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How to remove yellowing from an old Atari case


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#26 mimo OFFLINE  

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Posted Thu Jan 29, 2009 4:47 AM

I don't have any C= stuff to try this on, but I have not noticed any change in the texture of the surface of the 400 or 800XL that I treated. Maybe it is because the Atari products are already very textured, but I am happy with the results that I have personally seen (and touched).
All I say is that it worked for me, and I am really happy with the results (as are a lot of others that have done this)
If you are in any doubt about the short or long term effects this process will have then simply don't do it.
I will continue to restore all of my Atari products in this way.

#27 poobah OFFLINE  

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Posted Thu Jan 29, 2009 4:55 AM

All bleached items I have seen had that rougher surface.

There are many possible reasons for this. claiming the plastic is damaged is specious at best.

The original state of the plastic may have been 'rougher'. You may have observed that most yellowed plastics seem to have an artificial smoothness about them.

They may still have been dirty, the oxy/peroxide bath will certainly give them a good scrubbing.

You are actually removing some mass, replacing an oxygen atom with a hydrogen atom. but remember that this is getting back to where you belong, as the it is the oxidation of the bromine compounds that gave the yellow color to begin with.

#28 Fröhn OFFLINE  

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Posted Thu Jan 29, 2009 5:03 AM

The original state of the plastic may have been 'rougher'. You may have observed that most yellowed plastics seem to have an artificial smoothness about them.

Usually you can easily compare because the inside of a case often is not yellowed out and somehow the peroxide does not change the surface there.

You are actually removing some mass, replacing an oxygen atom with a hydrogen atom. but remember that this is getting back to where you belong, as the it is the oxidation of the bromine compounds that gave the yellow color to begin with.

No, the result is much much lighter than the original color. Look at the picture I posted. The two little cuts show the original color underneath the surface.

#29 atariksi OFFLINE  

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Posted Thu Jan 29, 2009 5:41 AM

...
The top left part was the one where peroxide was applied. The top right part is one which was left in the sunlight for some time and the bottom part is a reference part with the original color before doing anything.

Interesting is the fact that the top right non-bleached part got LIGHTER when it was left in the sun for 2 weeks, also the peroxide gone even lighter (to almost white) after 2 weeks of sun. And as I said: The peroxide part definitely changed it's surface to a rougher feel & look. The bottom side which wasn't yellowed hasn't changed though.

Maybe a few of them are stupid, and not realizing the damage you speak of is taking place, but I find it hard to believe that ALL of them are.. And this has been a well-known & explored method for several years now in the AMIGA community.

All bleached items I have seen had that rougher surface.


So just leave item in sun w/o applying anything for 2 weeks and yellowing goes away? That's a pretty safe solution although a slower one. Perhaps, there's a better and faster solution and one that does not involve using harmful chemicals. Harmful meaning dangerous to use for humans and perhaps damaging to surface.

#30 poobah OFFLINE  

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Posted Thu Jan 29, 2009 10:06 AM

The original state of the plastic may have been 'rougher'. You may have observed that most yellowed plastics seem to have an artificial smoothness about them.

Usually you can easily compare because the inside of a case often is not yellowed out and somehow the peroxide does not change the surface there.

You are actually removing some mass, replacing an oxygen atom with a hydrogen atom. but remember that this is getting back to where you belong, as the it is the oxidation of the bromine compounds that gave the yellow color to begin with.

No, the result is much much lighter than the original color. Look at the picture I posted. The two little cuts show the original color underneath the surface.


Most plastic items have different textures on the inner and outer surfaces, can't really use that as a basis for comparison.
The observation that the peroxide does not change the inner surface pretty much debunks the change in roughness bit. If the peroxide was harming the plastic (ie: causing surface roughness) the effect should be visible across the entire piece

Oxidation isn't a surface only phenomenon. Certainly the outer surface has the greatest exposure, and hence greatest oxidation, but even the interior of a 20 year old piece of plastic should show some internal oxidizing effects. Most plastics are gas permeable to some extent.

The surface result of the UV/peroxide thing should be close to the state when the item was moulded.

Mind you, I'm not saying that there are NOT changes to the plastic as a result of this process, only that the evidence posted so far is insufficient to prove any such claim, and that the observed effects could be from any of a number of alternate explanations.

The refined version of this peroxide process was partly developed by a chemist, even the site you reference acknowledges that. Considerable commentary on the chemical changes being made is provided in the original threads.

Edited by poobah, Thu Jan 29, 2009 10:08 AM.


#31 Fröhn OFFLINE  

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Posted Thu Jan 29, 2009 10:21 AM

Most plastic items have different textures on the inner and outer surfaces, can't really use that as a basis for comparison.

And that's exactly the reason why I posted that picture of 3 parts undergone different treatments and then compared. That the yellowed surface had changed and the non-yellowed backface was verified on that parts.

The observation that the peroxide does not change the inner surface pretty much debunks the change in roughness bit. If the peroxide was harming the plastic (ie: causing surface roughness) the effect should be visible across the entire piece

It seems it only harms the yellowed surface.

Mind you, I'm not saying that there are NOT changes to the plastic as a result of this process, only that the evidence posted so far is insufficient to prove any such claim, and that the observed effects could be from any of a number of alternate explanations.

So you say that the only surface changed was the yellowed one undergone peroxide has alternate explanations than the peroxide changing yellowed surfaces?

The refined version of this peroxide process was partly developed by a chemist, even the site you reference acknowledges that. Considerable commentary on the chemical changes being made is provided in the original threads.

I have seen so many bleached plastics which DID change the surface I will only believe such "magic peroxide processes" once I see it.

#32 Longhorn Engineer OFFLINE  

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Posted Thu Jan 29, 2009 10:58 AM

You know we can just do simple strength tests. I can give one half of a broken SNES in a bath and leave the other half original.

Drop tests, scratch tests, ect....

#33 MEtalGuy66 OFFLINE  

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Posted Thu Jan 29, 2009 12:24 PM

From eab.abime.net forum: http://eab.abime.net...?t=37808&page=9

Metalguy66:
Hey Merlin. Great work you have done here.. Ive read the entire thread and Im really impressed.

Several people have raised concerns about degredation of the plastic from this process. Specifically, changing the surface of the plastic, making it more rough, or brittle..

Also, there is some concern as to different plastic formulations and adverse reactions that may be more prominant in one type of plastic than another..

Could you please comment on these issues?

Merlin:
Certainly.

The main issue surrounds the use of Chlorine based bleaches to remove the yellowing. While there is little doubt that it works, you need to be aware that Chlorine is about half the size of Bromine in molecular terms (see page six of this thread). The result is that the Chlorine replaces the Bromine as it is more active, but at the expense of weakening the plastic structure by literally introducing holes into the plastic matrix. Chlorine can also latch onto oxygen from the air, so you haven't really gained anything as the plastic will still oxidise, but will yellow less than before.

The process that has been developed here does not use Chlorine; it just removes the oxygen from the bromine and replaces it with a hydrogen atom. Now, while this may sound like the same scenario as above, we are actually returning the plastic back to it's original state as manufactured and the bromine remains in place, so all is well regarding embrittlement. If you coat the piece after treatment with a clear lacquer, the yellowing won't return as you have sealed the surface so it can't react with oxygen.

Generally, Acetal Butadiene Styrene (ABS) is pretty generic and so far we have seen little difference between computer brands, e.g. Commodore, Atari, Osborne, Televideo, etc. The master batches of the plastic are made by large players in the industry and the only areas that tend to change are the pigments used to provide colour.

Flame retardants used to include chemicals like Antimony Tribromide (Bromine again) but this has fallen out of use due to heavy metal restrictions, particularly in toys (e.g. EN71 Parts 3 and 9). Poly Brominated Diphenyl Ethers (PDBEs) are the most widely used in plastics that need fire retardant properties, for example clear plastic diffusers on lighting, electrical enclosures, furniture etc.



#34 Merlin OFFLINE  

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Posted Thu Jan 29, 2009 2:04 PM

Hi guys, Metalguy66 suggested I pop over here to get trolled by you all....... :D

Greetings from English Amiga Board, Vintage Computer Forums and Amibay.... all retro sites together...

I am the alchemist who has been writing all of these articles about de-yellowing plastic. This is my first post on here and it's bound to be controversial.... :roll:

OK, let's lay this out once and for all as simply as I can. Whilst I am aware that acetal butadiene styrene (ABS) can oxidise under light to form the hydroperoxide as others have alluded to on here, here is one thing that you may not be aware of from the threads, as I am still trying to write this process up for a Wiki, but people keep asking me damn fool questions about it :cool:

The process ONLY works in the presence of UV light or sunlight; now, that may not seem like a big thing, but the only molecules in the finished plastic that react so quickly to UV light are Bromine molecules from the Poly Brominated Diphenyl Ethers (PDBEs) in the flame retardant. If you try the experiment in the dark with the same chemicals, the parts don't change colour and just get wet. If this wasn't down to Bromine chemistry in the flame retardant, the polymer would react in any conditions, even in the dark; clearly it doesn't.

The only scientific explanation that fits what we are seeing here is the reaction of Bromine under UV light conditions. Bromine has a single electron spare in it's outer p-shell (Does anyone remember electron shells?). Bromine is 1s2 2s2 2p6 3s2 3p5, hence the negative charge of a Bromine radical as it would prefer an even number of electrons. By neutralising it with a single hydrogen created by the catalysis of hydrogen peroxide by tetra acetyl ethylene diamine (TAED) we allow the Bromine to be reduced by the electron and it goes to a stable 3p4 in the outer p-shell.

The key is to use the optimum strength of hydrogen peroxide, which is around 10 to 15%. The white "bloom" you may see is down to peracetic acid which is one of the breakdown products of TAED and this is also a powerful bleach in it's own right. Too strong a solution and it does seem to etch the surface, which is probably the peracetic acid attacking the hydroperoxide of the oxidised polymer as well as working on the bromine molecules.

Now, anyone can feel free to troll this explanation, but after having put months of work and research into this, at least back your argument up with some sort of scientific critique. I am achemist with 25 year's experience and although I may not have a BSc, I could certainly write a thesis on this subject.

Over to you all for comment.

#35 Merlin OFFLINE  

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Posted Thu Jan 29, 2009 2:25 PM

Thanks to Metalguy66 for the copying and pasting for that, it saves me loads of typing. I think I've made the case for the defence now by the discussion about UV light; let's see if anyone has the cahonies to talk science with me........this should be fun, as the groundswell of proof that we are generating globally says this this is no hoax that we have discovered.

Edited by Merlin, Thu Jan 29, 2009 2:30 PM.


#36 Tezz OFFLINE  

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Posted Thu Jan 29, 2009 2:26 PM

First of all... Cool! it was a Mancunian invention :) Merlin, thanks for the extensive explanation. It's great that there is a total non destructive reversing solution to this age old (no pun) problem. Not so long ago we were all saying that painting was the only option in restoration.

Edited by Tezz, Thu Jan 29, 2009 2:27 PM.


#37 Mitch OFFLINE  

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Posted Thu Jan 29, 2009 2:28 PM

Do you have a recommendation about what type of container to do the process in? For instance would using a metal or plastic tub cause different results because of other possible reactions? I have not tried it yet but I also do not want to mess anything up. :)

Mitch

#38 Merlin OFFLINE  

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Posted Thu Jan 29, 2009 2:33 PM

@ Mitch

Sure.

I used a polypropylene washing up bowl. If you make the gel version by adding corn starch, arrow root or xanthan gum to thicken the brew up so it's like hair gel, you can paint it on and just lay the part on a polythene sheet. Tezza at VCF used cardboard when he did his VIC-20 case.

@ Tezz

Aren't all of the best inventions British? :D

By the way, I've started a support thread for this over at AmiBay, the retro computer trading site I help to run. It's in the AmiOracle section. Feel free to sign up as we have an Atari section that is a bit unloved right now.........

Edited by Merlin, Thu Jan 29, 2009 2:36 PM.


#39 KrazyKaiju OFFLINE  

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Posted Thu Jan 29, 2009 2:42 PM

Also, if your not a purist (I'm not) new colors look cool too.

My daughter loves blue so I made her a blue metallic 800xl. Looks great. I might make my main 1200xl black metallic.

(re: you can avoid the peroxide bath)

Krylon makes a wicked gunmetal paint for plastic. If you prime with navy blue and lightly brush between top coats, you can make a really neat blued steel effect.

#40 Merlin OFFLINE  

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Posted Thu Jan 29, 2009 4:23 PM

For more information on the science I am talking about above, you should look up subjects such as spd hybridisation, protonation and Lewis acids and bases, or even Bronsted-Lowry acids and bases. Google and Wikis will be your friends in your search for knowledge.

Edit: A small error in the Bromine electron shells, it should read 1s2 2s2 2p6 3s2 4s2 3d10 4p5, I was one layer short... it's still 5 in the outer shell though.

The theory and science behind what is happening in the plastic is fundamentally sound and I haven't been able to come up with another one that fits the results of the experiments completed so far. Other plastics engineers and guys with science backgrounds support the theory that we have postulated.

It works, and I stand by the process.

/Merlin waits for Fröhn to arrive...........

Edited by Merlin, Thu Jan 29, 2009 4:44 PM.


#41 mimo OFFLINE  

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Posted Thu Jan 29, 2009 5:51 PM

Thanks for your input Merlin (you sent me some TAED a while back)
I really don't understand the chemistry behind this, but it works bloody well :thumbsup:

#42 Guitarman OFFLINE  

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Posted Thu Jan 29, 2009 6:34 PM

Merlin,

Thanks for making the trip over. I have been flipping between here and the Amiga forum where this started. At the top of this forum (8 Bit Forum), there is a 'sticky' post for restoration info. Would you be willing to post the formula and process there so we could have it in an easy to find place?? I, myself, will probably go broke restoring all the systems I have!!! Great work!!

#43 MEtalGuy66 OFFLINE  

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Posted Thu Jan 29, 2009 6:35 PM

I think this picture from Tezza's page tells all:

2009_01_01_atari130_case_before_and_after.jpg

This process is OBVIOUSLY not "bleaching" the plastic, but in fact returning it to it's original color.
Look at the photo on the left.. Can you see the (still grey) areas that were never yellowed, due to the angle of UV exposure? If anything, I think the photo on the right actually shows a slightly DARKER shade of grey, no lighter...

Also notice by the amount of glare on various surfaces of the case, that the surface of the plastic seems to retain exactly the same "shine" or "luster" on both the before and after photos.. Making it very doubtful that the process has "over etched" or "roughened" the surface..

Edited by MEtalGuy66, Thu Jan 29, 2009 6:38 PM.


#44 warerat OFFLINE  

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Posted Thu Jan 29, 2009 9:19 PM

I think this picture from Tezza's page tells all:

2009_01_01_atari130_case_before_and_after.jpg

This process is OBVIOUSLY not "bleaching" the plastic, but in fact returning it to it's original color.
Look at the photo on the left.. Can you see the (still grey) areas that were never yellowed, due to the angle of UV exposure? If anything, I think the photo on the right actually shows a slightly DARKER shade of grey, no lighter...

Also notice by the amount of glare on various surfaces of the case, that the surface of the plastic seems to retain exactly the same "shine" or "luster" on both the before and after photos.. Making it very doubtful that the process has "over etched" or "roughened" the surface..


Looks good! I have a few 800s that could use this technique. What I'm wondering is if the 130XE badge was left on the case? If so, it doesn't look like the peroxide corroded the metalized fuji or faded the label.

#45 MEtalGuy66 OFFLINE  

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Posted Thu Jan 29, 2009 10:23 PM

Looks good! I have a few 800s that could use this technique. What I'm wondering is if the 130XE badge was left on the case? If so, it doesn't look like the peroxide corroded the metalized fuji or faded the label.


Yeah, it doesnt hurt plastic/metal labels, painted on lettering, keycap-lettering, etc.. paper labels will probably be adversely effected.. But if you make the "gel" version of the agent, you can selectively brush it onto just the areas that you want it to effect..

#46 Merlin OFFLINE  

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Posted Thu Jan 29, 2009 11:36 PM

@ Guitarman

Zetr0 and I are working on a definitive article about this that we will put up on Zetr0's project server with pictures to explain some of the chemistry at work. Once that is done (and it's not far away) we are happy for any site to host a link to it. The point of all this is to make it public domain, so that anyone who is interested can do this, irrespective of the computer platform.

For those that haven't see this, the link below shows a Commodore 64 case that I half masked up and treated with the gel version; this is about as extreme as it gets and this was achieved in eight hours under a UV lamp. The article we are writing has the full set of images I used for this test (they are also in the EAB thread) so you can get an idea of how long a certain amount of discolouration will take to remove.

http://eab.abime.net...?t=37808&page=7

The colour when the process was completed matched the inside that had never seen daylight. the surface texture remained the same. As Metalguy says, you should be able to make this out on the photographs as the amount of sheen revealed by the flash of the camera is the same.

@ Metalguy

Thanks for the Atari case photo; this project isn't all about Commodore machines you know!! :thumbsup: ;)

@ all

The only metal that doesn't like the process is Aluminium. This isn't too sprprising given that Aluminium is amphoteric. You can take the badge off, mask the badge as Metalguy suggests or use the gel version. The gel foams up so I would go for masking as the safest option.

Holy Moly! This has only been up here a day and it's had over 700 reads already!! :-o This seems to happen wherever I post information on this, it's certainly grabbing people's attention.......

If anyone on here tries this, there is only one condition; we want pictures. The more proof we have, the more we can convince the unbelievers.... Zetr0 and I also like our hardware pr0n.... :D

Edited by Merlin, Thu Jan 29, 2009 11:47 PM.


#47 Kilack OFFLINE  

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Posted Fri Jan 30, 2009 4:29 AM

Hi,

I have managed to obtain some hydrogen peroxide at 35%, it was either that or 3%...
Is this going to be too strong? or should I use some distilled water and dilute it down a bit?

I have an atari 800xl , atari 1040stfm and an atari 1050 drive I want to do.

Plus an a1200 and 2 a500's

Will send photos once I give them a good bath !

Edited by Kilack, Fri Jan 30, 2009 4:35 AM.


#48 mimo OFFLINE  

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Posted Fri Jan 30, 2009 5:49 AM

35% will be fine, it may be a bit quicker to complete the process.
Can't wait to see everyone's photos, hopefully I will be doing a 400 this afternoon :D

#49 Merlin OFFLINE  

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Posted Fri Jan 30, 2009 7:23 AM

35% is dangerous and can cause severe burns if handled incorrectly. I would suggest you dilute it down to 10 to 15%, so that you are guaranteed good results and the safety factor is way higher.

Remember, I would like pictures of the results..... :D

#50 mimo OFFLINE  

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Posted Fri Jan 30, 2009 7:38 AM

*embarrassed*




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