check in on it this weekend.

[ajk]

Wow, that is certainly at an advanced stage of yellowing

[whaka]

Originally Posted by Methanoid

The sunlight is a cause AND a cure for yellowinG?

this is totally personal, but i think artificial light is probably more guilty than sunlight for the yellowing process. and i specially suspect white neon to be the worse, but not only.

[Amigan123]

After watching a Youtube recommendation I decided to try some
12% Creme Peroxide to remove the yellow on some of my old Computers today, according to the video you do need to expose it to light to work so today
I tried it.

I painted the product on with a paintbrush and wrapped it in a clear plastic bag to stop it drying out too quickly as it was a hot day I put the case outside for around 6 hours in a sunny position and it seems to work really well.

You can get a 1 Litre bottle of this product for around £8 on eBay its nice and thick so stays on the plastic, you might want to wear gloves and make sure you rinse everything as its pretty strong and might cause a chemical rash or burn.

Here are the before and after pic of an Amiga 500 top case

[TjLaZer]

Wrapping in plastic is not recommended as it can cause blooming. Best to just leave it off and frequent out and re apply another layer with the brush.

[dJOS]

Originally Posted by TjLaZer

Wrapping in plastic is not recommended as it can cause blooming. Best to just leave it off and frequent out and re apply another layer with the brush.

Agreed, the best option is to put your yellow item in a plastic tub, then coat, then put cling wrap / plastic wrap over the tub itself. This keeps bugs away from it and boosts the greenhouse effect.

[Methanoid]

Originally Posted by dJOS

Agreed, the best option is to put your yellow item in a plastic tub, then coat, then put cling wrap / plastic wrap over the tub itself. This keeps bugs away from it and boosts the greenhouse effect.

Especially since recent experiments have shown that heat is arguably more important than sunlight. Its all about exciting those free radicals with energy after all :-)

[mattsoft]

Originally Posted by mattsoft

Before pic attached. It's sitting in direct sunlight for most of the day. We are expected to have full sun with 90F (32C) temps all week. Will check in on it this weekend.

I'll take some pics later this week, but direct sunlight alone appears to have no effect on this poor 128. I put some masking tape on sections as a control. A few more days in the sun certainly isn't hurting this old 128.

[mattsoft]

Attached is the top cover of the 128 case after 1 week in the sun with no peroxide. Notice the 2 dark strips? That was my "control" area with masking tape. So sun alone DID lighten the case! Craziness!

[Paulee_Bow]

Originally Posted by Amigan123

After watching a Youtube recommendation I decided to try some
12% Creme Peroxide to remove the yellow on some of my old Computers today, according to the video you do need to expose it to light to work so today
I tried it.

I painted the product on with a paintbrush and wrapped it in a clear plastic bag to stop it drying out too quickly as it was a hot day I put the case outside for around 6 hours in a sunny position and it seems to work really well.

You can get a 1 Litre bottle of this product for around £8 on eBay its nice and thick so stays on the plastic, you might want to wear gloves and make sure you rinse everything as its pretty strong and might cause a chemical rash or burn.

Here are the before and after pic of an Amiga 500 top case

That looks great! It’s exactly the same colour as my A500+.

[demolition]

Originally Posted by mattsoft

Attached is the top cover of the 128 case after 1 week in the sun with no peroxide. Notice the 2 dark strips? That was my "control" area with masking tape. So sun alone DID lighten the case! Craziness!

Either that or the tape caused it to yellow even more.
Since last, I have had an A600 top+keyboard in the sun (3 weeks I think now). These were retrobrighted about 5 years ago but it has since reyellowed somewhat, so I thought I would give the dry method a try as well. It has clearly improved and is looking a lot better. My C128D keyboard which was more or less dark brown is still quite yellow but still a lot better than before. Whether it will ever become close to the original color only time will tell. I know the C128 and keyboard was always quite beige and never as white as an A600, so that is not what I am going for.

The weather report doesn't seem to report any lack of sun over the next coming weeks, so while it is bad for nature with all this sun, at least it will help brighten my computers.

[mattsoft]

Originally Posted by demolition

Either that or the tape caused it to yellow even more.

Hah! That is quite possible!

It is strange that the 2 ingredients that seem to make these yellow (light + heat) also make them less yellow. Chemistry is a harsh mistress.

[TjLaZer]

I wonder if heat alone can cause yellowing? I was thinking about putting some keys that are retrobrited in a dark cool room and one in a freezer and one out in the garage for a year to see what will happen.

[demolition]

Originally Posted by mattsoft

It is strange that the 2 ingredients that seem to make these yellow (light + heat) also make them less yellow. Chemistry is a harsh mistress.

Well, increasing the temperature will speed up any chemical reactions, be it yellowing or deyellowing but the interesting question is what controls whether it goes one way or another.

Originally Posted by TjLaZer

I wonder if heat alone can cause yellowing? I was thinking about putting some keys that are retrobrited in a dark cool room and one in a freezer and one out in the garage for a year to see what will happen.

Some people had good success with retrobrighting with H2O2 only using heat off a heated floor and leaving out the UV light part.

It would be interesting to do some experiments like that, however you also need to take into account that the air composition is different in your three scenarios. If you wrap the keys in something like a plastic bag, that bag could release a lot of different chemicals into the air inside, affecting the outcome. It will also affect the oxygen level which I think is a key factor.

[dJOS]

Originally Posted by TjLaZer

I wonder if heat alone can cause yellowing? I was thinking about putting some keys that are retrobrited in a dark cool room and one in a freezer and one out in the garage for a year to see what will happen.

It absolutely can, I had 2 a500's in storage during a 40-45c week - they were bubble wrapped, boxed and in a giant storage shed and they went from not yellowed, to badly yellowed in the week.