How to remove yellowing from an old Atari case

[Tempest]

The blotcheness I'm seeing in some of these pictures worries me. What causes that? Uneven applciation of the gel or is it just bad luck?

 

Tempest

[Olds-kool gamer]

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.

 

That's why I said I may give it one more go.

I'm sorry if my attempt did not meet-up to "your expectations"

You "being sceptical" does not change the results, which are there for all to see.

Edited February 19, 2009 by Olds-kool gamer

[Longhorn Engineer]

I bet it is because of the paste. (blotcheness that is) The paste is probably hard to get an even coat over the case thus some areas will dry out and the concentration will rise there. Seems the best solution is just to soak it in a bath. Once I get the time I will do the bath method on a gross SNES I have. (must ship out A/V mods )

[Olds-kool gamer]

The blotcheness I'm seeing in some of these pictures worries me. What causes that? Uneven applciation of the gel or is it just bad luck?

 

Tempest

 

I would guess there may be many factors at work here e.g.

 

The strength of the Peroxide.

The Amount of UV exposure.

The correct proportions etc.

The master batch mix of the plastic.

 

I don't really know. All I can say is what I've experienced.

 

As I've previously mentioned be careful and try do a test area first.

 

I will try on some whiter pieces to see and post my results (if people are interested)

[MaXKiLLz]

When I did the top half from my Atari 810 case, I submerged it completely in 3% peroxide for two days using a combination of UV lamp at night and sunlight in the day. Cam out pretty even. Funny thing is, there was one corner that floated up and was in the direct sunlight. That area ended up with white residue baked on and almost impossible to remove. For future projects I will try only 30 or 40 volume + UV lamp. Nothing else and see if results are better.

[Tempest]

I was planning on doing this in a windowless room in my basement using a UV Lamp. That way I should get even coverage and hopefully it won't dry out as easily.

 

Tempest

[AndyR]

I would guess there may be many factors at work here e.g.

 

The strength of the Peroxide.

The Amount of UV exposure.

The correct proportions etc.

The master batch mix of the plastic.

 

As I mentioned earlier, I think the determining factor with your piece was simple length of exposure. This reaction seems to have a half-life behavior (i.e. the chances of any single bromine reacting are low, and not limited by the concentrations of any of the reactants or catalysts). Not all of your case is getting the same concentration of reactants (UV especially, as some areas are shadowed, etc...), and the original yellowing wasn't likely to be even either.

 

So each area of yellowing "decays" at the same half life, which mathematically means that the differences between them are getting larger early in the exposure process. But after time, they all settle to the same asymptote as the bromine atoms are pulled off. At least in principle, anyway. Clearly no one understands this completely yet.

 

But the point is that this takes time and reactants, and you don't seem to have given it very much. Specifically, if your sunlight wasn't direct, you're getting much, much less UV than the examples from the desert southwest.

[tezza]

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.

 

I'd agree with that. Weak and intermittent sunlight is likely to have low levels of UV especially in the UK in the winter.

 

I'm interested in how you made the recipe up? Did you get a good thick paste? I've used Arrowroot for all my treatments but it has to be heated in order for it to thicken. There is no need for glycerine (see http://classic-computers.org.nz/blog/2009-...ng%20recipe.htm ).

 

My advice is not to stop with the C64. It just seems unfinished. I'm sure more treatment would result in a better result.

 

Could the patchiness be a result of uneven application? I used the sun for my UV source but it was strong New Zealand summer sun with the highest UV levels in the world. I also rotated the units now and again so all the surfaces were full-on to the sun for a similar amount of time.

 

Tez

[Olds-kool gamer]

I would guess there may be many factors at work here e.g.

 

The strength of the Peroxide.

The Amount of UV exposure.

The correct proportions etc.

The master batch mix of the plastic.

 

As I mentioned earlier, I think the determining factor with your piece was simple length of exposure. This reaction seems to have a half-life behavior (i.e. the chances of any single bromine reacting are low, and not limited by the concentrations of any of the reactants or catalysts). Not all of your case is getting the same concentration of reactants (UV especially, as some areas are shadowed, etc...), and the original yellowing wasn't likely to be even either.

 

So each area of yellowing "decays" at the same half life, which mathematically means that the differences between them are getting larger early in the exposure process. But after time, they all settle to the same asymptote as the bromine atoms are pulled off. At least in principle, anyway. Clearly no one understands this completely yet.

 

But the point is that this takes time and reactants, and you don't seem to have given it very much. Specifically, if your sunlight wasn't direct, you're getting much, much less UV than the examples from the desert southwest.

 

 

I appreciate your comments (as far as I understand the process) my exposures times were stated as approximate. This piece was placed out-side from about 08:00 to 12:00 (midday) with about 3 hours of direct sunlight each time.

 

What I cannot understand is the level of colour bleaching / whitening (for the want of a better word)

 

I will give it one more round but it has already lost the "Commodore beige" that I was hoping to achieve.

[Olds-kool gamer]

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.

 

I'd agree with that. Weak and intermittent sunlight is likely to have low levels of UV especially in the UK in the winter.

 

I'm interested in how you made the recipe up? Did you get a good thick paste? I've used Arrowroot for all my treatments but it has to be heated in order for it to thicken. There is no need for glycerine (see http://classic-computers.org.nz/blog/2009-...ng%20recipe.htm ).

 

My advice is not to stop with the C64. It just seems unfinished. I'm sure more treatment would result in a better result.

 

Could the patchiness be a result of uneven application? I used the sun for my UV source but it was strong New Zealand summer sun with the highest UV levels in the world. I also rotated the units now and again so all the surfaces were full-on to the sun for a similar amount of time.

 

Tez

 

 

Hello Tez,

 

Thanks for your input, it was reading your Blog that gave me the desire to try this out.

(I was the guy who commented on your C64 Keyboard repair)

 

Re: uneven application.

I have read every page from your Blog, Vintage computer, EAB and of course this forum so I was very careful to follow the proportions and application to the letter. The mix I used was, as previously mentioned:-

 

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

 

 

Looking very closely at the cabinet the lighter areas seems to have gone very pale, as if the colour pigment has been removed. I tried it on an old C64 cabinet just in case something went wrong. I will do the C2N cassette deck and see what happens.

[Merlin]

@ Olds-kool gamer

 

I hit the C64 that's in the Retr0brite Wiki with 35% Peroxide, Xanthan Gum and Glycerine, with 1/4 teaspoonful Oxy; mine showed no signs of patchiness after 8 hours exposure. The gel I used foamed up as it worked. You are nearly there, stick with it....

 

The grey colour you are seeing is the colour Commodore intended it to be; believe it or not, it actually went slightly beige during the moulding process, which would have been at upwards of 130 to 150 Centigrade, purely because of the amount of Brominated material in the plastic.

 

@ KLund1

 

I would recommend a glass or plastic jar, preferably dark coloured; DO NOT add the Oxy until you are about to use it, I cannot stress this enough. Activated gel in a container will pressurise and burst it.

 

@ AndyR / Tezza

 

Thanks for helping me out here; sometimes, I can't answer the questions fast enough!!

[tezza]

Oh hi! (-:

 

Hmm... Yes, I'm concerned that it went whiter than it should. That certainly never happened to any of mine.

 

It's not quite the same recipe as I used though. I used 1/2 the concentration of perxoide (6%), more Arrowroot (about two heaped tablespoons) and no glycerine. I stirred in the arrowroot until it was free from lumps, then heated in a microwave. If you get the timing right, it forms a nice, thick, gel. With a 750W microwave check after 30 seconds, stir, then give it another 15 sec, stir and then few more seconds if needs be. Less time with a more powerful oven. If it's too thick, vigourous stirring will thin it a bit. Don't overcook it though.

 

There is a typo on the wiki I've asked Merlin to correct (hopefully he will do it today) which talks about a pint of peroxide. Actually it was only 1/2 to 2/3 of a cup. If you want to do this again, check the blog recipe I gave in the posting for the authoritive source, at least at the moment, until the wiki is corrected.

 

I wonder if...

 

* The ultrawhitening is due to peroxide being too concentrated in this method (maybe?), or some interaction between the Arrowroot and glycerine (unlikely). Or it could be just perception that it's whiter than is should be because it's blotchy.

 

*The patchiness is due to the paste being too thin due to too little Arrowroot, and therefore not even (was it thin? It should have been quite thick).

 

I've generally found it doesn't hurt to overdo the Arrowroot rather than to have too little. Too little and the mixture is too thin. It DEFINTELY needs heating though.

 

I'll be doing another case soon. This has black areas I'll have to try to avoid, as it's shown paste on these can lighten/blotch these areas. I'll post some pics.

Edited February 19, 2009 by tezza

[Merlin]

@ Tezza

 

I'll correct the Wiki tonight mate; I presume that your cup is about 250ml or so, making your mix about 200ml or around 1/2 pint?

[KLund1]

How do you keep the gel/paste wet for the 24 or so hours it take the formula to do it's work?

[Olds-kool gamer]

@ Olds-kool gamer

 

I hit the C64 that's in the Retr0brite Wiki with 35% Peroxide, Xanthan Gum and Glycerine, with 1/4 teaspoonful Oxy; mine showed no signs of patchiness after 8 hours exposure. The gel I used foamed up as it worked. You are nearly there, stick with it....

 

The grey colour you are seeing is the colour Commodore intended it to be; believe it or not, it actually went slightly beige during the moulding process, which would have been at upwards of 130 to 150 Centigrade, purely because of the amount of Brominated material in the plastic.

Hello Merlin,

 

 

Thanks for the above, I've read all your posts and in quite a few forums too!

I will give it another application.

 

Trouble is, were not getting the optimal amount of sun shine but the sun has to be better then a UV bulb.

 

I was totally gob smacked when I first read about this process so believe me I "really" want it to work.

 

I will post back the results as soon as possible.

[tezza]

@ Tezza

 

I'll correct the Wiki tonight mate; I presume that your cup is about 250ml or so, making your mix about 200ml or around 1/2 pint?

 

Err...yes it's about 200 mls. Is that 1/2 pint, or less? It's a long time since I visited the UK, so I'm just trying to visualise in my head the size of the pint of beer. I consumed quite a few of these when I was there, but (perhaps understandably) I don't remember much about it (-:

 

Tez

[+Guitarman]

Trouble is, were not getting the optimal amount of sun shine but the sun has to be better then a UV bulb.

 

IMHO, a UV light will probably give you better results, just because it removes the heat factor. Plus, a solid UV bulb will be better than patchy sunlight.

[tezza]

How do you keep the gel/paste wet for the 24 or so hours it take the formula to do it's work?

 

For me it took a bit of managing. In the hot NZ sun, the paste would dry out in about 30 mins. It kind of formed a "scale" or large flakes over the case. You can see what it looked like here. I didn't apply another coat immediately it was dry (this was just unmanagable) but each unit did get a re-application about 3 to 4 times a day. I just painted over the scale (actually most of it flaked away as I was painting). I also rotated the physical positioning of the computers while I did this. In other words, if one side had been out of the sun, I turned the case around so it WAS in the sun.

 

Even with the strong sunlight, one day usually wasn't enough. Most units got two days. The Atrari 130 XE got a third day several days after the main treatment, as I'm sure I could still see a tinge of yellow/green on one side (the extra day's treatment fixed that).

 

The VIC-20 seemed fully done after one day. This was quite remarkable as there was cloud cover that day and it was actually quite dull! However, the paste didn't dry so quickly either which perhaps contributed to the great result.

 

I used the sun (and Arrowroot), as I was looking for a method someone could use with a minimum expense i.e. without buying hard-to-get/find products or investing in a blacklight, setting up a room etc. . Really for people like myself who had less than 5 machines that needed the treatment, with no one machine being particularly rare or valuable.

 

However, if I had lots of cases to do, or they were very valuable machines I would have explored the blacklight option rather than the sun, simply because you can control the variables much better. Horses for courses I guess.

 

I'd be interested to hear of any results with the Arrowroot variation of the recipe and Blacklight exposure as opposed to sunlight. Anyone tried this, or intend to try it?

 

Tez

Edited February 19, 2009 by tezza

[Olds-kool gamer]

Trouble is, were not getting the optimal amount of sun shine but the sun has to be better then a UV bulb.

 

IMHO, a UV light will probably give you better results, just because it removes the heat factor. Plus, a solid UV bulb will be better than patchy sunlight.

 

 

I would prefer not to do it outside, as it dried out quite fast so I had to re-apply the paste a couple of times. At least with a bulb you have "more control" but I wanted to be confident all was well before I purchased a good quality UV bulb.

 

Just checked the forecast (London, UK) and it don't look too good in the way of constant sunshine.

[+Guitarman]

I don't use a blacklight. I use a reptile UV bulb, but I could get some arrowroot and try it on my next case.

[Merlin]

I would prefer not to do it outside, as it dried out quite fast so I had to re-apply the paste a couple of times. At least with a bulb you have "more control" but I wanted to be confident all was well before I purchased a good quality UV bulb.

 

Just checked the forecast (London, UK) and it don't look too good in the way of constant sunshine.

 

How do you think I get on in the Rainy City? I've seen a big yellow thing once or twice in the sky but I thought it was a UFO; I'll stick to my energy-saving UV bulb I think....

 

Edited February 19, 2009 by Merlin

[MaXKiLLz]

I'm trying a mixture of 4 ounces of Sally 30 Volume and 1/4 Teaspoon of Xanthan Gum under a Black light, on the bottom half of my A8. No Oxy and no Glycerine. If this doesn't work, I'll try the complete mixture again including the Oxy and Glycerin, but no Sun, just Black light. I don't want to encounter another mess like the top half of my A8.

Edited February 19, 2009 by MaXKiLLz

[Olds-kool gamer]

How do you think I get on in the Rainy City? I've seen a big yellow thing once or twice in the sky but I thought it was a UFO; I'll stick to my energy-saving UV bulb I think....

 

Yes but your probably surrounded by 100 acres of lush Green country side with bucolic vista's as far as the eyes can see…

 

Me thinks it's time to buy a bulb although I've read quite a few recommendations which is the best types but there seems to be no confirm consensus on one particular type...

[+Guitarman]

As far as a bulb, I am using a standard lamp type florescent UV bulb for reptile use. It has both UVA and UVB. They are available in different strengths. After using the bulb, I will probably go to the UV tube type, just because it will give better coverage. The bulb is very centralized.

[KLund1]

KLund1 from CA USA again.

Got some "developer' from a beauty supply store (went to 5) to use for my h-peroxide. But I want to make sure this will work. It is not pure h-peroxide. It is white colored, and already thickened. All the places I went to have about the same thing. It is called 'Dioxygen Cream Developer" 40 volume Stabilized cream peroxide . 16 fl. oz. Ingredients: (no %, but list in order) deionized water, h-peroxide, decyl oleate, cetly alcohol, cetearyl alcohol, PEG-40, caster oil, sodium cetearyl sulfate, propyl paraben.

It is already pretty thick. It seems to me, all I need to do with this is add the Oxy, mix well, paint on Atari case, and turn on the florescent black light I have from the 70's (still works). But will all the other ingredients melt my Atari case? I'd rather not be a test subject for this. I saw earlier that there were some posters with chemical backgrounds. Any thought, suggestions?

KLund1

ps got my long yellow rubber gloves, old clothes, and goggles ready...