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Old 14 February 2008, 12:29   #1
chiark
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The Definite "Cleaning Yellowed Plastic" thread

Ladies and Gents, let's collate what we know about yellowed plastic cleaning in one thread...

First off, what causes the yellowing:
- grime and years of use: possibly to remove with elbow grease and common household cleaners
- chemical reaction in the plastic: impossible to remove without removing a layer of the plastic, reversing the reaction or covering in paint/dye

Some people will swear blind that they've reversed chemical yellowing, others will say that it's impossible. What seems common is that if your case is yellowed due to a reaction taking place, you need to remove a thin layer (mechanical cleaning) or alternatively try to undo the reaction causing the colour (bleaching) or cover it (paint/dye)

http://forums.yojoe.com/showthread.php?t=24596

http://www.applefritter.com/node/21767

Cleaning

(Charlie's suggestion is originally here
Quote:
Originally Posted by Charlie
My plastic cleaning method:
-Kitchen sink
-Vanish OxyAction Multi spray ( or similar )
-PVC window cleaner ( the white creamy stuff )
-Warm soapy water
-Plastic pan scowerer cloth thingy ( not a brillo pad!!! )
-Wife's toothbrush ( well I wouldn't use mine obviously )
-Lots of cold water

-> Squirt on the Vanish, leave for a bit.
-> Squirt on the PVC cleaner, go @ it with plastic cloth thingy ( DON'T GO MAD - no need )
-> Wife's toothbrush for the nooks & crannies.
-> Wash off with soapy water.
-> Rinse thoroughly!
Many have pointed out that girlfriend/offspring's toothbrushes also work, but your own won't ;-)

Undoing chemical yellowing
- magic eraser wall cleaner thingy
- Solution of hydrogen peroxide (and optional UV light)

I'll be trying this on my extremely yellow 4000 bezel. I've got a 1541-ii drive that I've tried Charlie's method on and it's still yellow, and another 4000 with a not-too-bad-but-still-yellow bezel.

The idea is for people to post before/after and methods used, and we can try to make this sticky.

Any interest? Or should I get out more ?
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Old 14 February 2008, 13:21   #2
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This sounds like a good idea.
What is "elbow grease" and where can I buy it?
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Old 14 February 2008, 13:38   #3
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Available at all good hardware stores - ask for it by name.
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Old 14 February 2008, 14:25   #4
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Elbow Grease is sold by JML and is available from Woolworth's, Poundstretcher and Instore shops.



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Last edited by Merlin; 14 February 2008 at 14:49.
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Old 14 February 2008, 14:44   #5
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I've got two litres of "elbow grease", i'll sell for £30 incl p&p.
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Old 14 February 2008, 14:59   #6
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Quote:
Originally Posted by rare_j View Post
This sounds like a good idea.
What is "elbow grease" and where can I buy it?
If there was ever a post that needed to become a signature.
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Old 14 February 2008, 15:13   #7
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Hee Hee. I was just kidding with you.
I get mine from the same shop that does skyhooks and long weights.

Back on topic...
How are you supposed to know what the original colour was in the first place? I have an A500+ which is not white, it's kind of beige all over including the keys, it is definitely not the same shade as my A1200, but is it yellowed? It looks nice to me, but was it always like that?
We need a colour chart.
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Old 14 February 2008, 15:34   #8
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Just look at the inside of the case, the original colour is visible there.
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Old 14 February 2008, 15:50   #9
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I was thinking about how to sort that out, especially as a digital camera's white balance will be confused by all this... best we can do is use natural light, white balance against a sheet of paper and take before and after pics. However, your monitor etc will vary it...
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Old 14 February 2008, 16:09   #10
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Thanks for the plug
Good idea for a thread - sorry 'my method' didn't help you much.

Further thoughts:
Zetr0 (and others) swear by the dishwasher method.
-Disassemble (obviously)
-In the dishwasher as per your usual habits. (40-60c - no more)

This works a treat for getting plastic nice 'n clean & seems to be a good 'prep' method if you intend to spray/dye.

Problems..?
Not many...
-Some plastic requires v. little temp to warp. In general main cases, lids & keyboard keys are safe, bit's 'n bobs & some keyboard bases - not. Quick check: Can you fairly easily mark the plastic with a thumbnail? Don't dish-wash.
-Will do nothing for 'chemical yellowing'


Chemical Yellowing:
Some thoughts - not all will agree.

Causes...
1-Plastic may be non-biodegradable but does degrade with time. These chemical changes usually show up as yellowing. The process is usually accelerated by heat - the reason why PSU bricks often look bad despite being out of the sun.
2-UV damage will also speed up this process but will only affect the surface.

3-Most plastics will usually have bleach or 'more complex' antioxidants or even 'sun-blocks' added in an effort to slow down the visible signs of this inevitable degeneration, but this costs money...

So:
-If the manufacturer hasn't skimped on the protection the chances are any yellowing you see will be dirt & surface degeneration only.
A cleaning method that involves some bleaching & a little scowerering will clean things up a treat. (For want of a better name - my method)
-If the protection has been neglected (hey! That sounds like C=) then the obvious degeneration will be more than skin deep. Sadly no amount of cleaning will fix this. Even if you successfully bleach the surface the darker yellow underneath will show through.

This is why some Amigas that have had a hard life clean up a treat while some kept in their boxes are still yellow! It's down to how much was spent on protecting the plastic during that particular production run.
It would be interesting to see if there is any correlation between the production date of very yellow Amigas & one of C='s many crises. There will be differences between manufacturing plants.

P.S.
Yes - Dish washing will accelerate the aging of your plastic, but not so you'd notice.

Hope that helps a bit.
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Old 14 February 2008, 16:46   #11
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The chemical yellowing happens because flame retardent material in the plastic evaporates over time.

Some batches are worse, some are better.. I've seen C-64s so yellow and brittle that you could just snap off parts of the vent grille..
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Old 14 February 2008, 17:02   #12
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Charlie, that's superb, thanks!
I've not yet been brave enough to try cream cleaner (which is what I guess the pvc cleaner is) on the fascia. I went at the things with the vanish oxy-action spray (aimed at laundry, it seem?) and a green scrubby thing. It cleaned, but didn't remove yellow.

The 4000/40 I've just picked up, despite being yellower than a smoker's index finger, still has the plastic protective cover on the Commodore logo . Seems wrong to scour the poor thing.

Last edited by chiark; 14 February 2008 at 17:09.
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Old 14 February 2008, 17:22   #13
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Scour is probably too strong a word - I can't think of a more appropriate one. (without getting pervy)
The pads I use are those kitchen cloths that seem to be made of plastic hair.
To me the trick seems to be to apply sufficient abuse to do the job without causing any observable damage. (hence NO to brillo-pads)
Oh-yes. Watch out with cream cleaners. I'm on about the stuff used to do PVC window-frames (non-abrasive-ish). Household cream cleaners can have a lot of abrasives in them - not so good.

Quick tip: Once you've got the fascia off have a look at parts that have probably never come into contact with cr*p / sunlight etc...
...if there is any yellowing here you will probably have no success.

P.S.
As alluded to by Jope this is a bit of an unending subject. There are businesses dedicated just to such manufacturing problems. People have done Ph.D's on this question & there still isn't a 'proper' answer...
...the above does me for convenience.

Last edited by Charlie; 14 February 2008 at 17:27.
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Old 14 February 2008, 17:49   #14
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Scour really is the best word... And yep, the "plastic hair" thing is what I'm using. They're known in our family as green scrubby things - it's sorta stuck, that name!

The only PVC frame cleaner I've found to date is a spray, not a cream at all. I've bought some Cif with bleach and will have a **gentle** go with that.

I know I can get it back to white, because the fascia is white on the bottom edge...

I know it's unending, but it'd be good to get success/failure stories - some of the tales about people trying to restore the original colour of their storm troopers had me smirking until I realised I was about to attack a 20 year old hard drive enclosure
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Old 14 February 2008, 22:41   #15
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If cleaning doesn't help.....

The answer is Austin Rover acrylic car paint in Old English White, paint the case in white acrylic primer and top coat it with the above shade, it's as close as I've been able to get so far, I've painted PC cases and monitors with it too as it's close to PC "beige". If anyone has a closer colour of acrylic paint, please let us know...here's a swatch, bear in mind it depends on how your monitor is set up as to what colour it looks like below:

Ford Tuscan Beige may be another close colour but I couldn't find a swatch to post here, Plastikote Antique White is pretty good too.


The Science Bit....I used to be an industrial chemist by trade.....

Commodore mustn't have added a UV absorber into the plastic masterbatch, something like 0.5% of Tinuvin 327 additive from Ciba Geigy would have stopped all of this yellowing. UV light degrades the plastic and it becomes brittle because the polymer chains shorten and cross-linking breaks due to the action of the UV light.

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Old 15 February 2008, 11:21   #16
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Old English White? We've got a Morris Minor convertible in that colour
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Old 15 February 2008, 13:08   #17
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@ Chiark

Well, compare it to your Miggy and tell me how close the colour actually is to the original moulded colour...do you think it's a close match? A photo would be good showing an Amiga close to your Morris.

Miggy and Moggy, that works for me!!!

Edit: Ford Tuscan Beige is actually for Commodore 64s, I am getting at cross purposes.

Ivory White / Old English White / Antique White is the shade to go for, it's sort of a Magnolia colour and difficult to describe in words.


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Old 15 February 2008, 14:42   #18
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Unfortunately the moggy is in my grandma's garage, around 120 miles away. I'll take a 1010 diskdrive next time I'm down there and go and compare
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Old 17 February 2008, 20:10   #19
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Quote:
Originally Posted by chiark View Post
the "plastic hair" thing is what I'm using. They're known in our family as green scrubby things
In the army we used that stuff for cleaning rifle parts, the trade name is Scotch-Brite.
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Old 18 February 2008, 04:17   #20
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I found the solution for computer's yellowed plastics years ago...

women and kitchen'products or rare quimical products is pure negro's things


OK


a fine sandpaper and patience can remove the first layer of the yellowed plastic
I blanked some computer' partst using this method

it works perfect but sometimes the yellow penetration is deep and you must use thinner to go deep

but the thinner is dangerous because render the plastic...so you must proceed with care....

Attention for newbies: (before the use of thinner you must practice first with any useless yellowed plastic)


After the bleached you must protect the plastic with a fine transparent varnish yes or yes....
if you do not apply varnish .....the degrade process starts again



There is no solution for keyboard'keys....because if you remove a plastic 'layer you will erase the printed key



bye
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