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Retr0Bright: Does re-yellowing occur even in the absence of UV light?

Merlin said:
Full immersion versus a gel coating makes no discernable difference as far as I can make out.
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I just tried my first hand at Retr0Brite. I ran into several problems with the gel method. First, I could not get an even coat. I used a foam brush and put it on as evenly as I could. After a few hours, it looked like someone had paint-brushed it with bleach. In some areas where it had unintentionally blobbed a little thicker, it practically bleached the plastic white, beyond the original beige color. So it looks like an albino sneezed on it.

The second problem I ran into was trying to keep it moist and not dry out. I live in California, so we get lots of sun. I was spraying it and reapplying gel about every 10 minutes, and I still felt like it was drying out too fast.

I did this with an Apple IIe lid, so no big deal. I'm just gonna prime it and paint it Pantone 453 and it'll look good as new. I'm not certain I can get an even enough coating with the gel, so for the body I'm going to try the immersion method.
 
Manboy said:
They were treated indoors with uv light and retr0bright gel. I had another look tonight and no trace of yellowing 4 years after treatment. Im not saying that it was the method used that made the differene but it is the ony thing i could think of.
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I wonder if the key is the UV light? I.e. a constant exposure at a constant strength vs. the sun where a cloud come over and changing angles of light can diminish effects?

It would be interesting to see if the immersion technique with a UV light produces the same results. Of course it could be just dumb luck or the fact that that batch of plastic was better then the others. ;)
 
Shadow Lord said:
I wonder if the key is the UV light? I.e. a constant exposure at a constant strength vs. the sun where a cloud come over and changing angles of light can diminish effects?

It would be interesting to see if the immersion technique with a UV light produces the same results. Of course it could be just dumb luck or the fact that that batch of plastic was better then the others. ;)
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If the yellow color is caused by elemental bromine, it can be removed by heating to 137F under vacuum. Has anyone tried that?

Shadow Lord, I have a 7531. Are you near NYC?
 
BobCat_ said:
If the yellow color is caused by elemental bromine, it can be removed by heating to 137F under vacuum. Has anyone tried that?

Shadow Lord, I have a 7531. Are you near NYC?
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I don't believe so. That does not sound like a setup the typical hobbyist may have access to.

p.s. PM me on the 7531. Thanks!
 
I registered here so that I could share my Retr0bright experiences.

I treated a Macintosh 512k a Macintosh Plus and a Macintosh SE. I treated them about a week apart from each other and I treated the Mac 512k first.

The plus and the SE went almost immediately into boxes after treatment and were kept in pitch blackness the entire time. The 512K was setup on my desk immediately after treatment and has been exposed to Fluro and indirect sunlight daily.

My 512K still looks great, it has regressed ever so slightly. I pulled the Plus and SE out recently and was stunned to see that they were both completely yellow again.

So my thought is that perhaps exposure to sunlight continues the effect of the retr0bright process at some very low level.
So today I tried an experiment. I took my very yellow plus keyboard and left it in direct sunlight for the entire day and it was quite hot here in Australia today, about 30 DEG C. When I got home from work and checked the keyboard it has most definately become less yellow!

Anyone have any thoughts on this? Seems to be a similair result as your Lisa Tez...
 
Just a side note; if you would like to slow down the yellowing process you should apply a protective coating to it.

The best/easiest is to use a spray on plastic/vinyl protector that you get for your cars dashboard. I've used quite a few from Armor All through to Autoglym and they all seem to do the trick. It will protect it from the UV, as well as atmospheric oxidation which is just as prevalent (as those people who retrieve their items from sealed boxes can attest). Reapply every so often and it keeps everything shiny and new.

Also in my opinion the 'less yellow' by leaving things in the sun is probably due to the oxidising nature of the UV, heat of the day and oxygen in the air. Retr0brite is nothing more than strong oxidants; sunlight and heat will do the same thing BUT it will also degrade the plastic and turn it brittle.
 
I personally would suggest staying away from products like Armor All or Autoglym, I have experienced many vinyl dash pads in older cars drying up and cracking all to heck from application of these products. They're great at making things look all shiny and new for a while, but their long term effects seem less positive...
 
I actually use a good polymer car "wax". I do this on painted and plastic systems. Polymer finish protectant like RejeX protect it from more than UV.

I should mention on my "blue" painted systems like an Altair or Sol-20, I use blue tinted carnauba wax, then RejeX. Makes the color pop.

Cheers,
Corey
 
3pcedev said:
Just a side note; if you would like to slow down the yellowing process you should apply a protective coating to it.

The best/easiest is to use a spray on plastic/vinyl protector that you get for your cars dashboard. I've used quite a few from Armor All through to Autoglym and they all seem to do the trick. It will protect it from the UV, as well as atmospheric oxidation which is just as prevalent (as those people who retrieve their items from sealed boxes can attest). Reapply every so often and it keeps everything shiny and new.

Also in my opinion the 'less yellow' by leaving things in the sun is probably due to the oxidising nature of the UV, heat of the day and oxygen in the air. Retr0brite is nothing more than strong oxidants; sunlight and heat will do the same thing BUT it will also degrade the plastic and turn it brittle.
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I used a protectorant on all the machines I treated and as I said they went straight into boxes and into a cupboard and were kept in pitch darkness and they still yellowed.

I stuck my SE and Plus out in the sun for the day and the yellowing is significantly diminished.
 
Surfheart said:
Anyone have any thoughts on this? Seems to be a similair result as your Lisa Tez...
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Yes, interesting result. With my units it was those ones that were most yellowed initially, that re-yellowed the quickest. It's interesting that a sealant didn't make any different to the stored unit as this should have prevented oxygen from facilitating a further reaction. Hmm...I'm thinking maybe that retrobrighting (in some plastics) just whitens the top layer and then somehow the discolouration (which is perhaps deeper) migrates up...even without oxygen but maybe aided by heat (did you store yours in a hot place?).

Anyway, I'm no chemist but these experiences are interesting..thanks for sharing.

Tez
 
"The plastics most commonly used to make the structural cases for electronic equipment are polypropylene, impact styrene, and ABS," replied Deanin. "These all tend to discolor and embrittle gradually when exposed to UV and/or heat. They become oxidized and develop conjugated unsaturation, which produces color. They crosslink or degrade, which causes brittleness."

http://www.vintagecomputing.com/index.php/archives/189

"In the case of the SNES plastic, however, the trigger of the oxidation process is clearly not UV light, but simple and unavoidable exposure oxygen in the air over time, with heat possibly accelerating the process. Once the process is triggered, its effects cascade in a recursive cycle — as in the UV example above — eventually changing the physical nature of the plastic and its color."

Know your enemy:

1, UV Light
2, Heat
3, Oxygen

If you can combat all three then you have a chance of preserving old hardware indefinitely.

Credit to Benj Edwards for his excellent article.
Credit to Tezza for his work in understanding why this happens and producing most excellent youtube videos.
 
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Resurrecting this thread with a few questions. I don't know if anyone of the original authors of this thread is still here:
1- Has anyone learned anything more about the "degraded bromides from the original yellowing, migrating back to surface to re-yellow" theory. Are we any closer to proving this theory?
2- From Tez's original analysis, could we deduce that this migration in a retrobrighted plastic happens faster than the new yellowing that could happen to plastics from UV/heat?
3- Does heat speed up bromide migration.
3- If (2) and (3) are both correct than could we assume that if we repeatedly retrobrighted and heated the yellowed plastic, then could we eventually run out of bromide deep in the plastic that hasn't been retrobrighted (gradually curing the entire plastic)?

Best regards
 
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