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As many of you know, plastics used in our beloved computers from the 70's, 80's and 90's contained a fire retardant called Bromine. This chemical (along with exposure to the Sun's ultraviolet rays) cause a yellowing effect in the plastics. Sometimes orange, sometimes brown. Point is, their color changes at a chemical level.

Recent years have revealed that you can reverse this process with a solution (mostly hydrogen peroxide) and MORE exposure to ultraviolet light. This process has been termed "Retro-Brighting".

I have done this many times myself with various degrees of success. However, I have read many times that the whole process is only temporary and that, over time, the yellowing will always continue to happen.

So, has anyone experienced this first hand? I think Retro-Brighting has been around for a long time now so there should be some evidence if it's somewhat permanent or temporary.

Thanks.

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    FWIW I'm not entirely convinced this problem is caused by UV radiation. I had some ancient plastic computer parts that were stored in a lightproof cupboard in location that would never have received direct sunlinght anyway, and they ended up yellow-orange after about 40 years. (Sorry, no photos - I don't have them any more.)
    – alephzero
    May 16, 2017 at 1:10
  • @alephzero actually, I think the UV light will accelerate the process. However, it probably comes down to how much bromine was used. The ratio. But you're right about boxed equipment turning yellow. I've seen it too.
    – cbmeeks
    May 17, 2017 at 12:22
  • My anecdotal evidence is that UV accelerates the process, as does exposure to high temperatures. Attic storage - bad. Climate controlled closet storage - much better. Climate controlled and in heavy packaging - best. I have some forty year old systems that look brand new, and credit that mostly to their storage environment.
    – Brian H
    May 30, 2017 at 14:07
  • @BrianH same here. I also have a IIc PSU that the previous owner must have had near a window with a shade because the PSU is WHITE except for a small yellow strip across it. It's like a small beam of light was cast over it for years. Funny how they can change in bizarre ways.
    – cbmeeks
    May 30, 2017 at 19:18

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I do not have any anecdotal evidence, but scientific evidence seems to show that color restoration through use of hydrogen peroxide is a temporary solution to a long term problem.

A related question/answer on Chemistry SE reveals that plastics are damaged by UV light and that this damage does result in color changes. The bromine you mentioned additionally causes further coloring to the plastics.

From what I have gathered, UV light causes plastics to create free radicals - atoms with unpaired electrons - which causes the coloring of the plastic. Hydrogen peroxide is able to "capture" or bond to these radicals, effectively eliminating their presence in the plastic. This would explain the additional UV energy needed to reverse the reaction.

Since plastic degradation is inevitable over time, no amount of retrobrighting will permit plastics to remain white forever. :(

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  • Then, there is always spray paint. :-) I spray painted a Commodore 128D keyboard that was so orange that it would have taken 10 treatments to whiten. github.com/cbmeeks/Commodore128D
    – cbmeeks
    May 17, 2017 at 12:25
  • Technically, nothing is permanent :) I know a quality retr0bright treatment will last many years when the computer is stored in a friendly (low heat and UV) environment.
    – Brian H
    May 30, 2017 at 14:09
  • @BrianH correct...nothing is permanent....one day...the plastics and metals will bio-degrade into a blob of waste just before the Sun goes supernova. LOL
    – cbmeeks
    Jun 6, 2017 at 14:44

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