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Old 4th Jul 2018, 11:12 am   #1
G6Tanuki
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Default Restoring the whiteness to yellowed plastic.

What's the current thinking on restoring the whiteness to plastic which has turned that nasty nicotine-yellow over a couple of decades?

I've got several things here - some 3-pin 'Masterplug' mains connectors, a couple of classic Microsoft 'wheel'-mice and the flow/temperature-control knobs on my shower - that now look really rather sad.

Am prepared to try aggressive chemistry !
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Old 4th Jul 2018, 11:30 am   #2
FIXITNOW
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Default Re: Restoring the whiteness to yellowed plastic.

try this
https://www.classic-computers.org.nz...h-oxy-only.htm
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Old 4th Jul 2018, 1:16 pm   #3
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Default Re: Restoring the whiteness to yellowed plastic.

I have found that the plastic used on early computers and computer monitors, that yellows, looks absolutely new and fantastic with a spray coat of "Arctic White" automotive lacquer, its called Holts Duplicolor in AU. This type of lacquer microscopically etches into the plastic's surface and it dries very quickly. It then becomes incredibly durable and scratch resistant and doesn't flake off the surface either.

To see a vintage (once turned very yellow) Apple computer monitor treated this way look at the photo on the first and last page of this article:

http://worldphaco.com/uploads/ARCADE_MINI-PONG.pdf

While chemical oxidation and bleaching may improve the yellowing, it will never correct it completely and the surface finish probably won't be as good.

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Old 4th Jul 2018, 4:11 pm   #4
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Default Re: Restoring the whiteness to yellowed plastic.

With an ABS vauxhall indicator stalk aged by sun, heat, sweat, grime, (originally black in colour but oxidised to mid brown with patches of ivory) I confidently abraded it to remove the damage only to find it was way more than skin deep. This switch went out of production years ago so being in working condition it needed to be retained whatever it looked like. Giving it a final light sand I gave up on abrasion and overcoated it with black touch-up can acrylic.

It goes against the grain to be doing this (and time will tell on the durability) but the finish is certainly very good. It seems that with certain degraded plastics, if the friable surface is removed the grainy under-layer forms a superb bond with such paints. A new use for an existing technology..? (But try it on a test piece first)

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Old 4th Jul 2018, 5:22 pm   #5
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Default Re: Restoring the whiteness to yellowed plastic.

As several people are noting - the yellowing is almost certainly indicative of degradation of the (thermo)plastic, due to various ageing mechanisms, e.g., exposure to UV, ozone, atmospheric pollutants, etc. The degradation will be more than skin deep, although the discolouration is likely worse near the surface.

At best, I suspect the oxidizing agents / peroxides may give some (temporary) improvement of the surface discolouration, but the degradation will continue, unabated, as the various stabilisers and additives in the plastic are exactly as before, namely already depleted, and getting worse due to ongoing ageing.

As a chemist, I'd opt for the paint solution - it not only provides a new, clean, attractive surface layer, but to some extent it may even provide a partial 'barrier' to help slow further degradation of the plastic substrate (paints contain similar additives), albeit probably not for long.
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Old 4th Jul 2018, 5:29 pm   #6
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Default Re: Restoring the whiteness to yellowed plastic.

Thanks for the info - yes from reading elsewhere it does seem to be that the yellowing is somewhat more than just a surface-issue.

I was hoping for an easy/quick fix along the lines of "Squirt them with brand-X spray you can buy off Amazon, and wipe off - job done!" - the hassle of painting seems just too much effort to go to; it's not as if old Microsoft mice are really things of value.

The bathroom shower-control, I may just get a little man in to strip the control/outlet/riser out, retile, and replace with something a bit more up-to-date and non-yellow.
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Old 4th Jul 2018, 7:43 pm   #7
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Default Re: Restoring the whiteness to yellowed plastic.

Just do a bathroom makeover -
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Old 4th Jul 2018, 8:14 pm   #8
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Default Re: Restoring the whiteness to yellowed plastic.

I cleaned up a very yellow plastic grill on a Philips L3G type radio a while back with metallic t-cut and a damp cotton rag, with good results-

https://www.halfords.com/motoring/pa...restorer-500ml
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Old 4th Jul 2018, 9:31 pm   #9
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Default Re: Restoring the whiteness to yellowed plastic.

No consolation, but my Mira power shower is ca. 13 yrs old, working perfectly, but... with yellowing plastics.

It's so old, I managed to source a 2nd, used but fully working, unit for spares, as well as a new set of white plastics, all for < 20. They're stored packed in a plastic bag, in a cardboard box, in the dark - ready for when needed. Maybe an option for yours ?
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Old 4th Jul 2018, 9:40 pm   #10
60 oldjohn
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Default Re: Restoring the whiteness to yellowed plastic.

If the plastic can be separated from metal parts, soak in Peroxide under UV light. This works and you should find the process has been discussed on this forum if you search.


John.
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Old 5th Jul 2018, 7:53 am   #11
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Default Re: Restoring the whiteness to yellowed plastic.

A quick query if I may. How far will this yellowing process go? If in several thousand years our descendants discover 'white' plastic artifacts from our era, would they by then be dark brown or even black?

Steve
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Old 5th Jul 2018, 8:31 am   #12
G6Tanuki
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Default Re: Restoring the whiteness to yellowed plastic.

Quote:
Originally Posted by 60 oldjohn View Post
If the plastic can be separated from metal parts, soak in Peroxide under UV light. This works and you should find the process has been discussed on this forum if you search.
The plugs and the mouse could be disassembled to their plastic-only components for 'pickling', yes.

Alas to remove the major component of the yellowed shower-control would involve deplumbing, and removing some tiles/grout where the unit is recessed into the tiles in order to access some of the mounting screws. After going to such a rigmarole rather than trying to clean-up the old discoloured assemblies it's easier to just replace the lot and then I know the job's a good'un for the *next* 15 years.
Seems I can get a chromed-brass unit as a replacement for the plastic one. That shouldn't go yellow!
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Old 5th Jul 2018, 9:18 am   #13
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Default Re: Restoring the whiteness to yellowed plastic.

Quote:
Originally Posted by Panrock View Post
A quick query if I may. How far will this yellowing process go? If in several thousand years our descendants discover 'white' plastic artifacts from our era, would they by then be dark brown or even black?
It would most likely turn to dust after that amount of time.
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Old 5th Jul 2018, 10:46 am   #14
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Default Re: Restoring the whiteness to yellowed plastic.

I had a number of 700 type telephones in black plastic bags stored in my dark attic for a period of more than 20 years. The ivory ones went yellow right through to the inside. Exposure to light may play a part in the degradation, but I don't think it's the only factor.
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Old 5th Jul 2018, 11:21 am   #15
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Default Re: Restoring the whiteness to yellowed plastic.

Glad to hear it's not just me, Graham. I've got some old computer kit in my loft that is now much yellow-er, in fact some is nearer to brown, than it was when it went up there.

I wonder if it's the plastic bags that make it worse as the bromine can't escape like it could if things were in the open.
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Old 5th Jul 2018, 1:49 pm   #16
Argus25
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Default Re: Restoring the whiteness to yellowed plastic.

Quote:
Originally Posted by Goldie99 View Post
As a chemist, I'd opt for the paint solution - it not only provides a new, clean, attractive surface layer, but to some extent it may even provide a partial 'barrier' to help slow further degradation of the plastic substrate (paints contain similar additives), albeit probably not for long.
I agree. It is known that chemical cleaners degrade, oxidize and damage surfaces. The process of cleaning is often destructive to the surface. On the other hand the paint is protective and in this case it fuses with the surface to create a new plastic exterior finish.

(One of the more benign cleaners is just a slightly damp cloth and since more substances are known to dissolve in water than any other solvent, often it is not a bad option for many cleaning jobs, but of course it won't improve the appearance of yellow plastic).

I have attached a photo showing three items restored with Arctic White lacquer. (The Apple and two IBM 5153 VDU's)

Here is a link to the product:

https://www.repco.com.au/en/brands/d...50g/p/A9514584

It is the only one I would vouch for, for the application. Of course you can get more creamy colored or off white versions, but this one has the right "whiteness" for a new look, but not quite as white as the nearby shelving.
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