Retr0Bright: Does re-yellowing occur even in the absence of UV light?

[PDP7]

Hi,

I would wonder if it is actually the UV causing the problem originally or with trated items re-yellowing. I've noticed that white paint where covered goes quite yellow, but that areas not covered stay white. Do we have a similar situation with treated plastic ?, covering it up reducing air exchange actually promotes the yellowing.

Mike.

 

[tezza]

Early 2011, I treated some items:

1. Microwave oven door - Retr0bright gel
2. CD-ROM case bezel - generic oxy cleaner from supermarket
3. Microsoft Mouse - generic oxy cleaner from supermarket

Re item 1. Retr0bright gel. The door has definitely regressed. It is now very patchy, half of the patches are one shade of yellow, and the balance of patches are a lighter shade of yellow. Two years ago, I never did completely get rid of the yellow, but I got the colour down to a very very light yellow, and patch-less, enough for me to put off buying another oven.
A comment I'll make is that it now looks like what it did part way through the treatment. Then there were patches, which seemed to tie in with the thickness of applied gel. I think it is what others named "blooming".

Re item 2. Generic oxy cleaner. I accidentally left the bezel in the solution for way too long and that slightly damaged the plastic. Looking at the bezel now, it hasn't regressed at all. Over the past two years, the CD-ROM drive has been stored in a book case with the bezel against the back wall of book case, and so little exposure to light.

Re item 3. Generic oxy cleaner. The mouse originally was very yellow. Unfortunately, that mouse was returned to my box of mice and I can't distinguish it from the other mice. The fact that none of my Microsoft mice are significantly yellow suggests that the subject mouse has not regressed. And if it has, it hasn't regressed by much. Over the past two years, my mouse box has been open and exposed to indirect sunlight (curtained room).

Of course, the above sample size is not statistically significant.

Interesting. Yes, a lot more observations are needed.

Just looking at my own stuff, I can't detect any regression in the Lisa (yet). And this does sit out in the light (well..dim room light). However, it was only Retr0Brighted two years ago and was also the LEAST yellowed of those ones I did.

If the theory of mobile bromides from the initial yellowing moving back to the surface even in the absence of UV light is correct it would follow that those plastics most yellowed in the first place, would regress more quickly. They would have more of these free bromides in the plastic deeper down untouched by Retr0Bright. Quality/type of plastic would also have a bearing and I'm sure heat does too. Even given our very small sample size (Mine, Lorne's and yours), these result could still fit the theory.

In essence there might be a large variation in regression (re-yellowing) depending on many of the above factors.

Any more examples out there?

Tez

 

[tezza]

Hi,

I would wonder if it is actually the UV causing the problem originally or with trated items re-yellowing. I've noticed that white paint where covered goes quite yellow, but that areas not covered stay white. Do we have a similar situation with treated plastic ?, covering it up reducing air exchange actually promotes the yellowing.

Mike.

I think it's a different situation with these plastics Mike. Why they yellow in the first place is explained at http://retr0bright.wikispaces.com/ in "The Science bit". In that article the mobility of these bromine molecules is mentioned and the fact that Retr0Brighting only acts on the surface which is why I feel the hypothesis I propose (Regression even in the absence of light) seems to make sense.

Tez

 

[Gib]

I've noticed that white paint where covered goes quite yellow, but that areas not covered stay white.

Whoa! If paint is going to yellow, too, then should I re-think my intention to spray paint as an alternative to Retr0Bright? Early IIes were painted. Have they yellowed as much as the unpainted later ones?

(I realize that you're saying the paint yellows where covered, but I assume a lot of IIe owners are like me, taking their computers out of boxes from time to time to use them, but leaving them boxed, or at least covered, for long periods in between.)

 

[Arcady]

I have two untreated beige Apple IIe units. One was a 1983 model and was painted. The other is a 1985 model and was molded plastic. The 1983 box looks nearly original (including the spacebar that for some reason doesn't change color on these) and the 1985 model is badly yellowed and has a spacebar that is a different color than the rest of the keys. Both machines have been in the same rooms either in box or out of box since they were purchased. Of course the one from 1983 was in use for two more years than the one from 1985.

On the other hand, I have two platinum IIe's that were both made in 1987, and one looks like it came off the factory floor yesterday, and the other is so disgusting it looks like it sat on the surface of the sun. I don't know the complete history of these boxes though.

 

[Gib]

I have two untreated beige Apple IIe units. One was a 1983 model and was painted. The other is a 1985 model and was molded plastic. The 1983 box looks nearly original . . . and the 1985 model is badly yellowed . . . .

OK, so paint is a good alternative to Retr0Bright--if one uses the right kind of paint. So, does anyone know what kind of paint works best on 80's plastic computer cases?

 

[Chuck(G)]

If you're in the market for museum conservation-quality paint, this stuff looks like a good bet. Be sure to use a primer to ensure the uniformity of the final result.

 

[barythrin]

I dunno. I would think a painted system would look, feel, and smell painted. To me a yellowed computer is normal and looks natural still. Retr0bright is great as far as making something look brand spanking new, or making an item that was never actually white white but I've never found the need to really risk it. I do have a non working NEC laptop that is pretty yellowed that I was debating it on just as something I wouldn't care about too much. I'd like to fix the laptop of course but color wise it looks ugly yellow, not a natural UV aged yellow, although this was also common from systems that were in smoking environments. That's a big one I've seen, the tar, etc from our offices in the 90s before they banned smoking in the work place the computers that were in rooms of smokers were pretty disgusting and colored darker yellow. Sorta the same thing that happens to their walls and ceilings in their house.

Anyway, that was one of the original conversations whether to retrobright a system or not. A bleached system MIGHT have more frail plastic. The outcome however does look really nice if it's done right. If not you can get streaking, or other potentially unwanted patterns in which a lot of folks would have been happier to have their original aged case again. If the system looks fine and is just the natural occurring aged plastic color then I personally am more of a leave it alone guy myself. Even as a museum piece it'll get colored by the UV lights in the long run anyway and shows the age of the equipment.

 

[tezza]

These are my thoughts on the “to Retr0Bright or not” debate…

With a white or cream case I think you are pretty safe. I’ve never noticed any damage, thinning or an increase in brittleness after the process. In quite a few yellowed units the sun, heat and age have made the plastics pretty brittle anyway. Blooming is less of an issue on a white or cream case, but sometimes you can get a bit of streaking or blotchiness. This seems to depend on the plastic itself, how sever the initial yellowing was (the more yellowed, the more patchy the result might be) and how well the area was covered with Retr0Bright paste. However, this can still look better than a yellow case.

On a coloured case (say a C-64) it’s a lot more risky. The process can work well but blooming can occur if it’s overcooked.

Labels are at risk or fading or bleaching if exposed to the process

White Keys de-yellow well. However, there is a risk of the letters fading a bit with overcooking. Again, it depends on the plastic.

Coloured keys (grey keys for example) can also come up well but there is a risk of streaking if they are overcooked.

The process is not permanent. UV Light will accelerate regression by forming new degraded bromines but regression can also happen with minimal light exposure. Heat, the type of plastic and the degree of initial yellowing in the first place will determine how quickly this happens as degraded bromides not stabilised in the initial retr0brighting find their way to the top of the case (assuming this theory is correct).

Retr0Brighting again should clean these up, but again this may only be temporary. It depends how many degraded and mobile bromides are down there.

These are my observations, and thoughts based on my understanding of how the process works (from the info on the Retr0Bright wiki...which seems logical). Although I have a basic understanding of chemistry (to 1[SUP]st[/SUP] year college level) I’m not a chemist, and have an open mind on what other subtleties might be happening. In particular, the variables are never going to be the same. The type of plastic (even down to the batch), prior exposure to UV, degree of yellowing, concentration of H202, how well the person retr0brighting carried out the technique, consistency and length of exposure to UV during Retr0Brigting, what other products are in the activator (i.e. the Oxy), how well the paste was mixed etc.

What is needed is a PhD study on this, with lots of testing and microscopy work. In the absence of that though, people publishing their experiences adds to the knowledge base.

For myself, I might retr0bright the Vic 20 case again. It’s easy to do, and it is one of the ones where the yellowing most detracts from its appearance as a classic computer. The Atari 130XE is not really a classic and I don’t have quite the same nostalgic attachment. I might leave that. Same with the RX8000. The Apple IIe isn’t too bad (yet) and neither is the Lisa. The System 80 can stay yellowed. I already have two others which are not.

I was going to Retr0Bright my Apple IIGS. I might leave it as is though. The box is white but the keyboard trim (but not the keys) and screen are somewhat yellowed. It looks ok as a two-toned machine though, almost as if it was deliberate (-:

Tez

 

[Chuck(G)]

The nice thing about conservation paint is that it can be easily removed, for that mellow yellow look.

Paint is used on enclosures and fixtures form by RIM (reaction-injection molding) polyurethane foam, because it's a brownish root-beer ice-cream float color that's not visually appealing. I have several pieces of equipment with RIM cases and they look as good as they did when new, 30-some years later.

So don't knock paint. Colored injection-molded plastic looks cheap to me.

 

[Ole Juul]

So don't knock paint. Colored injection-molded plastic looks cheap to me.

I have a feeling that many people don't actually realize that the plastic is cheap. lol That's why it is used. In some ways trying to preserve plastic computer cases is like trying to preserve cake. At some point it is simply going to dry out and lose its colour.

As for paint. The modern titanium dioxide (aka titanium white) was mainly developed by the auto industry and has become the standard in fine arts paints. Binding vehicles now include epoxy (as opposed to oil). So yes, if one wants a stable white finish, paint is a real winner.

 

[Lorne]

I'd like to fix the laptop of course but color wise it looks ugly yellow, not a natural UV aged yellow, although this was also common from systems that were in smoking environments. That's a big one I've seen, the tar, etc from our offices in the 90s before they banned smoking in the work place the computers that were in rooms of smokers were pretty disgusting and colored darker yellow.

90's ? You should have seen the stuff in the offices in the 80's, when there was an ash tray on every desk, and sometimes they were emptied twice a day.
And never mind the walls and ceilings - imagine the lungs of the poor bastards working there.


If we'd all used the same concentration of H2O2, and used the same "recipe" we might be able to compare results better.
Maybe my stuff has held up better/longer because I used a much stronger, 30% H2O2 content.
Seeing as we all seem to have used something slightly different in the process, I'm not sure we can put it all down to just UV or time or anything else.
Maybe, as in my case, a higher H2O2 concentration lasts longer or lasts forever (wishful thinking).
Who knows?

 

[Gib]

If you're in the market for museum conservation-quality paint, this stuff looks like a good bet.

I was thinking more along the lines of commonly available spray paint. Last time I was at the hardware store, I noted that they carry plastic primer in spray cans, so I thought I might use that to prepare the surface. Then I need to identify a brand that has a match, or near match, for the flat beige color of a IIe. Has anyone actually had success with hardware store quality spray paint on a IIe?

 

[barythrin]

My only experience was when a friend and I were in high school, when we learned how to disassemble laptops pretty well he ended up taking his apart, spray painting it red and white (he sprayed over the key caps too which didn't bother us but novice computer users couldn't type on it). It could have been too much paint, etc but it felt like spray paint on plastic and could scrape off sorta. Wasn't a very desirable job or outcome imho. I suppose one could do better if they desired though or used proper paint.

 

[Arcady]

Speaking of paint, I have a fairly rare black Apple ADB keyboard that someone painted. What's a good way to get paint off of plastic without damaging it?

 

[Plasma]

One of my other hobbies is restoring cars...paint is what everyone uses to restore plastic parts on cars. I have personal experience with Krylon Fusion and it works well. If you spray a lot of very light coats you will get a nice even finish. You can get the stuff at Walmart or Meijer.

Other popular plastic paints are Rustoleum Plastic, SEM Color Coat, and Colorbond. I've used Rustoleum Plastic but wasn't particularly impressed. Colorbond is supposed to be real good but I haven't tried it.

 

[Chuck(G)]

90's ? You should have seen the stuff in the offices in the 80's, when there was an ash tray on every desk, and sometimes they were emptied twice a day.
And never mind the walls and ceilings - imagine the lungs of the poor bastards working there.

80s? How about 60s and 70s? At one point, I was surrounded by two cigar-smokers and one pipe smoker who stuffed his briar with the most odious concoctions. I survived it. The CEs used to get very perturbed when someone would grab an ashtray from the cafeteria and sit down at the system console with a cup of coffee and a pack of cigarettes.

 

[Shadow Lord]

2. CD-ROM case bezel - generic oxy cleaner from supermarket
3. Microsoft Mouse - generic oxy cleaner from supermarket

Out of curiosity which generic oxy cleaner did you use?

 

[Shadow Lord]

One of my other hobbies is restoring cars...paint is what everyone uses to restore plastic parts on cars. I have personal experience with Krylon Fusion and it works well. If you spray a lot of very light coats you will get a nice even finish. You can get the stuff at Walmart or Meijer.

Other popular plastic paints are Rustoleum Plastic, SEM Color Coat, and Colorbond. I've used Rustoleum Plastic but wasn't particularly impressed. Colorbond is supposed to be real good but I haven't tried it.

Problem is color matching. You really can't get that in a spray can. I personally have gotten parts color matched at Home Depot and used a paint/primer in one to repaint items. I use an industrial paint gun in a hood at the workshop so not something everyone has easy access to. Cans are nice but they are a pain to put on properly (streaks, globs, etc.), can eat the plastic, and if you need a particular color very hard to find...

 

[Plasma]

For cars I usually need black so color matching has not been an issue Using aerosol is not that difficult, you just need light coats. Never seen any paint "eat plastic"...

You are right, a paint gun is more convenient but most people don't have that (or the air compressor needed to run it). Home Depot doesn't do custom spray paint but a lot of automotive paint places can custom mix SEM and put it in aerosol.