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How to remove yellowing from an old Atari case


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#1 mimo OFFLINE  

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Posted Wed Jan 28, 2009 5:38 AM

A few people have suggested that I post this in the 8bit forums rather than it hiding in the Restoration sticky.
I stumbled across this method of getting rid of yellowing in it's infancy on the English Amiga Forumsand what can I say other than it really works.
As an example here are before and after shots of my very yellow 800XL.
This looked like it had been near a window as the yellowing was much worse on the right hand side. After a day and a half soaking the results speak for themselves.
before.jpg
After1.jpg
after2.jpg

I have also tried this on a 400 and that worked very well. I tried some keys off a XEGS, but results were not so good-I plan to try this again when I have some spare time.
I also plan on doing a 400,800,65XE and various other bits and bobs- stay tuned.

I take no credit for this, I am just following other peoples instructions

IF YOU DO THIS-IT IS ENTIRELY AT YOUR OWN RISK

Here is a brief resume of the how/why


1. We have learned that a magic concoction has been created that can reverse the years of yellowing of plastics, caused by the brominated flame retardants (which were added to the plastic when it was a masterbatch) migrating to the surface of the plastic and attracting oxygen molecules which become attached by a co-ordinate bond.

2. Bromine molecules are susceptible to ultra-violet light, in that chemical bonds involving bromine molecules can become destabilised if irradiated by UV light. This is what we are exploiting to remove the oxygen molecule from the brominated flame retardant.

3. The yellowing can be reversed to a degree by immersing parts in hydrogen peroxide or "Oxy" on their own, however, on their own they don't do that much; what is needed is a chemical called TAED (tetra acetyl ethylene diamine), which is a chemical found in the "Oxy" type laundry boosters. Why is this useful? It's useful because it catalyses perborates and percarbonates in the "Oxy" to produce peroxides; it can also catalyse hydrogen peroxide, which is exactly what we want. This is what makes the mixture much more potent.

4. The optimum mixture and conditions for reversing yellowing of plastics seems to be the following:-

A) Hydrogen peroxide solution, the strongest you can lay hands on;
B) UV light, either as sunlight or a UV lamp;
C) Approx 1/4 teaspoonful per gallon of "Oxy" laundry booster.

Parts immersed in this mixture will have the yellowing reversed in six to eight hours on average. Severe yellowing may take longer but it will only be a matter of a day or two. The mixture once made will last about four days before all of the peroxide is spent.

5. A more recent development is that the mixture can be made into a gel. Initial tests with Xanthan Gum added to the original mixture have shown that it can be made into a thicker material which can be brushed onto surfaces. This mixture foams up but still removes the yellowing when put under UV light, and can remove yellowing in four to six hours. This method also drastically cuts down on the amount of liquid required and means large areas can be treated at a relatively low cost. Other thickeners such as corn starch, hydroxy ethyl cellulose, wallpaper paste, latex or similar inert thickener may also work, however, tests are in the early stages, feel free to try some of these and report back if they work.

6. Recent tests by Lorne have shown that powdered hair bleach and hydrogen peroxide solution can give a similar effect to the original "Oxy" mixture, however, there may be side effects associated with using this material; early tests have seen adverse effects on paint and stickers may also be affected by this product. The original "Oxy" mixture does not affect paint or stickers, unless the stickers are held on with a water based glue or are paper stickers.

7. If you are planning to do this in a hot climate, please be aware that this mixture will heat up during the day. Lorne is in Arizona and found that temperatures in excess of 100F (38C) and beyond were encountered, which caused some warping and distortion of large pieces. If this is the case where you live, always add the component to a cold mixture and check the temperature during the day.

We will add to this original post in the thread as we learn more. If you wish to read the original thread, it's here:-

http://www.vintage-c....ad.php?t=11877

The story continues.........


Edited by mimo, Wed Jan 28, 2009 5:51 AM.


#2 Ross PK OFFLINE  

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Posted Wed Jan 28, 2009 6:51 AM

This is amazing stuff.

I always thought once plastic had yellowed then that was it, that there never could be anyway of removing it.

Edited by Ross PK, Wed Jan 28, 2009 6:53 AM.


#3 iwan-iwanowitsch-goratschin OFFLINE  

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Posted Wed Jan 28, 2009 7:15 AM

Wow, it works! I never thought that the yellowing is reversible! GREAT!! :)

#4 Fröhn OFFLINE  

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Posted Wed Jan 28, 2009 7:46 AM

Worth reading:

Plastic Discoloration in Classic Machines

And it's NOT reversible. You can remove the yellowing, but the methods have effects on the plastic itself too. Basically you cannot repeat bleaching techniques several times without the plastic getting more and more destroyed.

#5 yorgle OFFLINE  

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Posted Wed Jan 28, 2009 8:17 AM

Worth reading:

Plastic Discoloration in Classic Machines

And it's NOT reversible. You can remove the yellowing, but the methods have effects on the plastic itself too. Basically you cannot repeat bleaching techniques several times without the plastic getting more and more destroyed.


I dunno. Mimo's photos look pretty convincing.

#6 mimo OFFLINE  

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Posted Wed Jan 28, 2009 9:00 AM

I don't know if the process has been reversed, but the yellow has gone and that is what I wanted to achieve.
As for becoming more brittle, maybe so, but the aging process does that to plastic anyway (and my bones)

#7 Fröhn OFFLINE  

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Posted Wed Jan 28, 2009 9:10 AM

Worth reading:
And it's NOT reversible. You can remove the yellowing, but the methods have effects on the plastic itself too. Basically you cannot repeat bleaching techniques several times without the plastic getting more and more destroyed.

I dunno. Mimo's photos look pretty convincing.

Yes, but since it will yellow out again he will have to do it again, every time damaging the plastic a bit further. Do it several times and the plastic will break apart.

There are only two solutions which work for a longer time: Either paint the case or accept the yellow color.

#8 mimo OFFLINE  

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Posted Wed Jan 28, 2009 9:52 AM

Worth reading:
And it's NOT reversible. You can remove the yellowing, but the methods have effects on the plastic itself too. Basically you cannot repeat bleaching techniques several times without the plastic getting more and more destroyed.

I dunno. Mimo's photos look pretty convincing.

Yes, but since it will yellow out again he will have to do it again, every time damaging the plastic a bit further. Do it several times and the plastic will break apart.

There are only two solutions which work for a longer time: Either paint the case or accept the yellow color.

I understand that, but if I get 5-10 years before it happens again, that's fine with me. This is uncharted waters, so who knows how long before the yellowing is visible again. So far 5 months and not a sign.
Also I may paint the surface with a clear anti UV lacquer, as long as the paint stays on then I should be good until it's time to meet my maker or we run out of electricity.

#9 ProWizard OFFLINE  

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Posted Wed Jan 28, 2009 10:49 AM

In fact... I love the yellow color :s ... I love it that my atari looks old, and used.

#10 idavis OFFLINE  

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Posted Wed Jan 28, 2009 11:27 AM

Go ahead and continue discussing plastics, but can we all just agree to not let that Billy Mays guy see this? I can only imagine the late night infomercials "oxycute-ing" all the old classics...

#11 Tezz OFFLINE  

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Posted Wed Jan 28, 2009 11:42 AM

The Oxy process is THE best technique I've seen to reverse the yellowing. If you use a professional plastic polish with the UV filter additives after the bleaching process, it will lessen the yellowing from repeating again with UV exposure or at least slow it down. I use these type of products a lot in my day job.

Top job Mike, it looks mint.

Edited by Tezz, Wed Jan 28, 2009 11:43 AM.


#12 Fröhn OFFLINE  

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Posted Wed Jan 28, 2009 11:49 AM

There is also yellowing due to oxygen exposure.

#13 remowilliams OFFLINE  

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Posted Wed Jan 28, 2009 11:52 AM

I had read about this before, and the results are (to say the least) dramatic. My concern would be what kind of havoc is potentially being wreaked on the plastic itself though.

#14 sl0re OFFLINE  

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Posted Wed Jan 28, 2009 3:33 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)

Edited by sl0re, Wed Jan 28, 2009 3:39 PM.


#15 MEtalGuy66 OFFLINE  

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Posted Wed Jan 28, 2009 4:33 PM

Worth reading:

Plastic Discoloration in Classic Machines

And it's NOT reversible. You can remove the yellowing, but the methods have effects on the plastic itself too. Basically you cannot repeat bleaching techniques several times without the plastic getting more and more destroyed.


That article was written long before the guys on the english AMIGA board (former plastic engineers and chemists) came up with the peroxide/oxy solution.. If you read their explanation of the process, it makes sense from a chemical standpoint and it does in no way alter the chemical structure of the plastic. It merely reverses the chemical bonds in the SURFACE of the plastic that caused the yellowing in the first place.

And UV protectants are not necessary to keep the yellowing from returning.. Its the combination of UV and oxygen that causes the yellowing in the first place. So anything that seals the surface from the surrounding air will do just fine.. (eg. clear acrylic, etc.)

In fact, if you SCROLL DOWN and read the responses to that article you posted (its actually a blog,) you'll find this:

Merlin Says:

September 13th, 2008 at 9:16 am
This problem has been solved. I am a former industrial chemist and I have worked with rkauer (Hi Rogerio) of English Amiga Board, who is a plastics engineer. Respect to the guys at a1k.org for putting us on to this concept of using peroxide, we just fixed the process and put it on steroids….

You need hydrogen peroxide solution (at least 6%, the stronger the better), UV light (sunlight or a UV lamp) and some “Oxy” laundry detergent booster, any one with “Oxi Action” or “Oxy” in the title will do, the most famous one in the UK is Vanish Oxy Action. You add about 1/4 teaspoonful per gallon of the “Oxy” to the peroxide, immerse the pastic part to be cleaned and stick it under a UV source.

Does it work? Look here at these threads:-

http://eab.abime.net...ead.php?t=37808
http://www.vintage-c...ead.php?t=11877

So, how does it work? Well, as stated above, the oxygen links to the polybrominated phenyl ethers which were used as the flame retardant via a chemical bind similar to a co-ordinate bond, i.e. electron sharing. Bromine compunds are yellow / brown, does this sound familiar? It should….

The UV light bombards this bond and makes it unstable. At the same time, the TAED is undergoing reversible reactions with the peroxide, forming chemicals like peracetic acid and making free hydrogen atoms available.

This environment is enough to lever the oxygen from the bromine molecule and it gets replaced with a hydrogen; remember bromine is a negative halogen atom, just looking for a nice H+ to neutralise the odd free electron in the outer orbital. In effect, it re-caps the polymer chain.

This process continues and the oxygens get evolved as the gas, which is why you will see bubbles when you carry this out.

Does it work? Hell Yeah!! Check the threads, escpecially the Osborne 1 case treated in the Vintage Computer Forums thread. This was cleaned in about six hours under sunlight, this is mightily impressive…..

Once treated, if you clear coat the case with an acrylic matt lacquer this should stop the yellowing returning.

You can get 20% hydrogen peroxide solution from hairdressing trade supplies, in the UK they are chains like ‘Sally’. It can also be sourced as Urine Rescue as I believe it neutralises pet urine odours… ewwwww….

Now, for my next trick….


Edited by MEtalGuy66, Wed Jan 28, 2009 4:41 PM.


#16 Tezz OFFLINE  

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Posted Wed Jan 28, 2009 4:59 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....)

Coincidentally, I did a laptop in metalic blue too this week, it's a nice look. Do you have pics of the XL?

#17 Tezz OFFLINE  

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Posted Wed Jan 28, 2009 5:05 PM

Glad to read (and learn) that the process doesn't actually cause any damage to the plastic too. I'll not bother painting plastic again unless it's worn, scratched and/or damaged.

Edited by Tezz, Wed Jan 28, 2009 5:07 PM.


#18 sl0re OFFLINE  

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Posted Wed Jan 28, 2009 11:00 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....)

Coincidentally, I did a laptop in metalic blue too this week, it's a nice look. Do you have pics of the XL?


Not yet, but I'll snap one and put it up.

#19 Fröhn OFFLINE  

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Posted Wed Jan 28, 2009 11:07 PM

That article was written long before the guys on the english AMIGA board (former plastic engineers and chemists) came up with the peroxide/oxy solution.. If you read their explanation of the process, it makes sense from a chemical standpoint and it does in no way alter the chemical structure of the plastic. It merely reverses the chemical bonds in the SURFACE of the plastic that caused the yellowing in the first place.

I have yet to see a method which doesn't harm the plastic. The peroxide experiments I have seen also resulted in a significantly changed surface which already felt & looked a lot rougher than the original surface.

In fact, if you SCROLL DOWN and read the responses to that article you posted (its actually a blog,) you'll find this:

Without any proof and also without any mention of all the different plastics out there. They are not all the same and can react very different.

#20 MEtalGuy66 OFFLINE  

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Posted Thu Jan 29, 2009 12:20 AM

That article was written long before the guys on the english AMIGA board (former plastic engineers and chemists) came up with the peroxide/oxy solution.. If you read their explanation of the process, it makes sense from a chemical standpoint and it does in no way alter the chemical structure of the plastic. It merely reverses the chemical bonds in the SURFACE of the plastic that caused the yellowing in the first place.

I have yet to see a method which doesn't harm the plastic. The peroxide experiments I have seen also resulted in a significantly changed surface which already felt & looked a lot rougher than the original surface.

In fact, if you SCROLL DOWN and read the responses to that article you posted (its actually a blog,) you'll find this:

Without any proof and also without any mention of all the different plastics out there. They are not all the same and can react very different.


Really? According to all the guys I know who tried it, it doesnt change the surface at all. And theres tons of pictures and testimonials in the amiga forums on a1k.org, eab.abime.net, and amiga.org.. Your the very first person Ive ever heard say that it degrades the plastic in any way. Now, using chemicals like chlorine bleach, sodium hydroxide, etc.. are a different issue entirely.. But theres alot of vintage AMIGA guys that swear by the peroxide/oxy-catalyst/UV techniques, and I dont think theyd be repeating it on multiple pieces of hardware if it was causing damage to the plastic.. 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.

As far as the plastics being different, thats true.. The process is only designed to reverse the yellowing caused by oxidization of bromine based flame retardent additives in plastic. It may not work at all if the yellowing is resultant of some other agent/process.. Still, I have heard of all sorts of varying degrees of success with the process, by some pretty skeptical people.. And never have I read results that said it made the plastic rough, brittle, or otherwise degraded.. It simply either totally eliminated the yellowing, or not..

Edited by MEtalGuy66, Thu Jan 29, 2009 12:33 AM.


#21 sl0re OFFLINE  

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Posted Thu Jan 29, 2009 12:26 AM

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....)

Coincidentally, I did a laptop in metalic blue too this week, it's a nice look. Do you have pics of the XL?


Not yet, but I'll snap one and put it up.



Here it is.

800xl

#22 MEtalGuy66 OFFLINE  

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Posted Thu Jan 29, 2009 1:58 AM

Follow this thread for the very latest in devolopments on this process:
http://eab.abime.net...?t=37808&page=9

#23 mimo OFFLINE  

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Posted Thu Jan 29, 2009 2:27 AM

Follow this thread for the very latest in devolopments on this process:
http://eab.abime.net...?t=37808&page=9

Thanks Ken, that reply to your question sounds good to me.

Here is a link to a 130XE that has been done (not by me)
http://classic-compu...old-cases-2.htm

#24 Longhorn Engineer OFFLINE  

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Posted Thu Jan 29, 2009 2:43 AM

Thanks for the info Mimo! Going to do this on my SNES!

#25 Fröhn OFFLINE  

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Posted Thu Jan 29, 2009 4:08 AM

Really? According to all the guys I know who tried it, it doesnt change the surface at all.

Surface is rougher and definitely feels different and also doesn't get back it's original color but something much lighter.

Here a picture with peroxide:

vergleich.JPG
(from http://www.forum64.d...;postID=243748)

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.




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