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adam1977

New technique for whitening yellowed plastic

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nice. but you can still see there's a difference

the yellow is now the colour that the rest of the case was and

the rest of the case is now slightly lighter still.

Ya, it isnt perfect, but it still looks way better than before. It helps to keep it out from sun up to sun down, as it hits different angles for a more even look. Considering this technique requires almost no effort, the results are pretty awesome.

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I live in Queensland, with excess sun here, more than I like. I just hope this process won't warp my case.

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Posted (edited)

I live in Queensland, with excess sun here, more than I like. I just hope this process won't warp my case.

 

yes 100% yes it is a real concern if you live in an area where the sun gets INTENSE might I suggest putting it in a water bath to prevent that (never had warping issues with liquid retrobrite formula's in the south east USA August sun, where its so narsty your grass turns to dust)

 

I set some 5 mm accrylic out in the sun one day just to see what it would do and it started to make a 90 over the deck rail by the end of the day, you dont want that messing with a thin, old ABS part that's hard to replace

Edited by Osgeld
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I live in Queensland, with excess sun here, more than I like. I just hope this process won't warp my case.

 

You still coming to terms with the sun Steve? :)

 

But yeah, I'd be worried about warping in that heat too...

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I think there's a greater risk of items being carried away by flood-waters in the UK.

 

Anyway: I tried this briefly on Monday when we had good, strong sunlight, but since experiments were rapidly curtailed by the subsequent deluge of rain, it's still unclear whether anything is actually happening to the plastic.

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My XEGS’s plastic bits have been out on a bit of cardboard on the lawn for two days now.  Been a bit overcast here in the UK, but we don’t want blazing heat anyway!

 

Seems to be doing the job!  I’m using the keycaps as a reference since they’ve got a visible line between the yellowed plastic at the top of the key and the unyellowed sides.  That was very visible to begin with, but is very nearly gone.

 

Reckon most of the parts will be done by the end of tomorrow. The spacebar and the grey joystick top on base might need another day or two as they were worse to begin with.  

 

Will post some some before and after pics when it’s all back together.

 

This has worked so well I’m tempted to do the same with my STFM and Falcon. Neither of them were as bad as the XEGS, but they’re not quite what they once were.

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You might want to hold off for a little while and see how the XEGS fares over time, if it re-yellows or gets brittle or something. 

 

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I have a white PSOne controller that has yellowed badly over the years, i've been putting it out in the sun on and off for the last couple of months and it's at the point where the yellowing is barely noticeable; i'll post some pics of before and after ;-)

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wow, some of my previously retrobrighted stuff is looking a bit yellow again, time to hit the sunbed :D

 

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Post one, This takes too long!

Wow, I've posted this several times. It works.

1. Beauty supply store, get 'developer 30' cream white.

2. Have a clear plastic container, when upside down, will cover your parts. 

3. wash your case and parts.

4. Paint your parts with developer cream with a 2"-3" paint brush.

5. use a very low nap paint roller to 'smooth' out the cream on all surfaces. THIS IS THE MOST IMPORTANT STEP!!

  I use this:

https://www.amazon.com/Shur-Line-3060C-3-Inch-Touch-Roller/dp/B000FGZMHK/ref=sr_1_8?keywords=paint+roller+kit&qid=1562908925&refinements=p_n_size_four_browse-vebin%3A17870928011|17870929011&rnid=17870926011&s=hi&sr=1-8

6. wet cement with water where the case/part will sit facing the sun.

7. Place case/parts over cement so the water dose not touch parts. cover with plastic clear container.

8. Container should make a good flat/sealed contact with cement. Try not to let moister out.

9. Do this during mid day. At 70' wait 40 minutes. 80' - 30 minutes, 90'-20 minutes. 100' will risk blooming (white discoloring) check progress.

If done, wash, wash, and wash again.

10. if not done, add water to cement. You want a very humid/hot environment for the case/parts. Wait minus 10 minutes from schedule above. Check again. They should be done. If not wash, wash, wash, wash, try again the next day. If you do the same day you risk 'blooming".  Morning, Evening do not work, only midday when the cement is warm/hot.

 

Easy simple, works

 

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That doesn't sound very simple at all, with that method you have to buy products, containers etc. plus it's time consuming...

 

The beauty of this new method is that all you do is put your retro device in the sun and leave it till the yellow is gone, it's simplicity itself ;)

 

https://www.youtube.com/watch?v=8P1OVj0IcqY

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Don't want to re yellow? use this and the keep the computer cool and in the appropriate light...

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I'm impressed. I had a spare 400 cart flap that I left out over the weekend (half of it covered)
It really did work, my camera can't pick up the subtle difference as the flap was not too badly yellowed. 
I have since left it out totaly uncovered and the yellow half is now the same colour as the rest.
I now have a previously retrobrighted and re-yellowed 800XL sitting in the garden, obviously we now have a total blanket of cloud :)

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gah, folks just don't understand... keep the plastic cool, or the the bromides will migrate.. and again it's suggested to use what I listed... you are shortening the life of the plastic otherwise...

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Scientific literature on the effect of various wavelengths of light on degradation of ABS and similar polymers suggests the following:

 

1) Yellowing is accelerated by UV light, both UVA and UVB across the spectrum

2) Weakening is similarly accelerated by UVA & UVB but as the plastic ages and yellows, visible light also becomes increasingly damaging

3) Bleaching out of yellowing is due to visible light at the blue/violet end of the visible spectrum

4) Yellowing is accelerated by dark because, particularly in normal indoor lighting conditions behind glass, the bleaching effect of visible light exceeds the yellowing effect of UV light

5) Normal glass filters UVB completely but UVA only partially. Laminated glass/windscreen/windshield glass or UV-filtered glass completely filters out UVA also

 

The conclusion to be drawn from this is that in theory the best and safest way to reverse yellowing without damaging the plastic should be by exposure to bright light  in the visible spectrum e.g. bright daylight behind laminated or UV-shielded glass.

 

Note that although the windshield/windscreen of a car is usually UV-shielded, side windows usually are not and the dash of a car in full sunshine might get VERY hot unless it is very well ventilated.

 

Refs.

Searle, N. D., Maecker, N. L. and Crewdson, L. F. (1989), Wavelength sensitivity of acrylonitrile–butadiene–styrene. J. Polym. Sci. A Polym. Chem., 27: 1341-1357. doi:10.1002/pola.1989.080270418

Abstract

The wavelength sensitivity of unpigmented 100 mil thick ABS exposed to sunlight and filtered xenon are radiation was determined by the sharp cut filter technique based on three types of photochemical changes: bleaching, yellowing and loss in impact strength. Bleaching of the yellow‐colored species formed in the processed material is caused by wavelengths between 380 and 525 nm with maximum color change by the 475–485 nm region. Photochemical yellowing is due to wavelengths between 300 and 380 nm with all wavelengths being almost equally effective. The spectral sensitivity based on change in impact strength shifts from the UV to the visible region as photochemical yellowing progresses.

 

Pickett, James. (2004). Reversible post-exposure yellowing of weathered polymers. Polymer Degradation and Stability. 85. 681-687. 10.1016/j.polymdegradstab.2004.03.008.

 

Abstract

The commonly observed effect of weathered polymer samples continuing to change color in the dark was studied in some detail for polycarbonate, styrene–acrylonitrile copolymer (SAN), and various combinations with SAN–polybutadiene rubber graft (SRG) copolymer. All of the formulations became more yellow upon storage in the dark after accelerated weathering, and all behaved very similarly. There was a fairly rapid shift of 1–2b units (as defined in CIELAB color space) over the first two weeks followed by a slower, linear shift that continued for many months. This amount of color shift is enough to be visible to the eye in side-by-side comparisons. Most of the additional color generated in the dark could be bleached by exposing the samples to sunlight through a south-facing window. The samples usually reached the original color after 2–4 days of window exposure. Putting the samples back in the dark caused the yellowing to start up again, although the rapid yellowing often was not as much as the first time. Samples aged under natural conditions outdoors also underwent a small color shift upon storage for 5 months and substantial color shifts after two years.

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