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How to remove yellowing from an old Atari case


mimo

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When I did the 1200XL case, I ran it through the dishwasher first to get the plastics clean. I then did the de-yellowing and dishwashed again to remove the mixture after 8 hours. I would only use the 'Magic Eraser' on marks that don't come off with normal cleaning, magic markers, black marks, etc, and don't rub hard. The mark will come off with mild pressure. Also, make sure the 'Magic Eraser' is wet.

 

I started out today with a plan to do a few cases; a 800xl, 1050 and a power block. I was going to use sunlight for my UV, being here in central Florida, but with the reports of the mixture drying out during the procedure, I am going to use my black-light.

 

In prepping my cases, I did a first pass with the magic eraser and it actually did remove a lot of years of weathering from the plastic, though not the yellowing yet. I would recommend doing this step first, or does the Oxy accomplish the same results?

--Selgus

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I started out today with a plan to do a few cases; a 800xl, 1050 and a power block. I was going to use sunlight for my UV, being here in central Florida, but with the reports of the mixture drying out during the procedure, I am going to use my black-light.

 

In prepping my cases, I did a first pass with the magic eraser and it actually did remove a lot of years of weathering from the plastic, though not the yellowing yet. I would recommend doing this step first, or does the Oxy accomplish the same results?

--Selgus

 

the magic erasers are actually somewhat abrasive (basically a block of shredded melamine). i would not use them in this manner.

 

I usually start a good A8 cleaning with a trip through the dishwasher.

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Well, I've tried everything to get this white residue off, with no luck. So now it's time to start looking for a replacement case or non-functioning A8 computer. :(

 

If you're really going to scrap the thing, how about finishing the treatments until the color evens out, then cutting a portion of it in cross section to get a true comparison to the original color? That would settle the question of whether any bleaching is happening.

 

Edit: and on the subject of residue: have you tried soaking (for a good while -- not just a rinse cycle in the dish washer) in plain old hot water? It's entirely possible that the gunk you are looking at is leftover xanthan gum or oxy detergents that dried into powder in the sun. Those are water soluble.

Edited by AndyR
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Well, I've tried everything to get this white residue off, with no luck. So now it's time to start looking for a replacement case or non-functioning A8 computer. :(

 

If you're really going to scrap the thing, how about finishing the treatments until the color evens out, then cutting a portion of it in cross section to get a true comparison to the original color? That would settle the question of whether any bleaching is happening.

 

Edit: and on the subject of residue: have you tried soaking (for a good while -- not just a rinse cycle in the dish washer) in plain old hot water? It's entirely possible that the gunk you are looking at is leftover xanthan gum or oxy detergents that dried into powder in the sun. Those are water soluble.

 

 

I soaked it overnight in a mix of water and Mr.Clean Multi-Surfaces Liquid Cleaner. No improvement. Magic Eraser is the only thing that improved it at all. Here's a closeup photo, be sure to click on it to see it larger. Notice how the white residue is mostly in the pits and valleys of the A8's texture. If Magic Eraser could reach those areas, I'm sure it would remove it. Any ideas? Any chemicals I can use that would be safe on the plastic yet remove this?

img00281qm5.jpg

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Notice how the white residue is mostly in the pits and valleys of the A8's texture. If Magic Eraser could reach those areas, I'm sure it would remove it. Any ideas? Any chemicals I can use that would be safe on the plastic yet remove this?

 

OK, I'm switching sides now and agree with Merlin: I don't think you're seeing any bleaching of the case at all. The fact that the white discoloration concentrates in the crevasses is a really clear smoking gun that this is a solid deposit, and not a chemical effect.

 

And if it's a deposit, you want to remove it mechanically, not chemically. What you want isn't a cleaning solution, but just a brush. :) Try a tooth brush or something similar (soft plastic, something that won't scratch the case) on a small area, and work it until the deposit is removed. Adding a little water and soap will help to wash away the stuff you're scraping off. Then compare to the case color you want, and see if it matches.

 

I think the real failure mode here might just be: "If you have a textured case, don't let it dry out in the sun."

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AndyR:

 

I've tried a toothbrush already, many times. It just won't budge. It has a hell of a bond on the plastic. When the case is wet, it looks great, perfect color. But as it begins to air dry, the white residue shows once again.

 

 

yorgle:

 

The A8 has sat for a few years in my office, away from windows. The only thing I did to it was dust it occasionally.

 

Don't give up on me guys. I really want to salvage the original case. Keep the ideas coming.

Edited by MaXKiLLz
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OK then, let's think about what the white deposits could be....

 

TAED residue; this is alkaline and could be removed with white vinegar, as vinegar is acetic acid and definitely won't attack the plastic.

 

Xanthan Gum; try a mixture of warm water and alcohol, this should soften the gum up.

 

Perborates and Percarbonates, from the Oxy; these are salts and should be soluble in water. White vinegar may help again here.

 

Peracetic acid (an internediate breakdown product of TAED); a solution of washing soda (sodium carbonate) should be able to remove this.

 

Try these while I get my thinking cap on..........

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Hang on; don't take a knife to the case. I think I have just figured out what's happened here.

 

OK, the scenario was that you applied the gel, put the case outside and the gel dried out in the heat, yeah?

 

Now, what I think has happened is that the gel dried out into the textured surface and as it did so, the peroxide concentration went through the roof, due to water evaporation. The high concentration in the cracks has attacked the polymer and formed the hydroperoxide of the ABS plastic, this is the only explanation that fits with the mode of failure, as we kept the concentration in the gel deliberately low to avoid just this scenario.

 

Now you start to get an idea of why we really recommend a black light....

 

@ AndyR

 

I would appreciate your comments on the diagnosis.....

 

Now, unfortunately, the polymer degradation cannot be reversed, but as you stated that the white deposit disappears when you wet the case, my thoughts are that if you coat the case with a clear acrylic lacquer, it will mask the white deposit and also seal the case and prevent any further degradation. It has to be worth a try and an aerosol can of lacquer is going to be way cheaper than replacing the A800. It's worth a couple of dollars to find out.

Edited by Merlin
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Hang on; don't take a knife to the case. I think I have just figured out what's happened here.

 

OK, the scenario was that you applied the gel, put the case outside and the gel dried out in the heat, yeah?

 

Now, what I think has happened is that the gel dried out into the textured surface and as it did so, the peroxide concentration went through the roof, due to water evaporation. The high concentration in the cracks has attacked the polymer and formed the hydroperoxide of the ABS plastic, this is the only explanation that fits with the mode of failure, as we kept the concentration in the gel deliberately low to avoid just this scenario.

 

Now you start to get an idea of why we really recommend a black light....

 

@ AndyR

 

I would appreciate your comments on the diagnosis.....

 

Now, unfortunately, the polymer degradation cannot be reversed, but as you stated that the white deposit disappears when you wet the case, my thoughts are that if you coat the case with a clear acrylic lacquer, it will mask the white deposit and also seal the case and prevent any further degradation. It has to be worth a try and an aerosol can of lacquer is going to be way cheaper than replacing the A800. It's worth a couple of dollars to find out.

 

Sound like a very possible explanation. I'll just accept what's happened and move on. I will try to spray on some laquer. Another thing I may do is try to obtain another A8 and just give this one to a childhood friend of mine who threw his away years ago. He usually doesn't mind things like this. I, on the other hand, with my OCD... Well, you know. I should have just left it alone in the first place. I hope others can learn from my misfortune. That's the only positive that can come out of this.

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I think the lacquering of the case will fix this issue for you, OCD or not. If it looks right afterwards, accept it and don't go beating yourself up about it. Unless stuff like this happens we don't learn, but this hasn't been the disaster it could have been.

 

Do you mind if I use that picture as part of the Wiki, so that I can warn people about this?

Edited by Merlin
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I think the lacquering of the case will fix this issue for you, OCD or not. If it looks right afterwards, accept it and don't go beating yourself up about it. Unless stuff like this happens we don't learn, but this hasn't been the disaster it could have been.

 

Do you mind if I use that picture as part of the Wiki, so that I can warn people about this?

 

Yes, please use it.

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Just a thought, there are dyes for automotive interior plastics that vinyl that work extremely well and there are quite a few colors available. Google Eastwood automotive products and see what they have. My thinking is that if you were to find a close color match, spray it onto a rag and then rub down the case with it like you would apply a stain to wood. Because the majority of the case is high spots, even if the color was a little off, it probably wouldn't matter because only the low spots would actually get dyed.

Edited by yorgle
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Hi Guys,

 

I usually inhabit the Vintage Computer Forums, where Merlin has done a sterling job making us aware of this new technique.

 

I’ve carried out a few de-yellowings with my collection, all of them very successful. I’ve used a modification to the paste recipe, which included low concentration peroxide, Arrowroot food thickener rather than gum, and no glycerine.

 

Details are at http://classic-computers.org.nz/blog/2009-...ng%20recipe.htm

 

Like MaXKILLz I’ve let mine dry in the (hot) summer sun. I never saw any damage at all to my cases. The only negative thing I found was that labels could fade a little.

 

As far as a 6% peroxide SOAK is concerned (as opposed to the gel), BADLY discoloured keys could come out "streaky" and key markings could fade a bit after a long (3 day) soak. Probably overcooked. They still looked better than they used to though.

 

Regarding MaXKILLz’s result none of my units processed thus far were really textured. However, I tend to favour the “deposit” theory rather than the chemical change one. I would doubt if it was bleaching from the peroxide. I had a brown Atari 130XE which I returned back to grey through the process. No sign of whitening whatsoever, and the painted unit sat out in the hot sun for at least 2 days. A number of times, the paste completely dried up (in theory concentrating the peroxide). No bleaching whatsoever. (However, I did use only 6% hydroxide for starters AND they weren't textured cases).

 

Anyway, good luck with figuring out what happened here. This is a new technique and we are learning all the time. In the meantime it probably is worth avoiding the hot sun with textured cases. Until more is known, a blacklight might be safer.

 

Tezza

Edited by tezza
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Well, by using a combination of the green, scrubbing side of a Scotch-Brite sponge and following it up with Magic Eraser, I've almost got the case back to a usable condition. It's amazing how tough this plastic is. The problem now is the bottom half of the case, which hasn't been treated. It's completely mismatched compared to the top. Which means, I'm going to have to treat the bottom even though I don't want to go through this problem again. This time I'm going to use only Peroxide and Xanthan under a UV light on a small area first. Let's see what happens.

 

sponge_heavy_duty.jpg+ eraser_product.jpg

Edited by MaXKiLLz
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Again this is really good info to restore our machines.

 

A few points not well covered.

 

1) What store do you get H-Peroxide greater than 3%? I mean a main-stream stores like Walgreens, Longs etc. Not some special little outlet store that is only in your town. I've looked in a couple 'Beauty Supply' stores, and all they have H-Peroxide mixed with other hair care stuff in the bottle; ie alcohol, binder, soap, etc.

 

2) When using the gel formula with a black light, indoors; do you get the gel dry out. Do you re-apply as the gel starts to dry out? Or must it stay very wet during the process?

 

3) What would be a good container to hold the gel mixture for longer storage (before Oxy is added)

 

Thanks

KLund1

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1) What store do you get H-Peroxide greater than 3%? I mean a main-stream stores like Walgreens, Longs etc. Not some special little outlet store that is only in your town. I've looked in a couple 'Beauty Supply' stores, and all they have H-Peroxide mixed with other hair care stuff in the bottle; ie alcohol, binder, soap, etc.

 

Not sure about stores in other parts of the world but here in New Zealand I got the 6% H2O2 from a pharmacy. It was sold in unadulterated form as a hair bleach.

 

Tez

Edited by tezza
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Don't ask for hair 'bleach'. In a hair products store, it is called 'developer'. Here are the numbers you need to be aware of.

 

10vol=3% peroxide

20vol=6% peroxide

30vol=9% peroxide

40vol=12% peroxide

50vol=15% peroxide

 

I have been using the 40vol (12%) and it works great. It has been suggested not to use stronger than 15%, so a 30vol or 40vol developer would probably be the best range.

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For those in the US looking for a source of high-concentration peroxide, I found this site:

 

http://rebekahspureliving.com/index.html

 

They're a health supplier selling 35% (!!?!) peroxide for use in applications like replacement of household chemicals, disinfection, and "oxygenating the body" (sigh...). But it seems legitimate as far as I can tell.

 

And they're comparatively cheap. I ordered a gallon for $39. As they explain, regulations prohibit shipping this stuff cross-border, so this is useful only to folks in the USA. I'll let folks know how it turns out.

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Hi All,

 

 

 

Looooooong time reader, first time poster. :ponder:

 

I thought I'd share my experiences with this de-yellowing process, as the pictures will tell...

 

c64ywl.jpg

 

 

1 x a horribly Yellow C64

 

S5000182.jpg

Materials used 3/4 cup Peroxide @12%, 1xTbs ArrowRoot, I x TeSp Glycerin, 1/4 TeSp Oxy

 

 

 

 

S5000187.jpg

The result after 2 days. Approx 3 hours each day with very intermittent sun (here in the UK)

 

 

 

Conclusion:-

 

 

 

Although it's definitely better, I was hoping for a more "even colour finish"

 

I might give it one more go to see if it will loose some of the blotchiness

 

but I get the feeling it might make things worse.

 

 

 

This may be a better process for "whiter plastics", which I will try soon

 

Hopefully we will get some longer periods of sustained sunshine.

 

 

 

I think I'll leave my treasured Atari 400's / 800's well alone for now.

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The result after 2 days. Approx 3 hours each day with very intermittent sun (here in the UK) [...] Although it's definitely better, I was hoping for a more "even colour finish" I might give it one more go to see if it will loose some of the blotchiness but I get the feeling it might make things worse.

 

To be fair, I don't think any of the "good" results posted so far have been after only 6 hours of intermittent sunlight. What you have looks to me (and remember, I'm a skeptic) like just an unfinished piece.

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