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A major breakthrough in removing yellowing from old cases!!!

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Merlin

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Hi

Over in the Amiga forums a major discovery has been made that is too good to keep to ourselves. A way of completely reversing the yellowing of old computer cases has been developed and proven, details are here:

http://eab.abime.net/showthread.php?t=37808

This process only reverses the yellowing with no other effects on the plastic, if you really want to turn back the clock, this is the way to go, photos are in the thread.

Feedback is welcomed.

Merlin
 
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For the affected layers of polymer, the case will become brittle.
This does not have to be a problem if you don't overdo it.
 
Well, here in Canada, although there is a distributor of TAED not too far from here, hydrogen peroxide in concentrations greater that 8% seem to be pretty highly regulated.

However, if I can find some at, say, a beauty supply store, I might do some controlled experiments.
 
Well, here in Canada, although there is a distributor of TAED not too far from here, hydrogen peroxide in concentrations greater that 8% seem to be pretty highly regulated.

However, if I can find some at, say, a beauty supply store, I might do some controlled experiments.

Well, that is not too strange. It is a very reactive component.
Don't try to take it on a plane.
 
Controlled experiments have already been done, both at Amiga.org and English Amiga Board, I am an industrial chemist by trade and carried out tests under controlled conditions to prove the process.

By the way, some hair bleaching products contain up to 20% peroxide; 8% will be fine although the process may take a little longer, we have found that severe yellowing may take up to 72 hours to reverse, UV light from a black bulb accelerates the process. I thought that this may be useful information. Neat TAED will reduce the foaming that the "Oxy" products generate due to the added detergents, although the "Oxy" products work perfectly well and TAED isn't soluble above 1.5 grams per litre anyway.
 
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Yes, I read the entire thread.

I thought that the TAED allowed the process to be more effecient at lower temperatures (less that 40C), but, I might have been too tired to pick the whole process out of the general mish-mash of the thread.

I'll see what the highest concentration I can reasonably get without a permit is and go with that.

Any advance on the idea of gelling it to be able to use it on larger surfaces? I plan on using that giant thermonuclear device so conveniently located a mere 8 light minutes from here and doing it in stages. I have a low-slope section of roof that is in full sunlight from dawn to dusk and would just "re-paint" it every morning for the required amount of time based on the H202 concentration.
 
Hmmm, interesting! I have the worlds yellowest VIC-20 (bought as a motherboard donor for my pristine but dead one). Maybe something to try out...
 
For the affected layers of polymer, the case will become brittle.
This does not have to be a problem if you don't overdo it.

I also read *most* of the other thread (it was rather long). But I did not see anything about the parts becoming brittle. Can you elaborate?

Paul
 
I also read *most* of the other thread (it was rather long). But I did not see anything about the parts becoming brittle. Can you elaborate?

Paul

We are talking about free radicals here, that to some extend will snap polymer bonds.
It might not be that noticeable though as you are only treating the surface.
But it is a risk when overdoing.
 
As far as we can tell, this is just removing free radicals from the flame retardents which have migrated to the surface and have caused the yellowing (bromine based compounds). Most of the plastic polymer chains will have been capped when the acetyl butyl styrene (ABS) was reacted way before moulding. The heat of the moulding process will have further reduced the free polymer ends.

It's purely a surface effect, there will be plenty of strength left in the plastic and you aren't leaching any plasticisers out, so how will it become brittle?

rkauer is a former plastics engineer and I am a former industrial chemist, feel free to challenge our reasoning on this, plus, if you try it or not is up to you...besides, with 20% peroxide, 72 hours is long enough under UV to reverse even the worst yellowing we reckon.
 
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Oh, don't get me wrong here:
Applied as you describe it, I don't think it is a big risk at all, and the benefits are just too great.
I don't know if the yellowing just comes from the flame retardants.
Is there anything that points at that? (Not to question it, I would just be interested!).

But being yellowed, the polymer itself already is likely to have degraded. Attacking it again might make it worse.

Again, I don't see anything against the ways you describe- just a little warning for those to improve your method ('Hey lets put it in a tank with 30% Px and put it under my solarium for a week!').

I'm already eying my contact lens fluids, although that's only 0,3%.
Maybe it makes sense to buy a C128D after all (those keyboard often have terrible yellowing..)
 
No one is disputing your methodology or findings, I just want to do a test strip of the various combinations of light source vs time vs concentration to be able to control the process more accurately for matching cases where the top has yellowed and the bottom hasn't.

As for the gel aspect, well, not everything people have is a little 8-bitter and I think it might be a little difficult to find something to put the top of my Tandy Model 12 into, so, a homogeneous gel would do nicely for something like that or the top of a Tandy 1000
 
It may be worth trying wallpaper paste as a gelling agent, I've not had time to test anything else at work recently, things have been too busy and the things I was going to try aren't readily available to the average Joe, I would like to keep things so all the ingredients are available to all.
 
It may be worth trying wallpaper paste as a gelling agent, I've not had time to test anything else at work recently, things have been too busy and the things I was going to try aren't readily available to the average Joe, I would like to keep things so all the ingredients are available to all.

Ok, that sounds easier than my first two thoughts, which were Jello or Napalm :)

Actually, I was thinking of Alum, but, I'd have to work out if that would cause any unwanted chemical reaction.
 
Peroxides and metals tend to react. While peroxide on base plastic might not hurt anything, if you have plastic parts with metal parts the metal might rust (depending what it is). No idea what peroxide will do to the ink legends on plastic (not sure what was used for that), would hate to remove logos and other things like that.
 
Peroxides and metals tend to react. While peroxide on base plastic might not hurt anything, if you have plastic parts with metal parts the metal might rust (depending what it is). No idea what peroxide will do to the ink legends on plastic (not sure what was used for that), would hate to remove logos and other things like that.

Logos are unaffected from our experience, as most were either painted on or moulded in another colour. Agreed, metal parts are vunerable and we aren't sure what will happen to sprayed on metal coatings inside cases.
 
A question: did anyone try this process on any other plastic than white? E.g. if I had an old discoloured C64 breadbox which should be brownish grey, what colour could I expect after a bath? Would it become light whitish-grey or return close to its original colour?
 
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