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Yellow aging of your old computers and consoles

PostPosted: Sat Oct 29, 2016 7:35 pm
by mons2b
I found the below page which is the most informative I have seen about the yellowing of plastic computer and console cases. After reading it im thinking of at a minimum rubbing uv protection compounds over my computers. Another idea is to paint them in clear uv resistant paint. If you have used hydrogen peroxide to bleach your computer cases (I think it may make them brittle, but anyway..) then you should clear coat them to stop them going yellow again. Both to block UV and to block oxygen. It seems both oxygen and light attack the plastic. The oxygen attacks worse I believe after a bleach job. If we do nothing and just let them yellow more they will become so brittle bits will start breaking off during maintenance etc. At some point I may try this uv clear coat idea on a case that is already damaged so ok to experiment on, to see if it makes it look too shiny or something.

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

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Re: Yellow aging of your old computers and consoles

PostPosted: Sun Oct 30, 2016 10:42 am
by nzoomed
I believe that the bromide fire retardants is what makes it yellow (from releasing bromine i guess?)

IDK, but there seems to be a few retr0bright recipes, but is basically hydrogen peroxide sometimes mixed with ammonia.

Seems ironic that the UV light is needed to make this work.
I have read about it making the plastic brittle, but I think its only an issue if you leave it in there too long.

I dont know if there is another chemical that could work, bromine is extremely reactive, so you would think that there would be a number of
chemicals that could extract this from the plastic.

I do know that people report that it never yellows anywhere near as bad after treatment, and this is probably because a great deal of the bromine has been released over 20+ years?

My c64 breadbin has very little signs of yellowing, so obviously UV plays a part.

Now im worried that i may be doing damage even using with my fluorescent lights on even for the few hours I have them on.

But ideally i want to get another c64 that is more "rough" for general use and keep my one in its box.

Re: Yellow aging of your old computers and consoles

PostPosted: Sun Oct 30, 2016 9:03 pm
by LS120
there is one that uses laundry whitener that works ok and leave it out in the sun.. to do its job.. have done it and works ok.

Re: Yellow aging of your old computers and consoles

PostPosted: Mon Oct 31, 2016 12:37 pm
by tezza
That's quite an extensive article...

Yes, I'd done quite a bit of de-yellowing in my time. My experience has been...

- works best on plain white or cream cases. Care should be taken on coloured cases (e.g. breadbin C64) as it's easy to overcook and cause bloom.
- I agree that oxygen exposure is probably just as important as light for re-yellowing (having had a number of computers re-yellow after treatment even though kept in near complete darkness).

Re: Yellow aging of your old computers and consoles

PostPosted: Mon Oct 31, 2016 7:25 pm
by nzoomed
Has anyone tried ozone?

I reckon that could work.
I would need to use my tesla coil to produce enough though...

Re: Yellow aging of your old computers and consoles

PostPosted: Sun Nov 06, 2016 11:43 pm
by mons2b
You have a Tesla coil? Too cool. :)

After extensive reading of these bleach experiments I do not believe they are a good idea. When its bromide that has caused or accelerated the yellowing then bleaching just takes off the surface layer. Theres plenty more still in the plastic will will leach out again. It seems once you whiten the plastic you make the transfer of bromide happen even faster plus add a oxygen sensitivity to the mix. It seems the treatment gives the computer a oxygen allergy! I suggest if you totally cant stand a little yellowing then cover the treated plastic in a UV clear matte coating to block oxygen getting to the surface and to try to aid a little in reducing brittleness. Myself I will leave my yellowed computers and printers etc as they are. I really dont want to make that plastic brittle. I had one atari st case that had become so brittle with age that whatever I did new bits kept breaking off. Sad, the motherboard is ok so I will use it as games machine for my daughter to play with. Love that younger kids will give an older game a go and enjoy it.

Re: Yellow aging of your old computers and consoles

PostPosted: Mon Nov 07, 2016 9:16 am
by nzoomed
mons2b wrote:You have a Tesla coil? Too cool. :)

After extensive reading of these bleach experiments I do not believe they are a good idea. When its bromide that has caused or accelerated the yellowing then bleaching just takes off the surface layer. Theres plenty more still in the plastic will will leach out again. It seems once you whiten the plastic you make the transfer of bromide happen even faster plus add a oxygen sensitivity to the mix. It seems the treatment gives the computer a oxygen allergy! I suggest if you totally cant stand a little yellowing then cover the treated plastic in a UV clear matte coating to block oxygen getting to the surface and to try to aid a little in reducing brittleness. Myself I will leave my yellowed computers and printers etc as they are. I really dont want to make that plastic brittle. I had one atari st case that had become so brittle with age that whatever I did new bits kept breaking off. Sad, the motherboard is ok so I will use it as games machine for my daughter to play with. Love that younger kids will give an older game a go and enjoy it.


My c64 is not yellow enough to bother me.

Its probably the best one ive ever seen.

If its a real rough yellow one, it would not bother me too much if i bleached it anyway, but I really want to find another c64 that i can use as I think this one is better left in its box in the dark.

There are UV protector products for plastic in cars etc, you can get these from repco and supercheap, it could be worth a try with these?
They also can be cleaned off with isopropoyl alcohol easily enough. :)

Re: Yellow aging of your old computers and consoles

PostPosted: Mon Nov 07, 2016 9:50 am
by tezza
mons2b wrote:..I really dont want to make that plastic brittle.


I've found if cases are yellowed then damage has already taken place and the plastic is brittle anyway. In my experience the de-yellowing doesn't seem to increase brittleness. These are just my own observations though. I'd be interested in any valid research that shows de-yellowing treatments further damage plastics.

Re: Yellow aging of your old computers and consoles

PostPosted: Mon Nov 07, 2016 5:10 pm
by nzoomed
tezza wrote:
mons2b wrote:..I really dont want to make that plastic brittle.


I've found if cases are yellowed then damage has already taken place and the plastic is brittle anyway. In my experience the de-yellowing doesn't seem to increase brittleness. These are just my own observations though. I'd be interested in any valid research that shows de-yellowing treatments further damage plastics.



Yes, very true.
For the most part, its not a problem, and if the plastic is that far gone with yellowing, who really worries about it if you can make it look a darn sight better than before?

Re: Yellow aging of your old computers and consoles

PostPosted: Mon Jan 09, 2017 10:14 am
by SpidersWeb
I was talking with an Amiga collector who is outside of the normal groups, and he mentioned that he sprayed on a clear UV protectant and the yellow didn't return. This peaked my interest too, so I'll have to find out exactly what product he tried and see if I can replicate.

Just wanted to post up to +1 the UV protectant idea.

Re: Yellow aging of your old computers and consoles

PostPosted: Mon Jan 09, 2017 10:19 am
by tezza
SpidersWeb wrote:I was talking with an Amiga collector who is outside of the normal groups, and he mentioned that he sprayed on a clear UV protectant and the yellow didn't return. This peaked my interest too, so I'll have to find out exactly what product he tried and see if I can replicate.

Just wanted to post up to +1 the UV protectant idea.

Yes, I've heard that too but it seems that oxygen exposure plays a more significant role in re-yellowing than UV. At least in my experience. Some of my retrobrited units re-yellowed in closed boxes in a dark room where the only light was the faintest of glimmers through the cracks in the top of the box!

Terry