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Removing Yellowing from Plastics - Part 3

As I understand it, Oxygen is released by the reaction and that might cause problems if the case is tightly wrapped up.

One thing I would like to know though, is if cling film lets through UV ok. If so, then placing the case in a tray and sealing the top of the tray with cling film (maybe with one or two small holes to allow any O2 to escape) might be a good way to prevent drying out.

Tez
 
Tezza,

For the amounts we are talking about, I don't think the holes would be needed. Clingfilm, or even a large clear plastic bag taped shut, should be fine; all you are simulating is immersion of the part as if it were a tankful of liquid; either way you are preventing evaporation.

I must admit, the ideas that are coming out of this work are awesome; there must be loads of frustrated inventors our there......;)
 
Fantastic

Fantastic

Hello!

Just wanted to say I picked up this thread in the comp.sys.apple2 group when someone mentioned the wiki.

Fantastic work to everyone involved! So very very cool. I've been collecting a number of things out of storage for the last few months and had many cases that I wanted to restore.

Funny that I've been trying everything under the sun (with no success) and here you have the solution(s)!

Can't wait to give it a try this weekend on a terribly yellowed Apple IIe. I'll be sure to document everything and send it your way.

Thanks!

C
 
Welcome!

If it's Apples you want to clean, then Tezza and Krye are your mentors, as they have cleaned several Apple machines of varying vintage and have learned their little foibles.

:mrgreen:
 
As I understand it, Oxygen is released by the reaction and that might cause problems if the case is tightly wrapped up.

Tez

You're correct Tezza - when is first started using the liquid only solution, I had it in a Tupperware type container with the lid on it. After a couple hours I went out to stir it, and the lid almost popped off with all the pressure that had built up. If I'd left it a couple hours more, I'm sure the lid would have blown off. (I remember mentioniong this back in Part 1, but I'm not going to back look!).

I would recommend some holes in the cling warp, although if it's just a rubber band around the top securing the cling wrap, the gas will probably escape around the edges.
 
I've finished my trial with the c-64 case. The results showed damage could occur if paste is allowed to dry out for a long period under the hot sun. The full writeup is here.

I've now got a UV lamp and have made a de-yellowing chamber using a large storage box. I added water to the bottom of the box, put cling film over the top and found the paste stayed wet for over 8 hours! This surely is the way to go.

2009-03-22-de-yellowing-humid-chamber.jpg

Tez
 
Last edited:
I've finished my trial with the c-64 case. The results showed damage could occur if paste is allowed to dry out for a long period under the hot sun. The full writeup is here.

Tez

After reading this and your writeup, and thinking about the patchiness problem, I started wondering if maybe it could be the Oxy that hasn't dissolved enough. I've been dissolving mine (recently) in hot water before mixing it, but I wasn't doing that before. If there's a concentration of Oxy in the paste, could that possibly be a cause for the bleached looking spots?
 
After reading this and your writeup, and thinking about the patchiness problem, I started wondering if maybe it could be the Oxy that hasn't dissolved enough. I've been dissolving mine (recently) in hot water before mixing it, but I wasn't doing that before. If there's a concentration of Oxy in the paste, could that possibly be a cause for the bleached looking spots?

I was following your recipe of dissolving it first in hot water, so I'm not convinced it's that. I think it's more likely that with a combination of heat, and drying out under a "film" (espeically with the arrowroot), the preoxide gets to very active levels on the surface of the plastic. It then bleaches. Probably unnoticable when a case is white or cream, but not when it's beige or grey.

Some plastics might be more susceptible than others. My Atrari 130XE is a grey case and there is no sign of patchiness at all?

Now I have a humid treatement "chamber" and a UV light, it would be good to repeat the experiment with another brown c-64 case. I'm picking de-yellowing (or in this case de-browning) would be a lot more even.

Unfortunately I don't have another brown C-64 case.

Tez
 
A new convert to the Retr0bright religion

A new convert to the Retr0bright religion

I did it!
It works!
I ran a batch of Apple parts through the process today (for the first time) and got GREAT results! Most of the parts were perfectly restored. A couple (which were really yellow) are not perfect, but certainly not yellow any more. No problems with blooming or other discolorations.

A major goof was not to take before and after pictures! I won't do THAT again!

A couple of key points:
For UV I used a sun lamp at about 18" (perhaps half a meter) from the parts.
I got H2O2 from a Sally Beauty shop here in Michigan. By happenstance I got a "40 solution cream rinse". A 40 solution is about 12 percent Hydrogen Peroxide, I'm told. The cream rinse means that it's already thickened! It brushed on and stayed on quite well.
I gave the parts about 6 hours of exposure.
A major nuisance is that the parts dried out quite quickly. I responded by going over the parts and freshening the paste at about half hour intervals. A side benefit is this allowed me to re-position them to face the UV from all sides.

I will try another batch this week. This time I will try a bin of water covered by clear plastic wrap.

Thanks for letting me report my experiences!


() ()
Rich ('-')
 
I went out shopping for supplies today to give this a go. I managed to pick up 1 litre of 35% H2O2 for the princely sum of €8 from a friendly chemist's shop. Xanthan gum was harder to find and most of the online suppliers wanted silly money for shipping. In the end I ordered 200g of the stuff from a supplier of ingredients for making your own cosmetics, of all things.

Spent a few minutes setting up the de-yellowing chamber (you've coined a phrase there, Tez) in the utility room. The lady of the house is of course over the moon that I've managed to commandeer yet another room in the house for things computer-related ;-)

In preparation, I also stuck a C64 case in the dishwasher. Strangely enough, it has actually de-yellowed quite nicely where some drips were clinging to it when it came out. Maybe something in the dishwasher detergent? I may just dissolve a tablet of that stuff in water and see if it does anything de-yellowing-wise.
 
In preparation, I also stuck a C64 case in the dishwasher. Strangely enough, it has actually de-yellowed quite nicely where some drips were clinging to it when it came out. Maybe something in the dishwasher detergent? I may just dissolve a tablet of that stuff in water and see if it does anything de-yellowing-wise.

After reading this, it immediately popped in my head that perhaps the yellowing on your case is nicotine or something that doesn't necessarily change the case's chemical composition? I could be wrong, but it would make sense. Then again, maybe the phosphates or something in dishwasher detergent have an effect?

--Ryan
 
I did it!
It works!.....

A couple of key points:
For UV I used a sun lamp at about 18" (perhaps half a meter) from the parts.
I got H2O2 from a Sally Beauty shop here in Michigan. By happenstance I got a "40 solution cream rinse". A 40 solution is about 12 percent Hydrogen Peroxide, I'm told. The cream rinse means that it's already thickened! It brushed on and stayed on quite well.

Good one!

I've heard about this paste from another forum. Sounds like it might be ideal!

About the lamp though. "Sun lamp"? I'm not familiar with that term? Does it give out heat as well. If so, I wonder if that contributed to the quick drying out? Sealing it in a de-yellowing chamber might be the answer but it the light gives out heat, don't put it too close to the plastic wrap.

My UV light gave out very little heat. I wonder if your lamp is more infra-red than UV?

Anyway, congratulations on a succesful restoration.

Tez
 
After reading this, it immediately popped in my head that perhaps the yellowing on your case is nicotine or something that doesn't necessarily change the case's chemical composition? I could be wrong, but it would make sense. Then again, maybe the phosphates or something in dishwasher detergent have an effect?

--Ryan

Hmm..could be some release of H2O2 going on there, which when combined with the high temps in a dishwasher does something?? For the process to work though, UV is essential yes? Not much of that in a dishwaster unless there are particularly fancy ones in Holland which also gives the plates an antibacterial zap. :)

As I understand it, heat won't do it alone. Is that right Merlin?

Certainly I wouldn't surprise me at all if some yellowing at least isn't just plain old nicotine stains.

Tez
 
Pitfalls and Lessons learned

Pitfalls and Lessons learned

About the lamp though. "Sun lamp"? I'm not familiar with that term? Does it give out heat as well. If so, I wonder if that contributed to the quick drying out? Sealing it in a de-yellowing chamber might be the answer but it the light gives out heat, don't put it too close to the plastic wrap.

It is a large, spot-light type bulb that gives off high amounts of UV light. Quite a bit of heat, too, although at the distance I had it I didn't think it was heating much... some perhaps. (Memo to self; measure temperature on next attempt)

A surprising side-effect, though, is that I woke up this morning with a mild sun-burn on the left side of my face from all the work I did yesterday! (another memo to self)

I am in need of suggestions, though. Several of the pieces that I want to do are large and boxy (Apple IIGS CPU and a monitor, for example). I haven't figured out how to expose them to UV except for 6 hour exposure on each side. That would be six days of treatment! (Maybe five... the base is likely OK. Maybe I need five sun lamps!

I'll also be posting to the newsgroup "comp.sys.appleii".

. () ()
Rich ('-')
 
You are right Tezza; heat on it's own won't cut it, although above 40C, the perborates and percarbonates will start to break down on their own to release peroxides, so a partial result inside a dishwasher is possible.

Note to Rich113:

If one side of your face is tanned, please be careful regarding your eyes. High levels of UV and eyes don't mix and could lead to cataracts.
 
A dishwasher has heat and mechanical motion, plus don't most washing liquids have oxyclean type chemicals in them?

I know that just scrubbing old cases with water, a scrubber, and dishwasher soap with oxy does lighten up the cases a bit.

If you every seen a dentist do a whitening job they use peroxide based solutions and a UV light don't they?
 
New Techniques

New Techniques

please be careful regarding your eyes. High levels of UV and eyes don't mix and could lead to cataracts.

Good counsel! I tend to be a little cavalier about these things, but eyes (or even damage to skin) is nothing to be cavalier about.

I tried something new on Monday; I used some plastic wrap, but instead of covering a "deyellowing chamber" with it, I covered each piece separately. I slathered each piece with the 'cream mix' I'm using, then covered it with plastic wrap just as one might seal up some food for storage. Seemed to work well... the cream didn't dry out (although I opened it up at the half way point and refreshed it) and the UV easily penetrated the plastic wrap.

About the UV; two thoughts:
1) Distance from the UV light is important. For Monday's treatment I had the lamp more like a meter away from the parts. One was just OK, and two of them were much improved, but not satisfactory after six hours exposure. Output diminishes by the square of the distance, afterall. They'll get a second treatment today.
2) UV penetrates amazingly. It takes strong UV blockers to stop skin damage (will even penetrate a cotton T shirt). I'm confident the UV pentrates the opaque cream I'm using and sundry other mixes, unlike visible light.

I'm off to redo some parts today (March 31) and start some other parts. I think I'll do two batches; one with the Sun lamp and one with a black light.

I welcome suggestions on large blocky items (cpu cases and monitors) and I'll report back on my results!

Rich
 
Halogen Bulbs

Halogen Bulbs

Has anyone experimented with Halogen Bulbs as their UV light source? They seem to be more readily available than either fluorescent blacklights or Sun lamps and I was thinking of a five lamp array to get at a case from five sides at once.

A quick Google search suggests that the high-temperature halogen bulb does emit UV light, but I have no idea what spectrum nor how strong the UV light might be.

Any thoughts?

Rich
 
Does any of the swedes here have a shopping list for swedish equivalents of the retr0bright ingredients? I have no idea what Xanthan Gum is, or Oxy laundry booster for that matter. My laundry skills go about as far as using a different powder for color/white laundry and I usually throw in some softener as well...
 
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